Filter Arrangement Research Articles

Unified Second-Stage LC Filter Applied in the Three-State Switching Cell Buck–Boost Converter: Static and Dynamic Analysis and Experimentation

This paper presents a unified second-stage LC filter applied in the three-state switching cell buck-boost converter, which provides current and voltage with low ripple and low noise. The unified second-stage filter promotes a reduction in the number of devices while maintaining the filtering performance of the converter, with second-stage LC filters at the input and at the output. Moreover, the unified filter, when associated with a three-state switching cell buck- boost converter, allows a size reduction of filter devices, especially for designs with duty cycle range around 1/2. Furthermore, the unified filter arrangement provides nondissipative clamping of switching devices and reduce the system order when compared to the converter with second-stage LC filters. In this paper, the static and dynamic characteristics of the proposed converter in continuous conduction mode (CCM) are reported. Experimental data were obtained from a laboratory prototype with an input range of 32~72 V, constant output of 48 V, a load of 150 W, and switching frequency of 45 kHz. The measured efficiency for the rated load was 97% for maximum input voltage. A comparison of the size and performance of the proposed filter with the topology that uses second-stage LCfilters at the input and at the output is also presented.

Energy efficiency improvement of submersible pumps using in barind area of Bangladesh

Due to the fluctuating nature of ground water level, it becomes impossible to operate submersible pumps in the designed head and discharge. As a result, these pumps are running at lower efficiency (about 18% to 35%) compared to standard laboratory efficiency 64% around the year. This deficiency in efficiencies causes huge consumption of energy and corresponding costs. The total operating head of the submersible pumps includes a parameter known as “drawdown” which is the difference between pumping level and static water level. The drawdown parameter has a significant effect on pump performance. In the present work, the drawdown characteristics of a 3HP submersible pump have been studied in laboratory scale by varying the filter length and well diameter. The pump characteristic curves are plotted and compared for various well and filter arrangement. The maximum pump efficiency was 38% in 0.15m well diameter and 0.90 m filter length with 42 m head and discharge about 138 liter/min. It has observed that the amount of drawdown decreases significantly with increasing well diameter and filter length. However, beyond 0.90 m filter length, the drawdown starts decreasing and energy consumption increases. A specific arrangement of pump and well is suggested which will provide maximum efficiency under specific operating condition. A mathematical relation has also been developed by multiple regression model to account the effect of filter length and well diameter in submersible pump performance.

Acoustic Filters for Sensors and Transducers

The acoustic filter is used to filter unwanted frequencies of oscillations from a power system. It is a network with selective transmission for currents from a power system of varying frequency. The unwanted frequencies generated from a power system are removed by using an operational amplifier with different combination of filter arrangements. A new theory for noise protection and security from power systems is presented. The power systems are classified as per source signals of solar power, electric power, light power, sound power, heat power, fluid power and fire power. The acoustic filters as per source of noise signals are defined. The filters are differentiated as per source signal of unwanted frequencies from solar power, electric power, light power, sound power, heat power, fluid power and fire power. Some examples of noise filtering from power systems are illustrated: i) a vocal apparatus; ii) an airflow window with a photovoltaic solar wall; iii) a psychrometric air-conditioner; iv) a telephone line; v) a fire and smoke detection system; vi) sensors and transducers: energy balance for a human brain and vii) comfort and health. A slide rule for noise measurement is illustrated along with noise grades and flag colors under limiting conditions.

Leachate pre-treatment using non-woven geotextile filters

Geotextiles have been used as filters in geotechnical and geoenvironmental works for decades. They are cost-effective, easy to install and they reduce or avoid the need for exploitation and utilisation of natural granular filter materials. This study investigated the filtration function of geotextiles applied to the pre-treatment of leachate from a domestic waste landfill. Equipment was assembled where vertical panels of non-woven geotextiles were used as filters for raw leachate from a landfill. Five geotextiles with masses per unit area between 134 and 1800 g/m2 were tested, and up to three filter panels were employed in the tests. Several chemical and biological parameters of the leachate were measured before and after filtration. A local sand filter was also tested for comparison. The results obtained showed that the geotextile filters reduced the values of leachate parameters, with a reduction of up to 42% in the case of chemical oxygen demand. The toxicity of the pre-treated leachate was also reduced to some extent, and the geotextile filter performed better than the sand filter tested in most of the cases. The filter arrangement employed may be particularly relevant for the pre-treatment of leachate from landfills of small- to medium-sized communities.

