Effect Of Nonuniformity Research Articles

P‐6.9: Patterning of Quantum Dots Light‐emitting Diodes Based on IGZO Films

Patterned quantum dots light‐emitting diodes (QLED) with sputtered IGZO films as electron transport layers are fabricated. The pattered IGZO films can define pixels ~10 μm, while accompanied by the nonuniform current spreading effect. The localized current density distribution observed by luminance distribution during the aging degrades the device seriously. In order to overcome this issue, the patterned SiO2 layer as the bank is introduced. This work also shows a potential way to tune the out couple efficiency and micro‐cavity effect (optical length) in QLED by charge transport layer thickness.

Analysis of Transonic Bladerows With Non-Uniform Geometry Using the Spectral Method

Abstract Turbomachinery blade rows can have non-uniform geometries due to design intent, manufacture errors or wear. When predictions are sought for the effect of such non-uniformities, it is generally the case that whole assembly calculations are needed. A spectral method is used in this paper to approximate the flow fields of the whole assembly but with significantly less computation cost. The method projects the flow perturbations due to the geometry non-uniformity in an assembly in Fourier space, and only one passage is required to compute the flow perturbations corresponding to a certain wave-number of geometry variation. The performance of this method on transonic blade rows is demonstrated on a modern fan assembly. Low engine order and high engine order geometry non-uniformity (e.g., “saw-tooth” pattern) are examined. The non-linear coupling between the flow perturbations and the passage-averaged flow field is also demonstrated. Pressure variations on the blade surface and the potential flow field upstream of the leading edge from the proposed spectral method and the direct whole assembly solutions are compared. Good agreement is observed on both quasi-3D and full 3D cases. A lumped approach to compute deterministic fluxes is also proposed to further reduce the computational cost of the spectral method. The spectral method is formulated in such a way that it can be easily implemented into an existing harmonic flow solver by adding an extra source term and can be potentially used as an efficient tool for aeromechanical and aeroacoustics design of turbomachinery blade rows.

Recovering Marine Gravity Over the Gulf of Guinea From Multi-Satellite Sea Surface Heights

A regional gravity field product, comprising vertical deflections and gravity anomalies, of the Gulf of Guinea (15°W to 5°E, 4°S to 4°N) has been developed from sea surface heights (SSH) of five altimetry missions. Though the remove-restore technique was adopted, the deflections of the vertical were computed directly from the SSH without the influence of a global geopotential model. The north-component of vertical deflections was more accurate than the east-component by almost three times. Analysis of results showed each satellite can contribute almost equally in resolving the north-component. This is attributable to the nearly northern inclinations of the various satellites. However, Cryosat-2, Jason-1/GM, and SARAL/AltiKa contributed the most in resolving the east-component. We attribute this to the superior spatial resolution of Cryosat-2, the lower inclination of Jason-1/GM, and the high range accuracy of the Ka-band of SARAL/AltiKa. Weights of 0.687 and 0.313 were, respectively, assigned to the north and east components in order to minimize their non-uniform accuracy effect on the resultant gravity anomaly model. Histogram of computed gravity anomalies compared well with those from renowned models: DTU13, SIOv28, and EGM2008. It averagely deviates from the reference models by −0.33 mGal. Further assessment was done by comparing it with a quadratically adjusted shipborne free-air gravity anomalies. After some data cleaning, observations in shallow waters, as well as some ship tracks were still unreliable. By excluding the observations in shallow waters, the derived gravity field model compares well in ocean depths deeper than 2,000 m.

Mesoscale Process Modeling of a Thick Pultruded Composite with Variability in Fiber Volume Fraction.

Pultruded fiber-reinforced polymer composites are susceptible to microstructural nonuniformity such as variability in fiber volume fraction (), which can have a profound effect on process-induced residual stress. Until now, this effect of non-uniform distribution has been hardly addressed in the process models. In the present study, we characterized the distribution and accompanying nonuniformity in a unidirectional fiber-reinforced pultruded profile using optical light microscopy. The identified nonuniformity in was subsequently implemented in a mesoscale thermal–chemical–mechanical process model, developed explicitly for the pultrusion process. In our process model, the constitutive material behavior was defined locally with respect to the corresponding fiber volume fraction value in different-sized representative volume elements. The effect of nonuniformity on the temperature and cure degree evolution, and residual stress was analyzed in depth. The results show that the nonuniformity in fiber volume fraction across the cross-section increased the absolute magnitude of the predicted residual stress, leading to a more scattered residual stress distribution. The observed gradient promotes tensile residual stress at the core and compressive residual stress at the outer regions. Consequently, it is concluded that it is essential to take the effects of nonuniformity in fiber distribution into account for residual stress estimations, and the proposed numerical framework was found to be an efficient tool to study this aspect.

