Asymmetric Square Research Articles

Theoretical investigation of a five-band terahertz absorber based on an asymmetric split-ring resonator.

A simple five-band terahertz metamaterial perfect absorber, composed of an asymmetric double-gap square split ring and a metallic ground plate spaced by a thin polyimide dielectric layer, is proposed and theoretically investigated. The results show that it can perform absorption peaks at five resonant frequencies whose peaks average 98.85%. The perfect absorption is mainly attributed to the combined effect of LC, dipole, and surface response of the structure. Compared to previously reported multiband absorbers, our design only has a single and compact structure, which can drastically simplify the design and fabrication process. Furthermore, the resonance absorption properties of the absorber can be tuned by changing the geometric parameters of the structure. Such a simple and effective design holds great promise for potential applications in spectroscopic imaging, biological sensing, and detecting of drugs and explosives.

Magnetodielectric properties of the square cupola antiferromagnet Ba(TiO)Cu4(PO4)4

Magnetodielectric properties of the tetragonal magnetic insulator Ba(TiO)Cu4(PO4)4 consisting of asymmetric Cu4O12 square cupolas have been investigated in a magnetic field along the [001] axis (B[001]), where a metamagnetic transition occurs at Bc||[001] ~ 12T and 1.4K. Clear anomalies associated with the transition to the high-field phase are observed in dielectric constants both along the [100] (ε[100]) and [001] (ε[001]) axes. It is found that the B dependence of ε[001] and ε[100] across Bc||[001] is anisotropic: ε[001] decreases while ε[100] increases. The origin of this anisotropic magnetodielectric response is discussed.

A transfer matrix approach for structural–acoustic correspondence analysis of diesel particulate filter

Diesel particulate filter is impedance to elastic wave. In order to promote the anechoic performance of diesel particulate filter in designing process, the acoustic characteristics of which were analyzed on the basis of acoustic four-terminal method. The transfer matrix of simplified diesel particulate filter structure was derived to construct the acoustic simulation model, and a two-load experiment of impedance tube was implemented to calibrate the simulation model. On this basis, the correlation between diesel particulate filter structural parameters and acoustic characteristics was investigated. The results show that the transmission loss is sensitive to porosity, gap, layer thickness, and aspect ratio of porthole for a certain diameter diesel particulate filter. Furthermore, two types of diesel particulate filter structures which were octagonal inlet matches square outlet and asymmetric square channels possess superior noise elimination effect compared with the traditional square channel types. At a certain frequency range, the peak noise was reduced by 2–3 dB. The study could provide guidance to the designing of diesel particulate filter anechoic performance.

Design and implementation of dynamic logic gates and R-S flip-flop using quasiperiodically driven Murali-Lakshmanan-Chua circuit.

We report the propagation of a square wave signal in a quasi-periodically driven Murali-Lakshmanan-Chua (QPDMLC) circuit system. It is observed that signal propagation is possible only above a certain threshold strength of the square wave or digital signal and all the values above the threshold amplitude are termed as "region of signal propagation." Then, we extend this region of signal propagation to perform various logical operations like AND/NAND/OR/NOR and hence it is also designated as the "region of logical operation." Based on this region, we propose implementing the dynamic logic gates, namely, AND/NAND/OR/NOR, which can be decided by the asymmetrical input square waves without altering the system parameters. Further, we show that a single QPDMLC system will produce simultaneously two outputs which are complementary to each other. As a result, a single QPDMLC system yields either AND as well as NAND or OR as well as NOR gates simultaneously. Then, we combine the corresponding two QPDMLC systems in a cross-coupled way and report that its dynamics mimics that of fundamental R-S flip-flop circuit. All these phenomena have been explained with analytical solutions of the circuit equations characterizing the system and finally, the results are compared with the corresponding numerical and experimental analysis.

