Sweep Parameters Research Articles

High-isolation Quad-port MIMO Antenna for 5G Applications

This paper presents a compact, high-isolation MIMO antenna with physical dimensions of 68 × 68 × 0.8 mm, designed for use in 5G applications. The antenna's bandwidth ranges from 3.25 GHz to 4.34 GHz and it offers a gain of 4.3 dBi, making it suitable for applications relying on 5G technology. Several improvements have been introduced to improve its overall efficiency, such as adjustments to the ground plane and integrating apertures in the radiating patch. The alterations referred to above were optimized using the sweep parameter method to ensure that their best configurations are achieved. Furthermore, much attention has been paid to enhance isolation by ensuring all terminals are positioned precisely at 90° angles. The CST Studio Suite was utilized to design and thoroughly simulate the proposed MIMO antenna.

A Modified Polygon Shaped Microstrip Patch Antenna Array for Ultra-Wideband Applications

A single element and two elements array polygon shape microstrip antenna is proposed and analyzed in this paper for ultra-wideband (UWB) applications. The technique used to improve antenna performance is etching rectangular slots on the patch of the antenna with different dimensions and positions. Two Polygon Shape antenna patches are introduced to enhance the antenna properties. Also, multi-slots are reached to improve the antenna gain, impedance matching sweep parameter optimization technique is used to all antenna parameters to enhance antenna properties. The dimensions of the single element antenna are 30 x 33 mm2 and consist of a slotted polygon patch printed on an FR-4 substrate. The proposed antenna has a resonant frequency of 6.2 GHz, while the dimensions of two elements antenna array are 60 x 33 mm2 and the resonance frequency is 9.8 GHz. A technique of inset feed transmission line was utilized to match the 50 Ω microstrip feed line and the radiating patch. These considerations make the structure is suitable for fifth-generation generation (5G) mobile wireless applications. The proposed antenna was simulated by use Computer Simulation Technology (CST-2020) software.

A Numerical Investigation on Effects of Hydrogen Enrichment and Turbulence on NO Formation Pathways in Premixed Ammonia/Air Flames

ABSTRACT NO x emission reduction is one of the major challenges when using ammonia/hydrogen blends as an alternative fuel for carbon-free combustion. In this study, chemical reaction pathways of NO formation in planar premixed flames of stoichiometric ammonia/hydrogen/air at atmospheric pressure and reactants temperature of 298 K are investigated under laminar and decaying turbulent conditions using quasi-DNS with detailed chemistry and the mixture-averaged transport model. The sweep parameter, , is the volumetric ratio of hydrogen to the ammonia/hydrogen mixture. Here, for unstrained laminar conditions, = 0, 0.4, and 0.6 and for turbulent condition, = 0.4 within the thin reaction zones region ( 34.2) are studied. Under 1D laminar conditions, increasing enhances NO formation drastically, around 3 times when comparing = 0 and 0.6. At different , despite the high activity of the reactions which belong to the Zeldovich pathway, the contribution of this pathway is insignificant in NO formation. However, HNO and N2O pathways have the most significant roles. For instance, at = 0.4, R85 (NH+NO N2O+H) in the N2O pathway and R144 (HNO+H NO+H2) in the HNO pathway have major roles in NO formation. Higher NO formation at larger is found to be due to the increased H and O radicals within the reaction zone as well as the increased reaction rates because of the higher flame temperature. Under the 3D turbulent condition ( = 0.4), it is observed that turbulence does not switch the pathways trends across the flame brush compared to the laminar condition. In the reaction zone, however, it is observed that NO formation is lower (higher) in the regions convex (concave) toward the reactants. The underlying reason for this effect is the preferential diffusion of H2 to the regions of the flame front convex toward the reactants, which consumes NO and also depletes O and OH radicals, which are necessary for NO formation.