Study on Nonuniform Evolution Characteristics of Rock Friction and Sliding

By means of experimental research and theoretical analysis, the nonuniform evolution characteristics of rock friction and sliding were studied. Using digital speckle correlation (DIC) as observation method, the whole process of friction and sliding of a granite specimen in double-sided shear experiment is studied. A spring slider model considering the microscopic characteristics of interface asperities was established to simulate the microscopic process of rock friction and sliding. By comparing the theoretical analysis results with the experimental results, the effect of interface nonuniformity on rock friction sliding instability is studied. The results demonstrated that, with the increase of nonuniformity of sliding interface, the degree of local instability before stick-slip decreases, the stick-slip period shortens, and the value of shear drop during stick-slip period decreases. The nonuniformity of sliding interface will increase after local instability.

A new DCT-PCM method for license plate number detection in drone images

• A new problem of license plate/text detection in drone images is addressed. • The concept of Phase congruency in DCT domain is introduced for detection. • The combination of DCT and Phase congruency is new. • Deep learning is used in different way for eliminating false positives. • The combination of feature extraction and DCT-Phase is new. License plate number detection in drone images is a complex problem because the images are generally captured at oblique angles and pose several challenges like perspective distortion, non-uniform illumination effect, degradations, blur, occlusion, loss of visibility etc. Unlike, most existing methods that focus on images captured by orthogonal direction (head-on), the proposed work focuses on drone text images. Inspired by the Phase Congruency Model (PCM), which is invariant to non-uniform illuminations, contrast variations, geometric transformation and to some extent to distortion, we explore the combination of DCT and PCM (DCT-PCM) for detecting license plate number text in drone images. Motivated by the strong discriminative power of deep learning models, the proposed method exploits fully connected neural networks for eliminating false positives to achieve better detection results. Furthermore, the proposed work constructs working model that fits for real environment. To evaluate the proposed method, we use our own dataset captured by drones and benchmark license plate datasets, namely, Medialab for experimentation. We also demonstrate the effectiveness of the proposed method on benchmark natural scene text detection datasets, namely, SVT, MSRA-TD-500, ICDAR 2017 MLT and Total-Text.

Lateral migration of peptides in transversely sheared flows in water: An atomistic-scale-resolving simulation

For atomistic scale-resolving simulations of peptide diffusion, which are representative of molecular sorting in micro-fluidic device, a hybrid Fluctuating Hydrodynamics - Molecular Dynamics (FH/MD) model is implemented based on the two-phase flow analogy framework. Thanks to the used framework, in comparison with existing simulations in the literature, the suggested model captures inter-atomic forces between the peptides and the surrounding shell of water atoms at atomistic resolution while concurrently taking into account the non-uniform flow effect. In comparison with previous applications of the hybrid two-phase flow analogy method, multiple moving atomic-resolution zones are implemented for the first time here. The moving zones comprise one and two peptides solvated in water with a Poiseuille flow applied, where each diffusing peptide and the surrounding water shell are dynamically resolved. The models are validated in comparison with the pure all-atom molecular dynamics simulations for the no flow case and then used to investigate how the flow rate and the starting location of peptides in the parabolic flow profile affect their lateral migration over a range of flow Reynolds numbers. It is estimated that for the Poiseuille flows considered, the FH/MD model is 2–20 times faster in comparison with the conventional all-atom non-equilibrium molecular dynamics simulations.

Simulations on the multi-shell target ignition driven by radiation pulse in Z-pinch dynamic hohlraum* *Project supported by the Science Challenge Project (Grant No. TZ2018001), the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos. XDA25051200 and XDA25050200), the National Natural Science Foundation of China (Grant Nos. 11705282 and 11775305), and Hunan Graduate Scientific Research Innovation Project (Grant

We present the first simulation results of a multi-shell target ignition driven by Z-pinch dynamic hohlraum radiation pulse. The radiation pulse is produced with a special Z-pinch dynamic hohlraum configuration, where the hohlraum is composed of a single metal liner, a low-Z plastic foam, and a high-Z metallic foam. The implosion dynamics of a hohlraum and a multi-shell target are investigated separately by the one-dimensional code MULTI-IFE. When the peak drive current is 50 MA, simulations suggest that an x-ray pulse with nearly constant radiation temperature (∼ 310 eV) and a duration about 9 ns can be obtained. A small multi-shell target with a radius of 1.35 mm driven by this radiation pulse is able to achieve volumetric ignition with an energy gain (G) about 6.19, where G is the ratio of the yield to the absorbed radiation. Through this research, we better understand the effects of non-uniformities and hydrodynamics instabilities in Z-pinch dynamic hohlraum.

