Continuous Inverse Research Articles

Experimental investigation on the performance of Electrical Submersible Pump (ESP) operating with unstable water/oil emulsions

Electrical Submersible Pump (ESP) is one of the most commonly used artificial lift methods in petroleum production, due to its capacity to operate in several conditions with two or three-phase flows. When the ESP operates with emulsion flow, its performance is degraded, and operational instabilities occur. Therefore, this paper aims to carefully investigate phase inversion and to present, by the first time, the effective viscosity of unstable mineral oil/water emulsions, within the ESP. The first part of this work analyzes the phase inversion phenomenon for two oil types in three viscosities, five ESP rotational speeds, and three mixture flow rates. Logistic functions were fitted using the dimensionless head as a water cut function to determine the phase inversion within the ESP. The continuous phase inversion model, developed for emulsion pipe flow, did not present a satisfactory agreement to flow conditions tested. An indirect method to determine the emulsion effective viscosity within the ESP was proposed, which was obtained from the water/oil emulsion performance curves. The viscous performance data were used to determine the parameters of a dimensionless head empirical model for the tested ESP. Thus, the calculated values were compared with the effective viscosity obtained with oil and water emulsions, as well as the ESP performance, operating with emulsion and oil, which provides similar values for low rotational speeds. The different behavior of the effective viscosity between the pipeline flow and within the ESP was observed for water-in-oil emulsions and may be related to the high centrifugal field in the ESP.

Extended Inverse Class-F Continuum for Designing Broadband Power Amplifier

The impedance space of the continuous inverse class-F power amplifier (PA) is extended in this paper. Traditionally, for extending impedance space, a reactive term is introduced into the current waveform of the continuous inverse class-F PA. In this paper, two reactive terms are introduced into the current and voltage waveforms simultaneously. The proposed method results in an expansive impedance space for designing broadband continuous inverse class-F PAs. For validating the proposed theory, a broadband PA working over 1.2–4.0[Formula: see text]GHz is designed and fabricated. Experimental results indicate that the fabricated broadband PA delivers a saturation power of 40.2–42.8[Formula: see text]dBm and a drain efficiency of 50.7–69%.

Analytic solutions of convolution equations on convex sets in the complex plane with an open obstacle on the boundary

Conditions, including criteria, are established for the existence of a continuous linear right inverse to a surjective convolution operator in the space of germs of analytic functions on a convex subset of the complex plane which has a countable neighbourhood basis consisting of convex domains. These are stated in terms of the existence of special families of subharmonic functions and the boundary behaviour of convex conformal mappings related to the sets in question. Bibliography: 50 titles.

Design of Dynamic Diffusion Simulation System for Atmospheric Pollutants in Coastal Cities under Persistent Inverse Temperature

Gong, Y. and Luo, X., 2020. Design of dynamic diffusion simulation system for atmospheric pollutants in coastal cities under persistent inverse temperature. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 526–529. Coconut Creek (Florida), ISSN 0749-0208.The prediction of the dynamic diffusion of atmospheric pollutants in coastal cities under continuous inverse temperature is the key to establish the dynamic treatment of atmospheric pollutants. In view of the low accuracy of the traditional nonlinear feature estimation simulation method, a continuous inverse temperature simulation model for the dynamic diffusion of atmospheric pollutants in coastal cities under continuous inverse temperature is proposed. A self-similar regression model is constructed for the statistical information of atmospheric pollutant dynamic diffusion in coastal cities under continuous inverse temperature, and a multi-scale decomposition and factor analysis are carried out for the time series of atmospheric pollutant dynamic diffusion in coastal cities under continuous inverse temperature. The simulation results show that the model has high accuracy and good convergence in the simulation and prediction of atmospheric pollutant dynamic diffusion in coastal cities.

