Manipulation Of Field Research Articles

Active manipulation of EM fields in open waveguides

The central question addressed in this paper is whether we can introduce an antenna array into a circular cylindrical waveguide to accurately control or determine the local field around the array with vanishingly small reflection from the boundary of the waveguide. We ask this question since we perceive the answer to be important to the applied community through its relevance for applications to electromagnetic shielding or slot antennas. We make use of the results presented in Onofrei (2014) for the scalar Helmholtz equation and show, by using the Debye representation in waveguides, how they apply to the current EM waveguide model. We prove the existence of a class of solutions and include a feasibility discussion for the antenna synthesis problem together with relevant simulations.

Achieving bifunctional cloak via combination of passive and active schemes

In this study, a simple and delicate approach to realizing manipulation of multi-physics field simultaneously through combination of passive and active schemes is proposed. In the design, one physical field is manipulated with passive scheme while the other with active scheme. As a proof of this concept, a bifunctional device is designed and fabricated to behave as electric and thermal invisibility cloak simultaneously. It is found that the experimental results are consistent with the simulated ones well, confirming the feasibility of our method. Furthermore, the proposed method could also be extended to other multi-physics fields, which might lead to potential applications in thermal, electric, and acoustic areas.

Plasmon-drag-assisted terahertz generation in a graphene layer incorporating an asymmetric plasmon nanostructure

This Rapid Communication presents a structure and full theoretical analysis to exploit the photon drag effect for THz signal generation in a graphene layer integrated with a plasmonic structure. The plasmonic structure is composed of a periodic array of asymmetric nanoparticles patterned over a graphene layer. The nanoparticles are designed to accomplish two goals: field localization due to the plasmonic resonance and manipulating the phase of the near field to effectively drag the quasiparticles in graphene. Combining the asymmetry with the plasmon resonances of nanoparticles, we show that an enhancement as large as three orders of magnitude is attainable in the power of the generated THz wave. This level of unprecedented enhancement mostly stems from the phase manipulation of the near field caused by asymmetric nanoparticles. Using the achieved enhancement, it is demonstrated that an ultra-wideband THz signal carrying the power of $1\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{W}$ can be generated using a commercially available femtosecond pulsed laser.

Bifunctional metamaterials with simultaneous and independent manipulation of thermal and electric fields.

Metamaterials offer a powerful way to manipulate a variety of physical fields ranging from wave fields (electromagnetic field, acoustic field, elastic wave, etc.), static fields (static magnetic field, static electric field) to diffusive fields (thermal field, diffusive mass). However, the relevant reports and studies are usually limited to a single physical field or functionality. In this study, we proposed and experimentally demonstrated a bifunctional metamaterial which could manipulate thermal and electric fields simultaneously and independently. Specifically, a composite with independently controllable thermal and electric conductivity was introduced, on the basis of which a bifunctional device capable of shielding thermal flux and concentrating electric current simultaneously was designed, fabricated and characterized. This work provides an encouraging example of metamaterials transcending their natural limitations, which offers a promising future in building a broad platform for the manipulation of multi-physics fields.

The manipulation of magnetic coercive field and orientation of magnetic anisotropy via electric fields

We report the effects of the electric field on the magnetic coercive field (Hc) and uniaxial magnetic anisotropy (UMA) orientation of polycrystalline Ni film grown on an unpoled (0 1 1) [Pb(Mg1/3Nb2/3)O3](1−x)–[PbTiO3]x (PMN-PT) single crystal substrate. Under various electric fields, normalized magnetic hysteresis loops of Ni films change in width; this represents the change of coercive field (ΔHc). Loop shapes are found to depend on the angle between the magnetic field and the sample, where changes in the shape reveal a small rotation of UMA. All these changes show that the magnetic properties vary periodically with a periodic electric field, by strain-mediated magnetoelectric coupling in the Ni/Ag/PMN-PT/Ag heterostructure. The poled PMN-PT produces strains under electric fields in the range of −4.2 kV cm−1 ⩽ E ⩽ 4.2 kV cm−1, then transfers it to Ni films resulting in changes to its Hc and UMA. The curves of the in-plane Hc and strain, at two mutually orthogonal directions, represent butterfly patterns versus the applied electric field. In addition, the changes observed in both the Hc and strain show asymmetric features in two orthogonal directions, which results in a small rotation angle of the UMA of Ni as the electric field decreases. The effective manipulation of magnitude and orientation of magnetic anisotropy via electric fields in ferromagnetic/ferroelectric (FM/FE) heterostructures is an important step towards controlling the magnetic tunnel junctions.

