Optimal Coupling Conditions Research Articles

Enhancement of α to β phase transformation in poly (vinylidene fluoride) nanocomposites under uni-axial stretch: Contribution from restriction of nano-particles

Electroactive polyvinylidene fluoride (PVDF) with predominantly the β-phase is now challenging the fabricating of PVDF toward energy storage applications. Here, the comprehensive effect of BaTiO3 nano-particles and mechanical stretching on the improvement of the β-phase of PVDF was investigated. In situ synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) measurements were performed to investigate this behavior. Consequently, the transformation rate of β-crystal for both pure PVDF (BT0) and PVDF/BaTiO3 (90/10) nanocomposites (BT1) decreases as the stretching temperature increases, implying that the high temperature is unfavorable to the formation of β-crystal phase. A synergistic enhancement of the β-phase of nano-particle additives and stretching was discovered. It was surprisingly observed that α-phase of PVDF would completely transform into β-crystal in BT1 sample at 100 °C during stretching. The mechanism of the synergistic effect of BaTiO3 nano-particles and mechanical stretching was proposed. Moreover, machine learning was implemented to predict the fraction of β-crystal phase (F(β)) of the PVDF/BaTiO3 composites under various uni-axial stretching conditions by Python 3.8. The results show that the machine learning technique can rapidly and efficiently discover the ideal value of F(β) and the optimal multivariate coupling conditions.

Computational Design of an Electro-Organocatalyst for Conversion of CO2 into Long Chain Aldehydes.

Density functional theory calculations employing a hybrid implicit/explicit solvation method were used to demonstrate that an electro-organocatalyst designed in our previous work for reducing CO2 to formaldehyde could also be capable of coupling formaldehyde to form long chain aldehydes. The catalytic activity is enabled by an electron-rich vicinal enediamine (>N-C═C-N<) backbone that activates formaldehyde by reversing the polarity on the carbon atom, enabling it to act as a nucleophile in the subsequent aldol addition step. The catalyst then enables reductive dehydroxylation of the aldol addition product by facilitating outer-sphere electron transfer. The optimal pH as well as the limiting potential and formaldehyde concentration are identified and related to the kinetic balance between several rate limiting steps. Finally, the optimal conditions for coupling with the CO2 reduction cycle are discussed, demonstrating that the electro-organocatalyst is capable of efficiently converting CO2 into aldehyde products with a turnover frequency (per carbon atom) on the order of 0.1-1 s-1.

Laser‐Printed Plasmonic Metasurface Supporting Bound States in the Continuum Enhances and Shapes Infrared Spontaneous Emission of Coupled HgTe Quantum Dots

AbstractIn order to advance the development of quantum emitter‐based devices, it is essential to enhance light‐matter interactions through coupling between semiconductor quantum dots with high quality factor resonators. Here, efficient tuning of the emission properties of HgTe quantum dots in the infrared spectral region is demonstrated by coupling them to a plasmonic metasurface that supports bound states in the continuum. The plasmonic metasurface, composed of an array of gold nanobumps, is fabricated using single‐step direct laser printing, opening up new opportunities for creating exclusive 3D plasmonic nanostructures and advanced photonic devices in the infrared region. A 12‐fold enhancement of the photoluminescence in the 900–1700 nm range is observed under optimal coupling conditions. By tuning the geometry of the plasmonic arrays, controllable shaping of the emission spectra is achieved, selectively enhancing specific wavelength ranges across the emission spectrum. The observed enhancement and shaping of the emission are attributed to the Purcell effect, as corroborated by systematic measurements of radiative lifetimes and optical simulations based on the numerical solution of Maxwell's equations. Moreover, coupling of the HgTe photoluminescence to high quality factor modes of the metasurface improves emission directivity, concentrating output within an ≈20° angle.

