Index Gradient Research Articles

Fabrication of antireflective silver-capped tin oxide nano-obelisk arrays as high sensitive SERS substrate

Hybrid noble metal-semiconductor oxide nanostructures often provide unique and synergetic functionalities that are highly desirable in various practical applications. However, the fabrication of such systems with desired functionalities using cost-effective techniques is still a great challenge. In this work, we report a facile route for the preparation of novel Ag/SnO2 nano-obelisk arrayed thin films on silicon substrates by spray pyrolysis and thermal evaporation techniques. The prepared samples exhibited broadband antireflectance in both UV and visible regions attributed to the refractive index gradient and scattering provided by the nano-obelisk arrays. The localised surface plasmon resonance of silver nanocaps further enhanced the light absorption contributing to the antireflective property of the hybrid system. Ag/SnO2 nano-obelisk arrayed thin film exhibited excellent SERS performance with an enhancement factor of 1.13 × 108 with a limit of detection value of 10−12 M for the trace detection of R6G dye. In addition, Ag/SnO2 nano-obelisk arrayed thin film based SERS substrate exhibited good homogeneity across the measured spots and outstanding stability which are essential for quantitative field analysis. The results indicate that the Ag/SnO2 nano-obelisk arrayed thin films are efficient SERS substrates with the merits of having the ease of production, high sensitivity and stability for various practical sensing applications.

Experiment to observe an optically induced change of the vacuum index

Quantum electrodynamics predicts that the vacuum must behave as a nonlinear optical medium: the speed of light should be modified when the vacuum is stressed by intense electromagnetic fields. This optical phenomenon has not yet been observed. The DeLLight (Deflection of Light by Light) experiment aims to observe the optically-induced index change of vacuum, a nonlinear effect which has never been explored. The experiment is installed in the LASERIX facility at IJCLab, which delivers ultra-short intense laser pulses (2.5 J per pulse, each of 30 fs duration, with a 10 Hz repetition rate). The proposal is to measure the refraction of a probe laser pulse when crossing a transverse vacuum index gradient, produced by a very intense pump pulse. The refraction induces a transverse shift in the intensity profile of the probe, whose signal is amplified by a Sagnac interferometer. In this article, we describe the experimental method and setup, and present the complete theoretical calculations for the expected signal. With a minimum waist at focus of $5 \,\mu$m (corresponding to a maximum intensity of $\sim 3 \times 10^{20}$ W/cm$^2$), and with the nonlinear vacuum index derived from QED, the expected refraction angle is 0.13 prad. First results of the interferometer prototype are presented. It is shown that an extinction factor $\mathcal{F} = 0.4 \times 10^{-5}$ (corresponding to a signal amplification factor of 250) and a spatial resolution $\sigma_y = 10$ nm are achievable. The expected signal is then about 15 pm, and could be observed at a 5-sigma confidence level with about one month of collected data.

Impact of surgical aortic valve replacement on global and regional longitudinal strain across four flow gradient patterns of severe aortic stenosis.

To evaluate the impact of surgical aortic valve replacement (SAVR) on global (GLS) and regional longitudinal strain (RLS) across four flow-gradient patterns of severe aortic stenosis (AS) 3 months after surgery.A total of 103 patients with severe AS (aortic valve area < 1.0 cm2) were examined by speckle tracking echocardiography the day before SAVR and at 3-months follow-up. Patients were stratified into four flow-gradient patterns by stroke volume index (>35 mL/m2 vs. ≤35 mL/m2) and mean transaortic gradients (>40 mmhg vs. ≤40 mmhg): normal-flow, high gradient (NF/HG); low-flow, high gradient (LF/HG); normal-flow, low gradient (NF/LG); low-flow, low gradient (LF/LG). Strain analysis comprised GLS and RLS at a basal (BLS), mid-ventricular (MLS) and apical level (ALS).Patients with high gradients improved GLS (NF/HG: 16.1 ± 3.5 % vs. 17.3 ± 3.4 %, p = 0.03 and LF/HG: 15.4 ± 3.6 % vs. 16.9 ± 3.1 %, p = 0.03), BLS (NF/HG: 12.7 ± 3.1 % vs. 14.2 ± 3.1 %, p = 0.003 and LF/HG: 11.4 ± 3.2 % vs. 13.8 ± 2.7 %, p = 0.005) and MLS (NF/HG: 15.4 ± 3.3 % vs. 16.5 ± 3.3 %, p = 0.04 and LF/HG: 14.5 ± 3.1 % vs. 16.2 ± 2.7 %, p = 0.01) whereas patients with low gradients showed no improvements three months after SAVR. ALS did not change significantly in any group. Patients with high gradients demonstrated a reduction in left ventricular (LV) mass index (p < 0.001) and N-terminal pro-Brain Natriuretic Peptide levels (p < 0.001) following SAVR in contrast to patients with low gradients.Patients with high gradient severe AS improve GLS and RLS three months after SAVR with concomitant reduction of LV mass and neurohormonal activation whereas patients with low gradients do not improve longitudinal strain, LV mass or neurohormonal activation.