Demosaicing using Dual Layer Feedforward Neural Network

Color demosaicing is the problem of recovering full color/spectral channel from a subsampled image captured by single-chip digital cameras covered by Color Filter Array (CFA). Several algorithms have been proposed in the literature, however most of them are tuned to a particular arrangement of color filters. In this paper, we propose a generic algorithm based on a simple Neural Network (NN) architecture, which is trained on a small image database and which gives competitive results. To prove our statement, we test our network on several state of art CFAs and a 5 channel Spectral Filter Array (SFA). We demonstrate our result both on simulated images coming from standard image databases and also RAW images for a 5 channel SFA camera.

EEG-based brain connectivity analysis distinguishes children with low math achievements from their schoolmates

A mature mathematical technique to model power systems, aimed at computation of harmonics dynamics in a step-by-step fashion, is the extended harmonic domain (EHD). The EHD is capable of accounting for an arbitrary number of linearly-spaced sequentially-numbered harmonics; however, the dimensions of an EHD-based model are prone to explode if a large number of harmonics are considered. This fact makes computationally impossible the harmonics dynamics study when high-frequencies, inherent of electronic devices, are involved.This paper presents a flexible extended harmonic domain (FEHD) approach that permits to include an arbitrary number of (non-sequential) harmonics in any state variable of the system. The reasoning to use distinct harmonic content for each state variable is that in a general network (especially those involving alternative energy sources), state-variables exhibit distinct harmonic content. Such different contents mainly depend on the network topology, e.g., switched devices involved, filter arrangements utilized, etc.As shown in the paper, the proposed FEHD approach is able to provide reduced-order EHD models including high-frequency ripple information; thus, leading to computational savings while keeping accuracy compared to traditional EHD-based models and averaged-value models. A case study, involving a three-phase photovoltaic system in closed-loop operation, is presented to validate the proposed methodology. The results provided by the proposed methodology are verified with those given by the power system computer-aided design/electromagnetic transients including DC (PSCAD/EMTDC) simulation tool.

The Alternate Arm Converter (AAC)—“Short-Overlap” Mode Operation—Analysis and Design Parameter Selection

This paper presents converter operation principles and theoretical analyses for “short-overlap” mode operation of the alternate arm converter (AAC), which is a type of modular multilevel voltage source converter that has been proposed for HVdc transmission applications. Fourier series expressions for the ideal arm current and reference voltage are derived, for the first time, in order to develop an expression for the submodule capacitance required to give a selected peak–peak voltage ripple of the summed submodule capacitor voltages in an arm. The dc converter current contains nonnegligible low-order even harmonics; this is verified by deriving, for the first time, a Fourier series expression for this current. As the dc converter current needs to be filtered to form a smooth dc grid current, a novel dc filter arrangement is proposed, which uses the characteristics of a simplified dc cable model, as well as the capacitance of the dc link and additional dc-link damping resistance, in order to form a passive low-pass filter. Results obtained from a simulation model, which is based on an industrial HVdc demonstrator, are used in order to verify the presented converter operation principles and theoretical analyses.

Abrupt-tapered fiber filter arrangement for a switchable multi-wavelength and tunable Tm-doped fiber laser.

A switchable and tunable multi-wavelength Tm-doped fiber laser is successfully demonstrated using a filter constructed with two tapered fiber elements in the cavity. The proposed system design uses a low-cost simple filter that allows stable dual, triple, quadruple, and quintuple-wavelength emission operation in the region around 1.9 μm. In the dual wavelength regime, the laser is capable of independently tuning each wavelength. For switching and tuning, a curvature is applied to the tapered fibers.

