Two-dimensional Variation Research Articles

Performance comparison of different flow arrangements of 4-fluid internally-cooled liquid desiccant dehumidifiers

In this study, the performance of 10 different flow arrangements of 4-fluid internally-cooled liquid desiccant dehumidifiers were compared. The four fluids are supply air, exhaust air, liquid desiccant, and water. The comparison was performed using a two-dimensional heat and mass transfer model of the dehumidifier that was solved numerically. The model’s predictions of supply air outlet humidity ratio matched experimental measurements within 6.7%. The two-dimensional variation of the air temperature and humidity ratio in the supply channel showed the importance of using a two-dimensional heat and mass transfer model when at least one of the fluids is in cross-flow with the other fluids. Moreover, a sensitivity analysis was performed to evaluate the effect of nine input parameters (supply air temperature and humidity ratio, exhaust air temperature and humidity ratio, liquid desiccant temperature, concentration, and flow rate, supply air mass flow rate, and exhaust to supply air mass flow rate ratio) on the performance of the dehumidifiers. The results showed that the best performance, in terms of the supply air humidity ratio and enthalpy decrease, was obtained when the supply air was in counter-flow with the exhaust air, liquid desiccant, and water. While the poorest performance was obtained when the supply air was in parallel-flow with the exhaust air and in counter-flow with the liquid desiccant and water. The approximate difference between the best and poorest performing flow arrangements in terms of the decrease in supply air humidity ratio and enthalpy is 4.3% and 10.5%, respectively. The results of the sensitivity analysis showed that for the 10 flow arrangements, the liquid desiccant inlet temperature, and flow rate have the least effects on the performance of the dehumidifier.

Dispersion of Rayleigh Surface Waves and Electrical Resistivities Utilized to Invert Near Surface Structural Heterogeneities

The single-station Rayleigh surface wave group velocities and electrical resistivities are two data sets that we cooperatively employ to image the near surface (< 40-m) anomaly structures. We numerically simulate the corresponding field measurements where the anomaly structures are assumed to have two-dimensional (2D) variations. The surface waves are represented by fundamental mode dispersion curves, and the electrical resistivities are assumed to be measured by using direct currents. We consider two types of anomaly structures, i.e., cavity and ore body. These two heterogeneities are easily distinguished from the surrounding geomaterial by their distinct physical properties. The cavity is characterized by low seismic velocity and high electrical resistivity, while the ore body is characterized by high seismic velocity and low electrical resistivity. The Rayleigh surface wave data is assumed to be collected throughout the classical common-shot gather. Multiple electrodes, multiple core cables, and multiple arrays are assumed to be used in the electrical survey. Both surface wave group velocities and electrical resistivities are shown to properly invert the anomalous structures in the subsurface. The surface wave group velocities have good horizontal resolution, while the corresponding vertical resolution is somewhat lower. The electrical resistivities have good resolution for shallow structures, but the resolution becomes somewhat reduced with increasing depth. Doi: 10.28991/HEF-2022-03-01-01 Full Text: PDF

Exactly solvable 2D model for photon propagation in curved space: loss of interference and Bell inequality violation

We present an exact solution for the propagation of quantized massless scalar particles in a two-dimensional variation of the Alcubierre metric. Classical localized wavepacket solutions are derived using closed expressions for light-ray coordinates, and corresponding annihilation operators are constructed using the concept of locally positive and negative frequencies. The theory is used to describe the loss of fringe visibility in a single-photon interferometer, and the reduction of entanglement between two 2D photons, if one photon travels through a region with spacetime curvature. We derive an expansion of the field operator in terms of localized modes by means of an over-completeness relation. The quantization procedure also applies to massive and charged scalar fields in an n-dimensional globally hyperbolic spacetime.