Applicability of multiple stress creep and recovery test for the analysis of fatigue resistance of bituminous mastics

Rheological assessment of mastics can provide better insight into estimating the resistance of the mixtures against fatigue since it is the real binder coating the aggregate skeleton. The primary purpose of this study is to assess the suitability of MSCR test to analyze the fatigue resistance of bituminous mastics prepared using waste (GP and KS), composite (GL), and conventional SD fillers. Additionally, the fatigue resistance of mastics was also determined using Linear amplitude sweep (LAS) and fatigue parameter analysis and all results were compared with the fatigue performance of bituminous mixes. The correlation between mixtures and mastics prepared with SD filler is very strong in all the approaches, that is, LAS (R 2 = 0.92), % R (R 2 = 0.93), and fatigue parameter (R 2 = 0.95). For GP, it is strongest in % R (R 2 = 0.78) whereas for KS the correlation was highest in the LAS test (R 2 = 0.92) which shows that correlation analysis yields mixed results. The ranking methodology showed a similar ranking between fatigue life of mixes and the percent recovery whereas the ranking of other parameters was different. The test results showed that the % R can also be a promising parameter for the fatigue analysis of the bituminous mastics in addition to the existing fatigue damage parameters.

Numerical study on transverse mixing characteristics of flow sweeping in helical cruciform rod bundle

Fluoride salt serves as a coolant in the fluoride-salt-cooled high-temperature reactor and flows through the reactor core to remove heat produced by the nuclear fuel. To enhance the flow heat transfer performance of coolant in the fuel assembly, helical cruciform fuel rods are designed as a foundation fuel element. In the present study, the numerical method in helical cruciform rod bundle is used to analyze the transverse mixing characteristics of flow sweeping. A heat transfer fluid (Dowtherm A) flows and transfers heat by convection along the heated wall of helical cruciform rod. The fluid in the helical cruciform rod bundle exhibits a substantial flow sweeping crossflow phenomena as a result of the impact of the helical structure. The transverse mixing velocity and temperature profiles are analyzed. The subchannel conservation equation is optimized, and the correlation between flow sweeping mixing parameters and dimensionless local gap distance in various Reynolds number ranges is determined by fitting. Furthermore, the maximum of flow sweeping mixing parameter of the helical cruciform rod bundle is more than seventy times greater than the turbulent mixing parameter's maximum of the cylindrical rod bundle under an identical Reynolds number. It can be concluded that the helical cruciform rod bundle has considerable transverse mixing, which enhances the flow heat transfer performance of the reactor core. This study provides a guide for the numerical study of flow heat transfer in helical structures, and a foundation for the development of the subchannel mixing model.

Error revising of blade tip-timing parameter identification caused by frequency sweep rate

Blade tip-timing (BTT) is a rotating blade vibration measurement technology. It is a universal and effective method to acquire blade tip displacement data by frequency sweep and identify vibration parameters by single-parameter method. However, when the frequency sweep rate is too large, the vibration parameters obtained by single-parameter method will have large errors because the transient response cannot be immediately attenuated. For this problem, a dimensionless frequency sweep parameter is introduced, and two methods are proposed in this paper. When the engine order is known, an improved single-parameter method is proposed. For the unknown engine order, a revised method of vibration parameters is proposed. The effectiveness of the proposed two methods has been verified by simulation and experiment data. The results showed that when the frequency sweep parameter is between 0.3 and 15, the improved method and the revised method both significantly improve the vibration parameter identification accuracy.

Precise characterization of VCSEL in the 1550 nm band having a wavelength tuning range of 12 nm within 10 µs as light sources for fast sensor systems

Abstract. A wavelength tuning range up to 12 nm has been achieved over 12 µs pump current pulses within a usable time of 10 µs applied to VCSELs operating in the near infrared around 1550 nm. The instantaneous optical frequency shift has been measured with an interferometric setup; the overall tuning range has then been verified with an optical spectrum analyzer. The repetition rate of the current pulses can be as high as 20 kHz with almost no influence on the sweep parameters. These results can be used for fast spectroscopic gas analysis or for rapid interferometric swept-source distance sensors.