Susceptibility and remanent magnetization inversion of magnetic data with a priori information of the Köenigsberger ratio

SUMMARY Magnetic susceptibility and natural remanent magnetization of rocks are useful parameters to study geological structures and geodynamic processes. Traditional widely used algorithms for the inversion of magnetic data can recover the distribution of the apparent susceptibility or total magnetization intensity, but do not provide information on the remanent magnetization. In this paper, we propose a framework to directly invert for the magnetic susceptibility and the natural remanent magnetization vector using surface or airborne magnetic data, assuming that the Köenigsberger ratio of the rock is known or approximately deducible. The susceptibility and remanence are computed using two different approaches: (1) the susceptibility, intensity, and direction of the remanent magnetization are continuously recovered for each discretized cell and (2) the remanence direction is assumed to be uniform in each subzone and is iteratively computed as discrete values. Both processes are implemented using the preconditioned conjugate gradient algorithm. The method is tested on three synthetic models and one field data set from the Zaohuohexi iron-ore deposit, Qinghai Province, northwest China. The results of the continuous inversion show the trend of the remanent magnetization directions, while the discrete inversion yields more specific values. This inversion framework can determine the source bodies’ geometry and position, and also provide superposed and comprehensive information on the natural remanent magnetization, which may be useful to investigate geological bodies bearing stable primary remanent magnetization.

Retrieval of Fine-Resolution Aerosol Optical Depth (AOD) in Semiarid Urban Areas Using Landsat Data: A Case Study in Urumqi, NW China

The aerosol optical depth (AOD) represents the light attenuation by aerosols and is an important threat to urban air quality, production activities, human health, and sustainable urban development in arid and semiarid regions. To some extent, the AOD reflects the extent of regional air pollution and is often characterized by significant spatiotemporal dynamics. However, detailed local AOD information is ambiguous at best due to limited monitoring techniques. Currently, the availability of abundant satellite data and constantly updated AOD extraction algorithms offer unprecedented perspectives for high-resolution AOD extraction and long-time series analysis. This study, based on the long-term sequence MOD09A1 data from 2010 to 2018 and lookup table generation, uses the improved deep blue algorithm (DB) to conduct fine-resolution (500 m) AOD (at 550 nm wavelength) remote sensing (RS) estimation on Landsat TM/OLI data from the Urumqi region, analyzes the spatiotemporal AOD variation characteristics in Urumqi and combines gray relational analysis (GRA) and the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to analyze AOD influence factors and simulate pollutant propagation trajectories in representative periods. The results demonstrate that the improved DB algorithm has a high inversion accuracy for continuous AOD inversion at a high spatial resolution in urban areas. The spatial AOD distribution in Urumqi declines from urban to suburban areas, and higher AODs are concentrated in cities and along roads. Among these areas, Xinshi District has the highest AOD, and Urumqi County has the lowest AOD. The seasonal AOD variation characteristics are distinct, and the AOD order is spring (0.411) > summer (0.285) > autumn (0.203), with the largest variation in spring. The average AOD in Urumqi is 0.187, and the interannual variation generally shows an upward trend. However, from 2010 to 2018, AOD first declined gradually and then declined significantly. Thereafter, AOD reached its lowest value in 2015 (0.076), followed by a significant AOD increase, reaching a peak in 2016 (0.354). This shows that coal to natural gas (NG) project implementation in Urumqi promoted the improvement of Urumqi’s atmospheric environment. According to GRA, the temperature has the largest impact on the AOD in Urumqi (0.699). Combined with the HYSPLIT model, it was found that the aerosols observed over Urumqi were associated with long-range transport from Central Asia, and these aerosols can affect the entire northern part of China through long-distance transport.

Highly efficient broadband continuous inverse Class‐F power amplifier using multistage second harmonic control output matching network

A multistage second harmonic control output matching network is proposed in this article. Through the fundamental and harmonic impedance matching at multiple frequencies in the target band, the accuracy of the fundamental and harmonic impedance of the continuous power amplifier is improved. The efficiency is improved consequently. A highly efficient broadband continuous inverse Class-F power amplifier based on this structure is designed and fabricated using a CGH40010F GaN HEMT packaged device. The measurement results demonstrate that drain efficiency of 71% to 82% and output power of 40.1 to 41.5 dBm is achieved with more than 10 dB gain across 1.35 to 2.35 GHz.

