Parameter B0 Research Articles

The Riemann–Hilbert approach for the Chen–Lee–Liu equation with higher-order poles

This paper considers the Riemann–Hilbert problem (RHP) with higher-order poles for the Chen–Lee–Liu equation. By assuming the scattering coefficients have Nth order zero points, we obtain expressions of these scattering coefficients, the theta condition, and parallelization conditions between Jost solutions and their derivatives. Based on these parallelization conditions, it yields generalizations of residue conditions, which are essential for solving the RHP with higher-order poles. The explicit formulae for solutions of CLL equation are reconstructed from asymptotic behaviors of the RHP. As an example, we present the second-order pole soliton and illustrate that parameter b0 plays a principal role to determine the structures of solutions of the CLL equation.

Perturbation of Wavelet Frames of Quaternionic-Valued Functions

Let L2(R,H) denote the space of all square integrable quaternionic-valued functions. In this article, let Φ∈L2(R,H). We consider the perturbation problems of wavelet frame {Φm,n,a0,b0,m,n∈Z} about translation parameter b0 and dilation parameter a0. In particular, we also research the stability of irregular wavelet frame {SmΦ(Smx−nb),m,n∈Z} for perturbation problems of sampling.

Model Optimization of a Shell and Tube Heat Exchanger by Using HGAPSO

The demand to develop an efficient heat exchanger have been prompted in order to save the energy and materials as well as economic incentives within the industry. To establish a reliable heat exchanger that be able to operate under its normal operating conditions, a model should reflect the true behaviour of the process itself. Modelling of heat exchanger helps to understand process that occurs during the operation. Hence, the primary objective of the project is developing a structural model using an ARX (Auto-Regressive with eXogenous input) equation. The data from experiment was used to determine the parameter of ARX equation. Using HGAPSO (Hybrid Genetic Algorithm and Partical Swarm Optimization) algorithm, ARX parameters are optimized to obtain the transfer function that represents the plant for modelling. Validation test of autocorrelation and cross-correlation were used to validate between normalised data input and error. Based on the result on the six order model, parameter a0, a1, a2, a3, a4, and a5 values are -0.00083, -0.00202, -0.00253, -0.00095, -0.00213 and -0.00275 while parameter b0, b1, b2, b3, b4 and b5 values are -0.7642, -0.5759, 0.3118, 0.0715, 0.1140 and 0.0683 respectively. From validation test, all graphs are within the 95 percent of confident line.

Aerodynamic-Parameter Identification and Attitude Control of Quad-Rotor Model with CIFER and Adaptive LADRC

Current research on quadrotor modeling mainly focuses on theoretical analysis methods and experimental methods, which have problems such as weak adaptability to the environment, high test costs, and long durations. Additionally, the PID controller, which is currently widely used in quadrotors, requires improvement in anti-interference. Therefore, the aforementioned research has considerable practical significance for the modeling and controller design of quadrotors with strong coupling and nonlinear characteristics. In the present research, an aerodynamic-parameter estimation method and an adaptive attitude control method based on the linear active disturbance rejection controller (LADRC) are designed separately. First, the motion model, dynamics model, and control allocation model of the quad-rotor are established according to the aerodynamic theory and Newton–Euler equations. Next, a more accurate attitude model of the quad-rotor is obtained by using a tool called CIFER to identify the aerodynamic parameters with large uncertainties in the frequency domain. Then, an adaptive attitude decoupling controller based on the LADRC is designed to solve the problem of the poor anti-interference ability of the quad-rotor and adjust the key control parameter b0 automatically according to the change in the moment of inertia in real time. Finally, the proposed approach is verified on a semi-physical simulation platform, and it increases the tracking speed and accuracy of the controller, as well as the anti-disturbance performance and robustness of the control system. This paper proposes an effective aerodynamic-parameter identification method using CIFER and an adaptive attitude decoupling controller with a sufficient anti-interference ability.