A Novel Imaging Algorithm for High-Resolution Wide-Swath Space-Borne SAR Based on a Spatial-Variant Equivalent Squint Range Model

High-Resolution Wide-Swath (HRWS) is an important development direction of space-borne Synthetic Aperture Radar (SAR). The two-dimensional spatial variation of the Doppler parameters is the most significant characteristic of the sliding spotlight space-borne SAR system under the requirements of HRWS. Therefore, the compensation of the two-dimensional spatial variation is the most challenging problem faced in the imaging of HRWS situations. The compensatory approach is then proposed to address this problem in this paper. The spatial distribution of the Doppler parameters for the HRWS space-borne SAR data in the sliding spotlight working mode is firstly analyzed, based on which a Spatial-Variant Equivalent Slant Range Model (SV-ESRM) is put forward to accurately formulate the range history for the distributed target. By introducing an azimuth-varying term, the SV-ESRM can precisely describe the range history for not only central targets but also marginal targets, which is more adaptive to the HRWS space-borne SAR requirements. Based on the SV-ESRM, a Modified Hybrid Correlation Algorithm (MHCA) for HRWS space-borne SAR imaging is derived to focus the full-scene data on one single imaging processing. A Doppler phase perturbation incorporated with the sub-aperture method is firstly performed to eliminate the azimuth variation of the Doppler parameters and remove the Doppler spectrum aliasing. Then, an advanced hybrid correlation is employed to achieve the precise differential Range Cell Migration (RCM) correction and Doppler phase compensation. A range phase perturbation method is also utilized to eliminate the range profile defocusing caused by range-azimuth coupling for marginal targets. Finally, a de-rotation processing is performed to remove the azimuth aliasing and the residual azimuth-variance and obtain the precisely focused SAR image. Simulation shows that the SAR echoes for a 20 km × 20 km scene with a 0.25 m resolution in both the range and azimuth directions could be focused precisely via one single imaging processing, which validates the feasibility of the proposed algorithm.

A peridynamic approach for modeling of two dimensional functionally graded plates

This study investigates the crack initiation and its progression in two-dimensional functionally graded (FG) plates under dynamic and quasi-static loading conditions by using an ordinary state-based PeriDynamic (OSB PD) theory. Functionally gradient materials (FGMs) are a new class of advanced materials that provide a smooth transition among the layers of materials to meet the desired requirements in engineering structures. The effective material properties in the FG plate were functionally tailored in two directions by employing a rule of mixture. The present OSB PD theory is very suitable for the failure analysis of materials without the use of surface and volume correction factors. The robustness of the present approach on monitoring the mixed-mode fractures is established with the experimental results under various loading conditions. The PD predictions successfully captured the critical load levels and damage evolutions. Subsequently, numerical analyses were carried out to assess the influence of the one- and two-dimensional material variations, boundary, and loading conditions on the fracture behavior of the FG plates. The compositional gradient exponent played a major role on the reaction force levels and crack trajectories. It was observed that two-dimensional material variations paved the way for increasing the plate strength and fracture resistance.

Fornax 3D project: Assessing the diversity of IMF and stellar population maps within the Fornax Cluster

The stellar initial mass function (IMF) is central to our interpretation of astronomical observables and to our understanding of most baryonic processes within galaxies. The universality of the IMF, suggested by observations in our own Milky Way, has been thoroughly revisited due to the apparent excess of low-mass stars in the central regions of massive quiescent galaxies. As part of the efforts within the Fornax 3D project, we aim to characterize the two-dimensional IMF variations in a sample of 23 quiescent galaxies within the Fornax cluster. For each galaxy in the sample, we measured the mean age, metallicity, [Mg/Fe], and IMF slope maps from spatially resolved integrated spectra. The IMF maps show a variety of behaviors and internal substructures, roughly following metallicity variations. However, metallicity alone is not able to fully explain the complexity exhibited by the IMF maps. In particular, for relatively metal-poor stellar populations ([M/H] ≲ −0.1), the slope of the IMF seems to depend on the (specific) star formation rate at which stars were formed. Moreover, metallicity maps have systematically higher ellipticities than IMF slope ones. At the same time, both metallicity and IMF slope maps have at the same time higher ellipticities than the stellar light distribution in our sample of galaxies. In addition we find that, regardless of the stellar mass, every galaxy in our sample shows a positive radial [Mg/Fe] gradient. This results in a strong [Fe/H]–[Mg/Fe] relation, similar to what is observed in nearby, resolved galaxies. Since the formation history and chemical enrichment of galaxies are causally driven by changes in the IMF, our findings call for a physically motivated interpretation of stellar population measurements based on integrated spectra that take into account any possible time evolution of the stellar populations.