The Electric-Thermal Uneven Characteristics Simulation of Wide Mg Alloy Strip and Electroplastic Rolling Experiment

In order to solve the problem of wide magnesium strip uneven deformation in electroplastic rolling, an uneven field measurement device was designed. The device simulates the actual electro-thermal characteristics and provides as even and constant field conditions as possible for high-efficiency wide Mg strip rolling. Firstly, the effect of electrode position and distance on the electric field unevenness of magnesium strip is observed by setting the electric rolling condition, to provide the optimal electrical-thermal field quantity coupling conditions required by electric rolling. Secondly, in order to reveal the changing trend of the transient field in the actual rolling, the three-dimensional electric field of wide magnesium strip are simulated by the finite element method. The results show that the even temperature field and stable stress field required by the EPR of a wide Mg strip can be guaranteed to the greatest extent by setting electric field parameter Online. The case proves that the continuous EPR of Mg strip with a thickness of less than 0.13 mm without heat treatment can be realized by fine control of the EPR process.

Self-coupling: an effective method to mitigate thermoacoustic instability

The presence of undesirable large-amplitude self-sustained oscillations in combustors resulting from thermoacoustic instability can lead to performance loss and structural damage to components of gas turbine and rocket engines. Traditional feedback controls to mitigate thermoacoustic instability possess electromechanical components, which are expensive to maintain regularly and unreliable in the harsh environments of combustors. In this study, we demonstrate the quenching of thermoacoustic instability through self-coupling—a method wherein a hollow tube is used to provide acoustic self-feedback to a thermoacoustic system. Through experiments and modeling, we identify the optimal coupling conditions for attaining amplitude death, i.e., complete suppression of thermoacoustic instabilities, in a horizontal Rijke tube. We examine the effect of both system and coupling parameters on the occurrence of amplitude death. We thereby show that the parametric regions of amplitude death occur when the coupling tube length is close to an odd multiple of the length of the Rijke tube. The optimal location to place the coupling tube for achieving amplitude death is near the antinode of the acoustic pressure standing wave in the Rijke tube. Furthermore, we find that self-coupling mitigates thermoacoustic instability in a Rijke tube more effectively than mutual coupling of two identical Rijke tubes. Thus, we believe that self-coupling can prove to be a simple, cost-effective solution for mitigating thermoacoustic instability in gas turbine and rocket combustors.

Effects of design and coupling parameters on the performance of electromagnetic transducers in round-window stimulation.

Many studies have investigated factors contributing to large variations in the outcomes of round-window (RW) stimulation but most have focused on the floating mass transducer (FMT). To determine whether results for the FMT hold for a fixed-type transducer (FTT), this study constructs two coupled finite element models of the transducer and the human ear that incorporate the cochlear third windows and inner structures of these two electromagnetic transducers. We use these FE models of the human ear and transducers to investigate the influence of four design parameters and coupling conditions for the transducers, i.e., the support's Young's modulus, the coupling layer's cross sectional area and Young's modulus, and the transducer's cross sectional area. The results show that an increase in the support's Young's modulus reduces the output of the FMT but increases that of the FTT. Reducing the cross sectional area and Young's modulus of the coupling layer significantly increases the low-frequency response of the FMT but slightly reduces that of the FTT. Reducing the cross sectional area of the transducer increases the output of the FMT but reduces that of the FTT. This shows that inner structures of electromagnetic transducers should be considered in the optimal design parameters and coupling conditions for RW stimulation.

Objective Assessment of Covid-19 Severity Affecting the Vocal and Respiratory System Using a Wearable, Autonomous Sound Collar.

IntroductionSince the outbreak began in January 2020, Covid-19 has affected more than 161 million people worldwide and resulted in about 3.3 million deaths. Despite efforts to detect human infection with the virus as early as possible, the confirmatory test still requires the analysis of sputum or blood with estimated results available within approximately 30 minutes; this may potentially be followed by clinical referral if the patient shows signs of aggravated pneumonia. This work aims to implement a soft collar as a sound device dedicated to the objective evaluation of the pathophysiological state resulting from dysphonia of laryngeal origin or respiratory failure of inflammatory origin, in particular caused by Covid-19.MethodsIn this study, we exploit the vibrations of waves generated by the vocal and respiratory system of 30 people. A biocompatible acoustic sensor embedded in a soft collar around the neck collects these waves. The collar is also equipped with thermal sensors and a cross-data analysis module in both the temporal and frequency domains (STFT). The optimal coupling conditions and the electrical and dimensional characteristics of the sensors were defined based on a mathematical approach using a matrix formalism.ResultsThe characteristics of the signals in the time domain combined with the quantities obtained from the STFT offer multidimensional information and a decision support tool for determining a pathophysiological state representative of the symptoms explored. The device, tested on 30 people, was able to differentiate patients with mild symptoms from those who had developed acute signs of respiratory failure on a severity scale of 1 to 10.ConclusionWith the health constraints imposed by the effects of Covid-19, the heavy organization to be implemented resulting from the flow of diagnostics, tests and clinical management, it was urgent to develop innovative and safe biomedical technologies. This passive listening technique will contribute to the non-invasive assessment and dynamic observation of lesions. Moreover, it merits further examination to provide support for medical operators to improve clinical management.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12195-021-00712-w.