Reduction of rounding noise and lifting steps in non-separable four-dimensional quadruple lifting integer wavelet transform

The wavelet transform (WT)-based JPEG 2000 is a standard for the compression of digital images that uses a separable lifting structure in which a multidimensional image signal is transformed separately along its horizontal and vertical dimensions. A non-separable three-dimensional (3D) structure is used to minimize the number of lifting steps in existing methods and can reduce the delay between input and output as each process is implemented by cascading in lifting calculation. This structure reduces rounding noise and the number of steps of the lifting scheme in the transform. The non-separable 3D structure in the 5/3-type transform for lossless coding reduces rounding noise, but it increases in the 9/7-type transform for lossy coding in the structure. A combination of 2D and 3D non-separable structures for 4D integer WT has been proposed to solve this problem, but the original filter arrangements need to be preserved to reduce rounding noise. Therefore, in this study, a non-separable 2D structure for the integer implementation of a 4D quadruple lifting WT with a 9/7 filter is proposed. The proposed wavelet transform has the same output signal as the conventional separable structure except for the rounding noise. As the order of the original lifting scheme is preserved, rounding noise in pixels of the decoded image can be significantly reduced, and the upper bounds of quality and lossy decoded 4D medical images can be improved.

Harmonics reduction in standalone DFIG-DC system by shunt active filter controlled in stator flux reference frame

The presence of diode rectifier in standalone Doubly Fed Induction Generator-Direct Current (DFIG-DC) system leads to considerable current, voltage and torque harmonics and requires reactive power from the machine. A unique shunt active filter arrangement is proposed for addressing these requirements. The DC Link of DFIG-DC itself acts as input to shunt active filter and there is no requirement of creating and regulating a separate one. Since the stator flux reference frame is known in FOC of DFIG-DC system; the same can be used as PLL for the generation of current references for harmonics and reactive compensation in active filter control scheme. Hence, the AC voltage sensing is not needed in the proposed active filter control. In this paper, it is shown that current, voltage and torque harmonics are reduced with the help of shunt active filter, which have lower rating compared to the rotor side converter. The proposed scheme is verified by detailed experiments on a 5.5 kW slip-ring induction machine.

On-chip electro-optic multiplexing circuit using serial microring boxcar filters

© 2018 The Authors We propose a new variant of electro-optic multiplexing scheme using the boxcar filter arrangement. The circuits consist of multistage add-drop multiplexers that can offer external input-output connections. Input from a single light source can be fed into the system through the input port or through the free-space from light fidelity (LiFi) node. The light signal is fed into boxcar filters and the roll-off bands are obtained. The output of the circuits is formed at the drop, through and the whispering gallery mode (WGM) node of the circuit output. By using the electro-optic conversion in Si-Graphene-Au layer stack, time division (TDM), wavelength division (WDM), frequency division multiplexing (FDM) can be performed. The simulations have shown that a combination of 7 roll-off bands with the maximum spectral widths or bandwidths of ∼6.09 µm or ∼7.63 THz can be obtained.

Stepwise-Nanocavity-Assisted Transmissive Color Filter Array Microprints.

Visible-light color filters using patterned nanostructures have attracted much interest due to their various advantages such as compactness, enhanced stability, and environmental friendliness compared with traditional pigment or dye-based optical filters. While most existing studies are based on planar nanostructures with lateral variation in size, shape, and arrangement, the vertical dimension of structures is a long-ignored degree of freedom for the structural colors. Herein, we demonstrate a synthetic platform for transmissive color filter array by coordinated manipulations between height-varying nanocavities and their lateral filling fractions. The thickness variation of those nanocavities has been fully deployed as an alternative degree of freedom, yielding vivid colors with wide gamut and excellent saturation. Experimental results show that the color-rendering capability of the pixelated nanocavities can be still retained as pixels are miniaturized to 500 nm. Crosstalk between closely spaced pixels of a Bayer color filter arrangement was calculated, showing minimal crosstalk for 1 µm2 square subpixels. Our work provides an approach to designing and fabricating ultracompact color filter arrays for various potential applications including stained-glass microprints, microspectrometers, and high-resolution image sensing systems.

Flexible extended harmonic domain approach for transient state analysis of switched systems