Nonuniform Spatial Deformation of Light Fields by Locally Linear Transformations

Light-field cameras offer new imaging possibilities compared to conventional digital cameras. However, the additional angular domain of light fields prohibits direct application of frequently used image processing algorithms, such as warping, retargeting, or stitching. We present a general and efficient framework for nonuniform light-field warping, which forms the basis for extending many of these image processing techniques to light fields. It propagates arbitrary spatial deformations defined in one light-field perspective consistently to all other perspectives by means of 4D patch matching instead of relying on explicit depth reconstruction. This allows processing light-field recordings of complex scenes with non-Lambertian properties such as transparency and refraction. We show application examples of our framework in panorama light-field imaging, light-field retargeting, and artistic manipulation of light fields.

Nanofocusing of Hyperbolic Phonon Polaritons in a Tapered Boron Nitride Slab

Nanofocusing of light offers new technological opportunities for the delivery and manipulation of electromagnetic fields at sub-diffraction limited length scales. Here, we show that hyperbolic phonon polarity,HPP, modes in the mid infrared as supported by a hexagonal boron nitride, h-BN, slab can be nanofocused (i.e. both field enhanced and wavelength compressed) by propagation along a vertical taper. Via numerical simulations, we demonstrate that field enhancement factors of 90, for steep tapers, and wavelength compression of more than an order of magnitude for adiabatic tapers, can be expected. Employing scatteringtype scanning near field optical microscopy ,s SNOM, we provide for the first time proof of principle experimental evidence of a significant HPP wavelength compression. We expect these functionalities to provide diverse applications, from biosensing and non-linear optics to optical circuitry.

Stopping Narrow-Band X-Ray Pulses in Nuclear Media.

A control mechanism for stopping x-ray pulses in resonant nuclear media is investigated theoretically. We show that narrow-band x-ray pulses can be mapped and stored as nuclear coherence in a thin-film planar x-ray cavity with an embedded ^{57}Fe nuclear layer. The pulse is nearly resonant to the 14.4keV Mössbauer transition in the ^{57}Fe nuclei. The role of the control field is played here by a hyperfine magnetic field which induces interference effects reminiscent of electromagnetically induced transparency. We show that, by switching off the control magnetic field, a narrow-band x-ray pulse can be completely stored in the cavity for approximately 100ns. Additional manipulation of the external magnetic field can lead to both group velocity and phase control of the pulse in the x-ray cavity sample.

New punch design for the elimination of punch ejection load through manipulation of the elastic strain field in the punch nose

The extreme tribological conditions present during both the forward stroke and the punch ejection stroke of a backward cup extrusion process can adversely affect the quality of the extruded part and diminish the life of the punches. A novel punch design based on the segmentation of the extrusion punch into a main body and a nose cone insert is proposed to reduce or eliminate the pressure between the punch and work piece during the punch removal stroke. This is facilitated by manipulating the elastic strain field at the punch nose. With the aid of the finite element analysis, a parametric study on the segmented elastic punch assembly was carried out to establish optimal conditions and punch design guidelines. Experiments were carried out to determine the effectiveness of the segmented elastic punch. A significant reduction in the punch ejection load was observed along with a reduction in material pickup on the punch and galling on the surface of the part. The elastic deflection of the punch also allowed the researchers to discover that a significant amount of damage could occur during the punch ejection stroke.

