High Gain Values Research Articles

Consequences of flame geometry for the acoustic response of premixed flames

This study investigates the consequences of flame geometry for the linear response of laminar premixed flames to acoustic perturbations, as expressed by the flame transfer function (FTF). Analytical G-equation-based response models are derived for Slit, Bunsen and Wedge type flames; their respective characteristics are analyzed and validated against data obtained from high fidelity numerical simulations. Motivated by the poor agreement between numerical and analytical flame response predictions, particularly for Slit flames, an extension to the well-established incompressible-convective velocity model is proposed, which employs a Gaussian kernel function. Such a kernel disperses the flame response in time and leads to very good agreement with high fidelity numerical simulations. The validity of the model is further confirmed by comparing model predictions with experimental data taken from the literature. Analyzing the analytical flame response modeling concepts in detail, we find that the surface integration, which is required to compute the change of the global heat-release rate from the instantaneous flame front deflections, constitutes the most significant geometry-related property affecting the FTF. The linearized global heat-release rate of stiffly anchored Slit flames reacts only to movements of the flame tip and, hence, these flames respond time delayed to imposed flame front perturbations. Bunsen flames continuously transform convected flame front deflections to changes in the heat-release rate and, therefore, show a more pronounced low-pass behavior than Slit flames. The heat-release rate of Wedge flames reacts to both movements of the flame tip and the integral of instantaneous flame front deflections. Hence, perturbations of the flame front initially have a rather weak effect until they reach the flame tip, where a sudden and strong response is provoked. This leads to the occurrence of high peak gain values in the corresponding FTF.

Electrochemical noise measurement methodologies of chemical power sources

The electrochemical noise of a primary lithium battery was measured at an open circuit by two experimental approaches: with a filtering capacitor and with the same battery to eliminate open circuit voltage of the system under test. Both methodologies give the same results if they are applied correctly but they can sometimes cause experimental problems. Two experiments were carried out with battery discharge at resistive load. It was shown that it is very difficult to provide the conditions for properly operation of the two battery method to avoid saturation of measurement device when the amplifier uses high gain values.

Fabrication and Characterization of a High-Performance Multi-Annular Backscattered Electron Detector for Desktop SEM.

Scanning electron microscopy has been developed for topographic analysis at the nanometer scale. Herein, we present a silicon p-n diode with multi-annular configuration to detect backscattering electrons (BSE) in a homemade desktop scanning electron microscope (SEM). The multi-annular configuration enables the enhancement of the topography contrast of 82.11 nA/μm as compared with the commercial multi-fan-shaped BSE detector of 40.08 nA/μm. Additionally, we integrated it with lateral p-n junction processing and aluminum grid structure to increase the sensitivity and efficiency of the multi-annular BSE detector that gives higher sensitivity of atomic number contrast and better surface topography contrast of BSE images for low-energy detection. The responsivity data also shows that MA-AL and MA p-n detectors have higher gain value than the MA detector does. The standard deviation of measurements is no higher than 1%. These results verify that MA p-n and MA-AL detectors are stable and can function well in SEM for low-energy applications. It is demonstrated that the multi-annular (MA) detectors are well suited for imaging in SEM systems.

On Small Signal Frequency Stability under Virtual Inertia and the Role of PLLs

This paper presents a methodology that aims at identifying virtual inertia (VI) gain limitations from virtual synchronous generators (VSGs) while maintaining the frequency stability considering the delay associated with the frequency measurement process. The phase-locked loop (PLL) is typically used for frequency estimation that is used to calculate the rate of change of frequency (RoCoF) and it drives the VI loop. The PLL is generally accompanied by a low-pass filter that aims to suppress the impact of harmonics. This filter introduces a delay that when used with the VI control loop causes stability issues for high values of VI gain. A comparison of various PLL approaches suggests that certain variants tend to permit higher value of cut-off frequencies which can be utilized to increase the VI gain limit from VSG. This study presents a method by which the upper limit on VI gain can be quantified and related to the cut-off frequency of the PLL low pass filter that is indirectly representing the delay. It is performed using small signal frequency stability analysis on the frequency domain model of the grid with virtual inertia emulating VSG. The effective maximum VI gain from VSG is explored while satisfying the frequency measurement accuracy specification considering harmonics. The results show that the requirements of reaching a stable operation with sufficient stability margins can still be met with a faster PLL-based system and the potential increases in VI support from VSG can be quantified using the proposed method. The study has been first performed on a single machine single inverter bus (SMSIB) system and is generalized to the multi-machine and multi-inverter system.