Three-dimensional sweeping motion effects on hovering dragonflies

This paper describes numerical simulations of the typical hovering mode of dragonfly wings with different sweeping motions. The simulation process involves solving the three-dimensional unsteady Navier–Stokes equations and exploring the effects of the sweeping motion on aerodynamic performance. Various parameters related to the three-dimensional sweeping motion are studied, including the sweeping amplitude, phase difference between flapping and sweeping motions, asymmetry of sweeping amplitudes of the forewing and hindwing, and frequency of sweeping motion. The results show that as the sweeping amplitude of the forewing and hindwing increases from 0 to 35°, the time-averaged lift and the lift efficiency increase by ∼4 times and ∼3.6 times respectively, while the power consumption first decreases and then increases. Moreover, increasing the sweeping amplitude delays the shedding of the trailing edge vortex. A phase difference of ∼60° between flapping and sweeping maximizes efficiency and the change in phase difference can lead to vertical forces in opposite directions on the forewing and hindwing. Accordingly, the flow field interference between the two wings will be more serious. Greater symmetry between the sweeping amplitudes of the two wings leads to better lift performance. There is an optimal sweeping frequency which is also the same as the flapping motion, representing an elliptical trajectory that can make lift ∼0.75 times higher. The optimal combination of various sweeping motion parameters may contribute to better aerodynamic performance in the hovering state. This research provides theoretical guidance for the design of dragonfly-like aircraft with multiple degrees of freedom.

Enhanced frequency-modulated continuous-wave generation by injection-locking period-one oscillation in a semiconductor laser with an intensity modulated comb.

We report on an enhanced photonic generation of frequency-modulated continuous-wave (FMCW) signals by injection-locking a semiconductor laser operating in period-one (P1) nonlinear dynamic with an intensity modulated electro-optic frequency comb. When the cavity mode is injection-locked with respect to any of the comb modes, through linearly sweeping the frequency of the injected comb mode while synchronously modulating the injected intensity, the center wavelength of the cavity mode can be tuned following the injected comb mode. This way, it allows maintaining the phase-locking between the cavity mode and comb mode even if beyond the original locking bandwidth of the cavity mode, since it is tuned accordingly. It thus leads to the generation of FMCW signal with efficient phase noise suppression and improved achievable sweep range compared with the limited original injection-locking bandwidth. Such injection enhanced phase-locking is investigated and a demonstration with the injection of -4th order comb mode has realized photonic FMCW generation with enhanced sweep range and suppressed phase noise. Thanks to the flexibility in sweep parameters, this method can also be readily applied for the generation of arbitrary waveforms.

Sonoluminescence emission spectra of a 3.6 MHz HIFU in sweeping mode

Use of sweeping mode with a 3.6 MHz High Intensity Focused Ultrasound (HIFU) allows cavitation activity to be controlled. This is especially true in the pre-focal zone where the high concentration of bubbles acts as an acoustic reflector and quenches cavitation above this area. Previous studies attributed the enhancement of cavitation activity under negative sweep to the activation of more bubble nuclei, requiring deeper investigations. After mapping this activity with SCL measurements, cavitation noise spectra were recorded. The behavior of the acoustic broadband noise follows the sonochemical one i.e., showing the same attenuation (positive scan) or intensification (negative scan) of cavitational activity. In 1 M NaCl 3.7 mM 2-propanol solution saturated by a mixture of Ar-15.5%O2-2.2%N2, intensities of SL spectra are high enough to allow detection of several molecular emissions (OH, NH, C2, Na) under negative frequency sweeps. This is the first report of molecular emissions at such high frequency. Their intensities are low, and they are very broad, following the trend obtained at fixed frequency up to 1 MHz. Under optimized conditions, CN emission chosen as a spectroscopic probe is strong enough to be simulated, which is reported for the first time at such high frequency. The resulting characteristics of the plasma do not show any spectral difference, so bubble nature is the same in the pre-and post-focal zone under different sweeping parameters. Consequently, SL and SCL intensification was not related to a change in plasma nature inside the bubbles but to the number of cavitation bubbles.