Social insurance law and corporate financing decisions in China

This study investigates whether and how social security contributions affect corporate financing decisions. Treating the 2011 Social Insurance Law in China as a quasi-natural experiment, our difference-in-differences framework utilizes two-dimensional variations: initial social security contribution rates across firms (i.e., high vs. low) and year (i.e., before and after 2011). We find that more social security contributions cause firms to issue less debt in their capital structure, particularly firms with more severe labor market frictions, greater labor intensity, unhealthier financial status, tighter financial constraints, and those located in low-income areas with less developed financial systems and greater fiscal pressure. Mechanism tests show that firms’ operating leverage, bank credit default risk, and profitability volatility increase, while the supply of trade credit decreases, which is consistent with the financial distress hypothesis. The findings suggest that firms tend to choose conservative financing policies to mitigate the likelihood of financial distress caused by increasing social security contributions.

Numerical modeling of low-frequency waves on a reef island in the South China Sea during typhoon events

Low-frequency waves with infragravity and very-low-frequency bands have been found to induce coastal flooding and erosion on low-lying reef islands under storm conditions. The aim of this study is to investigate the dynamics of low-frequency waves around an atoll reef island in the South China Sea, Dongsha Island, during a large typhoon event. A Boussinesq-type wave model, FUNWAVE-TVD, is applied to reproduce nearshore wave dynamics that caused severe erosion on the southern coast of the island. The interactions between waves with different incident directions and the localized atoll topography are examined. Modeled alongshore significant wave heights, wave setups, infragravity waves and very-low-frequency waves on the southern coast are first examined. The results show that alongshore low-frequency waves increase, and wave setup decreases as incident wave angles decrease. Eastward low-frequency edge waves are dominant in all incident wave directions. Comprehensive two-dimensional wave variations are further used to illustrate the interplay between incident waves and the localized atoll geometry. Infragravity and very-low-frequency waves are energetic around the eroded position of the shoreline with nearly shore-normal incident waves. Specifically, the shapes of very-low-frequency waves are highly asymmetrical, suggesting that very-low-frequency waves play a crucial role in affecting erosion and sedimentation during the typhoon events.

CT and MRI image fusion algorithm based on hybrid [formula omitted] layer decomposing and two-dimensional variation transform

Image fusion of CT and MRI significantly improves the diagnosis of diseases. This study proposes a novel CT and MRI image fusion algorithm based on hybrid ℓ0ℓ1 layer decomposition and two-dimensional variation transforms to reduce the loss of complementary features. From the characteristics of CT and MRI images, the two-dimensional variation transform is used to separate the low-frequency and high-frequency features of the MRI image to preserve all detailed features of MRI. Then, the separated low-frequency feature images and the CT image are transformed by hybrid ℓ0ℓ1 layer decomposing to separate the edge features and contour features. Furthermore, the separated feature images are synthesized separately to obtain the fusion images of different features such as edge and contour feature fusion images. Finally, the fusion images of different features are reconstructed to obtain the final fusion images. Experiments show that the fusion algorithm better fuses the complementary features of different images and reduces the loss of information.