A mature mathematical technique to model power systems, aimed at computation of harmonics dynamics in a step-by-step fashion, is the extended harmonic domain (EHD). The EHD is capable of accounting for an arbitrary number of linearly-spaced sequentially-numbered harmonics; however, the dimensions of an EHD-based model are prone to explode if a large number of harmonics are considered. This fact makes computationally impossible the harmonics dynamics study when high-frequencies, inherent of electronic devices, are involved.This paper presents a flexible extended harmonic domain (FEHD) approach that permits to include an arbitrary number of (non-sequential) harmonics in any state variable of the system. The reasoning to use distinct harmonic content for each state variable is that in a general network (especially those involving alternative energy sources), state-variables exhibit distinct harmonic content. Such different contents mainly depend on the network topology, e.g., switched devices involved, filter arrangements utilized, etc.As shown in the paper, the proposed FEHD approach is able to provide reduced-order EHD models including high-frequency ripple information; thus, leading to computational savings while keeping accuracy compared to traditional EHD-based models and averaged-value models. A case study, involving a three-phase photovoltaic system in closed-loop operation, is presented to validate the proposed methodology. The results provided by the proposed methodology are verified with those given by the power system computer-aided design/electromagnetic transients including DC (PSCAD/EMTDC) simulation tool.

Elemental Contrast X-ray Tomography Using Ross Filter Pairs with a Polychromatic Laboratory Source

The majority of current laboratory based X-ray sources are polychromatic and are not tuneable. This lack of monochromaticity limits the range of applications for these sources and in particular it reduces the elemental specificity of laboratory based X-ray imaging experiments. Here we present a solution to this problem based on the use of Ross filter pairs. Although such Ross filter arrangements have been applied in proof-of-principle spectroscopy experiments, to date there have been no reports of this approach used for full-field X-ray imaging. Here we report on the experimental demonstration of Ross filter pairs being used for quasi-monochromatic, full-field imaging. This arrangement has several important benefits for laboratory based X-ray imaging including, as we demonstrate, elemental contrast enhancement. The method is demonstrated both for two-dimensional radiography and for three-dimensional X-ray tomography.

Comparative study of bisected proboscides of Pycnogonida

To comparatively describe “inner” pharynx armatures in pycnogonids, we bisected proboscides of Achelia langi (Dohrn, 1881), Anoplodactylus californicus Hall, 1912, Ascorhynchus castellioides Stock, 1957, Austrodecus glaciale Hodgson, 1907, Callipallene margarita (Gordon, 1932), Colossendeis macerrima Wilson, 1881, Endeis spinosa (Montagu, 1808), Nymphon macronyx Sars, 1877, Pallenopsis patagonica (Hoek, 1881), Pantopipetta sp., Pigrogromitus timsanus Calman, 1927, and Pycnogonum litorale (Strom, 1762) and analyzed them with the scanning electron microscope (SEM). Moreover, proboscides were stained with actin green to visualize the muscle arrangement with fluorescence and confocal microscopes (A. langi) and were analyzed with microcomputed X-ray tomography (μCT; Ascorhynchus japonicus). As a result of our observations, sets of characters that vary between taxa are established. These traits include length and width of proboscis, shape and structure of the inner mouth opening, borders and armature of the antimeres, shape and position of denticle arrays and rows, relative length of pharyngeal filter apparatus, and arrangement and structure of the filter bristles. Analyses of these characters indicate a substantial variability on the pantopod’s proboscis inner surface probably as an adaptation to different food sources. Finally, we suggest that the presence of the oyster basket represents a ground pattern character of Pycnogonida.

The effect of time delay on control stability of an electromagnetic active tuned mass damper for vibration control

The aim of this paper is to investigate the effect of time delays on the stability of a zero-placement position and velocity feedback law for a vibratory system comprising harmonic excitation equipped with an electromagnetic active tuned mass damper (ATMD). The purpose of the active control is broadening the vibration attenuation envelope of a primary mass to a higher frequency region identified as from 50±0.5Hz with a passive tuned mass damper (TMD) to a wider range of 50±5Hz with an ATMD. Stability conditions of the closed-loop system are determined by studying the position of the system closed-loop poles after the introduction of time delays for different excitation frequencies. A computer simulation of the model predicted that the proposed control system is subject to instability after a critical time delay margin dependent upon the frequency of excitation and the finding were experimentally validated. Three solutions are derived and experimentally tested for minimising the effect of time delays on the stability of the control system. The first solution is associated with the introduction of more damping in the absorber system. The second incorporates using a time-delayed ATMD by tuning its original natural resonant frequency to beyond the nominal operational frequency range of the composite system. The third involves an online gain tuning of filter coefficients in a dual arrangement of low-pass and high-pass filters to eliminate the effect time delays by manipulating the signal phase shifts.

Photodiode-based cutting interruption sensor for near-infrared lasers.