Gradient pretilt angle alignment materials with different photosensitivity for tunable polarization‐independent self‐aligned liquid crystal lens

AbstractAlignment of benzaldehyde materials with different photosensitivity thresholds, capable of changing the pretilt angles of nematic liquid crystal (LC) from 90° to 0° in a controlled manner under UV‐B exposure, has been developed. Inhomogeneous exposure of uniform rubbed alignment layers allows the formation of a refractive index gradient inside the LC cell. The concept of tunable polarization‐independent self‐aligned LC lens based on gradient pretilt angle alignment materials with different photosensitivity is demonstrated. Self‐alignment of two polarization‐dependent sub‐lens is achieved due to a single exposure act of two alignment layers, which are located on the same piece of glass on both sides, forming one common optical axis for a polarization‐independent LC lens. The sub‐lens cells have uniform cell gap and are independently controlled using low‐voltage driving. Devices based on gradient benzaldehyde alignment materials can be used in many modern optical and photonic devices.

Accuracy of dose-volume metric calculation for small-volume radiosurgery targets.

PurposeFor stereotactic radiosurgery (SRS), accurate evaluation of dose‐volume metrics for small structures is necessary. The purpose of this study was to compare the DVH metric capabilities of five commercially available SRS DVH analysis tools (Eclipse, Elements, Raystation, MIM, and Velocity).MethodsDICOM RTdose and RTstructure set files created using MATLAB were imported and evaluated in each of the tools. Each structure set consisted of 50 randomly placed spherical targets. The dose distributions were created on a 1‐mm grid using an analytic model such that the dose‐volume metrics of the spheres were known. Structure sets were created for 3, 5, 7, 10, 15, and 20 mm diameter spheres. The reported structure volume, V100% [cc], and V50% [cc], and the RTOG conformity index and Paddick Gradient Index, were compared with the analytical values.ResultsThe average difference and range across all evaluated target sizes for the reported structure volume was − 4.73%[−33.2,0.2], 0.11%[−10.9, 9.5], −0.39%[−12.1, 7.0], −2.24%[−21.0, 1.3], and 1.15%[−15.1,0.8], for TPS‐A through TPS‐E, respectively. The average difference and range for the V100%[cc] (V20Gy[cc]) was − 0.4[−24.5,9.8], −2.73[−23.6, 1.1], −3.01[−23.6, 0.6], −3.79[−27.3, 1.3], and 0.26[−6.1,2.6] for TPS‐A through TPS‐E, respectively. For V50%[cc](V10Gy[cc]) in TPS‐A through TPS‐E the average and ranger were − 0.05[−0.8,0.4], −0.18[−1.2, 0.5], −0.44[−1.4, 0.3], −0.26[−1.8, 2.6], and 0.09[−1.4,2.7].ConclusionThis study expanded on the previously published literature to quantitatively compare the DVH analysis capabilities of software commonly used for SRS plan evaluation and provides freely available and downloadable analytically derived set of ground truth DICOM dose and structure files for the use of radiotherapy clinics. The differences between systems highlight the need for standardization and/or transparency between systems, especially when evaluating plan quality for multi‐institutional clinical trials.