Spectroscopic behavior of alloxazine-based dyes with extended aromaticity: Theory vs Experiment

Abstract The chemical and electronic structure of parent (iso)alloxazine and their eight aromatic derivatives as possible candidates for dyes usage were systematically investigated by the Density Functional Theory. The effect of condensation by various (mostly benzene-like) aromatic moieties to the initial benzo[g]pteridine moiety on the energies of frontier molecular orbitals and spectroscopic properties - absorption, and emission characterization, was discussed. The spectroscopic behavior experimentally measured in alkaline dimethylsulfoxide for parent alloxazine, and its four available derivatives were compared with the theoretical predictions. In this context, the optical properties of iso-tautomers and deprotonated species were also theoretically quantified. Impact of chain modification relating to several linear and two-dimensional structure variations on electron structure and optical properties was analyzed. The correlations between theoretical estimation and experiment were proposed and could be helpful for future synthesis of novel molecules in optoelectronics or biosensing technology.

Mathematical Study of Two-Dimensional Temperature Variation in Tumor Embedded Breast Tissue

The human body is made by 100 trillion cells. The uncontrolled and abnormal growth of cells causes tumors. Due to the presence of tumor, the skin surface temperature of body provides abnormal behavior than normal. Most of the breast tumor develops in lobules and milk ducts of glandular layer. In this study, tumor is assumed in glandular layer. The study of this work is focused to find the temperature distribution in tumor embedded female breast tissue with different tumor location and different tumor size. For this, the finite element method is used to solve two-dimensional Pennes bio heat equation. The results show that the skin surface temperature of breast is higher with nearest tumor from areola. The temperature variation in breast tissue with tumors located at symmetrical position about the central line of the breast are identical.

2D model simulating the hydro-rheological behavior of leather during convective drying

An experimental and numerical study of a two-dimensional spatio-temporal variation of the temperature, moisture content, and mechanical stress during the convective drying process of unsaturated and deformable products (leather) were conducted. The bovine leather sample response under convective drying is described by a mathematical model. The leather sample was modeled by an elastic medium, and the mass, heat, and momentum transfer principles are applied. The numerical results agreed well with the corresponding experimental data. The variation of the internal temperature and moisture content was simulated for different drying conditions. A reduction by 15 °C was noted in the optimum temperature for best product quality when the drying air relative humidity was 20%. The cost to achieve a better quality product was found to be minimized due to the decrease in the optimum temperature. The presented simulation results of the elastic material could be applied to the leather, which will reduce the needed time of exposure for predetermined final water content. The damage of the sample is more likely to occur at the beginning of the drying in the time interval of 300–400 s. According to these simulations, the sample’s face, which is exposed to the drying air, has the highest stress; therefore, the sample’s face is at a high risk of cracking. It is also observed that the risk of damage to the sample corresponding to the maximum level of the stress is higher for the highest drying temperature of 60 °C. The peak of the three thicknesses of leather can be achieved for normal stresses in the interval of 60,000 to 140,000 MPa at around 10,000 s.

Elevation Spatial Variation Analysis and Compensation in GEO SAR Imaging

Due to geosynchronous synthetic aperture radar’s (GEO SAR) high orbit and low relative speed, the integration time reaches up to hundreds of seconds for a fine resolution. The short revisit cycle is essential for remote sensing applications such as disaster monitoring and vegetation measurements. Three-dimensional (3D) scene imaging mode is crucial for long-term observation using GEO SAR. However, this mode will bring a new kind of space-variant error in elevation. In this paper, we focus on the analysis of the elevation space-variant error. First, the decorrelation problems caused by the spatial variation are presented. Second, by combining with the SAR imaging geometry, the elevation spatial variation is decomposed into two-dimensional (2D) space variation of range and azimuth. Third, an imaging algorithm is proposed to solve the 3D space variation and improve the focusing depth. Finally, simulations with dot-matrix targets and distributed targets are performed to validate the imaging method.

