Fabrication of a patterned TiO2 nanotube arrays in anodic oxidation

In general, the fabrication of self-ordered TiO₂ nanotube arrays, under conventional constant-voltage anodization, results in only straight nanotube arrays. In the present work, we report on variation of nanotube morphology by modifying the anodization conditions. This approach offers substantial advantages over conventional anodization processes in terms of the fabrication of flexible dimensional architectures. We could see small variation of the nanotube diameter in the experiments using rocking voltage applied anodization in the ethylene glycol based electrolyte. Applying of abruptly increased voltage induced to separate into two nanotube segments having different diameters. We suggest that these new types of nanotube array architecture will be useful for new base materials for the development of nano-scale devices.     

Virtual active touch using randomly patterned intracortical microstimulation

Intracortical microstimulation (ICMS) has promise as a means for delivering somatosensory feedback in neuroprosthetic systems. Various tactile sensations could be encoded by temporal, spatial, or spatiotemporal patterns of ICMS. However, the applicability of temporal patterns of ICMS to artificial tactile sensation during active exploration is unknown, as is the minimum discriminable difference between temporally modulated ICMS patterns. We trained rhesus monkeys in an active exploration task in which they discriminated periodic pulse-trains of ICMS (200 Hz bursts at a 10 Hz secondary frequency) from pulse trains with the same average pulse rate, but distorted periodicity (200 Hz bursts at a variable instantaneous secondary frequency). The statistics of the aperiodic pulse trains were drawn from a gamma distribution with mean inter-burst intervals equal to those of the periodic pulse trains. The monkeys distinguished periodic pulse trains from aperiodic pulse trains with coefficients of variation 0.25 or greater. Reconstruction of movement kinematics, extracted from the activity of neuronal populations recorded in the sensorimotor cortex concurrent with the delivery of ICMS feedback, improved when the recording intervals affected by ICMS artifacts were removed from analysis. These results add to the growing evidence that temporally patterned ICMS can be used to simulate a tactile sense for neuroprosthetic devices.     

Signal separation theory using adaptive arrays

The signal separation technique using adaptive arrays is a new area in array data processing. The model considered in this paper is that of an array consisting of N elements; the number of signal sources, which are separated in spatial location, is M and M ≥ N. In the case of narrow band signals, the pre-envelope form of the incident signal can be obtained from the original signal and its Hilbert transform. The directional bearing-angle matix G is formed in terms of the conventional beam-forming system. By using a special implementation, the inverse matrix of G is derived. Finally, a matrix transform is operated on the received signal so that the output signal is separable, i.e. each output channel has only one incident signal. In the case of wide band signals, the DFT of the input signal or heterodyne is required. The block diagrams of the signal separation technique are given and some important results of this technique are derived. The results of system simulation experiments in digital computers prove that this theory is effective for separating signals.     

Endoneural selective stimulating using wire-microelectrode arrays.

In acute experiments eight 5- to 24-wire-microelectrode arrays were inserted into the common peroneal nerve of the rat, to investigate whether the electrodes could selectively stimulate motor units of the extensor digitorum longus (EDL) muscle. Twitch-force-recruitment curves were measured from the EDL for each array electrode. The curves were plotted on a double-logarithmic scale and parameterized by the low-force slope (which represents the power p in the power-law relationship of force F versus stimulus current I, or F approximately I(p)) and the threshold current. The slopes and threshold currents measured with array electrodes did not differ significantly from those obtained with randomly inserted single wire-microelectrodes. This indicates that, although involving a more invasive insertion procedure, electrode arrays provide neural contacts with low-force recruitment properties similar to those of single wires. Array results revealed partial blocking of neural conduction, similar to that reported with microneurographic insertion with single needles. The efficiency of the array was defined as the fraction of array electrodes selectively contacting a motor unit and evoking the corresponding threshold force. Efficiency thus expresses the practical value of the used electrode array in terms of the total number of distinct threshold forces that can be stimulated by selecting the appropriate electrodes. The eight arrays were capable of evoking threshold forces selectively with an average efficiency of 0.81 (or 81%).     

Optoelectronic parallel computing using optically interconnectedpipelined processing arrays

We describe our research on optoelectronic parallel computing systems. Our architecture is based on a multilayer pipeline of two-dimensional optoelectronic device arrays in which each pixel is composed of an optical input channel, a general purpose programmable processor, local memory, and a surface-emitting laser diode as an optical output channel. Free-space optics provides parallel, global communication between layers in the pipeline via optical paths which are dynamically reconfigurable. Demonstration systems and some applications are described     

Three dimensional arrays of hollow gadolinia-doped ceria microspheres prepared by r.f. magnetron sputtering employing PMMA microsphere templates

Preparation of macroporous gadolinia-doped ceria (CGO) films was attempted by r.f. magnetron sputtering. A polymethylmethacrylate (PMMA) microsphere film was fabricated as a template on a Pt-coated silicon substrate by dripping a PMMA microsphere aqueous dispersion onto the substrate. CGO was deposited onto the PMMA microspheres by sputtering; the PMMA microspheres were found to shrink during the sputtering, and thus the CGO also coated the surface of PMMA microspheres beneath the top layer of the film. Films (ca. 1.5 μm thick) consisting of three dimensional arrays of hollow CGO microspheres (ca. 700 nm in diameter) with large porosity were obtained after annealing the CGO/PMMA microsphere composite film.     