Amplified spontaneous emission in polymer films doped with CdSe/CdS/ZnS colloidal quantum dots

Cd- and Pb-based colloidal quantum dots (QDs) and nanoplatelets are perspective materials for fabrication of active layers in photonic and plasmonic devices due to high values of optical gain (hundreds to 1200 cm−1) under sufficient pump conditions [1, 2]. To obtain an optical gain, these nanocrystals are usually deposited densely and close-packed. Several drawbacks like scattering and difficulties associated with fabrication of such layers limit their use. We report successful aggregate free doping of polymer layers with homogeneously dispersed CdSe/CdS/ZnS QDs and provide description of two compositions that can accommodate up to 30-50 mass. % of QDs. The compositions can be polymerized with usual acrylate photoinitiation process or via thiol-ene polymerization process. QDs are well dispersed before and after heat- and photopolymerization, form no aggregates and, thus, the formed layers are almost free from scattering losses. Amplified spontaneous emission (ASE) in QD doped polymers was observed with 532 nm wavelength laser excitation in the variable stripe length (VSL) configuration.

Charge Transport in Trap-Sensitized Infrared PbS Quantum-Dot-Based Photoconductors: Pros and Cons.

Control of quantum-dot (QD) surface chemistry offers a direct approach for the tuning of charge-carrier dynamics in photoconductors based on strongly coupled QD solids. We investigate the effects of altering the surface chemistry of PbS QDs in such QD solids via ligand exchange using 3-mercaptopropionic acid (MPA) and tetrabutylammonium iodide (TBAI). The roll-to-roll compatible doctor-blade technique was used for the fabrication of the QD solid films as the photoactive component in photoconductors and field-effect phototransistors. The ligand exchange of the QD solid film with MPA yields superior device performance with higher photosensitivity and detectivity, which is due to less dark current and lower noise level as compared to ligand exchange with TBAI. In both cases, the mechanism responsible for photoconductivity is related to trap sensitization of the QD solid, in which traps are responsible of high photoconductive gain values, but slow response times under very low incident optical power (<1 pW). At medium–high incident optical powers (>100 pW), where traps are filled, both MPA- and TBAI-treated photodevices exhibit similar behavior, characterized by lower responsivity and faster response time, as limited by the mobility in the QD solid.

THE MORPHOLOGY FEATURES OF NANOSTRUCTURE OF ZIRCONIUM, MOLYBDENUM AND WOLFRAM OXIDES SYNTHESISED BY LASER ABLATION OF METALS IN WATER

The paper gives the investigation results of composition and morphology of oxide nanostructures of transition metals – zirconium, molybdenum and wolfram synthesized by laser ablation pure metals in water. High temperatures and pressures in zone of interaction of the pulse laser beam with the surface of metal in water contribute to the intensive synthesis of oxides in the form of clusters of particles with size about 1−2 nanometres. This is characteristic for metals with high ionization potential. As it follows from the data of X-ray diffraction analysis and scanning electron microscopy, specifically, the clusters are amorphous building material for nanostructures of the oxides of the metals enumerated above. The paper demonstrates the general pattern of their structure, namely, the stratification of the material from which the foam formations, thin-walled hollow round particles, plates, filaments, and other forms of nanostructures are composed. The research of morphological features of the nanostructures of zirconium, molybdenum and wolfram oxides obtained by the authors indicates that their use as substrates will achieve high gain values of Raman scattering ~ 10 4 −10 8 . In this range, there are the gain data previously obtained by the authors in the experiments on the synthesis of zirconium nano-oxides when using them as a substrate. This indicates that the nanostructures of molybdenum and wolfram nano-oxides also can serve as the effective substrates and can be used as a sensor in the high sensitive composition of substances analyzers based on surface enhanced Raman scattering.