Formula omitted]-plume geothermal in fluvial formations: A 2D numerical performance study using subsurface metrics and upscaling

CO2-plume geothermal (CPG) operations are considered for sufficiently permeable formations due to their superiority compared to conventional water-based geothermal systems. The fluvial heterogeneity in sedimentary reservoirs can significantly affect the pumping energy losses and heat extraction from hot sedimentary aquifers. In the present study, we have implemented the braided type of fluvial channels to account for the geological uncertainty, and investigated the subsurface performance metrics of a CPG system with a checkers-board pattern. An optimization of doublet/well spacing is performed based on the coefficient of performance (CoP), energy sweep parameter, and an objective function (f) defined specifically for optimization of the process. In addition, a sensitivity analysis on the grid resolution, braided channel thickness and orientation, and the injection flow rate and span of the supercritical (sc)-CO2 is performed. The upscaled grid resolution mainly affects the pressure-related parameters, including CoP and f, resulting in an average error of 80% and 60% between the fine- (120 × 120) and the coarse-scale (15 × 15), respectively. As a result, the grid resolution of 60 × 60 with dx≈16.5 m is found to have both acceptable average error and optimum runtime. The optimum doublet/well spacing for the present case is about L=450 m, in which the CPG system provides about 9 to 13 times higher values of f compared to cases with doublet/well spacing higher or lower than the optimum value. Moreover, injection wells with I1-I2 line parallel to channels’ orientation, provide about 30% higher f compared to the perpendicular case. However, channels’ orientation does not change the optimum doublet/well spacing (L=450 m).

Enhancement of gain using a multilayer superstrate metasurface cell array with a microstrip patch antenna

This research presents a new idea in the use of wireless communication antennas: it uses a multi-layered array of cells called a superstrate multi-layer metasurface (MTM) and is placed in front of a patch of microstrip antenna to absorb surface waves and prevent them from passing through the insulating material, which reduces the permeability of the insulator and thus improves the Antenna properties, The proposed hexagonal cell with resonators is placed on the flame resistant (FR4) substrate, with a relative permittivity of 4.3 and an area (14×14) mm2 . It was tested when the metasurface layer is 4 mm in front of the patch and the distance between the metasurface layers is 2 mm. The optimum distances were calculated by the sweep parameter, and the improved antenna gain and the input reflection coefficient were obtained together. (S11) has been improved from -31.217 to -38.338 dB and, the gain from 3.28 dB to 6.554 dB.

A Super Wideband Directional Compact Vivaldi Antenna for Lower 5G and Satellite Applications

In this paper, a super wide band (SWB) Vivaldi antenna has been proposed for lower 5G bands in Sub-6 GHz and satellite applications (S, C, X, Ku, and K band) using various performance improvement techniques. In the presented Vivaldi antenna, different slots are applied not only to increase the gain and directivity but also to get operating frequency at the intended specific frequency range. All dimensions of those slots were chosen by using the sweep parameter method. Ten corrugated side slots, two circular slots, and one via have been used to enhance the performance especially bandwidth and gain of the antenna. At the edge of wireless communication, we want to enhance two key aspects within the communication systems: the quality of service and the cost. The proposed antenna incorporates a simple structure and small size with dimensions of 45 × 35 × 0.79 mm3. Thus, after design, optimization, and simulation, the antenna produces a good reflection coefficient over the very large operating bandwidth of 23.19 GHz, 1 < VSWR < 2, maximum gain of 10.2 dBi, and average radiation efficiency of above 90%, which can be recommended as a suitable antenna for lower 5G as well as satellite applications. The antenna is designed, simulated, and analyzed by using computer simulation technology microwave studio (CST-MWS). Finally, the performance of the Vivaldi antenna has been validated by FEKO and HFSS software, and we achieved a very good matching among the results.