Vortex identification methods in marine hydrodynamics

In this paper, several commonly used vortex identification methods for marine hydrodynamics are revisited. In order to extract and analyse the vortical structures in marine hydrodynamics, the Q, λ2 — criterion and modified normalized Liutex/Rortex $$\it {\tilde\Omega_R}$$ method are utilized for vortex identification for propeller open water test, ship drag test, ship propeller-rudder interaction, VIV of a marine riser and VIM of a Spar platform. The limitation of Q and λ2 — criterion is discussed. The Liutex/Rortex $$\it {\tilde\Omega_R}$$ method is promising for convenient and accurate vortex identification and visualization. However, care should be taken when choosing the small parameter b0 for $$\it {\tilde\Omega_R}$$. We proposed recommended values of b0 for marine hydrodynamic problems.

Tuning spin-orbit coupling towards enhancing photocurrent in hybrid organic-inorganic perovskites by using mixed organic cations

Abstract The presence of the heavy elements leads to strong spin-orbit coupling (SOC) in hybrid organic-inorganic perovskites (HOIPs), which plays an important role in the photovoltaic performance of HOIPs by changing the populations between bright and dark states. The organic cation is a critical composition and affects SOC via the interaction with the inorganic cage. In this work, we use magneto-photocurrent measurement to explore the SOC effect upon using mixed organic cations (methylammonium (MA) and formamidinium (FA)) with different dipole moments in Pb based perovskites. Magneto-photocurrent measurements showed that the internal magnetic parameter B0 is decreased from 402.41 mT to 180.18 mT and 104.58 mT with decreasing the MA/FA ratio. This provides evidence that changing the internal dipole moment by using mixed organic cations can essentially change the SOC in HOIPs. Simultaneously, the photocurrent is increased from 21.46 mA/cm2 to 22.60 mA/cm2 and 23.08 mA/cm2 when the MA/FA ratio is changed from 1:0 to 0.9:0.1 and 0.7:0.3. Above all, our results indicate that the change in SOC by different organic cations can also be a factor affecting the performance of perovskite solar cells.

A simple model of bubble cluster dynamics in an acoustic field.

The dynamics of bubble clouds induced by ultrasound field are investigated in a regime where the cloud size is much smaller than the ultrasound wavelength. Two frequently used models describing the dynamics of individual bubbles inside a bubble cluster in an acoustic field are studied, one based on the homogeneity assumption, and the other based on the simultaneous motion assumption. A modified formula of the homogenization-based model is presented, and an inherent distinction in bubble-bubble interaction term is found in comparison to the simultaneous motion model. To gain insight into the mechanisms of such distinction, a reduced model unifying these two models is presented, and such distinction is explained by the spatial dependence of the bubble-bubble interaction in a bubble cluster accordingly. To validate the reduced model, the normalized distance γbb and the cloud interaction parameter B0 are used as two scaling parameters, and the comparison between the present model and the coupled Rayleigh-Plesset type equations is made. A conclusion is that, in the weak bubble-bubble interaction case (γbb>10), the reduced model can well reproduce the radial motion of bubbles in the cluster during the growth stage and the collapse stage in each acoustic cycle; in the strong bubble-bubble interaction case (γbb<10), the growth phase of bubbles in the cluster can be accurately predicted by the reduced model only if B0 or the amplitude of driving field is small.

On the Sources of the Ionospheric Variability in the South American Magnetic Anomaly During Solar Minimum

AbstractWe investigate for the first time the variability of the F2 layer critical frequency (foF2), its peak height (hmF2), the thickness parameter B0, and the E region critical frequency (foE) over Santa Maria (29.7° S, 53.7° W, dip angle = −37°), a station located in the central region of the South American Magnetic Anomaly. The selected ionospheric parameters were obtained from ionograms recorded by a recent Digisonde Portable Sounder 4‐D. The time period covers 309 days from 1 September 2017 to 30 August 2018. The diurnal analyses revealed a large day‐to‐day ionospheric variability, with some peculiarities as a strong semiannual pattern superimposed to expected ionospheric behavior. Furthermore, the results show significant differences between the averaged foF2 in December and June solstices, revealing a possible presence of the annual asymmetry. The coefficient of variation (CV) is used as a quantitative description of the variability of each parameter versus time and season. Considering low solar flux and geomagnetically quiet days only, we note that CV is smaller during the daytime and larger during nighttime for all parameters. The least variable ionospheric parameter in our study is foE, while the most variable one is B0. Regarding the F2 layer parameters, we observe that foF2 is much more variable than hmF2. We attribute the observed CV to the neutral atmosphere source over Santa Maria. The ionospheric variability is in general enhanced during geomagnetically disturbed periods. The estimated CV is higher over Santa Maria than Wuhan, China (30.5° N, 114.4° E, dip angle = 46°), a station with no influence of the South American Magnetic Anomaly.

