Channel Mode Research Articles

Control of transverse wakefields via phase-matched laser modes in parabolic plasma channels

The use of higher-order modes is proposed to control the transverse wakefield structure generated by a laser pulse propagating through a plasma channel. This can be done in the quasilinear regime in both the Laguerre-Gaussian and Hermite-Gaussian bases for appropriate laser-plasma parameters, independent of the longitudinal field. Control of the wake can be achieved by using modes of different mode numbers but with matched phase velocities to generate tunable, matched laser propagation. The wake can be tuned by modifying the initial phase and amplitude of each mode. In addition, it is shown that two different higher order modes can propagate at the same group velocity by appropriately tuning the frequencies. Geometric and frequency tuning of the laser driver allows for greater control of the transverse phase-space of the accelerated electron bunch.

40 Gbps Laguerre-Gaussian and Hermite-Gaussian Optical Mode Division Multiplexing for Radio over Fiber System

Abstract Radio over Fiber technology is utilizing the high capacity of optical fiber system and wireless mobility network. In this work, we proposed two different optical propagation modes namely Laguerre-Gaussian (LG) and Hermite-Gaussian (HG) setting to (0.1), (0.2) mode types generated by a special CW laser source at varying wavelength from 800 nm to 1150 nm with 50 nm spacing channel Mode division Multiplexing (MDM) technique. These wavelengths transmitted×5Gb/s data modulated on PSK modulator having 100 GHz radio frequency subcarrier over 5 km Parabolic-Index Multimode Fiber link. Q factor value and eye diagram used to evaluate system performance which showed the maximum Q factor value found at 800 nm channel 1 equal to 12.0113 for both LG 0 1 and HG 0.1. While the maximum Q factor appears at 800 nm channel 1 equal to 8.49756 for LG 0,2 and 3.56785 at 1000 nm channel 5 for HG 0.2.

RBS/C, XRR, and XRD Studies of Damage Buildup in Er‐Implanted ZnO

Accumulation and transformation of defects formed in bulk ZnO crystals at room temperature upon 300 keV Er ions bombardment have been thoroughly examined using complementary techniques: Rutherford Backscattering Spectrometry in ion Channeling mode (RBS/C), X‐Ray Reflectivity (XRR), and X‐Ray Diffraction (XRD). Evaluation of RBS/C spectra has been performed using Monte Carlo (MC) simulations (McChasy software). Two defect types have been indicated: point defects (randomly displaced atoms, RDA) and extended ones (edge dislocations, DIS). Depth‐distributions of RDA and DIS turned out to be shifted toward deeper regions of ZnO crystals (relative to Er‐ions range) while DIS are localized even deeper than RDA. The MC simulations reveal three regions of defects accumulation separated by two regions of rapid defects transformation occurring at a certain critical Er fluence. Strain, suggested to be a driving force of defect transformation, has been determined using simulations of the XRD profiles based on the dynamical theory of X‐ray diffraction (MROX software). The presented research can help to better understand the interaction between impurity Er ions and ZnO target atoms during the implantation process. Hence, implantation conditions, for example, for luminescence purpose may now be more efficiently chosen based on the results discussed.

In Situ Modification and Analysis of the Composition and Crystal Structure of a Silicon Target by Ion-Beam Methods

The method of Rutherford backscattering (RBS) with channeling is widely used in compositional analysis and structural determination. An experimental process line for in situ ion implantation and RBS spectrometry is presented, and its technical parameters are given. The parameters of a probing beam needed to reach a several-percent error in the study of distribution profiles of impurities and defects are detailed. The resolution of this method was estimated using the spectrum of alpha particles produced in the decay of 239Pu and based on the RBS spectrum from a silicon monocrystal. The implantation of Xe+ ions with an energy of 100 keV into a silicon monocrystal and the RBS analysis of targets in the channeling mode were performed without breach of vacuum conditions. The distribution profiles of implanted atoms and defects in irradiated monocrystals were examined.