DESIGN OF ULTRA-WIDEBAND ANTENNA WITH NOTCHED BANDS TO REJECTING UNWANTED BANDWIDTH

Design of Ultra-Wideband ring patch antenna with a band notch is presented in this study. The elliptical antenna is modified to Ultra-wideband at a range (3.1-10.6) GHz using a Microstrip patch antenna with the feedline impedance 50 ohm and rectangular each side of the elliptical patch has a slot. The dimensions optimized by the sweep parameter for the proposed antenna are (40 x 40 x 1.6) mm3 to provide a band notch and remove the (3.1–3.7 GHz) WiMAX band and (7.1 GHz) X-band, a rectangular-shaped slot etched on the patch is used. Inserting slots changing the current distribution is used in the patch to control the band notches. The results demonstrate that the suggested X-band and WiMAX designs are removed, with a 5.35dB peak gain and an omnidirectional radiation pattern, and suited for UWB.

Analysis of the DRT as Evaluation Tool for EIS Data Analysis

The Distribution of Relaxation Times (DRT) is an important analysis tool that is capable of giving initial information from Electrochemical Impedance Spectra (EIS) with respect to the number of relaxation processes occurring in the system and their corresponding relaxation frequencies. From this the possible number of circuit elements for the equivalent circuit model in the nonlinear least square fit of the data can be selected. There are several techniques and possibilities to perform the transformation [1–3], nevertheless every possibility has its limitation and/or will remain an ill-posed problem [4]. For our EIS data, the DRT transformation with the Tikhonov regularization is used for further analysis. Hence, we want to understand and more precisely describe the effects of this transformation together with occurring pitfalls on the most commonly implemented circuit elements used to describe EIS data for characterizing Solid Oxide Fuel or Electrolysis Cells (SOFC/SOEC) operating at high temperatures. Therefore, a database with the future possibility of pattern recognition is created for DRT transformations on selected circuit elements like a resistor in series with a finite length diffusion or Warburg-short element (R-Ws) or a resistor in parallel with a constant phase element (RQ). A parameter interval is selected for each occurring element. The origin for these data comes from a series of experiments where quite well fitting Equivalent Circuit Models (ECM) were analyzed with respect to their minimum and maximum values per element. Depending on the coverage of the interval, useful intermediate numbers are selected in order to perform parameter sweeps for every possible combination together with a downstream DRT transformation step. We obtain the behavior of the DRT transformation as a function of the individual circuit element parameters and can evaluate which occurring peaks belong to a circuit element and which ones are artefacts or numerical issues in the transformation. Additionally, the regularization parameter (λ) is taken as a sweep parameter as well to see its influence on the transformation. From both perspectives, we can state a range of optimal numbers of recorded data points per decade of frequency for experiments. We also can give a direction for selecting λ depending on what exactly is to be evaluated with the respective DRT transformation. Additionally, we are able to categorize peak-forming behavior of the transformation since the selected ECMs are known and so, in theory, its transformation result. Knowledge for the DRT behavior is also useful for modeling the electrolysis process where theoretical characteristics (i-V, EIS data) are calculated in order to validate and evaluate the model. Figure caption: Figure 1: The DRT transformation of the model RQ-RQ is converted into the frequency domain with a variation of αP1 from 0.5 to 1.0. The fixed parameters are q1 = 10-1 S, r1 = 0.303 Ω, q2 = 10-2 S, r2 = 0.303 Ω, αP2 = 0.8, λ = 10-7.

Analysis of the DRT as Evaluation Tool for EIS Data Analysis

The Distribution of Relaxation Times (DRT) is an important analytical tool that is capable of giving initial information from Electrochemical Impedance Spectra (EIS) with respect to the number of relaxation processes occurring in the system and their corresponding relaxation frequencies. The DRT transformation with the Tikhonov regularization is used for analysis of EIS data obtained from the characterization Solid Oxide Fuel and Electrolysis Cells (SOFC/SOEC) operating at high temperatures. The effects of this transformation together with occurring pitfalls on the most commonly implemented circuit elements used to describe EIS data was investigated to gain a better understanding. The behavior of the DRT transformation as a function of the individual circuit elements is reported, the regularization parameter λ is taken as a sweep parameter to investigate its influence and optimal ranges for the selection of λ are presented.