Utilizing the Shift-or-Shrink Algorithm to Optimize the Direct Coupling from Laser Diodes to Diffused Channel Waveguides

Several formulae for computing the direct coupling efficiencies from laser diodes to diffused channel waveguides, based on mathematic models for approximating the corresponding laser beams and the waveguiding modes, have been derived in this paper. Then, the authors utilize a simple shift-or-shrink (SOS) algorithm to seek their optimal coupling conditions, including the incident positions of the laser beams and the corresponding horizontal and vertical beam widths. The simulation results are presented and compared.

Stepwise optimization of a Flexible Microtube Plasma (FµTP) as an ionization source for Ion Mobility Spectrometry

The ionization source is the central system of analytical devices such as mass spectrometers or ion mobility spectrometers. In this study, a recently developed flexible microtube plasma (FμTP) is applied as an ionization source for a custom-made drift tube ion mobility spectrometer (IMS) for the first time. The FµTP is based on a highly miniaturized, robust and a small-footprint dielectric barrier discharge design with an outstanding ionization efficiency. In this study, the experimental setup of the FµTP was further improved upon to achieve optimal coupling conditions in terms of the ion mobility spectrometry sensitivity and the plasma gas consumption. One major focus of this study was the adjustment of the electrical operation parameters, in particular, the high voltage amplitude, frequency and duty cycle, in order to minimize the electric field disturbances and yield higher signals. Additionally, the consumption of helium plasma gas was reduced by refining the FµTP. It was found that the ionization efficiency could be significantly enhanced by increasing the plasma high voltage and through application of a duty cycle up to 90:10. Plasma gas flows could be reduced down to 3 mL min-1 by increasing the plasma high voltage amplitude. Furthermore, a smaller wire electrode design enables the operation of the FµTP with nitrogen and clean air. Moreover, detection limits of a homologous series of ketones in the range of 330 pptv (N2-FµTP, 2-decanone) down to 20 pptv (He-FµTP, 2-octanone) could be reached in the optimized setup. To sum up, this feasibility study demonstrates the potential of the optimized FµTP as a powerful ionization source for ion mobility spectrometry especially with regard to ionization efficiency.

Optimal coupling condition analysis of free-space optical communication receiver based on few-mode fiber

Abstract Effective coupling between space light and optical fiber is one of the key technologies in free space optical communication. Few-mode fiber coupling is becoming a promising method to improve the performance of free space optical communication receiver. The dependence of the few-mode fiber coupling efficiency on the focal ratio, the central occlusion ratio and the numerical aperture are analyzed in this paper. The research results may be beneficial for the design of the receiver based on FMF coupling in the FSOC system.

Purification of plant-derived anti-virus mAb through optimized pH conditions for coupling between protein A and epoxy-activated beads