A New Hierarchical $M$ -ary DCSK Communication System: Design and Analysis

Multiresolution $M$ -ary differential chaos shift keying (MR- $M$ -DCSK) modulation using non-uniformly spaced phase constellation is a promising technique that can satisfy different bit-error-rate (BER) requirements within one symbol over multipath fading channels. However, the BER performance always deteriorates as the modulation order $M$ becomes larger. To overcome this shortcoming, a new hierarchical square-constellation-based $M$ -DCSK communication system using non-uniformly spaced distance constellation is proposed, which can be easily extended to other-constellation scenarios, e.g., rectangular, star, and asymmetrical square constellations. Furthermore, an adaptive transmission scheme is designed by modifying the distance between the two constellation points in the last hierarchical level. In addition, theoretical BER expressions of the proposed systems are derived over multipath Rayleigh fading channels, which are consistent with the simulated results. Analytical and simulated results show that the proposed system not only can provide lower energy consumption as compared with the conventional MR- $M$ -DCSK system but also can efficiently adjust BER performance based on the signal-to-noise ratio information. Therefore, the proposed system can serve as a desirable alternative for energy-efficient short-range wireless-communication applications.

An SVM-like approach for expectile regression

Expectile regression is an interesting tool for investigating conditional distributions beyond the conditional mean. It is well-known that expectiles can be described with the help of the asymmetric least square loss function, and this link makes it possible to estimate expectiles in a non-parametric framework with a support vector machine like approach. For the underlying optimization problem, an efficient sequential-minimal-optimization-based solver is developed and its convergence derived. The behavior of the solver is investigated by conducting various experiments, and the results are compared with the solver for quantile regression and the recent R-package ER-Boost.

Investigation of fatigue behavior of Pb(Zr0.45Ti0.55)O3 thin films under asymmetric polarization switching

The fatigue of lead zirconate titanate (PZT) thin films was measured under repetitive switching using asymmetric square waves. The remnant polarization and coercive voltage were found to present regular changes in the initial 10 s, independent of the asymmetry or frequency of switching waves. We attributed the change to the relaxation of stress in the film and identified a coercive voltage V0 of 0.6 V for the stress-free film. By comparing the coercive voltage and V0, we found that a built-in electric field was induced by asymmetric switching, where the direction and magnitude were dependent on the degree of waveform asymmetry. Furthermore, the fatigue speed was suggested to be closely related to the generation rate of oxygen vacancies. It was confirmed by our result that a faster decay of remnant polarization can be obtained by applying square waves with a higher degree of asymmetry or symmetry of square waves with a lower frequency.

ID 215 – Transcutaneous trigeminal nerve stimulation induces a long-term depression-like plasticity of the human blink reflex

Objective To test the after-effects of 20-min, cyclic transcutaneous trigeminal nerve stimulation (TNS) on the excitability of the blink reflex (BR). Methods The areas of the R1 and R2 components of the BR were measured in 20 healthy subjects before and at 0–5, 15, 20, 30 and 45 min after TNS (asymmetric biphasic square wave pulses: duration 250 μ s, intensity 1–20 mA, frequency 120 Hz, alternating 30s ON, 30s OFF for 20 min) delivered bilaterally to the infraorbitary nerve. Results The areas of the R2 components of the BR were significantly suppressed at each time interval tested after TNS ( p Conclusions 20-min TNS did not affected the R1 component of the BR, while inducing a long lasting inhibition of the R2 component, possibly through a long-term depression (LTD)-like mechanism. The different effect on the two components of the BR suggests that only polysynaptic brainstem pathways may be modulated by TNS. Key message TNS is a useful tool to investigate the LTD-like plasticity of brainstem polysynaptic circuits in healthy subjects.