The effect of corrosion spatial randomness and model selection on the ultimate strength of stiffened panels

ABSTRACT The main objective of this study is to investigate the effect of non-uniform thickness reduction and model selection on the predicted ultimate strength of stiffened panels under longitudinal compression. Random fields theory is used to describe the two-dimensional variation of thickness over the plates’ surface. Non-Gaussian sample functions are thus generated using the spectral representation method in combination with translation fields, whereas Monte Carlo simulation is employed to compute the response statistics. The paper provides an insightful guide for the implementation of stochastic finite element method (SFEM) into a deterministic FE software such as Abaqus. The evaluation of stiffened panel's ultimate strength variation due to the described inherent uncertainties of thickness and model selection, namely, the CSR load-end shortening curves analytical relations versus SFEM, is implemented. The results revealed that the uniform thickness approach of CSR using the net-50 scantlings provides a reasonable conservatism on the predicted ultimate strength.

Fluid–Structure Interaction Modeling of Elastohydrodynamically Lubricated Line Contacts

Abstract This paper presents a partitioned fluid–structure interaction (FSI) solver to model elastohydrodynamic lubrication (EHL) of line contacts. The FSI model was constructed using the multiphysics simulation software ansys, wherein an iterative implicit coupling scheme is implemented to facilitate the interaction between fluid and solid components. The model uses a finite volume method (FVM) based computational fluid dynamics (CFD) solver to determine the lubricant flow behavior using the Navier–Stokes equations. Additionally, the finite element method (FEM) is utilized to model the structural response of the solid. Fluid cavitation, compressibility, non-Newtonian lubricant rheology, load balance algorithm, and dynamic meshing were incorporated in the FSI model. The pressure and film thickness results obtained from the model are presented for a wide range of loads, speeds, slide to roll ratios (SRR), surface dent, material properties (elastic plastic), etc. The model presents a detailed understanding of EHL contacts by removing any assumptions relative to the Reynolds equation. It provides the (i) two-dimensional variation of pressure, viscosity, etc., in the fluid and (ii) stress, elastic/plastic strain in the solid, simultaneously. The FSI model is robust, easy to implement, and computationally efficient. It provides an effective approach to solve sophisticated EHL problems. The FSI model was used to investigate the effects of surface dents, plasticity and material inclusions under heavily loaded lubricated line contacts as can be found in gears and rolling element bearings. The results from the model exhibit excellent corroboration with published results based on the Reynolds equation solvers.

Semi-analytical solution for gable roofs under uplift wind loads

A common type of failure observed during hurricane events is the detachment of the roofs of light-frame wood houses because of the inability of the roof-to-wall connection (RTWC) to transfer uplift wind loads acting on the roofs. This paper introduces a computationally efficient procedure for conducting nonlinear analysis of the roofs to determine the connections forces using a semi-analytical solution. The new procedure simulates an entire roof as a continuous beam resting on elastic supports through the use of statically indeterminate slope deflection equations that include shear deformations. It accounts for the two-dimensional spatial variation of the uplift wind pressure. The new model was validated against a three-dimensional finite element model and also through a comparison with the results of experimental testing of a gable roof house previously conducted at the University of Western Ontario, Canada. The model was used to determine the load sharing among the trusses under a realistic load. It was also used to assess the adequacy of using the tributary area method under a code load. Based on the validation results, the semi-analytical solution model demonstrated an ability to predict the response of a roof under uplift wind loads that vary both in time and space. The main advantage of the new model is the efficient computational time compared to three-dimensional finite element modeling. As such this model can be used in the future for conducting probabilistic analysis of the roof taking into account the variation of the connection properties.

Matrix-based incremental updating approximations in multigranulation rough set under two-dimensional variation

Multigranulation rough set model (MGRS) uses multiple equivalence relations on the universe to calculate the approximations, which can solve problem in mutigranulation spaces. In practical applications, information systems often dynamically update due to the variation of objects, attributes or attribute values. Incremental approach is an effective method to calculate approximations for dynamically updated information system. However, existing incremental updating approximations in MGRS mainly focus on single-dimensional variation of objects, attributes or attribute values respectively, without considering multi-dimensional variation of objects, attributes and attribute values. In this paper, we propose matrix-based incremental updating approximations in multigranulation rough set under two-dimensional variation of objects, attributes and attribute values. One is the simultaneous variation of objects and attributes (VOA). The other is the simultaneous variation of objects and attribute values (VOV). First, we give the incremental approaches to update the relevant matrices for the dynamically updated information system due to VOA and VOV. Second, based on the updated matrices, we propose two matrix-based incremental algorithms to update approximations. Finally, examples and experimental results demonstrate the effectiveness of the proposed algorithms for incremental updating approximations in multigranulation rough set under two-dimensional variation.