Cation Exchange Mediated Synthesis and Tuning of Bimodal Plasmon in Alloyed Ternary Cu3BiS3–xSex Nanorods

We report a robust methodology for synthesizing monodisperse alloyed Bi2S3–xSex nanorods (NRs) to tune optical properties with the variation of Se concentration. The intercalation of Cu(I) into the presynthetic Bi2S3–xSex NRs converted to ternary Cu3BiS3–xSex NRs via cation exchange process. The transformation was monitored through the formation of core/shell Bi2S3–xSex/Cu3BiS3–xSex nanorod heterostructures. Shape anisotropy results in near-infrared bimodal localized surface plasmon resonance (LSPR) in Cu3BiS3–xSex nanorod over a broad range from 600 to 3500 nm with increase of Se:S ratio. The LSPR sensitivity, defined as the change in the LSPR peak wavelength per unit change in the refractive index (RI) of the medium, was estimated to be 250–350 nm/RI unit, much higher than other copper chalcogenides like Cu2S/Cu2Se. A fast photodetector was fabricated by Cu3BiS3–xSex NRs with high photocurrent gain value (∼125) with Se alloying. The intrinsic Cu vacancies and the effective mass of charge carriers play i...

Highly Er3+ doped fluorotellurite glass for 1.5 µm broadband amplification and 2.7 µm microchip laser applications

The fluorescence properties in IR region of fluorotellurite glass with high Er3+ concentration up to 13 mol% are investigated and optimum concentration of 2.7 µm emission is 11 mol%, followed by a decrease in fluorescence intensity. The thermal characteristic parameter (ΔT = 98 °C) based on DSC curve shows a good thermal stability. The FWHM corresponding to 1.5 µm broadens as Er3+ increases and reaches a maximum of 110 nm (13 mol%) which shows superior bandwidth properties. The high amplifier gain value(σemi × τmea) of 11.87 × 10–21 cm2 ms, along with longer lifetime (1.72 ms), which benefits from the low phonon energy (612 cm−1) and hydroxyl content (0.03 cm−1), indicates the ideal 2.7 µm laser characteristics. Hopefully, the glass studied here may be find potential applications in the fields of fiber amplifier and MIR microchip lasers.

Sensor less control of PMSM fed from three phase four switch inverter based on back EMF observer and sliding mode controller with fast reaching law

Closed Loop control of PMSM drives require rotor position and angular velocity information, the use of position sensor increases cost of the drive and increases complexity in motor construction. A position sensor less vector control technique is proposed where a back EMF observer is used to estimate motors speed and position signal. Back EMF observer method is simple and has high accuracy in estimating speed of PMSM motor. Permanent magnet synchronous motor is fed from a three-phase four-switch inverter and sliding mode controller is used as a speed regulator. Fast reaching law is added to sliding mode speed controller, which replaces constant switching gain function by variable switching function based on sliding surface. Variable switching function for SMC eliminates the chattering problem that occurs due to high value of constant switching gain. The proposed reaching law for sliding mode controller reduces the time taken for the controller to reach convergence and also increases robustness of the drive during parameter variation and full load conditions. Use of sensor less control technique and four-switch inverter reduced the overall cost of the drive whilst maintaining the performance of the system. Merits of pro-posed sensor less control technique and sliding mode controller with fast reaching law is verified by simulations using MATLAB/Simulink software.