The main goal of this research was to determine optimum pH conditions for coupling between protein A and epoxy-activated Sepharose beads for purification of monoclonal antibodies (mAbs) expressed in plants. To confirm the effect of pH conditions on purification efficacy, epoxy-activated agarose beads were coupled to protein A under the pH conditions of 8.5, 9.5, 10.5, and 11.5 (8.5R, 9.5R, 10.5R, and 11.5R, respectively). A total of 300 g of fresh leaf tissue of transgenic Arabidopsis expressing human anti-rabies mAb (mAbP) SO57 were harvested to isolate the total soluble protein (TSP). An equal amount of TSP solution was applied to five resin groups including commercial protein A resin (GR) as a positive control. The modified 8.5R, 9.5R, 10.5R, and 11.5R showed delayed elution timing compared to the GR control resin. Nano-drop analysis showed that the total amount of purified mAbPSO57 mAbs from 60 g of fresh leaf mass were not significantly different among 8.5R (400 μg), 9.5R (360 μg), 10.5R (380 μg), and GR (350 μg). The 11.5R (25 μg) had the least mAbPSO57. SDS–PAGE analysis showed that the purity of mAbPSO57 was not significantly different among the five groups. Rapid fluorescent focus inhibition tests revealed that virus-neutralizing efficacies of purified mAbPSO57 from all the five different resins including the positive control resin were similar. Taken together, both pH 8.5 and 10.5 coupling conditions with high recovery rate should be optimized for purification of mAbPSO57 from transgenic Arabidopsis plant, which will eventually reduce down-stream cost required for mAb production using the plant system.

Design of silicon-wire waveguide ultracompact racetrack resonators: geometrical parameters for optimal coupling.

In this paper, it is shown that a suitable choice of the geometrical parameters of a silicon-wire waveguide microracetrack resonator structure can lead to a substantial improvement in the control of coupling coefficients and, hence, the design of ultracompact devices for high-performance channel add-drop filters and all-optical switching applications. On the one hand, some simple theoretical arguments and simulation results indicate that the reduction of the silicon-wire rectangular waveguide cross-section area (width×height) is possible, from standard (450 nm×220 nm) to (380 nm×200 nm) on both the bus and the resonator waveguides; this action, apart from still guaranteeing a quasi-TE single-mode operation, would provide an effective improvement into scale-of-integration by a 1.30 factor per device volume. On the other hand, it will be shown by a semianalytical method (analytical calculation + numerical simulation) that achieving the waveguide-racetrack optimal coupling condition for a particular application can be reduced to a prime calculation of the main resonator geometrical parameters (bend radius, straight length, air gap and overall coupling length). In particular, the design of high-performance ultracompact waveguide-racetrack resonator structures, with pre-established Q factor (Q≥2000), free spectral range (FSR≥15 nm), full width at half-maximum (FWHM≤5 nm), finesse (F≥40) or extinction ratio signals (ER≥20 dB) can be systematically obtained with this procedure.

Performance analysis of the infrared imaging system for aircraft plume detection from geostationary orbit.

In view of the optical detection requirements of wide-area and continuous surveillance of air targets, the detection ability of an infrared imaging system in geostationary orbit for aircraft plumes is studied. The point spread model of the subpixel imaging of the full chain, including the aircraft plume, the sea surface, the environmental atmosphere, the optical system, and the imaging detector is established. The detection ability of the typical imaging system in geostationary orbit is analyzed from the signal-to-noise ratio (SNR) and the detection range in combination with the effect of the point spread function (PSF) of the optical system. Meanwhile, the optimal coupling condition of the PSF to the spatial resolution is discussed. The imaging characteristics of the aircraft target on the focal plane of the infrared imaging system under different spatial sampling rates are simulated and verified. Research shows that the SNR of the system first increases, and then decreases gradually with an increase of the spatial sampling rate. The detectable range covered by the pixel footprint decreases as the detector size increases. When the detector size is 15, 20, and 30μm, the target can be detected with a spatial resolution of 200-700, 300-700, and 400-600m, respectively.

Experimental Determination of Optimal Conditions for Reactive Coupling of Biodiesel Production With in situ Glycerol Carbonate Formation in a Triglyceride Transesterification Process.