Analogic CNN algorithms for 3D interpolation-approximation and object rotation using controlled switched templates

Analogic CNN algorithms are presented for various interpolation and approximation tasks in 3D. They are designed on the basis of mechanical analogies. Symmetric space-variant operations are implemented by the CNN algorithms; with switched templates, a key example is object rotation. Direction and speed coding are shown in detail.     

A computer-aided design of EMC microstrip dipole arrays using nonlinear optimization techniques

This paper describes a method for designing electromagnetically coupled (EMC) printed dipole arrays. The advantages of EMC dipoles include greater bandwidth, higher efficiency, and an easier match to the feed lines, when compared to classically fed printed antennae. The excitation mechanism is provided by a strip transmission line embedded inside the substrate which couples energy parasitically to the microstrip antenna. Electromagnetically coupled microstrip dipoles have been investigated by empirical or approximate analysis techniques. As a result an approximate model has been derived for microstrip dipoles. The method is based on the method of moments solution to an integral equation derived from the approximate Green function for a grounded dielectric slab. The element lengths and offsets and the stub length of the EMC dipole array are determined by the direct search optimization method of Hooke and Jeeves. To show the feasibility of the proposed method, a mathematical formulation and numerical results are presented for Chebyshev arrays. © 1998 Scripta Technica, Electr Eng Jpn, 125(4): 60–66, 1998     

Efficient synthesis of 4D antenna arrays using a bitwise evolutionary genetic algorithm

In this paper, a bitwise evolutionary genetic algorithm (GA) is proposed to synthesize the power patterns of 4D antenna arrays efficiently. Within the binary optimized time sequences of 4D antenna arrays, the genes of 1 and 0 represent switch‐on and switch‐off period of antennas, respectively. Gene retention probability, which relates to the fitness values of each individual in the whole group, is proposed to evaluate how good each gene is. With the proposed gene retention probability, the crossover operator in traditional GA is replaced with a new method to generate the next generation. The proposed algorithm is applied to the synthesis of 4D antenna arrays with binary optimized time sequences, and the performance of the proposed algorithm is compared with that of traditional GA on the condition of the same parameter settings. The comparison results show that bitwise evolutionary GA improves the optimization efficiency significantly, which reduces the computation time as much as 85% on average of the traditional GA with the same goal. Copyright © 2014 John Wiley & Sons, Ltd.     

2D‐DOA estimation performance using split vertical linear and circular arrays

This paper presents a new approach to reduce the computational complexity in two‐dimensional (2D) matrix pencil (MP) method for direction of arrival (DOA) estimation of plane wave signals using a combination of vertical uniform linear array (VULA) and uniform circular array (UCA). By applying phase mode excitation based beamforming to the UCA, we can apply the matrix pencil (MP) method to the beamspace data using only a single snapshot. The technique is based on the split array, which is composed of two perpendicular arrays. The vertical uniform linear array used to determine the elevation DOA components is located perpendicularly at the center of the uniform circular array in the horizontal plane used to calculate the azimuth angles. Unlike common planar and circular arrays, this antenna array with its particular geometry requires no pair‐matching between the azimuth and the elevation angle estimation and can also remove the drawbacks of estimation failure problems. Using this particular geometry for the 2D MP method leads to an efficient computational methodology for real‐time implementation on a digital signal processor. The obtained simulation results of the MP method applied to both uncorrelated and correlated narrow‐band sources in the presence of white noise show good performance estimation. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

An ATM-based intelligent optical backplane using CMOS-SEED smartpixel arrays and free-space optical interconnect modules

The architecture, smart pixel array chip design, and optical design of an intelligent free-space digital optical backplane for ATM switching are presented. The smart pixel chip uses reflective SEED (self-electrooptic effect device) optical modulators and detectors flip-chip bonded to CMOS circuitry. This chip is one of the most complex designs ever reported in this technology, and it operates at a simulated backplane clock rate of 125 MHz. The low-loss optical system employs f/4 diffractive minilenses and microlenses to interconnect clusters of smart pixels, and it is shown to allow 2060 connections per chip if 1-cm² -sized smart pixel chips are used. This gives a predicted bisection bandwidth of around 1 Tb/s across a 10-in circuit board edge for a full-sized system     

Angular domain imaging of objects within highly scattering media using silicon micromachined collimating arrays