Natural frequency analysis of a functionally graded rotor-bearing system with a slant crack subjected to thermal gradients

Abstract The present work aims to analyze the natural and whirl frequencies of a slant-cracked functionally graded rotor-bearing system using finite element analysis for the flexural vibrations. The functionally graded shaft is modelled using two nodded beam elements formulated using the Timoshenko beam theory. The flexibility matrix of a slant-cracked functionally graded shaft element has been derived using fracture mechanics concepts, which is further used to develop the stiffness matrix of a cracked element. Material properties are temperature and position-dependent and graded in a radial direction following power-law gradation. A Python code has been developed to carry out the complete finite element analysis to determine the Eigenvalues and Eigenvectors of a slant-cracked rotor subjected to different thermal gradients. The analysis investigates and further reveals significant effect of the power-law index and thermal gradients on the local flexibility coefficients of slant-cracked element and whirl natural frequencies of the cracked functionally graded rotor system.

Natural frequency analysis of a functionally graded rotor-bearing system with a slant crack subjected to thermal gradients

Abstract The present work aims to analyze the natural and whirl frequencies of a slant-cracked functionally graded rotor-bearing system using finite element analysis for the flexural vibrations. The functionally graded shaft is modelled using two nodded beam elements formulated using the Timoshenko beam theory. The flexibility matrix of a slant-cracked functionally graded shaft element has been derived using fracture mechanics concepts, which is further used to develop the stiffness matrix of a cracked element. Material properties are temperature and position-dependent and graded in a radial direction following power-law gradation. A Python code has been developed to carry out the complete finite element analysis to determine the Eigenvalues and Eigenvectors of a slant-cracked rotor subjected to different thermal gradients. The analysis investigates and further reveals significant effect of the power-law index and thermal gradients on the local flexibility coefficients of slant-cracked element and whirl natural frequencies of the cracked functionally graded rotor system.

Recurrent neural network reveals transparent objects through scattering media.

Scattering generally worsens the condition of inverse problems, with the severity depending on the statistics of the refractive index gradient and contrast. Removing scattering artifacts from images has attracted much work in the literature, including recently the use of static neural networks. S. Li et al. [Optica5(7), 803 (2018)10.1364/OPTICA.5.000803] trained a convolutional neural network to reveal amplitude objects hidden by a specific diffuser; whereas Y. Li et al. [Optica5(10), 1181 (2018)10.1364/OPTICA.5.001181] were able to deal with arbitrary diffusers, as long as certain statistical criteria were met. Here, we propose a novel dynamical machine learning approach for the case of imaging phase objects through arbitrary diffusers. The motivation is to strengthen the correlation among the patterns during the training and to reveal phase objects through scattering media. We utilize the on-axis rotation of a diffuser to impart dynamics and utilize multiple speckle measurements from different angles to form a sequence of images for training. Recurrent neural networks (RNN) embedded with the dynamics filter out useful information and discard the redundancies, thus quantitative phase information in presence of strong scattering. In other words, the RNN effectively averages out the effect of the dynamic random scattering media and learns more about the static pattern. The dynamical approach reveals transparent images behind the scattering media out of speckle correlation among adjacent measurements in a sequence. This method is also applicable to other imaging applications that involve any other spatiotemporal dynamics.

Echocardiographic measures and subsequent decline in kidney function in older adults: the Atherosclerosis Risk in Communities Study.

Heart failure increases the risk of kidney disease progression. However, whether cardiac function and structure are associated with the risk of incident chronic kidney disease (CKD) is not well characterized in a community setting. Among 4188 participants (mean age 75 years and 22% blacks) of the Atherosclerosis Risk in Communities Study without prevalent CKD in 2011-13, we examined the association of echocardiographic measures of left ventricular (LV) mass index, ejection fraction, left atrial volume index (LAVi), right ventricular (RV) fractional area change, and peak RV-right atrium (RA) gradient, with the subsequent risk of incident CKD, as defined by >25% decline to estimated glomerular filtration rate (eGFR) <60 mL/min/1.73m2, hospitalization with CKD diagnosis, or incident end-stage kidney disease. Multivariable Cox regression models were used to estimate hazard ratios (HRs). The risk of incident CKD was monotonically increased with each of higher LV mass index [adjusted HR 2.61 (1.92-3.55) for highest quartile (Q4) vs. lowest (Q1)], lower ejection fraction [1.54 (1.17-2.04) for Q1 vs. Q4], higher LAVi [2.12 (1.56-2.89) for Q4 vs. Q1], and higher peak RV-RA gradient [2.17 (1.45-3.25) for Q4 vs. Q1] but not with RV function. The associations were consistent between subgroups by sex and race. Among community-dwelling older individuals, LV mass index, ejection fraction, LAVi, and peak RV-RA gradient were independently associated with the risk of incident CKD. Our results further support that heart disease is associated with the risk of kidney disease progression and suggest the value of echocardiography for assessing cardiac and kidney health in older populations.