Using Mechanical Stress to Investigate the Rashba Effect in Organic-Inorganic Hybrid Perovskites.

Organic-inorganic hybrid perovskites simultaneously possess strong spin-orbit coupling (SOC) and structure inversion asymmetry, establishing a Rashba effect to influence light emission and photovoltaics. Here, we use mechanical bending as a convenient approach to investigate the Rashba effect through SOC in perovskite (MAPbI3-xClx) films by elastically deforming grains. It is observed that applying a concave bending can broaden the line shape of the magnetophotocurrent, increasing the internal magnetic parameter B0 from 121 to 205 mT, which indicates an enhancement on SOC. Interestingly, the PL lifetime is found to be enlarged from 9.9 to 14.8 ns under this bending, which suggests that introducing compressive strain can essentially increase the Rashba effect through SOC, leading to an increase upon indirect band transition. Furthermore, the PL peak associated with the Rashba effect is shifted from 776 to 780 nm under this mechanical bending. Therefore, mechanical bending provides a convenient experimental method to approach the Rashba effect in hybrid perovskites.

Characterizing the crystal structure and formation induced plasticity of γ-hydride phase in zirconium

The crystal structures of γ-hydride in zirconium (Zr) in published literature has been reviewed. The confusion between two reported space groups for γ-hydride, namely tetragonal P42/n, and orthorhombic Cccm is then addressed experimentally in combination with crystal structure modelling. Micron-sized hydrides were determined to be γ-type through electron diffraction in Zr. Electron diffraction patterns (DPs) were acquired along different zones, from which firm criteria for the identification of γ-hydride was hence established. The lattice parameters of γ-hydrides were measured along two orthogonal directions, which reveal a non-equal lattice parameter a0 and b0, suggesting an orthorhombic structure. The γ-hydride formation induced plasticity in the surrounding matrix is determined by TEM characterization, including via in situ dissolution/precipitation studies. The dislocations are characterized to be type <a> dislocations, with various configurations depending on the size of the hydride.

Organic Single-Crystal Spintronics: Magnetoresistance Devices with High Magnetic-Field Sensitivity.

Organic spintronics is a new emerging field that deals with the spin-related phenomena of organic materials under the influence of a magnetic field. However, there remain some challenges in organic spintronics including (i) low conductivity and massive disorders of organic thin films blocking the way to controllable spin transport, (ii) relatively low magnetic-field sensitivity of organic magnetoresistance (OMAR) devices with tangled working mechanisms and short of methods for sensitivity improvement. Here, we report the realization of OMAR devices based on organic single crystals. The lesser amount of impurities and defects in crystals guarantees a reduction in spin and charge scatterings, so that the OMAR devices exhibit both a small Lorentz function fitting parameter B0 of 2.3 mT and a non-Lorentz function fitting parameter B1 of 0.86 mT in the strictly limited bipolaron model. Moreover, we demonstrate the effect of aggregation and intrinsic trap states, pointing out a way for the improvement of the sensitivity.