Effect of sweep parameters on correlation wavelet

Vibroseis is an important seismic exploration method whose sweep signal parameters vary with rock layers deep in the earth. Controlling of sweep signal frequency band is extremely useful method in vibroseis data acquisition. The vibrator is a controlled energy source employed in seismic methods. Nowadays it is widely used and preferable seismic source for land seismic exploration. Suitable input signal is typically a sinusoid that changes frequency within a bandwidth. To obtain high-quality subsurface images, amplitude of the sweep signal and Klauder wavelet is important parameter of vibroseis. In this study, amplitude of Klauder wavelet variations with respect to different sweep parameters are investigated; tests have been made based on a variety of sweep numbers, sweep length, peak force ratio and sweep bandwidth. The results have been compared with theoretical values and the tested parameters are evaluated in the shot and processing domain.

Numerical Modeling of Schottky Barrier Diode Characteristics

Herein, a comprehensive model is presented for the calculation of entire current–voltage (IV) characteristics of Schottky contacts (SCs). This treatment allows to analyze in detail the physical and technological origins of empirical fit parameters like the ideality factor. This model considers variations of the semiconductor net doping density in growth direction and barrier height inhomogeneities. The only input parameters required are the doping profile, the mean value, and the standard deviation of the barrier height distribution as well as material parameters. As measuring conditions like the integration time impact measured IV characteristics, similar sweep parameters as applied during a measurement are included in the model and proven to be necessary for the understanding of charging currents and the shift of the voltage for zero current. Using this model, various nonidealities reported in literature are explained. Further, the influence of differently doped interfacial layers on the characteristics is studied. Finally, the model is applied to multiple datasets of IV characteristics of SCs on different materials published in literature and from this laboratory, enabling a fundamental understanding of the origins of the nonidealities observed as well as the distinction between the contributions of different transport mechanisms to the total current.

Modeling of detection techniques for FMCW lidar using OptiSystem

In this paper, we investigated the frequency modulation continuous wave (FMCW) lidar rang measurement principle, then designed a simulated distance measurement scheme and building the model. Using the OptiSystem system modeling simulation, the relationship between frequency modulation (FM) bandwidth, FM time and rang measurement accuracy is investigated, and the effect of different sweep parameters on the accuracy of the final rang measurement results is discussed in the time and frequency domains. The simulation tests the delay of the target at 30, 60 and 90 meters respectively, and the distance is derived by beating the frequency of the optical echo signal with the local oscillation optical signal and calculating the beat frequency.

Nondestructive, Self-Contained Extraction Method of Parasitic Resistances in HEMT Devices

This article addresses the classical problem of determining the extrinsic resistances ( $R_{G}$ , $R_{S}$ , and $R_{D}$ ) of field-effect transistors (FETs) and, in particular, of high-electron-mobility transistors (HEMTs). The presented approach relies on small-signal measurements of open-channel transistors, as often proposed both for traditional metal–semiconductor FETs (MESFETs) and HEMTs. Unlike what is common practice with HEMTs, the method proposed here does not oversimplify the model of the active channel. On the contrary, we retrieve from the literature a possible analytical model for the open-channel HEMT and use it to determine the triplet of extrinsic resistances without the need of stressing the gate junction with too high currents. Another result of the approach, valid both for MESFETs and HEMTs, is a deterministic way to remove the contribution of the gate junction from the small-signal parameters of the measured devices. All extractions process data that are available on suitable ranges in frequency or in bias voltage, without taking to the limit the sweep parameters or seeking specific resonances. Also, optimizations are only allowed to refine the nominal values, not as the main technique of extraction. These goals are achieved by setting up different subproblems in the form of overdetermined linear systems and then solving by pseudoinversion. The validity of the approach is demonstrated on the measurements of devices from advanced HEMT technologies realized by OMMIC, both GaAs-based (40-nm gate length) and GaN-based (100 and 60 nm).