Improving the beam quality of DPALs by refractive index gradients induced by the pump beam in the heated gain medium: experimental verification of the theoretical prediction

We recently predicted [J. Opt. Soc. Am. B 35, 558 (2018)JOBPDE0740-322410.1364/JOSAB.35.000558] that large radial gradients of the refractive index induced by the pump beam in the heated gain medium of diode-pumped alkali lasers (DPALs) could lead to improved DPAL beam quality. This effect depends on the composition of the buffer gas in the cell. We report here on verifying this counterintuitive finding by careful measurements of the beam quality factor M 2 in static Cs DPALs with different compositions of the buffer gases.

Ray Tracing Method of Gradient Refractive Index Medium Based on Refractive Index Step

For gradient refractive index media with large refractive index gradients, traditional ray tracing methods based on refined elements or spatial geometric steps have problems such as low tracing accuracy and efficiency. The ray tracing method based on refractive index steps proposed in this paper can effectively solve this problem. This method uses the refractive index step to replace the spatial geometric step. The starting point and the end point of each ray tracing step are on the constant refractive-index surfaces. It avoids the problem that the traditional tracing method cannot adapt to the area of sudden change in the refractive index and the area where the refractive index changes sharply. Therefore, a suitable distance can be performed in the iterative process. It can achieve high-efficiency and precise ray tracing in areas whether the refractive index changes slowly or sharply. According to the comparison of calculation examples, this method can achieve a tracing accuracy of 10−5 mm. The speed and precision of ray tracing are better than traditional methods.

Charge-Induced Birefringence in a Room-Temperature Ionic Liquid.

We have reported previously on the existence of a surface charge-induced free charge density gradient (ρf) in room-temperature ionic liquids (RTILs) with a characteristic persistence length of ca. 50 μm [Ma, K. Langmuir 2016, 32, 9507-9512]. The free charge density gradient is related to the dielectric response of the RTIL. We report here on the existence of a surface charge-induced gradient in the RTIL refractive index and quantify the relationship between the index gradient and ρf. Because ρf is uniaxial, the induced refractive index gradient is manifested as an induced birefringence. The RTIL sample holder has a curved surface such that the RTIL can function as a lens, and ρf is controlled by the surface charge density (σs) of the (concave) RTIL support. Current passed through an indium-doped tin oxide (ITO) surface layer on the support surface controls σs. The far-field image of light passed through the RTIL lens as a function of σs is used to measure the charge-induced changes of n in the RTIL. We demonstrate a modulation of the refractive index on the order of 15%, proportional to σs. This report places the relationship between ρf and RTIL dielectric response on a quantitative footing and suggests the utility of RTILs for electro-optic applications.

A Collaborative Multiagent Reinforcement Learning Method Based on Policy Gradient Potential.

Gradient-based method has been extensively used in today's multiagent reinforcement learning (MARL). In a gradient-based MARL algorithm, each agent updates its parameterized strategy in the direction of the gradient of some performance index. However, studies on the convergence of the existing gradient-based MARL algorithms for identical interest games are quite few. In this article, we propose a policy gradient potential (PGP) algorithm that takes PGP as the source of information for guiding the strategy update, as opposed to the gradient itself, to learn the optimal joint strategy that has a maximal global reward. Since the payoff matrix and the joint strategy are often unavailable to the learning agents in reality, we consider the probability of obtaining the maximal reward as the performance index. Theoretical analysis of the PGP algorithm on the continuous model involving an identical interest repeated game shows that if the component action of every optimal joint action is unique, the critical points corresponding to all optimal joint actions are asymptotically stable. The PGP algorithm is experimentally studied and compared against other MARL algorithms on two commonly used collaborative tasks-the robots leaving a room task and the distributed sensor network task, as well as a real-world minefield navigation problem where only local state and local reward information are available. The results show that the PGP algorithm outperforms the other algorithms in terms of the cumulative reward and the number of time steps used in an episode.