Photoplethysmography-Based Heart Rate Monitoring Using Asymmetric Least Squares Spectrum Subtraction and Bayesian Decision Theory

Motion artifacts (MAs) are strong interference sources in wearable photoplethysmography (PPG) signals, significantly affecting estimation of heart rate (HR) and other physiological parameters. In this paper, a novel method called SPECTRAP is proposed for accurate motion-tolerant estimation of HR using a PPG signal and a simultaneous acceleration signal. The method first calculates the spectra of the PPG signal and the acceleration signal, and then removes the MA spectral components from the PPG spectrum using a new spectrum subtraction algorithm. The new spectrum subtraction algorithm is based on asymmetric least square and overcomes drawbacks of the conventional spectrum subtraction algorithms. To find the spectral peak corresponding to HR on the resulting spectrum, SPECTRAP formulates the problem into a pattern classification problem and uses the Bayesian decision theory to solve it. Experimental results on the PPG database used in 2015 IEEE Signal Processing Cup showed that the proposed algorithm has excellent performance. The average absolute error on the twelve training sets was 1.50 beat per minute (BPM) (standard deviation: 1.95 BPM). The average absolute error on the ten testing sets was 2.13 BPM (standard deviation: 2.77 BPM).

Application of terahertz time-domain spectroscopy combined with chemometrics to quantitative analysis of imidacloprid in rice samples

Terahertz time-domain spectroscopy (THz-TDS) has been utilized as an effective tool for quantitative analysis of imidacloprid in rice powder samples. Unlike previous studies, our method for sample preparation was mixing imidacloprid with rice powder instead of polyethylene. Then, terahertz time domain transmission spectra of these mixed samples were measured and the absorption coefficient spectra of the samples with frequency range extending from 0.3 to 1.7THz were obtained. Asymmetric least square (AsLS) method was utilized to correct the slope baselines that are presented in THz absorption coefficient spectra and improve signal-to-noise ratio of THz spectra. Chemometrics methods, including partial least squares (PLS), support vector regression (SVR), interval partial least squares (iPLS), and backward interval partial least squares (biPLS), were used for quantitative model building and prediction. To achieve a reliable and unbiased estimation, bootstrapped Latin partition was chosen as an approach for statistical cross-validation. Results showed that the mean value of root mean square error of prediction (RMSEP) for PLS (0.5%) is smaller than SVR (0.7%), these two methods were based on the whole absorption coefficient spectra. In addition, PLS performed a better performance with a lower RMSEP (0.3%) based on the THz absorption coefficient spectra after AsLS baseline correction. Alternatively, two methods for variable selection, namely iPLS and biPLS, yielded models with improved predictions. Comparing with conventional PLS and SVR, the mean values of RMSEP were 0.4% (iPLS) and 0.3% (biPLS) by selecting the informative frequency ranges. The results demonstrated that an accurate quantitative analysis of imidacloprid in rice powder samples could be achieved by terahertz time-domain transmission spectroscopy combined with chemometrics. Furthermore, these results demonstrate that THz time-domain spectroscopy can be used for quantitative determinations of other pesticides in other agricultural products.

Bidirectional PWM Converter Integrating Cell Voltage Equalizer Using Series-Resonant Voltage Multiplier for Series-Connected Energy Storage Cells

In conventional energy storage systems using series-connected energy storage cells such as lithium-ion battery cells and supercapacitors (SCs), an interface bidirectional converter and cell voltage equalizer are separately required to manage charging/discharging and ensure years of safe operation. In this paper, a bidirectional PWM converter integrating cell voltage equalizer is proposed. This proposed integrated converter can be derived by combining a traditional bidirectional PWM converter and series-resonant voltage multiplier (SRVM) that functionally operates as an equalizer and is driven by asymmetric square wave voltage generated at the switching node of the converter. The converter and equalizer can be integrated into a single unit without increasing the switch count, achieving not only system-level but also circuit-level simplifications. Open-loop control is feasible for the SRVM when operated in discontinuous conduction mode, meaning the proposed integrated converter can operate similarly to conventional bidirectional converters. An experimental charge-discharge cycling test for six SCs connected in series was performed using the proposed integrated converter. The cell voltage imbalance was gradually eliminated by the SRVM while series-connected SCs were cycled by the bidirectional converter. All the cell voltages were eventually unified, demonstrating the integrated functions of the proposed converter.