Coupled experimental assessment of physico-biochemical characteristics of municipal solid waste undergoing enhanced biodegradation

Seven municipal solid waste (MSW) specimens with variable initial waste compositions were biodegraded in large (d = 300 mm, h = 600 mm) laboratory landfill simulators under leachate-recirculation-enhanced anaerobic biodegradation conditions to investigate changes in the biochemical and physical characteristics of solid waste, leachate and biogas during biodegradation. The evolution with time of the monitored characteristics of the three phases was presented and the characteristics empirically correlated. The impact of the initial composition of waste on the biodegradation process was quantified. Although removal of soluble compounds in leachate, and methane (CH4) generation from waste was practically completed after around 300 days, changes in vertical strain, total unit weight and volumetric moisture content of waste continued in decreasing rates even after 1000 days. Methane generation potential (L0) of the waste was correlated to the percentage of biodegradable waste prior to degradation expressed by parameter B0. Maximum methane generation rate (rCH4,max) increased with increasing L0 and maximum soluble chemical oxygen demand in leachate. Final strain (or settlement) of waste due to anaerobic biodegradation (εB,f) increased with increasing B0 and L0. The compression ratio was found to vary during the process, although it is commonly assumed to be constant. The maximum long-term compression ratio increased with increasing εB,f and rCH4,max. The total unit weight at submerged and field capacity states and volumetric moisture content of waste were also dependent on the initial composition and compression (quantified by strain) of waste. The trends presented in this study contribute to the quantitative understanding of coupled processes during enhanced biodegradation of MSW of variable waste composition.

The Influence of Crude Oil on Mechanistic Detachment Rate Parameters

Iraqi soil contamination greatly influenced soil detachment. Previous researchers have not been able to predict the influence of crude oil soil contamination on either the mechanistic dimensional detachment parameter b0 or the threshold parameter b1 of the mechanistic detachment model (Wilson model). The aims of this research were (1) to investigate the influence of crude oil on deriving Wilson model parameters, b0 and b1, with two setups at different scales and different soil moisture contents and (2) to predict b0 and b1 in crude oil contaminated dry soils with varying levels of contamination. The “mini” JET apparatus was implemented under laboratory conditions for soil specimens packed at both a small (standard mold) and a large (in-situ soil box) scale. The results showed an inverse correlation between b0 and water content for clean soil. No correlation between b0 and soil moisture content was observed for contaminated soils. There was a huge reduction in the b0 value as the contamination time increased compared to the clean soil. This was related to the role crude oil plays in soil stabilization. Crude oil contamination significantly increased lead contamination level while slightly increasing the pH and total organic carbon. The influence of crude oil on mechanistic soil detachment can be predicted with a priori JET experiments on soils without crude oil based on crude oil parameters.

Bottom side profiles for two close stations at the southern crest of the EIA: Differences and comparison with IRI-2012 and NeQuick2 for low and high solar activity

Bottom side electron density profiles for two stations at the southern crest of the Equatorial Ionization Anomaly (EIA), São José dos Campos (23.1°S, 314.5°E, dip latitude 19.8°S; Brazil) and Tucumán (26.9°S, 294.6°E, dip latitude 14.0°S; Argentina), located at similar latitude and separated by only 20° in longitude, have been compared during equinoctial, winter and summer months under low (year 2008, minimum of the solar cycle 23/24) and high solar activity (years 2013–2014, maximum of the solar cycle 24) conditions. An analysis of parameters describing the bottom side part of the electron density profile, namely the peak electron density NmF2, the height hmF2 at which it is reached, the thickness parameter B0 and the shape parameter B1, is carried out. Further, a comparison of bottom side profiles and F-layer parameters with the corresponding outputs of IRI-2012 and NeQuick2 models is also reported. The variations of NmF2 at both stations reveal the absence of semi-annual anomaly for low solar activity (LSA), evidencing the anomalous activity of the last solar minimum, while those related to hmF2 show an uplift of the ionosphere for high solar activity (HSA). As expected, the EIA is particularly visible at both stations during equinox for HSA, when its strength is at maximum in the South American sector. Despite the similar latitude of the two stations upon the southern crest of the EIA, the anomaly effect is more pronounced at Tucumán than at São José dos Campos. The differences encountered between these very close stations suggest that in this sector relevant longitudinal-dependent variations could occur, with the longitudinal gradient of the Equatorial Electrojet that plays a key role to explain such differences together with the 5.8° separation in dip latitude between the two ionosondes. Furthermore at Tucumán, the daily peak value of NmF2 around 21:00 LT during equinox for HSA is in temporal coincidence with an impulsive enhancement of hmF2, showing a kind of “elastic rebound” under the action of the EIA. IRI-2012 and NeQuick2 bottom side profiles show significant deviations from ionosonde observations. In particular, both models provide a clear underestimation of the EIA strength at both stations, with more pronounced differences for Tucumán. Large discrepancies are obtained for the parameter hmF2 for HSA during daytime at São José dos Campos, where clear underestimations made by both models are observed. The shape parameter B0 is quite well described by the IRI-2012 model, with very good agreement in particular during equinox for both stations for both LSA and HSA. On the contrary, the two models show poor agreements with ionosonde data concerning the shape parameter B1.