Functional Paleoecology and the Pollen-Plant Functional Trait Linkage

Paleoecological investigations using the pollen-plant functional trait linkage are increasing in value as new insights to past ecological function and dynamics are revealed. These retrospective approaches link pollen sequences to plant functional trait measurements to reveal long-term changes in ecosystem properties that are difficult to resolve using traditional paleoecological methods. Despite these methodological improvements and the newfound perspectives, there has yet to be thorough testing of whether transforming pollen to ecological function tracks functional trait distributions in geographic space. We assess this in North America by linking surface pollen samples to measurements of three functional traits that represent major axes of plant ecological strategy. Pollen-derived estimates of function were first used to investigate occupied trait space at different scales. These estimates were used to reconstruct the latitudinal functional diversity gradient of North America, and results were compared to the continent’s functional diversity gradient estimated from tree assemblages and gradients based on pollen richness and evenness. Results indicated that the patterns in pollen-based function sufficiently track ecological function in trait and geographic space and the macroecological biodiversity pattern was reconstructed, although there were minor differences between the slopes of the functional diversity and each of the pollen index gradients. Taken together, the outcomes of our investigation indicate reliability in extending the pollen-plant functional trait linkage into deeper time, at least for examining North American functional dynamics.

Spatial variation of East Asian winter monsoon evolution between northern and southern China since the last glacial maximum

AbstractThe East Asian winter monsoon (EAWM) is one of the most dynamic components of the global climate system. Although poorly understood, knowledge of long-term spatial differences in EAWM variability during the glacial–interglacial cycles is important for understanding the dynamic processes of the EAWM. We reconstructed the spatiotemporal characteristics of the EAWM since the last glacial maximum (LGM) using a comparison of proxy records and long-term transient simulations. A loess grain-size record from northern China (a sensitive EAWM proxy) and the sea surface temperature gradient of an EAWM index in sediments of the southern South China Sea were compared. The data–model comparison indicates pronounced spatial differences in EAWM evolution, with a weakened EAWM since the LGM in northern China but a strengthened EAWM from the LGM to the early Holocene, followed by a weakening trend, in southern China. The model results suggest that variations in the EAWM in northern China were driven mainly by changes in atmospheric carbon dioxide (CO2) concentration and Northern Hemisphere ice sheets, whereas orbital insolation and ice sheets were important drivers in southern China. We propose that the relative importance of insolation, ice sheets, and atmospheric CO2for EAWM evolution varied spatially within East Asia.

Optimal vortex formation time index in mitral valve stenosis.

Left ventricular vortex formation time (VFT) is a novel dimensionless index of flow propagation during left ventricular diastole, which has been demonstrated to be useful in heart failure and cardiomyopathy. In mitral stenosis (MS), flow propagation in the LV may be suboptimal. We studied VFT in varying degrees of MS. Echocardiography was performed on 20 healthy controls and 50 cases of rheumatic MS. Patients with atrial fibrillation, LV ejection fraction < 50% and other valvular heart diseases were excluded. VFT was obtained using the length-to-diameter ratio (L/D), where L is the continuous-wave Doppler velocity time integral stroke distance, divided by D, the mitral leaflet separation index. This was correlated against varying degrees of MS severity, left atrial (LA) volume and function. In controls, VFT was 3.92 ± 2.00 (optimal range) and was higher (suboptimal) with increasing severity of mitral stenosis (4.98 ± 2.43 in mild MS; 7.22 ± 2.98 in moderate MS; 11.55 ± 2.67 in severe MS, p < 0.001). VFT negatively correlated with mitral valve area (R2 = 0.463, p < 0.001) and total LA emptying fraction (R2 = 0.348, p < 0.001), and positively correlated with LA volume index (R2 = 0.440, p < 0.001) and mean transmitral pressure gradient (R2 = 0.336, p < 0.001). More severe MS correlated with suboptimal (higher) VFT. The restricted mitral valve opening may disrupt vortex formation and optimal fluid propagation in the LV. Despite the compensatory increase in LA size with increasingly severe MS, reduced LA function also contributed to the suboptimal LV vortex formation.