A Comparative Study of the Damping Force and Energy Absorbtion Capacity of Regenerative and Conventional-Viscous Shock Absorber of Vehicle Suspension

This paper presents a comparative study of the damping force and energy absorbtion capacity of a typical conventional-viscous and a regenerative shock absorber for vehicle suspension. Regenerative shock absorber (RSA) is a shock absorber which can regenerate the dissipated vibration energy from vehicle suspension into electricity. In this research, a prototype of regenerative shock absorber was developed, its damping force and energy absorbtion capacity were tested, and the results were analized and compared with those of a typical conventional-viscous shock absorber. The regenerative and viscous shock absorber were compressed and extended in various excitation frequency using damping force testing equipment to obtain force-velocity and the force-displacement curves. The force-velocity and force-displacement curves indicate the damping force and energy absorbtion capacity of the shock absorber. The results show that the damping force of the typical-viscous shock absorber closed to linear at all exciation frequencies. For regenerative shock absorber, nonlinearity and large hysteresis area of the damping force occur at all excitation frequencies. Further, the energy absorbtion capacity of the typical-viscous shock absorber shows an elliptical area with the compression part bigger than the extension one, while those of the regenerative shock absorber shows an asymmetric square area, which indicates a smaller energy absorbtion capacity. These phenomena indicate the significant effect of implementing dry friction damper and elctrical damper to the characteristics of regenerative shock absorber.

Synchronization of tunable asymmetric square-wave pulses in delay-coupled optoelectronic oscillators.

We consider a model for two delay-coupled optoelectronic oscillators under positive delayed feedback as prototypical to study the conditions for synchronization of asymmetric square-wave oscillations, for which the duty cycle is not half of the period. We show that the scenario arising for positive feedback is much richer than with negative feedback. First, it allows for the coexistence of multiple in- and out-of-phase asymmetric periodic square waves for the same parameter values. Second, it is tunable: The period of all the square-wave periodic pulses can be tuned with the ratio of the delays, and the duty cycle of the asymmetric square waves can be changed with the offset phase while the total period remains constant. Finally, in addition to the multiple in- and out-of-phase periodic square waves, low-frequency periodic asymmetric solutions oscillating in phase may coexist for the same values of the parameters. Our analytical results are in agreement with numerical simulations and bifurcation diagrams obtained by using continuation techniques.

Systematic syntheses and metalloligand doping of flexible porous coordination polymers composed of a Co(III)-metalloligand.

A series of flexible porous coordination polymers (PCPs) RE-Co, composed of a Co(III)-metalloligand [Co(dcbpy)3](3-) (Co; H2dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and lanthanide cations (RE(3+) = La(3+), Ce(3+), Pr(3+), Nd(3+), Sm(3+), Eu(3+), Gd(3+), Tb(3+), Er(3+)), was systematically synthesized. X-ray crystallographic analysis revealed that the six carboxylates at the top of each coordination octahedron of Co(III)-metalloligand were commonly bound to RE(3+) cations to form a rock-salt-type porous coordination framework. When RE-Co contains a smaller and heavier RE(3+) cation than Nd(3+), the RE-Co crystallized in the cubic Fm-3m space group, whereas the other three RE-Co with larger RE(3+) crystallized in the lower symmetrical orthorhombic Fddd space group, owing to the asymmetric 10-coordinated bicapped square antiprism structure of the larger RE(3+) cation. Powder X-ray diffraction and vapor-adsorption isotherm measurements revealed that all synthesized RE-Co PCPs show reversible amorphous-crystalline transitions, triggered by water-vapor-adsorption/desorption. This transition behavior strongly depends on the kind of RE(3+); the transition of orthorhombic RE-Co was hardly observed under exposure to CH3OH vapor, but the RE-Co with smaller cations such as Gd(3+) showed the transition under exposure to CH3OH vapors. Further tuning of vapor-adsorption property was examined by doping of Ru(II)-metalloligands, [Ru(dcbpy)3](4-), [Ru(dcbpy)2Cl2](4-), [Ru(dcbpy)(tpy)Cl](-), and [Ru(dcbpy)(dctpy)](3-) (abbreviated as RuA, RuB, RuC, and RuD, respectively; tpy = 2,2':6',2″-terpyridine, H2dctpy = 4,4″-dicarboxy-2,2':6',2″-terpyridine), into the Co(III)-metalloligand site of Gd-Co to form the Ru(II)-doped PCP RuX@Gd-Co (X = A, B, C, or D). Three Ru(II)-metalloligands, RuA, RuB, and RuD dopants, were found to be uniformly incorporated into the Gd-Co framework by replacing the original Co(III)-metalloligand, whereas the doping of RuC failed probably because of the less number of coordination sites. In addition, we found that the RuA doping into the Gd-Co PCP had a large effect on vapor-adsorption due to the electrostatic interaction originating from the negatively charged RuA sites in the framework and the charge-compensating Li(+) cations in the porous channel.