Optical imaging of objects within highly scattering media, such as tissue, requires the detection of ballistic/quasi-ballistic photons through these media. Recent works have used phase/coherence domain or time domain tomography (femtosecond laser pulses) to detect the shortest path photons through scattering media. This work explores an alternative, angular domain imaging, which uses collimation detection capabilities of small acceptance angle devices to extract photons emitted aligned closely to a laser source. It employs a high aspect ratio, micromachined collimating detector array fabricated by high-resolution silicon surface micromachining. Consider a linear collimating array of very high aspect ratio (200: 1) containing 51/spl times/1000 /spl mu/m etched channels with 102-/spl mu/m spacing over a 10-mm silicon width. With precise array alignment to a laser source, unscattered light passes directly through the channels to the charge coupled device detector and the channel walls absorb the scattered light at angles >0.29/spl deg/. Objects within a scattering medium were scanned quickly with a computer-controlled Z axis table. High-resolution images of 100-/spl mu/m-wide lines and spaces were detected at scattered-to-ballistic ratios of 5/spl times/10/sup 5/: 1, with objects located near the middle of the sample seen at even higher levels. At >5/spl times/10/sup 6/: 1 ratios, a uniform background of scattered illumination degrades the image contrast unless recovered by background subtraction. Monte Carlo simulation programs designed to test the angular domain imaging concept showed that the collimator detects the shortest path length photons, as in other optical tomography methods. Furthermore, the collimator acts as an optical filter to remove scattered light while preserving the image resolution. Simulations suggest smaller channels and longer arrays could enhance detection by >100.     

An efficient medium access control protocol for mobile ad hoc networks using antenna arrays

In recent years, the use of directional antennas in wireless networks has been widely studied. Since the medium access control (MAC) protocol of the IEEE 802.11 standard was initially designed for systems with omnidirectional antennas, it cannot perform efficiently when directional antennas are used. In this paper, an efficient two-channel MAC protocol is designed for ad hoc networks that are equipped with directional antennas. The proposed protocol utilizes the large throughput offered by directional antennas using two frequency-division multiplexed channels. The first channel is used for control information, and the second for user-data transmission. The proposed MAC protocol operates in two main modes: the omnidirectional mode, in which one antenna is used for the transmission of users? control frames, and the directional mode, in which antenna arrays are used for the transmission of data frames. The proposed protocol is assessed by means of computer simulations based on randomly generated network topologies reflecting the random movement of nodes in the network. Based on these topologies, performance comparisons with the existing MAC protocols are presented for different system parameters. In all cases, the proposed MAC protocol is shown to offer a significant throughput improvement relative to the existing protocols.     

1.55-μm InGaAsP-InP laser arrays with integrated-mode expandersfabricated using a single epitaxial growth

We report on two techniques for the realization of expanded-mode laser arrays with a single epitaxial growth step and conventional fabrication techniques. Laser arrays with integrated adiabatic-mode expanders (AME) based on a tapered active region and an underlying passive coupling waveguide are demonstrated at the 1.55-μm wavelength. These lasers butt couple to standard cleaved single-mode fibers (SMF's) with a loss of only 3.6 dB. This coupling efficiency compares with a theoretical calculation of 3.2 dB. We also propose a novel realization of a laser with an integrated-mode expander based on resonant coupling between a tapered active waveguide and an underlying coupling waveguide. Three-dimensional (3-D) beam propagation method (BPM) results are presented which show that compact, efficient mode expanders with a mode transformation loss of only 0.36 dB can be realized using this method. Butt-coupling efficiencies of 2.6 dB are possible to standard cleaved single-mode fibers     

Improving conflicting specifications of time‐modulated antenna arrays by using a multiobjective evolutionary algorithm

By using the time modulation technique in antenna arrays, the stringent requirements on excitation error tolerance can be relaxed. However, the sideband signals spaced at multiples of the modulation frequency need to be suppressed in some applications. Multiobjective optimization is an important tool in the design of arrays with conflicting goals, such as low sidelobe level, low sideband level, and narrow beamwidth in the time‐modulated antenna arrays. In this paper, a novel multiobjective evolutionary algorithm based on objective decomposition (MOEA/D) with differential evolution operator and objective normalization technique is employed for the time‐modulated array synthesis, which is typically a problem with disparately scaled conflicting objectives. The effectiveness of the method is demonstrated by comparing the performances obtained by MOEA/D with those of previously reported results obtained by a single‐objective differential evolution algorithm and simulated annealing technique. Copyright © 2011 John Wiley & Sons, Ltd.     

A large dynamic‐range,high dB‐linearity VGA using switch arrays and second‐order mismatch‐shaping DEM technique

A new large dynamic‐range variable gain amplifier (VGA) with improved dB linearity is presented. The traditional cascade VGA has the disadvantages of gain mismatch between sub‐stages and difficulty of employing mismatch cancelation or suppression algorithms. In this paper, switch arrays were used to make the sub‐stages or called gain cells in the coarse‐tuning stage (CTS) work independently and therefore prevent the integral operation of the gain errors. Then, a second‐order mismatch‐shaping DEM was applied conveniently to the CTS and shown to be a useful design technique in improving the dB‐linearity performance. The cascade VGA and its second‐order mismatch‐shaping DEM had been integrated in a 2.4‐GHz receiver chip which was fabricated in a 0.18‐µm CMOS technology with a supply voltage of 1.8 V. Measurement results showed that the gain errors were significantly reduced with second‐order mismatch‐shaping DEM with respect to the traditionally thermometric decoding over a temperature range of [?40, 80] °C. Copyright © 2015 John Wiley & Sons, Ltd.