GMDS-ZNN Model 3 and its Ten-Instant Discrete Algorithm for Time-Variant Matrix Inversion Compared With Other Multiple-Instant Ones

The online time-variant matrix inversion problem has attracted extensive attention and study, because of its considerable appearance and application in scientific research and industrial production. For various control optimization problems, the demand for the high-precision and rapid-convergence of matrix inversion algorithm is increasing. It remains an ongoing challenge due to the rigorous requirements of precision and convergence of the algorithm. In this paper, on the basis of our previous works, by using Zhang neural network (ZNN) method, a continuous time-variant matrix inversion model, which is also a Getz-Marsden dynamic system (i.e., GMDS-ZNN model 3), is proposed. Besides, a general ten-instant Zhang et al discretization (ZeaD) formula is presented and investigated, with corresponding theoretical results being provided. Next, by applying this general formula to discretize the continuous time-variant matrix inversion model, a general ten-instant discrete time-variant matrix inversion (DTVMI) algorithm with the sixth-order precision is proposed. For comparison, four other DTVMI algorithms, with the second-, third-, fourth-, and fifth-order precisions, are also proposed and presented, respectively, by using other ZeaD formulas to discretize the continuous time-variant matrix inversion model. Besides, for the situation of coefficient matrix derivative being unknown, we provided the formula of estimating it with the fifth-order precision. With the help of the proposed matrix derivative estimation formula, the actual application field of GMDS-ZNN model 3 is expanded evidently. Finally, theoretical analyses and simulation experiment results highlight the effectiveness and accuracy of the proposed GMDS-ZNN model 3 and DTVMI algorithms.

Subordinated compound Poisson processes of order k

In this article, the compound Poisson process of order k (CPPoK) is introduced and its properties are discussed. Further, using mixture of tempered stable subordinators (MTSS) and its right continuous inverse, the two subordinated CPPoK with various distributional properties are studied. It is also shown that the space and tempered space fractional versions of CPPoK and PPoK can be obtained, which generalize the process defined in [Statist. Probab. Lett. 82 (2012), 852–858].

Solution to the Stieltjes moment problem in Gelfand–Shilov spaces

We characterize the surjectivity and the existence of a continuous linear right inverse of the Stieltjes moment mapping on Gelfand-Shilov spaces, both of Beurling and Roumieu type, in terms of their defining weight sequence. As a corollary, we obtain some new results about the Borel-Ritt problem in spaces of ultraholomorphic functions on the upper half-plane.

Exterior multiplication with singularities: a Saito theorem in vector bundles

Let $E$ be a vector bundle over a suitable differential manifold $M$ and let $\wedge^p E$ denote $p$-exterior product of $E$. Given sections $\omega_1,\dots,\omega_k$ of $E$ and a section $\eta$ of $\wedge^p E$, we consider the problem if $\eta$ can be written in the form $$\eta=\sum \omega_i\wedge\gamma_i,$$ where $\gamma_i$ are sections of $\wedge^{p-1}E$. An obvious necessary condition $\Omega\wedge\eta=0$, where $\Omega=\omega_1\wedge\cdots\wedge\omega_k$, has to be supplemented with a condition that the form $\Omega$ has sufficiently regular singularities at points where $\Omega(x)=0$. Such a local condition is suggested by an algebraic theorem of K. Saito and is given in terms of the depth of the ideal defined by coefficients of $\Omega$. Working in the smooth, real analytic and holomorphic (with $M$ Stein manifold) categories, we show that the condition is sufficient for the above property to hold. Moreover, in the smooth category it is sufficient for existence of a continuous right inverse to the operator defined by $(\gamma_1,\dots,\gamma_k)\mapsto\sum \omega_i\wedge\gamma_i$. All these results are also proven in the case where $E$ is a bundle over a suitable closed subset of $M$.