Correction method for the physical dose calculated using Clarkson integration at the center of the spread-out Bragg peak for asymmetric field in carbon-ion radiotherapy

PurposeWe previously proposed a calculation method using Clarkson integration to obtain the physical dose at the center of the spread-out Bragg peak (SOBP) for a treatment beam, the measurement point of which agrees with the isocenter [Tajiri et al. Med. Phys. 2013; 40: 071733–1–5]. However, at the measurement point which does not agree with the isocenter, the physical dose calculated by this method might have a large error. For this error, we propose a correction method. Materials and methodsTo confirm whether the error can be corrected using in-air off axis ratio (OAR), we measured the physical dose at the center of an asymmetric square field and a symmetric square field and in-air OAR. For beams of which the measurement point does not agree with the isocenter, as applied to prostate cancer patients, the physical dose calculated using Clarkson integration was corrected with in-air OAR. ResultsThe maximum difference between the physical dose measured at the center of an asymmetric square field and the product of in-air OAR and the physical dose at the center of a symmetric square field was – 0.12%. For beams as applied to prostate cancer patients, the differences between the measured physical doses and the physical doses corrected using in-air OAR were −0.17 ± 0.23%. ConclusionsThe physical dose at the measurement point which does not agree with the isocenter, can be obtained from in-air OAR at the isocenter plane and the physical dose at the center of the SOBP on the beam axis.

An asymmetrical dinuclear copper(II) β-amino-oxime/oximato-diamine compound with Cu–(OH)–Cu and Cu–(N–O)–Cu bridging; [Cu2(detenoxH)(detenox)(OH)](ClO4)2 (detenoxH = 4,4-dimethyl-7-(N,N-diethylamine)-5-azaheptan-2-one oxime)

The dark blue compound [Cu2(detenoxH)(detenox)(OH)](ClO4)2 (detenoxH=4,4-dimethyl-7-(N,N-diethylamine)-5-azaheptan-2-one oxime), [Cu2(C12H27N3O)(C12H26N3O)(OH)](ClO4)2, is formed by reaction of (N,N-diethyl-ethane-1,2-diamine)copper(II) perchlorate, 4-methylpent-3-ene-2-one oxime and base. The asymmetrical dinuclear cation has ion Cu1 in asymmetrical square pyramidal coordination by the oxime nitrogen atom (Cu1–Noxime=2.041(3)Å) and the secondary amine nitrogen atom (Cu1–Nsecondary=1.995(3) Å) of a detenoxH ligand, the bridging oximato oxygen atom of the detenox− ligand bonded to Cu2 (Cu1–Ooximato=1.928(2)Å) and the bridging OH− ion (Cu1–OOH=1.928(3)Å) with rms displacements from the N2O2 plane±0.246(1) with Cu1 in the plane). The tertiary amine nitrogen atom of the detenoxH ligand is weakly coordinated axially (Cu1–Ntertiary=2.328(3)Å). Ion Cu2 is in tetrahedrally twisted square-planar coordination by a detenox− ligand, with Cu2–Noxime=1.992(3), Cu2–Nsecondary=1.979(3), Cu2–Ntertiary=2.053(3), and by the bridging hydroxide ion (Cu2–O=1.878(3)Å), with rms displacements from the N3O best plane ±0.178(2)Å, with Cu2 in the plane). The dinuclear cation has Cu1–O=N–Cu2 bridging by the oximato group of detenox− and Cu1–(OH)–Cu2 bridging by a hydroxide ion, with Cu⋯Cu=3.3136(6)Å. The components of the dinuclear cation are further linked by a hydrogen bond between the oxime OH and oximato O− groups. The effective magnetic moment of 2.21 B.M. indicates that there is no significant spin coupling.

