Multichannel Wire Research Articles

Plasma characteristics and material erosion mechanism in multi-channel wire electrical discharge machining

Multi-channel wire electrical discharge machining (MC-WEDM) is an advanced and high-efficiency machining technology, but its material erosion mechanism remains unclear. In this study, dual-channel wire electrical discharge machining was utilized as a case study to investigate the impact of the plunging current on both the plasma characteristics and material erosion under complex discharge conditions. Force analysis was conducted on the charged particles in the plasma, revealing that the plunging current can influence the trajectory of the plasma by modifying the self-magnetic field. The particle tracking method was employed to simulate the motion of electrons, revealing that in MC-WEDM, electrons exhibited a larger and more uniform distribution. The evolution of the plasma within a single-pulse discharge was observed using high-speed photography technology, and the discharge signals collected from different channels were analyzed. It was observed that the plasma in MC-WEDM experienced more intense back-and-forth sweeping on the workpiece surface, facilitating the ejection of molten metal from the molten pool. The oscillating plasma exhibits a larger processing area and a more uniform distribution of energy, resulting in the formation of larger and shallower discharge craters. Furthermore, the influence of the amplitude and time point of the plunging current on the volume and area of the discharge craters was summarized. Finally, MC-WEDM significantly reduced the occurrence of holes and micro-cracks and exhibited a thinner recast layer in the continuous discharge experiment.

Mesoscopic conductance fluctuations and noise in disordered Majorana wires

Superconducting wires with broken time-reversal and spin-rotational symmetries can exhibit two distinct topological gapped phases and host bound Majorana states at the phase boundaries. When the wire is tuned to the transition between these two phases and the gap is closed, Majorana states become delocalized leading to a peculiar critical state of the system. We study transport properties of this critical state as a function of the length $L$ of a disordered multichannel wire. Applying a non-linear supersymmetric sigma model of symmetry class D with two replicas, we identify the average conductance, its variance and the third cumulant in the whole range of $L$ from the Ohmic limit of short wires to the regime of a broad conductance distribution when $L$ exceeds the correlation length of the system. In addition, we calculate the average shot noise power and variance of the topological index for arbitrary $L$. The general approach developed in the paper can also be applied to study combined effects of disorder and topology in wires of other symmetries.

Wigner–Smith matrix, exponential functional of the matrix Brownian motion and matrix Dufresne identity

We consider a multichannel wire with a disordered region of length L and a reflecting boundary. The reflection of a wave of frequency ω is described by the scattering matrix , encoding the probability amplitudes to be scattered from one channel to another. The Wigner–Smith time delay matrix is another important matrix, which encodes temporal aspects of the scattering process. In order to study its statistical properties, we split the scattering matrix in terms of two unitary matrices, (with in the presence of time reversal symmetry), and introduce a novel symmetrisation procedure for the Wigner–Smith matrix: , where k is the wave vector and v the group velocity. We demonstrate that can be expressed under the form of an exponential functional of a matrix Brownian motion. For semi-infinite wires, L → ∞, using a matricial extension of the Dufresne identity, we recover straightforwardly the joint distribution for ’s eigenvalues of Brouwer and Beenakker (2001 Physica E 9 463). For finite length L, the exponential functional representation is used to calculate the first moments , and . Finally we derive a partial differential equation for the resolvent in the large N limit.

The effect of β-endorphin on the functional parameters of the isolated heart and lymphatic vessels of the white rat

Objective. The work is devoted to the comparison of the mechanisms of β-endorphin action in isolated rat heart and lymphatic vessels.
 Materials and methods. The experiments were performed using the Langendorff System perfusion device (Panlab, Spain) and the multichannel wire myograph 620M (DMT). During the study, selective opioid receptor blockers, K + channel blockers were used.
 Conclusion. In the course of experimental studies it was found that the most likely target for β-endorphin in an isolated rat heart are δ-opioid receptors, in isolated lymphatic vessels of a rat - μ- and δ-opioid receptors. The inhibitory effect of β-endorphin in the heart muscle is associated with stimulation of ATP-sensitive K + channels. In isolated lymphatic vessels, the effect of β-endorphin is realized through the activation of both potential-dependent and ATP-sensitive K+ channels.