Torrential Flood Water Management: Rainwater Harvesting through Relation Based Dam Suitability Analysis and Quantification of Erosion Potential

In this study, a relation-based dam suitability analysis (RDSA) technique is developed to identify the most suitable sites for dams. The methodology focused on a group of the most important parameters/indicators (stream order, terrain roughness index, slope, multiresolution valley bottom flatness index, closed depression, valley depth, and downslope gradient difference) and their relation to the dam wall and reservoir suitability. Quantitative assessment results in an elevation-area-capacity (EAC) curve substantiating the capacity determination of selected sites. The methodology also incorporates the estimation of soil erosion (SE) using the Revised Universal Soil Loss Equation (RUSLE) model and sediment yield at the selected dam sites. The RDSA technique identifies two suitable dam sites (A and B) with a maximum collective capacity of approximately 1202 million m3. The RDSA technique was validated with the existing dam, Gomal-Zam, in the north of Sanghar catchment, where RDSA classified the Gomal-Zam Dam in a very high suitability class. The SE estimates show an average of 75 t-ha−1y−1 of soil loss occurs in the study area. The result shows approximately 298,073 and 318,000 tons of annual average sediment yield (SY) will feed the dam A and B respectively. The SE-based sediment yield substantiates the approximate life of Dam-A and Dam-B to be 87 and 90 years, respectively. The approach is dynamic and can be applied for any other location globally for dam site selection and SE estimation.

A novel interface method for two-dimensional multiphase SPH: Interface detection and surface tension formulation

A novel interface method is developed in this paper for two-dimensional smoothed particle hydrodynamics (SPH) modelings of multiphase flows. The present interface method aims to resolve two essential issues in the multiphase flow simulations: the interface detection and the implementation of surface tension force. Specifically, a novel and easy-to-implement algebraic indicator is proposed to detect the interface particles. And the surface tension force is locally implemented on the interface particles by reconstructing arc lines connecting three adjacent interface particles. Compared with the previous surface reconstruction method, the present method utilizes fewer particles in the local evaluation of surface tension. The novel algebraic indicator provides more accurate and efficient detection of the interface particles, especially for the sparse or aggregated particle distributions. In the meantime, the present surface tension formulation removes the tedious process of evaluating gradient of the color index and thus significantly improves the numerical efficiency. The accuracy, flexibility and efficiency of the present interface method are comprehensively evaluated through four numerical examples, namely the sloshing in a rectangular tank, oscillation of elliptic droplet, Laplace law for a stationary droplet, and air bubble rising in water. The good agreement of the present numerical results with the published results demonstrates that the novel interface method proposed in this paper can precisely detect the interface particles with appealing sharpness, and recover the surface tension force accurately and efficiently.

An efficient dominant failure modes search strategy and an extended sequential compounding method of system reliability analysis and optimization

The structural system is a complex structural form in engineering practice. Under the condition of uncertainty, multiple failure modes may happen simultaneously and lead to the failure of the overall structure. To identify the dominant failure modes of structural systems, this paper proposes a dominant failure mode search method based on the differential evolution algorithm, which generates sample points on the limit state surface and uses the differential evolution algorithm to evolve. It can search for several dominant failure modes of structural systems without much structural analysis function calls. For the evaluation of the reliability of structural systems, this paper further proposes an extended sequential compound method, which can solve the correlation coefficients between compound events and its internal events. Therefore, it can calculate the failure probability for various failure modes and the correlation coefficient between failure modes simultaneously. Besides, a system reliability-based design optimization method is proposed under the framework of the reliability index method with an analytical method for solving the gradient of the system reliability index. Finally, several numerical examples are given to verify the efficiency and accuracy of the proposed methods.

An Improved Fourier-Mellin Transform-Based Registration Used in TDI-CMOS

Time-delayed integration (TDI) is a common imaging mode used in airborne cameras to compensate for image motion. The paper presents an improved Fourier-Mellin transform (FMT)-based registration method, which can be used to realize the registration-based TDI. It first analyzes the noise influences on the FMT spectrum by comparing the curve changes in the standard-deviation versus column plots under the various intensity of noise, then designs a special filter called WCSDF according to the amount of variation of each column in the FMT spectrum, which can reduce the noise affection on registration process to the larger extent. And an improved FMT-based registration method is finally proposed to form a framework of registration-based TDI. In computer simulations, the proposed method shows a significant improvement in robustness to noise (noise level up to 40). Compared with the existing method, its low computational complexity makes the method easy to be implemented in hardware and can estimate the larger relative shifts among dim noisy images, moreover, the TDI images generated by the proposed framework have higher quality in the index of information entropy, average gradient, and spatial frequency response.