МОДЕЛИРОВАНИЕ ПРОЦЕССА ПНЕВМОСЕПАРАЦИИ СЕМЯН ПОДСОЛНЕЧНИКА В ВОЗДУШНОМ ПОТОКЕ

The mathematical model of air separation of sunflower seeds in the horizontal air flow was given. The system of differential equations that take into account lateral forces and resistance of seeds in the air stream was obtained. The behavior of sunflower seeds, impurities and dust particles on the seed surface at different input and control parameters of air separation was simulated. The developed mathematical model and established geometric and aerodynamic parameters of single seeds allow replacing the classical forms of a ball or cylinder with real asymmetric forms of sunflower seeds. The results of numerous studies of the mathematical model lead to the improvement of following parameters: the length of aspiration channel, the height of the upper and lower parts of the aspiration channel and technological modes: the angle and speed of seed ejection and air flow rate.

The stochastic modeling of proton pumping in cytochrome c oxidase: the contribution of the K-channel

The influence of pH on the activity of cytochrome c oxidase is investigated using the stochastic modelling based on Markov processes. The functioning of the K-channel is considered on four different schemes. A change of channel modes can be observed under high values of pH: the fraction of K-protons transferred through the membrane increases significantly while D-proton flow disappears. Moreover, the pumping efficiency at high pH values rises more than twice under the circumstances when at the beginning of the pumping there are three or four protons in the binuclear center under pumping both D- and K-protons.

Active Modes and Dynamical Balances in MRI Turbulence of Keplerian Disks with a Net Vertical Magnetic Field

Abstract We studied dynamical balances in magnetorotational instability (MRI) turbulence with a net vertical field in the shearing box model of disks. Analyzing the turbulence dynamics in Fourier ( -)space, we identified three types of active modes that define the turbulence characteristics. These modes have lengths similar to the box size, i.e., lie in the small wavenumber region in Fourier space labeled “the vital area” and are (i) the channel mode, uniform in the disk plane with the smallest vertical wavenumber; (ii) the zonal flow mode, azimuthally and vertically uniform with the smallest radial wavenumber; and (iii) the rest (parasitic) modes. The rest modes comprise those harmonics in the vital area whose energies reach more than 50% of the maximum spectral energy. The rest modes individually are not so significant compared to the channel and zonal flow modes; however, the combined action of their multitude is dominant over these two modes. These three mode types are governed by the interplay of the linear and nonlinear processes, leading to their interdependent dynamics. The linear processes consist of disk flow nonmodality modified classical MRI with a net vertical field. The main nonlinear process is the transfer of modes over wavevector angles in Fourier space—the transverse cascade. The channel mode exhibits episodic bursts supplied by linear MRI growth, while the nonlinear processes mostly oppose this, draining the channel energy and redistributing it to the rest modes. As for the zonal flow, it does not have a linear source and is fed by nonlinear interactions of the rest modes.

Downlink Multi-User MIMO Transmission for Radiation Pattern Reconfigurable Antenna Systems

MU-MIMO transmission relies on exploiting multi-user diversity among a multitude of users. In this paper, to enhance MU-MIMO transmission, techniques for designing and exploiting reconfigurable antennas (RAs) are developed. A single-element RA is capable of generating modes with different radiation pattern and polarization states resulting in multiple different channel states for each user. This capability expands the search space for user-pairing optimization. To reduce complexity, an iterative user and antenna mode selection algorithm is proposed. Based on parasitic tuning, an RA optimized for MU-MIMO transmission and capable of creating four pattern types is designed using a genetic algorithm and full-wave electromagnetic analyses. Pattern- and channel-aware mode-set generation methods are developed, where mode groups are determined to reduce channel estimation overhead and mode selection complexity while achieving superior performance. Simulation results indicate that the proposed schemes need a lower number of users and/or relax user selection requirements to benefit from MU-MIMO transmissions. It is also seen that more legacy antennas are needed to achieve similar MU-MIMO performance provided by the RA system. Simulations show up to 16-dB signal-to-noise ratio gains for a single cell with 12 users, where the base station has four RAs and four single-antenna users are simultaneously served via MU-MIMO transmission.

Ultrafast water harvesting and transport in hierarchical microchannels.