This study investigated a reactive coupling to determine the optimal conditions for transesterification of rapeseed oil (RSO) to fatty acid methyl ester (FAME) and glycerol carbonate (GLC) in a one-step process, and at operating conditions which are compatible with current biodiesel industry. The reactive coupling process was studied by transesterification of RSO with various molar ratios of both methanol and dimethyl carbonate (DMC), using triazabicyclodecene (TBD) guanidine catalyst and reaction temperatures of 50–80°C. The optimal reaction conditions obtained, using a Design of Experiments approach, were a 2:1 methanol-to-RSO molar ratio and 3:1 DMC-to-RSO molar ratio at 60°C. The FAME and GLC conversions at the optimal conditions were 98.0 ± 1.5 and 90.1 ± 2.2%, respectively, after 1 h reaction time using the TBD guanidine catalyst. Increase in the DMC-to-RSO molar ratio from 3:1 to 6:1 slightly improved the GLC conversion to 94.1 ± 2.8% after 2 h, but this did not enhance the FAME conversion. Methanol substantially improved both FAME and GLC conversions at 1:1–2:1 methanol-to-RSO molar ratios and enhanced the GLC separation from the reaction mixture. It was observed that higher methanol molar ratios (>3:1) enhanced only FAME yields and resulted in lower GLC conversions due to reaction equilibrium limitations. At a 6:1 methanol-to-RSO molar ratio, 98.4% FAME and 73.3% GLC yields were obtained at 3:1 DMC-to-RSO molar ratio and 60°C. This study demonstrates that formation of low value crude glycerol can be reduced by over 90% compared to conventional biodiesel production, with significant conversion to GLC, a far more valuable product.

Spectral and transmission properties of periodic 1D tight-binding lattices with a generic unit cell: an analysis within the transfer matrix approach

We report on the electronic structure, density of states and transmission properties of the periodic one-dimensional tight-binding (TB) lattice with a single orbital per site and nearest-neighbor hoppings, with a generic unit cell of u sites. The determination of the eigenvalues is equivalent to the diagonalization of a real tridiagonal symmetric u-Toeplitz matrix with (cyclic boundaries) or without (fixed boundaries) perturbed upper right and lower left corners. We solve the TB equations via the Transfer Matrix Method, producing analytical solutions and recursive relations for its eigenvalues, closely related to the Chebyshev polynomials. We examine the density of states and provide relevant analytical relations. We attach semi-infinite leads, determine and discuss the transmission coefficient at zero bias and investigate the peaks number and position, and the effect of the coupling strength and asymmetry as well as of the lead properties on the transmission profiles. We introduce a generic optimal coupling condition and demonstrate its physical meaning.

Design, Fabrication, and Characterization of a High Q Silica Nanobeam Cavity With Orthogonal Resonant Modes

We design and fabricate a high $Q$ silica nanobeam cavity that supports both transverse electric (TE) and transverse magnetic modes in the 1.55 $\mathrm{\mu }$ m wavelength range. The $Q$ values obtained for both modes exceed $10^4$ and are the highest reported values for photonic crystal (PhC) nanocavities made of silica. We also investigate the optimum conditions for coupling with the cavity in a side-coupled configuration. We achieve a coupling efficiency of 87% with the TE mode while maintaining a loaded $Q$ of more than $10^4$ . We also found that the presence of a coupled waveguide reduces the intrinsic $Q$ of the cavity, depending on the gap distance. This provides useful quantitative information for establishing an efficient scheme for coupling with low-index PhC nanocavities.

Detection of biomolecules and bioconjugates by monitoring rotated grating-coupled surface plasmon resonance

Plasmonic bio-sensing chips were prepared by fabricating wavelength-scaled sinusoidal dielectric-metal interfacial gratings on polymer film covered bimetal layers. Lysozyme biomolecules (LYZ) and gold nanoparticle bioconjugates (AuNP-LYZ) were seeded onto the biochip surfaces. Comparison of the reflectance curves measured in a modified Kretschmann arrangement and computed numerically proved that monitoring of the narrower secondary reflectance minima under optimal rotated-grating coupling condition makes it possible to achieve enhanced sensitivity in biodetection. The enlarged reflectance minimum shift is due to the horizontally and vertically antisymmetric long-range plasmonic mode, which originates from surface plasmon polariton Bragg scattering and propagates at the border of the valley and hill. The sensitivity is significantly increased in case of bioconjugates due to the coupled localized resonances on the gold nanoparticles.

Covalent coupling of high-affinity ligands to the surface of viral vector particles by protein trans-splicing mediates cell type-specific gene transfer.