3D Impedance Mapping of Internal Concrete Block by Using Multichannel Wire Grid

Monitoring method to evaluate the corrosion environment for reinforced steel inside the concrete structure was investigated using impedance mapping technique. In this method many iron wires were embedded in a test concrete block in parallel or grid alignments and impedance between two iron wires sequentially chosen from the grid was measured to obtain the conduction (resistance) map inside the concrete block. From the resultant conduction map, corrosion environment for steel inside the concrete such as penetration of water or salt can be speculated.

3D Impedance Mapping of Internal Concrete Block By Using Multichannel Wire Grid

Monitoring of corrosion environment for reinforced steel inside the concrete structure was investigated using 3D impedance mapping method. In this method many iron wires in grid alignment were embedded in a test cement block and impedance between two iron wires sequentially chosen from the grid was measured to obtain the resistance map inside the cement block. From the resultant 3D impedance map, corrosion environment for steel inside the concrete such as penetration of water or salt can be speculated. In the experiment, test cement block of 200 mm x 200 mm x 60 mm in size was made in which iron wires of 99.5% impurity and 0.2mmφ in diameter were embedded in a grid alignment of 8 line with 20 mm spacing in lateral direction and 4 layer with 10 mm spacing in depth, a total number of iron wires was 8 x 4 = 32. Top face of cement block was open to air and the other faces were covered with PVC plates as a casting mold. Impedance was measured for a combination of crossing two wires in two neighbor layers, and a number of combination was 8 x 8 x 3 = 192. To choose the appropriate two wires from 32 embedded wires to connect impedance analyzer, computer controlled analog multiplexer array was used. Impedance analyzer was built in laboratory using one-chip impedance converter (Analog Devices, model AD5933) which integrates components necessary for impedance analysis as direct digital synthesizer (DDS) as AC source, digital signal processor (DSP) engine for FFT (DFT, discrete fourier transformation), operational amplifier as AC output driver and input current / voltage converter, and 12bit analog digital converter. In this study, impedance was measured at a fixed frequency of 270Hz with modulation voltage of 20mV. About 1400 s was required to complete a single impedance mapping. Example of impedance map inside the test cement block is shown in Fig.1. The value of resistance was in the range from ca. 3kΩ at the central area of deep (30-40 mm) cement block to a several 100kΩ close to the surface (10-20 mm). Relatively low resistance deep inside the cement block indicates that the inside of the cement block was not dried out. On the other hand, not only the surface but also the side faces of cement block were dried because a gap was formed between the PVC mold and side faces of the cement block due to volume shrinking when a cement block had set. Transition of impedance map during drying and penetration of water from the top face were also investigated. Figure 1

Simultaneous Long-term Recordings at Two Neuronal Processing Stages in Behaving Honeybees

In both mammals and insects neuronal information is processed in different higher and lower order brain centers. These centers are coupled via convergent and divergent anatomical connections including feed forward and feedback wiring. Furthermore, information of the same origin is partially sent via parallel pathways to different and sometimes into the same brain areas. To understand the evolutionary benefits as well as the computational advantages of these wiring strategies and especially their temporal dependencies on each other, it is necessary to have simultaneous access to single neurons of different tracts or neuropiles in the same preparation at high temporal resolution. Here we concentrate on honeybees by demonstrating a unique extracellular long term access to record multi unit activity at two subsequent neuropiles1, the antennal lobe (AL), the first olfactory processing stage and the mushroom body (MB), a higher order integration center involved in learning and memory formation, or two parallel neuronal tracts2 connecting the AL with the MB. The latter was chosen as an example and will be described in full. In the supporting video the construction and permanent insertion of flexible multi channel wire electrodes is demonstrated. Pairwise differential amplification of the micro wire electrode channels drastically reduces the noise and verifies that the source of the signal is closely related to the position of the electrode tip. The mechanical flexibility of the used wire electrodes allows stable invasive long term recordings over many hours up to days, which is a clear advantage compared to conventional extra and intracellular in vivo recording techniques.

Simultaneous long-term recordings at two neuronal processing stages in behaving honeybees.