Physical properties modulation of Fe3O4/Pb(ZrTi)O3 heterostructure via Fe diffusion

The manipulation of material properties in perovskite oxide heterojunctions has been increasingly studied, owing to their interacting lattice, charge, spin and orbital degrees of freedom. In this work, the switching, ferroelectricity and magneto-transport properties of epitaxially grown perovskite Pb(Zr0.52Ti0.48)O3 layers sandwiched between Fe3O4 (top electrode) and SrRuO3 (bottom electrode) are investigated. These films show a typical ferroelectric polarization of ∼50 μC/cm2. Once the Pb(Zr0.52Ti0.48)O3 films become thinner (∼30 nm), one can set (reset) the Fe3O4/Pb(Zr0.52Ti0.48)O3/SrRuO3 structures into a low (high) resistance state via formation (rupture) of an Fe-related filament in Pb(Zr0.52Ti0.48)O3 through manipulation of an electric field. Interestingly, at the low-resistance state, a prominent magnetoresistance signal of ∼3% was observed. There is no magnetoresistance signal detected in the virgin Pb(Zr0.52Ti0.48)O3 film (before switching), high-resistive state Pb(Zr0.52Ti0.48)O3 film and Au/Pb(Zr0.52Ti0.48)O3/SrRuO3. These phenomena are attributed to the diffusion of Fe-related ions into the Pb(Zr0.52Ti0.48)O3 film, turning a non-magnetic and insulating layer of perovskite Pb(Zr0.52Ti0.48)O3 into a magnetic and semiconducting-like Pb(Zr0.52Ti0.48)O3. The magneto-transport properties of Fe3O4/Pb(Zr0.52Ti0.48)O3/SrRuO3 have been studied extensively. Such resistance–ferroelectric–ferromagnetic coupling in a single compound paves the way to the realization of a non-volatile multiple-state Pb(ZrTi)O3 hybrid memory, as well as new computing approaches.

Mapping of bionic array electric field focusing in plasmid DNA-based gene electrotransfer.

Molecular medicine through gene therapy is challenged to achieve targeted action. This is now possible utilizing bionic electrode arrays for focal delivery of naked (plasmid) DNA via gene electrotransfer. Here, we establish the properties of array-based electroporation affecting targeted gene delivery. An array with eight 300 μm platinum ring electrodes configured as a cochlear implant bionic interface was used to transduce HEK293 cell monolayers with a plasmid-DNA green fluorescent protein (GFP) reporter gene construct. Electroporation parameters were pulse intensity, number, duration, separation and electrode configuration. The latter determined the shape of the electric fields, which were mapped using a voltage probe. Electrode array-based electroporation was found to require ~100 × lower applied voltages for cell transduction than conventional electroporation. This was found to be due to compression of the field lines orthogonal to the array. A circular area of GFP-positive cells was created when the electrodes were ganged together as four adjacent anodes and four cathodes, whereas alternating electrode polarity created a linear area of GFP-positive cells. The refinement of gene delivery parameters was validated in vivo in the guinea pig cochlea. These findings have significant clinical ramifications, where spatiotemporal control of gene expression can be predicted by manipulation of the electric field via current steering at a cellular level.

Manipulation of Playing Field's Length/Width Ratio and Neutral Players' Positioning: Activity Profile and Motor Behavior Demands during Positional Possession Soccer Small Sided Games in Young Elite Soccer Players

This study aimed to examine how changes in pitch length/width ratio and neutral players' positioning could modify the activity profile and motor behaviour demands during small-sided positional possession soccer games. 22 young male elite players divided in 2 teams (A and B) of 11 players participated in the study. All players participated in a positional possession game (4-a-side + 3 neutral players) on two different pitch formats with opposite length/width ratios (WIDE: 25 x 35 m; LONG: 35 x 25 m) and two different kinds of positioning for neutral players (VERTICAL: positioned high; HORIZONTAL: wide). The time motion variables of each player were recorded using a 15 Hz portable GPS. Average player displacement in width was significantly higher in WIDE format, while average player displacement in depth was significantly greater in LONG format (p < .001). Moreover, an increased activity profile was observed in regular team players with respect to neutral players (p < .001). These results highlight the physical and motor behaviour demands in small sided positional possession games. Furthermore, the different physical tasks required by various pitch formats and player positions were underlined. This information can help coaches to set up game-based training sessions.