We have established a novel approach for the covalent coupling of large polypeptides to the surface of fully assembled adeno-associated viral gene transfer vector (AAV) particles via split-intein mediated protein-trans-splicing (PTS). This way, we achieved selective gene transfer to distinct cell types. Single-chain variable fragments (scFvs) or designed ankyrin repeat proteins (DARPins), exhibiting high-affinity binding to cell surface receptors selectively expressed on the surface of target cells, were coupled to AAV particles harboring mutations in the capsid proteins which ablate natural receptor usage. Both, the AAV capsid protein VP2 and multiple separately produced targeting ligands recognizing Her2/neu, EpCAM, CD133 or CD30 were genetically fused with complementary split-intein domains. Optimized coupling conditions led to an effective conjugation of each targeting ligand to the universal AAV capsid and translated into specific gene transfer into target receptor-positive cell types invitro and invivo. Interestingly, PTS-based AAVs exhibited significantly less gene transfer into target receptor-negative cells than AAVs displaying the same targeting ligand but coupled genetically. Another important consequence of the PTS technology is the possibility to now display scFvs or other antibody-derived domain formats harboring disulfide-bonds in a functionally active form on the surface of AAV particles. Hence, the custom combination of a universal AAV vector particle and targeting ligands of various formats allows for an unprecedented flexibility in the generation of gene transfer vectors targeted to distinct cell types.

Catalytic Performance of Dicationic Ionic Liquids and ZnBr2 in the Reaction of Epichlorohydrin and Carbon Dioxide: Kinetic Study

Cyclic carbonate synthesis is an attractive route to utilize CO2 and reduce green house gas. Numbers of studies have been reported on catalytic synthesis of cyclic carbonate, however, very few studies reported on kinetic analysis of cycloaddition reaction. Present study reports a kinetic analysis for coupling reaction of epichlorohydrin (ECH) and carbon dioxide catalyzed by various dicationic ionic liquids (DILs) and zinc bromide. Effects of structural change of DILs on its catalytic activity towards cycloadditiion reaction have also been explored. In addition an attempt has also been made to discuss the plausible reaction mechanism at optimal reaction conditions for coupling of ECH and CO2. At a catalyst loading of 0.5 mmol% C6 (mim) (mim) Br2 and 0.25 mmol% ZnBr2, ECH conversion of 98% can be obtained at 90 °C and 3 MPa in 40 min. Maximum conversion efficiency (98%) and minimum activation energy (20 kJ/mol) was associated with catalytic system comprising of C6 (mim) (mim) Br2 and ZnBr2. Thus, from industrial application point of view C6 (mim) (mim) Br2 and ZnBr2 are potential catalysts for cyclic carbonate synthesis.

Application of weak ultrasonic treatment on sludge electro-osmosis dewatering

ABSTRACTUltrasonic treatment is a good method of facilitating sewage sludge dewatering characteristics. It can also promote the potential of sludge electro-osmosis dewatering (EDW), which is an accepted method of deep dewatering, but the treatment method and optimizing conditions should be determined by performing experiments. In this study, we consider two treating methods: ultrasonic pre-treatment, which uses ultrasonic treatment as sludge pre-treatment before electro-osmosis dehydration, and ultrasonic coupling, which uses ultrasonic and electric fields simultaneously. Using sludge from the Tianjin Jizhuangzi sewage treatment plant, we analyze the influence of ultrasonic intensity and treatment time on sludge dewatering by performing two different methods. The results show that they effectively facilitated sludge EDW. Under the same conditions, i.e. 2 cm cake initial thickness, voltage of 60 V for 5 min, and 0.1 MPa mechanical pressure for 5.5 min, the optimum processing conditions for ultrasonic pre-treatment were found to be 0.510 W/cm2 and 3.5 min, the dehydration rate reached 34.71%, and the optimum conditions for ultrasonic coupling were 0.255 W/cm2 and 3.5 min, while the dehydration rate reached 40.78%. The dehydration rates for both approaches were clearly better than 17.40%, which was obtained under pure electro-osmosis dehydration. To compare the effects of ultrasonic pre-treatment and ultrasonic coupling on the electro-osmosis dehydration process, in this paper, we present the curves of dehydration rate, electric current, electro-osmosis flow, and scanning electron microscopy for dewatered sludge. Compared with the ultrasonic pre-treatment method, the effect of ultrasonic coupling on electro-osmosis dehydration was more obvious.