Various natural materials have hierarchical microscale and nanoscale structures that allow for directional water transport. Here we report an ultrafast water transport process in the surface of a Sarracenia trichome, whose transport velocity is about three orders of magnitude faster than those measured in cactus spine and spider silk. The high velocity of water transport is attributed to the unique hierarchical microchannel organization of the trichome. Two types of ribs with different height regularly distribute around the trichome cone, where two neighbouring high ribs form a large channel that contains 1-5 low ribs that define smaller base channels. This results in two successive but distinct modes of water transport. Initially, a rapid thin film of water is formed inside the base channels (Mode I), which is followed by ultrafast water sliding on top of that thin film (Mode II). This two-step ultrafast water transport mechanism is modelled and experimentally tested in bio-inspired microchannels, which demonstrates the potential of this hierarchal design for microfluidic applications.

Angular momentum of radiation at axial channeling

We study theoretically the angular momentum of radiation emitted at axial channeling of the fast particles in a crystal or in a bunch of micro- or nanotubes placed in strong magnetic field. It is shown that high energy particles channeled in the presence of magnetic field are effective source of vortex radiation in the X-ray and gamma-range of photons energies. We show that there are two factors that increase the angular momentum of emitted radiation in the presence of magnetic field. First, the magnetic field favours additional “twisting” of the channeled particles in a certain direction and, secondly, the particles that have the corresponding initial angular momentum are predominantly captured into the channeling mode. Dependence of the angular momentum of radiation on the value of magnetic field and on the incident angle is studied.

The Electron-Conformational Model of Ryanodine Receptors of the Heart Cell

The main ideas of an electron-conformational (EC) model of ligand-activated ryanodine channels (RyR) that reduces many degrees of freedom of this gigantic nanoscopic molecular complex to two so-called electron and conformational degrees of freedom are presented. In the toy model, the conformational potential or energy profile of the RyR channel represents two branches that describe the dependence of energy on the conformational coordinate (reaction coordinate) in the initial and ligand-activated states, respectively. A model extension that takes into account both the tetrameric structure of the RyR channel and additional (orthogonal) rotational conformational mode has been considered. The EC model has been demonstrated to give a biophysical basis to the traditional phenomenological model of Markov chains. To demonstrate the possibilities of the EC model, we refer to examples of model description of the dynamics of isolated RyR channels and clusters of RyR channels in release units of the heart cell.

Symmetry breaking in UCA-based vortex waves

In literature, it is often said that a uniform circular array (UCA) composed of a sufficient number of radiating elements is able to generate a vortex wave with arbitrary topological charge. While providing a very simple and intuitive solution without the need for any synthesis method, the excitation of UCAs by means of a progressive phase shift does not always guarantee that vortex waves are correctly generated, since a major role is played by the symmetry and radiation properties of each individual element which constitutes the array. When the UCAs are employed in vortex communication links, these symmetry properties strongly affect the orthogonality of the channel modes and, therefore, the communication efficiency. In this work, the symmetry breaking associated with the radiation of vortex waves by UCAs and its impact on the mode orthogonality are explored in detail.

The OPE of bare twist operators in bosonic SN orbifold CFTs at large N

In this work, we explore the twist operator OPEs of a generic bosonic symmetric product (SN) orbifold CFT. We conjecture that at large N the OPE of bare twist operators contains only bare twists and excitations of bare twists with fractional Virasoro modes. These fractionally excited operators are the only ones that depend exclusively on the lengths of the twists and the central charge, agreeing with the general structure of correlators of bare twists at large N found in the literature. To provide evidence for this, we study the coincidence limit of a four point function of bare twist operators to several non-leading orders. We show how the coefficients of these powers can be reproduced by considering bare twist operators excited by fractional Virasoro modes in the exchange channels.

FEATURES OF THE WIRELESS ENERGY TRANSFER’S CHANNEL IN A DYNAMIC MODE

Work is devoted to wireless energy transfer to the removed devices by means of laser radiation. This problem is actual in some practical applications. The dynamic mode of the laser wireless energy transfer's channel is considered. The mathematical model is offered. Influence of terminal loading on dynamic processes in the channel is investigated. The factors increased of energy transfer channel's efficiency are analyzed. Parameters of lenses and beam expanders, accuracy of optical component's installation, uniformity of a photocell's light spot are investigated. It is shown, that in a pulse mode efficiency of energy channels depends also on an impedance of loading. Additional impedance increased of fluctuation's amplitude and reduced channel's efficiency. The description of experimental setup, data of measurements and their analysis are resulted.