Genotype-by-environment effects on the performance of recombinant inbred lines of Virginia-type peanut

Peanut (Arachis hypogaea L.) is known to be sensitive to genotype-by-environment interaction (GEI) effects. While previous studies have reported strong GEI effects on peanut yield, most of those studies involved a relatively small number of unrelated genotypes. We examined the extent of GEI effects in elite Virginia-type peanut using a large population of recombinant inbreed lines (RILs). Two-hundred-sixty-six F7 RILs derived from different cultivars were grown in three environments. Net pod yield (NPY) was evaluated along with 11 other traits. ANOVA revealed that genotype and environment affected all of the examined traits, except for the triplet trait. The substantial influence of the environment was also demonstrated in a genetic-parameter analysis, in which the phenotypic variation coefficients were almost double those for genotypic variation. Still, relatively high heritability and genetic gain values were found for pod weight and NPY. Since NPY is the main target for selection, it was analyzed further. Path analysis showed that NPY is most directly influenced by pod weight and the shelling ratio. A significant GEI effect on NPY was identified using an AMMI model that described 42.7% of the total variation. This GEI component was subjected to a principal components analysis, which confirmed that the variability due to the different environments was greater than the variability that could be attributed to the different genotypes. Yet, several lines had stable yields across environments. These results demonstrate the importance of multi-location phenotyping for QTL analyses and crop improvement in peanut.

The performance evaluation of wideband rectangular patch antenna with elliptical slots for wireless communications

The aim of this paper is to design a novel rectangular microstrip patch antenna for different wireless applications. Antenna design composed of elliptical slots and is fed by microstrip transmission line. Here the partial ground plane is adopted to increase the impedance bandwidth of proposed antenna in comparison to variation in the length of ground plane. The antenna consists of partial ground plane length 31 mm exhibits the bandwidth of 1440 and 2160 MHz ranging from 1.56 to 3.00 GHz and 6.37 to 8.53 GHz, respectively. Proposed antenna is fabricated and the measured results are in good agreement with the simulated results. From the results, the impedance bandwidth of proposed antenna covers bluetooth (2400–2484 MHz), WiMAX (2500–2700 MHz), WLAN (2400–2485 and 5150–5850 MHz), downlink for X-band satellite communication (7250–7760 MHz) and point to point high speed wireless communication (5925–8500 MHz). Moreover the proposed antenna exhibits near omnidirectional radiation pattern and a high value of gain within the operating frequency ranges.

Wearable planar inverted‐F antenna with stable characteristic and low specific absorption rate

AbstractA dual band PIFA antenna with EBG structure in application to wearable communication system is investigated in this article. The proposed antenna is designed to work at 2.4/5.8 GHz WLAN band by two horizontal radiation units, and then the dual band EBG with two rectangular rings is designed, which is quite a simple structure. The two zero‐reflection phases and band‐gaps of S21&lt;−20 dB are observed in the designed working bands. Both of the measurement and simulation show that the performance of the proposed antenna under bending condition is stable, and by virtue of the EBG structures, several significant characteristics are obtained such as the unidirectional radiation, high gain, and low SAR value, which are necessary for WBAN applications.

A high gain dual-band printed antenna for LTE base stations with a corner reflector

A high gain dual-band printed antenna is proposed for LTE base stations applications. The established 60 × 60 mm2 broadband antenna structure is composed of two perpendicular U-shaped and L-shaped monopole antennas which are located vertically on ground plane printed on 1.6 mm thick FR4 substrate. A metallized wall is connected to the substrate which forms a corner reflector. A coaxial cable at the common center of the monopoles is adopted to excite the antenna. Wise implementation of the conductive elements and finely tuning of the monopoles dimensions yield the excitation of two resonances and dual band operation achievement. The presented antenna achieves bandwidths of 1.61–1.86 GHz and 2.25–2.45 GHz suitable for LTE applications. Stable radiation pattern, small size, cost effective fabrication, and high peak gain values of 10 dBi and 9.5 dBi at two operating bands are the prominent features of the proposed antenna topology.