Design of Simulation System for Dynamic Diffusion of Marine Pollutants under Continuous Inversion

Wang, L. and Wang, Y., 2019. Design of simulation system for dynamic diffusion of marine pollutants under continuous inversion. In: Li, L.; Wan, X., and Huang, X. (eds.), Recent Developments in Practices and Research on Coastal Regions: Transportation, Environment and Economy. Journal of Coastal Research, Special Issue No. 98, pp. 129–132. Coconut Creek (Florida), ISSN 0749-0208.At present, research on the migration and transformation of pollutants in the ocean is limited to the single study of a certain pollutant, and there is no systematic summary. Most of them are qualitative descriptions, lacking quantitative calculation, which is not conducive to application. This paper systematically summarizes and expounds on the migration and transformation of pollutants in the ocean. With the continuous development of industry, marine pollution is becoming more and more serious. It is urgent to control marine pollution. Therefore, it is urgent to study quantitative systems. This urgency shows the importance and purpose of this research. This paper aims to systematically summarize and expound on the migration and transformation mechanism of pollutants in the ocean and establish its own pollutant migration and transformation system, which can be used in actual cases and test the effectiveness of the system through case studies.

Gaussian process models—II. Lessons for discrete inversion

Summary By starting from a general framework for probabilistic continuous inversion (developed in Part I) and introducing discrete basis functions, we obtain the well-known algorithms for probabilistic least-squares inversion set out by Tarantola & Valette (1982). In doing so, we establish a direct equivalence between the spatial covariance function that must be specified in continuous inversion, and the combination of basis functions and prior covariance matrix that must be chosen for discretised inversion. We show that the common choice of Tikhonov regularisation ($\mathbf {C_m^{-1}} = \sigma ^2\mathbf {I}$) arises from a delta-function spatial covariance, and that this lies behind many of the artefacts commonly associated with discretised inversion. We show that other choices of spatial covariance function can be used to generate regularisation matrices yielding substantially better results, and permitting localisation of features even if global basis functions are employed. We are also able to offer a straightforward explanation for the spectral leakage problem identified by Trampert & Snieder (1996).

Gaussian process models—I. A framework for probabilistic continuous inverse theory

SUMMARYWe develop a theoretical framework for framing and solving probabilistic linear(ized) inverse problems in function spaces. This is built on the statistical theory of Gaussian Processes, and allows results to be obtained independent of any basis, avoiding any difficulties associated with the fidelity of representation that can be achieved. We show that the results of Backus–Gilbert theory can be fully understood within our framework, although there is not an exact equivalence due to fundamental differences of philosophy between the two approaches. Nevertheless, our work can be seen to unify several strands of linear inverse theory, and connects it to a large body of work in machine learning. We illustrate the application of our theory using a simple example, involving determination of Earth’s radial density structure.

Investigation of Input–Output Waveform Engineered Continuous Inverse Class F Power Amplifiers

An in-depth analysis of the continuous inverse Class F power amplifier (PA) accounting for nonlinear input and output active device properties is presented. The analyses show possible ways of exploiting input nonlinearity to improve and maintain PA performance in a broadband operation and propose a flexible source second-harmonic design space which reduces the input matching network (MN) design complexities. Such exploitation of input nonlinearity can also alleviate performance degradation due to dynamic knee behavior of a practical field-effect transistor (FET) in continuous inverse Class F PA operation. The analyses are validated with vector load–pull (VLP) measurements and utilized to implement a broadband PA design. High-drain efficiency (DE) over 75% and output power more than 38 dBm are achieved over 0.8–1.4 GHz at constant 3-dB gain compression.

Controlling bifurcated continuous‐mode parameter for the continual operation of Class‐F−1 15 W GaN power amplifier

AbstractIn this article, we suggest a design method for an efficient inverse Class‐F 15 W Gallium Nitride (GaN) power amplifier (PA) that is minimally sensitive to the output parasitic capacitance. By utilizing the parasitic capacitance to control the bifurcated harmonic continuous mode parameters, the suggested design makes the power amplifier operate in continuous mode so that the output power and efficiency are maintained. Therefore, PA's performance degradation and uncertainty due to the parasitic component with its distribution values can be avoided or minimized. The implemented continuous inverse Class‐F mode PA demonstrated an output power of 42 dBm at 2.1 GHz, and an efficiency of more than 60% over 1.8 GHz to 2.4 GHz with a maximum efficiency of 71.9%.