Structural study and ion-beam channelling in Si 〈1 0 0〉 modified by Kr+, Ag+, 2+ and Au+, 2+ ions

A Si-crystal layer on SiO2/Si was irradiated using 0.4 MeV Kr+, Ag+, Au+ and 5.0 MeV Ag2+, Au2+ at ion fluences of 0.5 × 1015–5.0 × 1015 cm−2. The induced structural modification in a Si crystal strongly influences ion-beam channelling phenomena through the introduced point defects, damage accumulation and induced internal strain. He+ ion channelling in the ion-implanted Si structure was studied, simultaneously with the structure and surface-morphology characterization of Si-irradiated layers, in connection with the ion-implantation parameters and prevailing energy-stopping type. The dislocated atom-depth profiles in the Si layer and the Si sub-surface layer were extracted from Rutherford backscattering spectrometry in the channelling mode (RBS-C). RBS-C shows the density of gradually displaced atoms as a function of ion fluence and ion mass for 5.0-MeV-ion implantation. The relative disorder grows more progressively for Au-ion implantation, where the thicker disordered layer was also observed in connection to the higher density collision cascade comparing to Ag+ ions. This phenomenon was discussed in the frame of the structural RBS-C and surface morphological data from AFM. The axial channelling effect of He+ ions measured in the 5.0-MeV-ion-implanted Si layer is varying during 2.0-MeV-He+ channelling in consequences of the various implantation fluences. The narrowing of axial channels observed in RBS-C was correlated to the number of produced vacancies in the Si layer after ion implantation and compared to MC simulations performed by FLUX. Nanostructured surface morphology modification has been detected mainly in 0.4-MeV-implanted Si layers using atomic force microscopy (AFM) studies, where the nuclear stopping is a prevalent phenomenon. Fourier transformation infrared spectroscopy (FTIR) has shown SOI modification mainly done by Si rearrangement and modified by possible SiOSi bonds creation.

Structural damage and ion‐channelling effects in a single‐crystal Si layer modified by medium‐heavy ions

Structural modification after medium‐heavy ion irradiation was characterised by Rutherford backscattering spectrometry in the channelling mode (RBS‐C) for silicon‐on‐insulator (SOI) material. Silicon on insulator was irradiated using C+, 2+, N+, 2+, and O+, 2+ ions at fluences of 1 × 1014 and 1 × 1015 cm−2 and energies of 0.4, 3, and 5 MeV to follow the interplay of electronic and nuclear stopping and its influence on damage accumulation. The relative amount of displaced atoms in the surface‐irradiated layer was extracted from RBS‐C spectra and used, along with axial channel analysis, to study ion‐channelling effects in the modified crystalline lattice. The discussion of ion penetration through the modified crystalline layer of the SOI structure in channelling direction was supported by a Monte Carlo simulation (FLUX code) of He ion flux maps in a gradually modified Si crystalline upper layer taking into account the experimentally determined relative disorder extracted from RBS‐C.The RBS‐C measurement shows an increase of the relative amount of displaced atoms mainly after irradiation using 0.4‐MeV ions at an ion fluence of 1 × 1015 cm−2. The narrowing effect of channels for He ion‐beam channelling experiment was observed in the irradiated silicon layers and discussed in connection with the irradiation parameters. The FLUX simulation, provided with the experimentally given value of the displaced atoms, has confirmed that it is not only the vacancies that can cause such a narrowing effect of the angular scan. The angular scan narrowing can be explained for predominately electronic stopping by induced crystalline‐cell modification.