Constraints on a k-dependent bias from galaxy clustering

We forecast the future constraints on scale-dependent parametrizations of galaxy bias and their impact on the estimate of cosmological parameters from the power spectrum of galaxies: in our approach we perform a Fisher matrix analysis with two different parametrizations of scale-dependent bias. The two main results obtained from the analysis are: first, allowing for a scale-dependent bias does not significantly increase the errors on the other cosmological parameters apart from the rms amplitude of density fluctuations, σ8, and the growth index γ, whose uncertainties increase by a factor up to two, depending on the bias model adopted. Second, we find that the accuracy in the linear bias parameter b0 can be estimated to within 1-2% at various redshifts regardless of the fiducial model. The non-linear bias parameters have significantly large errors that depend on the model adopted.

Variations of the ionospheric parameters and vertical electron density distribution at the northern edge of the EIA from 2010 to 2015 along 95°E and comparison with the IRI-2012

The vertical electron density profiles over Dibrugarh (27.5°N, 95°E, 43° dip) a low mid latitude station normally located at the northern edge of the EIA for the period of July 2010 till October 2015 are constructed from the measured bottom side profiles and ionosonde-GPS TEC assisted Topside Sounder Model (TSM) topside profiles. The bottom side density profiles are obtained by using POLAN on the manually scaled ionograms. The topside is constructed by the modified ionosonde assisted TSM model (TaP-TSM assisted by POLAN) which is integrated with POLAN for the first time. The reconstructed vertical profile is compared with the IRI predicted density profile and the electron density profile obtained from the COSMIC/FORMOSAT radio occultation measurements over Dibrugarh. The bottom side density profiles are fitted to the IRI bottom side function to obtain best-fit bottom side thickness parameter B0 and shape parameter B1. The temporal and solar activity variation of the B-parameters over Dibrugarh are investigated and compared to those predicted by IRI-2012 model with ABT-2009 option. The bottom side thickness parameter B0 predicted by the IRI model is found to be similar to the B0 measured over Dibrugarh in the night time and the forenoon hours. Differences are observed in the early morning and the afternoon period. The IRI doesn’t reproduce the morning collapse of B0 and overestimates the B0 over Dibrugarh in the afternoon period, particularly in summer and equinox. The IRI model predictions are closest to the measured B0 in the winter of low solar activity. The B0 over Dibrugarh is found to increase by about 15% with solar activity during the period of study encompassing almost the first half of solar cycle 24 but solar activity effect was not observed in the B1 parameter. The topside profile obtained from TaP profiler is thicker than the IRI topside in equinox from afternoon to sunrise period but is similar to the IRI in summer daytime. The differences in the bottom side may be attributed to the non-inclusion of ground measurements from 90°E to 100°E longitude in the ABT-2009 model while differences in the topside could be due the non-uniform longitudinal distribution of topside sounder profiles data and the stronger fountain effect in this longitude.

Spin–orbit interaction for the double ring-shaped oscillator

The spin–orbit interactions (SOI) for the single and double ring-shaped oscillator potentials are studied as an energy correction to the Schrödinger equation. We find that the degeneracy for the energy levels with angular quantum number m=0 keeps invariant in the case of the SOI. The degeneracy is still 2 for single ring-shaped potential and 4 for double ring-shaped potential. However, for the energy levels with angular quantum number m≠0 the degeneracy is reduced from original 4 for the single ring-shaped potential and 8 for the double ring-shaped potential to 2. That is, their energy levels in the case of the SOI are split to 2 (single) and 4 (double) sublevels. There exists an accidental degeneracy for the cases |m|=2,3,4,…. We note that around the critical value b0, the energy levels are reversed. We also discuss some special cases for η=2,3,4,5,6,…, and the b=0,c>0. It should be pointed out that the parameter b0 is relevant for the angular part parameter b in the single and double ring-shaped potentials and it makes the energy levels changed from positive to negative, but the parameter c corresponds to the angular part parameter in double ring-shaped potential and the η is related to it. This model can be useful for investigations of axial symmetric subjects like the ring-shaped molecules or related problems and may also be easily extended to a many-electron theory.