Nd3+-doped heavy metal oxide based multicomponent borate glasses for 1.06 μm solid-state NIR laser and O-band optical amplification applications

Nd3+-doped glasses in the composition (50-x) B2O3-10 PbO-10 BaO-10 Al2O3-10 ZnO-10 Na2O-(x) Nd2O3 (x = 0.0, 0.1, 0.25, 0.5, 0.75, 1.0, 1.5, and 2.0 mol %) were fabricated using melt quenching method. Upon 592 nm visible and 808 nm LD excitations, the luminescence spectra show a strong 4F3/2 → 4I11/2 (1.06 μm) emission transition, and two less intense 4F3/2 → 4I9/2 (0.89 μm) and 4F3/2 → 4I13/2 (1.331 μm) emission transitions. The intensity of such emissions increases up to 0.5 mol % Nd3+, and above this doping level, quenching occurs. For 0.5 mol % Nd3+-doped glass, following Judd–Ofelt intensity parameters and emission spectrum, AR, τR, βR and βexp, including Δλeff,σem(λp), (σem × (Δλeff)) and (σem × (τrad)), are derived for Nd3+ ion 4F3/2 → 4I11/2 and 4F3/2 → 4I13/2 fluorescence transitions. The highest σem(λp) for the 1.06 and 1.331 μm fluorescence bands are found to be 6.216 × 10−20 and 2.295 × 10−20cm2, respectively. The 4F3/2 level lifetimes are found to decrease with an increase in Nd2O3 content and the decay curves of the glass up to 1.5 mol % Nd3+ exhibit single exponential nature. From ‘τexp’ of the Nd3+: 4F3/2 level, quantum efficiency (η), (σem × (τexp)), and saturation intensity (IS) are 48.87%, 51.09 × 10−25 cm2s and 3.67 × 108 W/m2, respectively, for the 0.5 mol % Nd3+-doped glass. Higher thermal stability, very low χ, high AR, large βexp., moderate τR, large gain bandwidth and high optical gain values indicate that 0.5 mol % Nd3+-doped glass could be a potential gain medium for solid-state NIR lasers at 1.06 μm. Moreover, for the 1.331 μm emission, large Δλeff and the theoretical gain coefficient value of 1.579 dB/cm, evaluated with an excited Nd3+ ion fractional factor of 0.6, indicate that this glass might be a promising candidate in developing O-band optical fiber amplifiers.

Thin Film Logic Circuits with Amorphous SiInZnO Channel Layer Annealed at Different Atmospheres for Next‐Generation Integrated Circuits

In this study, amorphous‐oxide‐based thin film logic circuits are fabricated using only an n‐type silicon‐indium‐zinc‐oxide (a‐SIZO) active channel layer annealed at different atmospheres (N2 or air). More carriers are present in the N2 atmosphere than in the air because the number of oxygen vacancies (VO) formed is higher. The inverters (NOT logic circuits) are simply fabricated by adopting different Vth, adjusted by using different annealing atmospheres. The inverters have high voltage gain values of 11.64 and 9.99 at VDD = 5 V. A higher gain is obtained when the thin film transistor annealed in N2 is used in the enhancement mode. The reason for this is closely related to the subthreshold slope value. Furthermore, more complex n‐type‐based NAND and NOR thin‐film circuits are fabricated by simply adopting different annealing atmospheres, and are confirmed to operate like the logic gates. This simple fabrication method of thin‐film logic circuits can open up the possibility for the implementation of next‐generation integrated circuits.

Colloidal lead iodide nanorings.