基于矢量光场调控的宽波带全晶体型光瞳滤波器

基于矢量光场调控的宽波带全晶体型光瞳滤波器

Computational Investigation of Synchronized Multibeam Strategies for the Selective Laser Melting Process

The selective laser melting process features a nearly incomparable freedom of design. But its potential is still limited due to remaining porosity, cracking, distortion, low build-up rates and a limited range of materials. While there is some progress in process control and multiple parallel scan fields to tackle these issues, the potential of synchronized multibeam strategies has not yet been investigated. The presented synchronized multibeam approach is characterized by two widely overlapping scan fields fed by two independent laser sources that can be controlled to work in a synchronized manner with or without a defined offset. This allows a selective manipulation of the local temperature field and thus of melt pool dynamics, the temperature gradients and cooling rates, which are all influencing the processes’ porosity, cracking and distortion behavior. Therefore the influences of these strategies on the melt pool dimensions and dynamics as well as the temperature gradients are investigated in this work.

Manipulation of cells with electric fields via addition of carbon nanoparticles

Event Abstract Back to Event Manipulation of cells with electric fields via addition of carbon nanoparticles Fan-Yi Li1 and Yi-Chang Chung1 1 National University of Kaohsiung, Chemical and Materials Engineering, Taiwan In this study, we used polydopamine nanoparticles to prepare fluorescent carbon nanoparticles (CNPs). Using zwitterionic phosphatidylcholine (PC) molecules, we could control the sizes of polydopamine nanoparticles and increase their dispersion in water. We also developed a fast and safe hydrothermal microwave heating process to dehydrate the polydopamine nanoparticles into carbon nanoparticles. We investigated the effect of fluorescent carbon nanoparticles for dying cells in vitro, as well as the effect of PC on the carbon nanoparticles. Due to the polydopamine-derived CNPs having good electrical conductivity, we manipulated some cell uptake with conductive CNPs to observe the influence on cell attachment and growth under an electric field. In the characterization of physical properties of our CNPs, X-ray diffraction (XRD) patterns revealed the graphite structure of the polydopamine-prepared CNPs, and their Fourier transform infrared (FTIR) and UV-vis spectroscopic figures showed that the carbonized polydopamine nanoparticles retained polypeptide structures. Fluorescence spectroscopy was used to confirm the excitation of CNPs under UV irradiation. Pure CNPs and 1%-PC CNPs emitted a blue band light; while 10%-PC CNPs showed two bands, located in blue and green bands. Quinine sulfate solution was used as a calculation standard of fluorescent quantum efficiency and we could find that pure CNPs, 1%-PC CNPs, and 10%-PC CNPs displayed high fluorescence quantum efficiency of 21.4%, 20.3%, and 6.2%, respectively. According to observation of transmission electron microscopy (TEM) images, the sizes of pure CNPs, 1%-PC CNPs, and 10%-PC CNPs were 27±19 nm, 2±1 nm, and 7±2 nm, respectively, showing excellent dispersion in aqueous solution via addition of PC. In cell culture tests, L929 mouse fibroblasts were incubated with the three different kinds of CNPs to explore cell fluorescence images of the CNPs, showing that each kind could dye cells without fading even after a week of incubation. After cell co-culture for a period of 1 or 7 days, MTT assay tests revealed no cytotoxicity among those CNPs. Cell attachment measurements after electrical stimulation for one hour showed that the cell attachment numbers for cell uptake with CNPs were significantly different from those of the L929 cell control. Due to the good electrical conductivity of CNPs, the nanoparticles swallowed by cells seemed more easily attracted to the electric field. Therefore, CNP uptake can increase the attachment of cells onto a conductive plate electrode in a short time. When the source of the electric field was changed to rod electrodes in the medium, cells that had been pre-adsorbed onto a non-conductive plate were desorbed from the plate and destroyed. Therefore, addition of CNPs during cell incubation can allow control of cell growth and death via manipulation of electric fields. Ministry of Science and Technology, R.O.C.

Sol-Gel Material-Enabled Electro-Optic Polymer Modulators.