Probing [formula omitted] cosmology with sterile neutrinos via measurements of scale-dependent growth rate of structure

In this paper, we constrain the dimensionless Compton wavelength parameter B0 of f(R) gravity as well as the mass of sterile neutrino by using the cosmic microwave background observations, the baryon acoustic oscillation surveys, and the linear growth rate measurements. Since both the f(R) model and the sterile neutrino generally predict scale-dependent growth rates, we utilize the growth rate data measured in different wavenumber bins with the theoretical growth rate approximatively scale-independent in each bin. The employed growth rate data come from the peculiar velocity measurements at z=0 in five wavenumber bins, and the redshift space distortions measurements at z=0.25 and z=0.37 in one wavenumber bin. By constraining the f(R) model alone, we get a tight 95% upper limit of log10⁡B0<−4.1. This result is slightly weakened to log10⁡B0<−3.8 (at 2σ level) once we simultaneously constrain the f(R) model and the sterile neutrino mass, due to the degeneracy between the parameters of the two. For the massive sterile neutrino parameters, we get the effective sterile neutrino mass mν,sterileeff<0.62 eV (2σ) and the effective number of relativistic species Neff<3.90 (2σ) in the f(R) model. As a comparison, we also obtain mν,sterileeff<0.56 eV (2σ) and Neff<3.92 (2σ) in the standard ΛCDM model.

Synthesis and characterization of Zn-doped LiFePO4 cathode materials for Li-ion battery

Synthetic LiFe1-xZnxPO4 (0 ≤ x ≤ 0.26) samples have been prepared using wet chemistry method. The samples have been characterized by means of Rietveld structure refinement of Powder-XRD data and by Mössbauer spectroscopy. Impurities such as Li3PO4 and Fe2P have been detected in small amount and quantified by Rietveld analysis. No Zn-bearing impurity has been detected up to x=0.15, but significant amounts of LiZnPO4 have been observed in the samples with x ≥ 0.2. The unit cell volume of LiFePO4 decreases anisotropically with increasing Zn content (−0.7% of initial volume of 291.343Å3). Cell parameter (orthorhombic Pbnm space group, #62) b0 and c0 decrease with increasing Zn content, whereas a0 parameter is almost constant. The average <Li–O> and <Fe–O> interatomic distances in the M1 and M2 sites are almost constant, whereas the <P–O> distance slightly decreases (−1.4% of the initial value). Interestingly, O2–O1–O2 bond angle along the [001] direction decreases with increasing Zn-content, thus resulting in a marked decrease of the c0 axis length although the <M1-O> distance remains essentially constant. Mössbauer analyses show the majority of Fe to be divalent and located in an octahedral site similar to available literature data for LiFePO4. The Fe3+/(Fe3++Fe2+) ratio ranges from 0.10 to 0.17, and is not related to the Zn content. Preliminary electrochemical analyses of Zn doped samples in comparison to pristine LiFePO4 are reported.

Undrained Dynamic Strength Behavior of Saturated Nanjing Fine Sand under Wave Load

Cyclic vertical-torsional coupling tests were performed on saturated Nanjing fine sand with a relative density of 50% using a hollow cylinder apparatus. The effect of complex initial stress conditions on undrained dynamic strength of saturated Nanjing fine sand was investigated. It is shown that the initial confining pressure, p0, the initial stress ratio, R0, and the initial angle of maximum principal stress direction, α0, have great effects on the characteristics of the dynamic strength of Nanjing fine sand. The dynamic strength increases with p0 and R0, while it decreases with α0. The effect of initial intermediate principal stress parameter b0 on the dynamic strength is slight.