In both mammals and insects neuronal information is processed in different higher and lower order brain centers. These centers are coupled via convergent and divergent anatomical connections including feed forward and feedback wiring. Furthermore, information of the same origin is partially sent via parallel pathways to different and sometimes into the same brain areas. To understand the evolutionary benefits as well as the computational advantages of these wiring strategies and especially their temporal dependencies on each other, it is necessary to have simultaneous access to single neurons of different tracts or neuropiles in the same preparation at high temporal resolution. Here we concentrate on honeybees by demonstrating a unique extracellular long term access to record multi unit activity at two subsequent neuropiles1, the antennal lobe (AL), the first olfactory processing stage and the mushroom body (MB), a higher order integration center involved in learning and memory formation, or two parallel neuronal tracts2 connecting the AL with the MB. The latter was chosen as an example and will be described in full. In the supporting video the construction and permanent insertion of flexible multi channel wire electrodes is demonstrated. Pairwise differential amplification of the micro wire electrode channels drastically reduces the noise and verifies that the source of the signal is closely related to the position of the electrode tip. The mechanical flexibility of the used wire electrodes allows stable invasive long term recordings over many hours up to days, which is a clear advantage compared to conventional extra and intracellular in vivo recording techniques.

Multichannel wire gas electron multipliers

A simple technique for manufacturing electrodes of multichannel wire gas electron multipliers was developed. The maximum proportional multiplication factor of ionization electrons Kmax = 103 was obtained when the chamber containing a multichannel wire gas electron multiplier was filled with a mixture of Ar + 10%C2H4 at a pressure of 1 atm (abs.) and the drift (ionization) gap of the chamber was irradiated with β particles (63Ni). Under irradiation with α particles, Kmax = 103 at a pressure of 1 atm (abs.) and 3 × 103 at 0.4 atm (abs.). When the chamber was filled with a mixture of Ne + 10%C2H4 at a pressure of 1 atm (abs.) and exposed to β particles, Kmax = 4 × 103 was obtained.

Methods for detecting events in double-phase argon chambers

Multichannel wire gas electron multipliers in combination with pin anodes are proposed for detection of events in the gas phase of a double-phase argon chamber. Hydrogen with a concentration of 10 vol % is added to argon to eliminate feedbacks by photons emitted by excited argon molecules in avalanche development processes while detecting events in the argon gas. A maximum electron multiplication coefficient of ∼300 has been obtained for the multichannel wire gas electron multipliers with a 1-mm gap used to detect α particles in the Ar + 10% H2 mixture at a pressure of 1 atm (abs.). When a pin anode is used, the maximum electron multiplication factor is ∼2.5 × 105 for α particles and 3 × 106 for β particles (63Ni). It has been experimentally shown that adding H2 with a concentration of 100 ppm to liquid argon has no effect on the singlet component of the scintillation signal in the liquid argon and reduces the emission efficiency relative to the pure argon gas phase only slightly (by 20%).

Multichannel wire gas electron multipliers with 1- and 3-mm gaps

The operation of multichannel wire gas electron multipliers (MWGEMs) with gaps between electrodes δ = 1 and 3 mm, when the chamber is filled with commercial neon under a 0.4- and 1.0-atm (abs.) pressure and irradiated with α and β particles, is studied. The following maximal proportional electron multiplication coefficients are obtained: 6 × 103 (α, irradiation, δ = 3 mm, 1 atm, and 20% streamers), 1.2 × 104 (β−, 3 mm, 1 atm, and 50% streamers), 6 × 103 (α, 3 mm, 0.4 atm, and 20% streamers), and 105 (β−, 3 mm, 0.4 atm, and 50% streamers). The maximal proportional electron multiplication coefficients are obtained in the MWGEM and its anode (induction) gap in the sequential electron multiplication mode: 1.08 × 105 (β−, 1 mm, 0.4 atm, 50% streamers), 2 × 106 (β−, 3 mm, 0.4 atm, 20% streamers), and 1.12 × 105 (α, 3 mm, 0.4 atm, 50% streamers).

A multichannel wire gas electron multiplier

A novel and relatively simple method of production of electrodes for a multichannel wire gas multiplier was developed. Two modifications of the multipliers have been tested: with a multiplication of electrons between two wire electrodes, MWGEM, and between a wire electrode and continuous anode, MWCAT. For both MWGEM and MWCAT detectors, filled with neon under pressure of 760 Torr and irradiated by β-particles (63Ni), the coefficient of proportional multiplication of electrons up to ∼104 was obtained. For the MWGEM detector irradiated by α-particles (239Pu), the coefficient of proportional multiplication of 300 was obtained. It is observed, that in contrast to the GEM detectors, produced by perforation of a metal-clad plastic foil, in a MWGEM the discharges do not destroy its electrodes even for the potentials above the threshold of discharges. The results on operation of the MWCAT filled with Ar, Ar + 20% CH4, and Ar + 1% Xe are also presented.