A natural toroidal microswimmer with a rotary eukaryotic flagellum.

We describe Idionectes vortex gen. nov., sp. nov., a unicellular microeukaryote that swims by continuous inversion of its surface, similar to a vortex ring. This previously unreported mode of motility approximates a hypothetical concept called the 'toroidal swimmer', in which a doughnut-shaped object rotates around its circular axis and travels in the opposite direction to its outer surface motion. During swimming, the flagellum of Idionectes rotates relative to its cell body, which is normally a hallmark of prokaryotic rather than eukaryotic flagella.

Penalty method with Crouzeix–Raviart approximation for the Stokes equations under slip boundary condition

The Stokes equations subject to non-homogeneous slip boundary conditions are considered in a smooth domainΩ⊂ ℝN(N= 2,3). We propose a finite element scheme based on the nonconforming P1/P0 approximation (Crouzeix–Raviart approximation) combined with a penalty formulation and with reduced-order numerical integration in order to address the essential boundary conditionu · n∂Ω = gon∂Ω. Because the original domainΩmust be approximated by a polygonal (or polyhedral) domainΩhbefore applying the finite element method, we need to take into account the errors owing to the discrepancyΩ ≠ Ωh, that is, the issues of domain perturbation. In particular, the approximation ofn∂Ωbyn∂Ωhmakes it non-trivial whether we have a discrete counterpart of a lifting theorem, i.e., continuous right inverse of the normal trace operatorH1(Ω)N→H1/2(∂Ω);u↦u⋅n∂Ω. In this paper we indeed prove such a discrete lifting theorem, taking advantage of the nonconforming approximation, and consequently we establish the error estimatesO(hα+ε) andO(h2α+ε) for the velocity in theH1- andL2-norms respectively, whereα = 1 ifN = 2 andα = 1/2 ifN = 3. This improves the previous result [T. Kashiwabaraet al.,Numer. Math.134(2016) 705–740] obtained for the conforming approximation in the sense that there appears no reciprocal of the penalty parameterϵin the estimates.

Coupling phenomenon of anti-connected hybrid alignment nematics in thin cell: From submicron to nanoscale

Within Landau–de Gennes theory, we modeled a system consisting of two anti-connected hybrid alignment nematics (HAN). Our numerical simulation results indicated the occurrence of four states denoted as I, II, III and IV. The states undergo a structure transition as a function of the cell gap d. For d [Formula: see text] d0, where d0is the maximum value for the structure transition to occur, state I and II are bistable, whereas state III and IV are metastable and quadruply degenerate. We found that d0= 15[Formula: see text], where [Formula: see text] is the biaxial characteristic coherence length. When d[Formula: see text] [Formula: see text] d [Formula: see text] d0, where d[Formula: see text] = 7[Formula: see text] and d[Formula: see text] is the critical cell gap for order reconstruction (OR), continuous inversion walls appear both in state III and IV. We first found that the structure transition from inversion walls to defect walls occurs with decreasing d from the submicron to nanoscale. During this process, quadruply degenerate states in state III and IV transformed into doubly degenerate states. Meanwhile, states I and II remained bistable. When d = d[Formula: see text], all states reached a new type of OR pattern with two biaxial walls cross-linked with each other by a novel approach; i.e., from defect walls to OR.

Convexity and continuous linear operators with respect to the f-norm

In this paper, the analogues of various results are obtained in terms of a generalization of the norm called the f-norm. Convex sets are defined with respect to the f-norm and properties obtained. In addition, conditions are presented for the continuity of linear operators and also for the existence of a continuous inverse of a linear operator.