Sol-gels are an important material class, as they provide easy modification of material properties, good processability and are easy to synthesize. In general, an electro-optic (EO) modulator transforms an electrical signal into an optical signal. The incoming electrical signal is most commonly information encoded in a voltage change. This voltage change is then transformed into either a phase change or an intensity change in the light signal. The less voltage needed to drive the modulator and the lower the optical loss, the higher the link gain and, therefore, the better the performance of the modulator. In this review, we will show how sol-gels can be used to enhance the performance of electro-optic modulators by allowing for designs with low optical loss, increased poling efficiency and manipulation of the electric field used for driving the modulator. The optical loss is influenced by the propagation loss in the device, as well as the losses occurring during fiber coupling in and out of the device. In both cases, the use of sol-gel materials can be beneficial due to the wide range of available refractive indices and low optical attenuation. The influence of material properties and synthesis conditions on the device performance will be discussed.

OPTICS. 150 years of Maxwell's equations.

Powerful tools are available for the manipulation of electromagnetic fields

Topological transitions in spin interferometers

We show that topological transitions in electronic spin transport are feasible by a controlled manipulation of spin-guiding fields. The transitions are determined by the topology of the fields texture through an effective Berry phase (related to the winding parity of spin modes around poles in the Bloch sphere), irrespective of the actual complexity of the nonadiabatic spin dynamics. This manifests as a distinct dislocation of the interference pattern in the quantum conductance of mesoscopic loops. The phenomenon is robust against disorder, and can be experimentally exploited to determine the magnitude of inner spin-orbit fields.

Epitaxial Bi2 FeCrO6 Multiferroic Thin Film as a New Visible Light Absorbing Photocathode Material.

Ferroelectric materials have been studied increasingly for solar energy conversion technologies due to the efficient charge separation driven by the polarization induced internal electric field. However, their insufficient conversion efficiency is still a major challenge. Here, a photocathode material of epitaxial double perovskite Bi(2) FeCrO(6) multiferroic thin film is reported with a suitable conduction band position and small bandgap (1.9-2.1 eV), for visible-light-driven reduction of water to hydrogen. Photoelectrochemical measurements show that the highest photocurrent density up to -1.02 mA cm(-2) at a potential of -0.97 V versus reversible hydrogen electrode is obtained in p-type Bi(2) FeCrO(6) thin film photocathode grown on SrTiO(3) substrate under AM 1.5G simulated sunlight. In addition, a twofold enhancement of photocurrent density is obtained after negatively poling the Bi(2) FeCrO(6) thin film, as a result of modulation of the band structure by suitable control of the internal electric field gradient originating from the ferroelectric polarization in the Bi(2) FeCrO(6) films. The findings validate the use of multiferroic Bi(2) FeCrO(6) thin films as photocathode materials, and also prove that the manipulation of internal fields through polarization in ferroelectric materials is a promising strategy for the design of improved photoelectrodes and smart devices for solar energy conversion.

A multiplexed device based on tunable nanoshearing for specific detection of multiple protein biomarkers in serum.

Microfluidic flow based multiplexed devices have gained significant promise in detecting biomarkers in complex biological samples. However, to fully exploit their use in bioanalysis, issues such as (i) low sensitivity and (ii) high levels of nonspecific adsorption of non-target species have to be overcome. Herein, we describe a new multiplexed device for the sensitive detection of multiple protein biomarkers in serum by using an alternating current (ac) electrohydrodynamics (ac-EHD) induced surface shear forces based phenomenon referred to as nanoshearing. The tunable nature (via manipulation of ac field) of these nanoshearing forces can alter the capture performance of the device (e.g., improved fluid transport enhances number of sensor-target collisions). This can also selectively displace weakly (nonspecifically) bound molecules from the electrode surface (i.e., fluid shear forces can be tuned to shear away nonspecific species present in biological samples). Using this approach, we achieved sensitive (100 fg mL−1) naked eye detection of multiple protein targets spiked in human serum and a 1000-fold enhancement in comparison to hydrodynamic flow based devices for biomarker detection. We believe that this approach could potentially represent a clinical diagnostic tool that can be integrated into resource-limited settings for sensitive detection of target biomarkers using naked eye.