Tunable bandwidth of the terahertz metamaterial absorber

We propose a broadband terahertz metamaterial absorber that utilizes the coupling effect of the sub-unit elements of the structure consisted of two asymmetric metallic square rings and a metallic ground plane separated by a dielectric layer. The bandwidth of the absorber is tunable over a range from 0.88 to 1.28THz by the coupling distance of the two patterned square rings. The proposed absorber has the tunability from broadband to single-band by the polarization angle of the system. Moreover, the proposed concept also applies to other types of asymmetric absorber structure and can be readily extended to other frequency regimes for a host of applications such as detection, imaging and solar cell.

Performance Comparison of Scramjet‐Driven Experimental DCW‐MHD Generators with Different Cross‐Sections

SUMMARYThe purpose of this study is to examine the influence of the shape of the cross‐section of a scramjet engine‐driven experimental diagonal conducting wall (DCW)‐MHD generator on generator performance by three‐dimensional numerical analyses. We have designed MHD generators with symmetric square and circular cross‐sections, based on an experimental MHD generator with an asymmetric square cross‐section. Under the optimum load conditions, the electric power output reaches 26.6 kW for the asymmetric square cross‐section, 24.6 kW for the symmetric square cross‐section, and 22.4 kW for the circular cross‐section. The highest output is obtained for the experimental generator with the asymmetric square cross‐section. The difference in the electric power output is induced by the difference of flow velocity and boundary layer thickness. For the generator with the asymmetric square cross‐section, the average flow velocity is highest and the boundary layer is thinnest. The compression wave is generated with dependence on the channel shape. The difference in the flow velocity and boundary layer thickness is induced by the superposition of the compression wave. © 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(2): 9–16, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22403

Screen Printed Potentiometric Chloride Sensors

Potentiometric chloride sensors were fabricated by electrochemically chloridizing the surface of screen printed silver electrodes using amperostatic coulometry or asymmetric square wave voltammetry. In the case of coulometric chloridization, the effect of different chloride ion sources was also investigated. The response to chloride ions by each type of sensor was determined by measuring their potentials with respect to a commercial Ag/AgCl reference electrode over the chloride concentration range 1.8 to 3,545mg/L (approximately 50μM to 100mM). Results reveal that irrespective of fabrication method, all sensors exhibit near Nernstian responses with no significant relationships between fabrication and response parameters.

Prediction of tyrosinase inhibitory activities of Morus alba root bark extracts from HPLC fingerprints

A correlation model between tyrosinase inhibitory activities and HPLC chromatograms of Morus alba root bark extracts was calibrated and validated. The correlational approach has been suggested as an alternative technique for quality control and study of natural products. However, this method requires a large number of various samples with similar chemical compositions. In the present study, 42 different extracts were obtained from 6 samples of M. alba root bark under 7 different extraction solvent conditions using an automated pressurized liquid extraction system. HPLC chromatograms and mushroom tyrosinase inhibitory activities of these extract samples were obtained, and the chromatograms were preprocessed with asymmetric least square smoothing and correlation optimized warping algorithms. The partial least squares (PLS) regression model between the preprocessed chromatograms and the bioactivities of samples was created. The full cross validations were performed by changing the selection method of the test sets; plant sample based, extraction method based validation set selections were used for the validation tests. In both validation tests, the PLS models showed excellent performance of prediction. The predictive models showed averagely RMSEP of 9.4309 and R2 values of 0.8717 in the validation test based on plant samples, and RMSEP of 8.1541 and R2 values of 0.8778 in the validation test based on extraction methods. Additionally, an estimation of the bioactive component was made from the regression coefficient, and the result of the estimation was similar to the experimental results of reference papers.