Particle-in-cell Simulations of Decaying Plasma Turbulence: Linear Instabilities versus Nonlinear Processes in 3D and 2.5D Approximations

Abstract Particle-in-cell (PIC) simulations are used to examine the decay of strongly intermittent Alfvénic turbulence in a collisionless, homogeneous, and magnetized plasma. Results from three computational models are compared in simulations with similar plasma parameters and dimensions of approximately 100 d i, where d i is the ion inertial length. Each model utilizes three-dimensional velocities, but spatial variations differ: the 2.5D perpendicular PIC model uses two-dimensional spatial variations with the background magnetic field B o perpendicular to the simulation plane, the 2.5D parallel PIC model uses two-dimensional spatial variations with B o in the simulation plane, and the 3D model includes spatial variations in full three-dimensional space. Results from the three models are compared using plots of the joint probability distribution functions (PDFs) of maximum local linear instability growth rates versus the maximum local nonlinear frequencies. All results agree with previous demonstrations that linear growth rates are generally slower than the nonlinear frequencies of the turbulence at kd i = 1.0. However, it is the 3D PIC joint PDFs that most closely resemble joint PDFs recently observed in space plasmas because the 3D PDFs capture both the linear and nonlinear plasma processes, whereas the 2.5D parallel PIC runs do not represent the nonlinear turbulence processes and the 2.5D perpendicular PIC computations do not well represent the consequences of microinstabilities. These results suggest that 3D simulations are needed to properly capture important features of both microinstabilities and nonlinear turbulence.

3‐5 GHz multifinger CMOS LNA using a simultaneous noise and impedance matching technique by a significant reduction of broadband impedance variation of metal–oxide–semiconductor field effect transistor

This work provides a new simultaneous noise and impedance matching (SNIM) methodology for designing a 3–5 GHz ultrawideband low-noise amplifier (LNA) in 0.18 μm complementary metal–oxide–semiconductor (CMOS) process using the advanced design system platform. To justify the proposed method, common gate (CG)- and common source (CS)-input-matched LNAs are designed where the variation of input impedance over the whole operating band is significantly reduced by applying the multifinger layout technique and employing shunt passive elements for the input device without degenerating the structure, respectively. As part of the proposed SNIM method, a two-dimensional contour plot-based process variation tolerant bias voltage set up protocol is developed which can optimise forward gain (S21), noise figure (NF) and stability factor simultaneously. The regulation of amplifier port parameters with bias settling contour plots and finger parameters results in the proposed SNIM technique. For the CG-input-matched LNA, the post-layout electromagnetic simulated NF is between 3.08 and 4.1 dB, the average power gain of 25.52 dB with a power consumption of 20.19 mW and the CS-input-matched LNA achieves an NF in between 2.772 and 3.04 dB, the average power gain of 17.98 dB while the dissipated power is 20.73 mW.

Penalized logspline density estimation using total variation penalty

We study a penalized logspline density estimation method using a total variation penalty. The B-spline basis is adopted to approximate the logarithm of density functions. Total variation of derivatives of splines is penalized to impart a data-driven knot selection. The proposed estimator is a bona fide density function in the sense that it is positive and integrates to one. We devise an efficient coordinate descent algorithm for implementation and study its convergence property. An oracle inequality of the proposed estimator is established when the quality of fit is measured by the Kullback–Leibler divergence. Based on the oracle inequality, it is proved that the estimator achieves an optimal rate of convergence in the minimax sense. We also propose a logspline method for the bivariate case by adopting the tensor-product B-spline basis and a two-dimensional total variation type penalty. Numerical studies show that the proposed method captures local features without compromising the global smoothness.