Hybrid photonic crystal fiber for highly sensitive temperature measurement

A hybrid photonic crystal fiber (PCF) is proposed and demonstrated for highly sensitive temperature measurement. The hybrid PCF is formed by selectively infiltrating liquid crystal 5CB into the first ring of air holes around one silica core of a twin-core PCF (TCPCF). In the modified TCPCF, one silica core guides light with a total internal reflection (TIR) mechanism, while the other silica core guides light through a photonic bandgap (PBG) mechanism, due to the infiltration of high refractive index 5CB. The co-existing of TIR and PBG waveguiding mechanisms in the TCPCF leads to a hybrid light guiding mechanism PCF, i.e. hybrid PCF. Theoretical analysis reveals that the TIR-guided core mode, PBG-guided core modes and 5CB channel modes in the hybrid PCF can concurrently propagate and interfere with each other, which is further verified by experimental results. Besides, experimental investigation on the temperature response of the hybrid PCF shows that the temperature sensitivities can be up to 4.91 nm °C−1 for nematic phase of 5CB, and −3.68 nm °C−1 for isotropic phase of 5CB, respectively. The proposed hybrid PCF is promising for applications of temperature-tunable optical filtering in optical fiber communication, sensing and laser systems.

Fully Kinetic Large-scale Simulations of the Collisionless Magnetorotational Instability

Abstract We present two-dimensional particle-in-cell simulations of the fully kinetic collisionless magnetorotational instability (MRI) in weakly magnetized (high β) pair plasma. The central result of this numerical analysis is the emergence of a self-induced turbulent regime in the saturation state of the collisionless MRI, which can only be captured for large enough simulation domains. One of the underlying mechanisms for the development of this turbulent state is the drift-kink instability (DKI) of the current sheets resulting from the nonlinear evolution of the channel modes. The onset of the DKI can only be observed for simulation domain sizes exceeding several linear MRI wavelengths. The DKI and ensuing magnetic reconnection activate the turbulent motion of the plasma in the late stage of the nonlinear evolution of the MRI. At steady-state, the magnetic energy has an MHD-like spectrum with a slope of k −5/3 for kρ < 1 and k −3 for sub-Larmor scale (kρ > 1). We also examine the role of the collisionless MRI and associated magnetic reconnection in the development of pressure anisotropy. We study the stability of the system due to this pressure anisotropy, observing the development of mirror instability during the early-stage of the MRI. We further discuss the importance of magnetic reconnection for particle acceleration during the turbulence regime. In particular, consistent with reconnection studies, we show that at late times the kinetic energy presents a characteristic slope of ϵ −2 in the high-energy region.

Implications of Channel Structure and Operational Mode Upon a Manufacturer's Durability Choice

We explore the interactions between channel structure and mode of operations (leasing versus selling) and their implications for a manufacturer's willingness to invest in making her product more durable. Using a centralized manufacturer who leases her product as a point of reference, we find that an isolated change in either the channel structure (centralized to decentralized), or the operational mode (leasing to selling) can decrease the manufacturer's willingness to provide durability. However, if combined, these two changes together may strengthen the manufacturer's willingness to invest in durability. Consequently, a manufacturer who sells through an intermediary may invest more in durability than one who leases directly to end consumers. This result challenges the conventional wisdom in two different paradigms. First, from the perspective that durability is a dimension of quality, it challenges the conventional view that decentralization will decrease a manufacturer's incentive to provide a high quality product. Second, from the perspective of the externality that is created when a firm sells a durable product to strategic consumers who anticipate declining prices, it challenges the conventional view that a manufacturer who leases will provide more durability than one who sells.

Innovating Collection Modes for Waste Electrical and Electronic Equipment in China

The huge amount of waste electrical and electronic equipment (WEEE) has aroused global concern with its importance of environmental performance for resources reutilization being recognized. The incomplete collection management system is required to be improved for a more environmental and orderly recycling way. Based on the public survey, field research and information search on the Internet, we present the existing framework and problems of WEEE collection in China, according to which four innovative WEEE collection modes are put forward: (i) Unified collection channels mode; (ii) Manufacturer alliance mode; (iii) Innovative enterprise self-built network platform mode; and (iv) Third-party integrated network platform mode. The characteristics, merits and deficiencies of the four modes are compared and analyzed, combined with which, we match the four modes with regions of different economic levels and Internet application. Third-party integrated network platform integrating online and offline resources is expected to be generalized under rapid development of information technology and e-commerce in China. The purpose of our research is to explore appropriate innovative WEEE collection modes and give suggestions for countries or economies whose WEEE collection situation or system are similar with China. Besides, government support and laws implementation are emphasized in mode promotion.