Colloidal chemistry of nanomaterials experienced a tremendous development in the last decades. In the course of the journey 0D nanoparticles, 1D nanowires, and 2D nanosheets have been synthesized. They have in common to possess a simple topology. We present a colloidal synthesis strategy for lead iodide nanorings, with a non-trivial topology. First, two-dimensional structures were synthesized in nonanoic acid as the sole solvent. Subsequently, they underwent an etching process in the presence of trioctylphosphine, which determines the size of the hole in the ring structure. We propose a mechanism for the formation of lead iodide nanosheets which also explains the etching of the two-dimensional structures starting from the inside, leading to nanorings. In addition, we demonstrate a possible application of the as-prepared nanorings in photodetectors. These devices are characterized by a fast response, high gain values, and a linear relation between photocurrent and incident light power intensity over a large range. The synthesis approach allows for inexpensive large-scale production of nanorings with tunable properties.

Genetic parameters estimation in quantitative traits of a cross of triticale (x Triticosecale W.)

Abstract Triticale (x Triticosecale Wittmack) is a cereal used in Argentina as a winter seasonal pasture or feeding grain. Efforts made on breeding have led to varieties with potential grain yield similar or greater than with wheat. The aim of this study was to determine the gene effects, heritability, genetic gain, heterosis and inbreeding depression in various quantitative traits of a cross from contrasting lines of triticale using generation means analysis. The thousand kernel weight was adjusted to a model of additive-dominance, while the rest of the traits exhibited significant epistatic effects: additive x additive (i) for hectoliter weight, additive x dominance (j) for number grains per spike and grain yield per plant. Other traits showed a more complex as inheritance additive x additive (i) and additive x dominance (j) interactions effects for spike length or additive x dominance (j) and dominance x dominance (l) interactions effects for number of spikes per plant and number of spikelets per spike. High values of heritability and genetic gain were also detected for grain yield, spikelets per spike, spike per plant and hectoliter weight. All traits except spike per plant had positive relative mid-parent heterosis, but none resulted in positive heterobeltiosis, therefore this cross is not recommended for obtaining hybrids varieties. Selection in early generations by thousand kernel weight and hectoliter weight would be efficient, while the selection in advanced generations where segregation is minimal would be recommended for the remaining traits.

Amorphous silicon-based micro-channel plate detectors with high multiplication gain

With their fast response time and a spatial resolution in the range of a few microns, microchannel plates (MCPs) are a prominent choice for the development of detectors with highest resolution standards. Amorphous silicon-based microchannel plates (AMCPs) aim at overcoming the fabrication drawbacks of conventional MCPs and the long dead time of their individual channels. AMCPs are fabricated via plasma deposition and dry reactive ion etching. Using a state-of-the-art dry reactive ion etching process, the aspect ratio, so far limited to a value of 14, could be considerably enhanced with a potential for very high gain values. We show first fabricated AMCP devices and provide an outlook for gain values to be expected based on the fabrication results.

Investigations on Mandarin Aspiratory Animations Using an Airflow Model

Various three-dimensional (3-D) talking heads have been developed lately for language learning, with both external and internal articulatory movements being visualized to guide learning. Mandarin pronunciation animation is challenging due to its confusable stops and affricates with similar places of articulation. Until now, less attention has been paid to the biosignal information of aspiratory airflow, which is essential in distinguishing Mandarin consonants. This study fills a research gap by presenting the quantitative analyses of airflow, and then designing an airflow model for a 3-D pronunciation system. The airflow information was collected by Phonatory Aerodynamic System, so that confusable consonants in Mandarin could be discerned by mean airflow rate, peak airflow rate, airflow duration, and peak time. Based on the airflow parameters, an airflow model using the physical equation of fluid flow was proposed and solved, which was then combined and synchronized with the existing 3-D articulatory model. Therefore, the new multimodal system was implemented to synchronously exhibit the airflow motions and articulatory movements of uttering Mandarin syllables. Both an audio-visual perception test and a pronunciation training study were conducted to assess the effectiveness of our system. Perceptual results indicated that identification accuracy was improved for both native and nonnative groups with the help of airflow motions, while native perceivers exhibited higher accuracy due to long-term language experience. Moreover, our system helped Japanese learners of Mandarin enhance their production skills of Mandarin aspirated consonants, reflected by higher gain values of voice onset time after training.