We report on a photodiode-based sensor system to detect cutting interruptions during laser cutting with a fiber laser. An InGaAs diode records the thermal radiation from the process zone with a ring mirror and optical filter arrangement mounted between a collimation unit and a cutting head. The photodiode current is digitalized with a sample rate of 20 kHz and filtered with a Chebyshev Type I filter. From the measured signal during the piercing, a threshold value is calculated. When the diode signal exceeds this threshold during cutting, a cutting interruption is indicated. This method is applied to sensor signals from cutting mild steel, stainless steel, and aluminum, as well as different material thicknesses and also laser flame cutting, showing the possibility to detect cutting interruptions in a broad variety of applications. In a series of 83 incomplete cuts, every cutting interruption is successfully detected (alpha error of 0%), while no cutting interruption is reported in 266 complete cuts (beta error of 0%). With this remarkable high detection rate and low error rate, the possibility to work with different materials and thicknesses in combination with the easy mounting of the sensor unit also to existing cutting machines highlight the enormous potential for this sensor system in industrial applications.

Frequency-Domain Volterra-Based Equalization Structures for Efficient Mitigation of Intrachannel Kerr Nonlinearities

Toward reduced-complexity digital implementation, frequency domain Volterra-based nonlinear equalization (VNLE) structures for multistep fiber nonlinearity compensation are proposed. In the cascade structures, nonlinear equalization is performed before (cascade-1) or after (cascade-2) the dispersion compensation in each step. Superior performance with the shorter discrete Fourier transform (DFT) lengths and fewer equalization steps compared to the conventional VNLE with parallel structure is demonstrated in a transmission experiment. The experimental results are obtained for 256 Gb/s single-carrier dual-polarization 16-ary quadrature-amplitude-modulation with root-raised-cosine pulse shaping and a roll-off factor of 0.1. The new cascade structures demonstrate superior robustness to insufficient DFT lengths and/or a limited complexity budget. Compared to the conventional parallel arrangement of linear and nonlinear compensation filters, the cascade-1 structure provides more than 90% complexity reduction without any notable performance penalty. The structure enables the extension of the transmission reach by 1570 km, a 48% increase compared to the linear solution that uses only electronic dispersion compensation.

Reducing shield thickness and backscattered radiation using a multilayered shield for 6–10 MeV electron beams.

Intraoral and external electron shields used in radiotherapy are designed to minimize radiation exposure to non-treatment tissue. Sites where shields are used include but are not limited to, the treatment of lips, cheeks and ears whilst shielding the underlying oral cavity, tongue, gingival or temporal region. A commonly known and published effect, concerns the enhancement in dose that can occur on the beam side on an electron shield caused by an increase in electron backscatter radiation. In this work a lead shield has been designed incorporating copper, aluminium and wax in a step down filter arrangement to minimise backscatter whilst minimizing overall shield thickness for better clinical setup and ease of use. For electron beams ranging from 6 to 10 MeV, a standard shield design of 4 mm lead, 0.6 mm copper, 1.0 mm aluminium and 1.5 mm wax (3.1 mm added filtration, 7.1 mm total thickness) provided adequate backscatter and transmission reduction to match a standard 4.5 mm lead and 10 mm wax (total thickness 14.5 mm) electron shield. Dose enhancement values of no more than 10 % were measured utilising this shield design with a 50 % reduction in shield thickness. The thinner shield will not only allow easier patient set up but should be tolerated better by patients when mucosal reactions occur as they place less physical pressure on these sites during treatment due to their smaller size.

DEVELOPMENT OF THE NEW GLASS BADGE.

The glass dosemeter, which is a component of the glass badge (GB), is used on the basis of radiophotoluminescence phenomenon. Chiyoda Technol Corporation has been providing it for personal monitoring services since the year 2000. Through the experience acquired over 15 y, Chiyoda Technol Corporation has developed the New GB, which was brought into service in Japan for radiation monitoring in January 2014. The New GB was developed with the aim of improving radiation measurement methods, streamlining the provision of GB monitoring services and realising a user-friendly dosemeter. As the result, in this study, the measurable energy range covered for beta rays was expanded to include those emitted from 147Pm, the directional dependency was improved, a film was designed to remove secondary electrons arising from interactions between incident photons and the metallic filters, and the arrangement of the metallic filters was optimised.