Inelastic cotunneling through a long diffusive wire

We show that electron transport through a long multichannel wire, connected to leads by tunnel junctions, at low temperatures T and voltages V is dominated by inelastic cotunneling. This mechanism results in experimentally observed power-law dependence of conductance on T and V, in the diffusive regime where usual Coulomb anomaly theory leads to exponentially low conductance. The power-law exponent α* is proportional to the distance between contacts L.

Magnetoconductance oscillations in quasiballistic multimode nanowires

We calculate the conductance of quasi-one-dimensional nanowires with electronic states confined to a surface-charge layer in the presence of a uniform magnetic field. Two-terminal magnetoconductance (MC) between two leads deposited on the nanowire via tunnel barriers is dominated by density-of-states (DOS) singularities when the leads are well apart. There is also a mesoscopic correction due to a higher-order coherent tunneling between the leads for small lead separation. The corresponding MC structure depends on the interference between electron propagation via different channels connecting the leads, which in the simplest case, for the magnetic field along the wire axis, can be crudely characterized by relative winding numbers of paths enclosing the magnetic flux. In general, the MC oscillations are aperiodic due to the Zeeman splitting, field misalignment with the wire axis, and a finite extent of electron distribution across the wire cross section, and are affected by spin-orbit coupling. The quantum-interference MC traces contain a wealth of information about the electronic structure of multichannel wires, which would be complimentary to the DOS measurements. We propose a four-terminal configuration to enhance the relative contribution of the higher-order tunneling processes and apply our results to realistic InAs nanowires carrying several quantum channels in the surface charge-accumulation layer.

Interaction-Induced Resonance in Conductance and Thermopower of Quantum Wires

We study the effect of electron-electron interaction on the transport properties of short clean quantum wires adiabatically connected to reservoirs. Interactions lead to resonances in a multichannel wire at particular values of the Fermi energy. We investigate in detail the resonance in a two-channel wire. The (negative) conductance correction peaks at the resonance, and decays exponentially as the Fermi energy is tuned away, the resonance width being given by the temperature. Likewise, the thermopower shows a characteristic structure, which is surprisingly well approximated by the so-called Mott formula. Finally, fourfold splitting of the resonance in a magnetic field provides a unique signature of the effect.

Modification of Turbulent Boundary Layer Flow by Local Wall Vibration

In this study, the modification of turbulent boundary layer flow by local wall vibration is investigated. The wall is locally vibrated using a wall deformation actuator, which moves up and down at the frequencies of 100Hz and 50Hz. Simultaneous measurements of the streamwise velocities in the spanwise direction are performed at several wall-normal and streamwise locations using an in-house multi-channel hot wire anemometer and a spanwise hot-wire-probe rake. The mean velocity is reduced in most places due to the wall vibration and its reduced amount becomes small as flow goes downstream. Interestingly, the mean velocity is found to increase very near the wall and near the actuator. This is due to the motion induced by the streamwise vortices which are generated by the downward motion of the actuator. In case of the streamwise velocity fluctuations, their magnitude increases as compared to the unperturbed turbulent boundary layer, and the increased amount becomes small as the flow moves downstream. The modified flow field at the forcing frequency of 50Hz is not much different from that of 100Hz, except the reduced amount of modification.

Resonant tunneling in a multi-channel wire

We calculate analytically the transmission coefficient through two delta function barriers in a quasi-one-dimensional wire as the Fermi energy and distance between scatterers are varied. In a purely one-dimensional or single-mode system, the transmission coefficient is periodic as a function of distance between scatterers with successive resonances separated by half the wavelength of the incident electron. In a two-mode system we find unusual modifications to this result when the Fermi energy is near the second subband minimum. First, the presence of the evanescent mode causes successive resonances in the transmission coefficient to be separated by a full wavelength rather than by a half wavelength. Furthermore, when the Fermi energy coincides with the second subband minimum, the transmission approaches unity for scatterer separations larger than a few wavelengths and is therefore no longer a periodic function of distance between scatterers.

A common carrier multi-channel television wire broadcasting system

The factors governing the choice and design of a television relay system and the history and background of the development of various systems are surveyed. The basic technical features of a system carrying four television and four radio programmes are discussed. Information is given regarding various types of cable and their specifications. Network jointing and matching fittings are described and the method of using the system characteristics to plan a network is explained with examples and an indication of the sort of coverage that can be obtained. Various types of subscriber installations can be provided and their characteristics are defined and typical examples given of subscriber's equipment. The operation of the main receiving station and repeater equipment is explained in some detail and finally test methods and test equipment are described.