Effect of different geometrical non-uniformities on nonlinear vibration of porous functionally graded skew plates: A finite element study

This article presents the investigation of nonlinear vibration analysis of tapered porous functionally graded skew (TPFGS) plate considering the effects of geometrical non-uniformities to optimize the thickness in the structural design. The TPFGS plate is analyzed considering linearly, bi-linearly, and exponentially varying thicknesses. The plate's effective material properties are tailor-made using a modified power-law distribution in which gradation varies along the thickness direction of the TPFGS plate. Incorporating the non-linear finite element formulation to develop the kinematic equation's displacement model for the TPFGS plate is based on the first-order shear deformation theory (FSDT) in conjunction with von Karman's nonlinearity. The nonlinear governing equations are established by Hamilton's principle. The direct iterative method is adopted to solve the nonlinear mathematical relations to obtain the nonlinear frequencies. The influence of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the TPFGS plate for different skew angles and variable thicknesses are studied for various geometrical parameters. The influence of taper ratio, variable thickness, skewness, porosity distributions, gradation, and boundary conditions on the plate's nonlinear vibration is demonstrated. The nonlinear frequency analysis reveals that the geometrical non-uniformities and porosities significantly influence the porous functionally graded plates with varying thickness than the uniform thickness. Besides, exponentially and linearly variable thicknesses can be considered for the thickness optimizations of TPFGS plates in the structural design.

Inclined MHD and Radiative Maxwell Slip Fluid Flow and Heat Transfer due to Permeable Melting Surface with a Non-linear Heat Source

The study analyzed a non-Newtonian Maxwell fluid flow past a permeable and melting surface with non-linear thermal radiation, inclined magnetic field chemical reaction with higher-order and non-uniform heat sources effects numerically. The governing PDEs are transformed into non-linear ODEs and solved by the shooting technique based on Runge Kutta with MATLAB toolbox. The results are shown graphically and in tabular form. The apprehensions of pictorial and tabular notations are used to analyze the effect of physical parameters governing velocity, energy, and mass. The obtained result thus confirms that an excellent agreement is achieved with those available in the open literature. The outcomes are represented as a magnetic parameter, porosity parameter and Maxwell fluid parameter have reduced the momentum boundary layer thickness.

Investigation of the performance and flow characteristics of two-phase reaction turbines in total flow geothermal systems

In a total flow geothermal system, the two-phase turbine can generate output power and recover fresh water for the water-deficient area. The performance of the two-phase turbine under various working conditions is significantly affected by operation parameters of the geothermal system. This paper presented performance evaluation methods of two-phase turbines, including one-dimensional (1D) method, two-dimensional (2D) method and three-dimensional (3D) method. The 1D method was a fast iteration approach and could reflect average flow parameters along the impeller channel. The 2D method included nonuniform effects in the rotational direction and the 3D method could derive the complete 3D flow in the channel using CFD methods. The three models were validated with experimental results under various rotational speeds. Compared with the 3D method, the 1D method and the 2D method could significantly reduce computational time. The performance of the two-phase reaction turbine was evaluated under various working conditions. A correction method based on 1D and 3D results was proposed to generate the performance map and evaluate the influence of operation parameters of the geothermal system on the turbine performance. Proposed methods and analysis can be widely used in the design, selection and operation of two-phase reaction turbines for various thermal systems.

타코펄스 불균일성으로 인한 펄스개수측정방법 영향성

펄스개수측정방법은 반작용휠의 속도를 측정하는 고전적인 방법이다. 본 연구에서는 펄스개수측정방법을 수식으로 표현하였다. 반작용휠의 회전을 속도가 아니라 샘플링 시간 동안의 회전각도로 모델링하였다. 제안된 모델의 유효성은 모델에서 얻어진 펄스개수 변화와 이동평균의 효과가 기존 연구결과와 동일함을 확인하는 방법으로 검증하였다.BR 이렇게 검증된 모델에 타코펄스 불균일성을 추가하고 펄스개수측정방법의 오차에 대해서 살펴보았다. 불균일성으로 인해서 증가하는 측정오차의 크기를 수식으로 표현하였으며, 측정오차를 상쇄하기 위해서 취해야 하는 이동평균의 개수 조건을 제시하였다.

Effect of Non-uniformity on Time-of-Flight Measurement of Critically Refracted Longitudinal Waves for Stress Evaluations of Carbon Composite Materials

Acoustoelasticity is an inexpensive and reliable technique for measuring stresses in mechanical structures, provided the influencing factors are controlled. However, ultrasonic waves propagating inside solid bodies are affected by temperature, roughness, differences in microstructure, defects, and others. Non-uniformity is one of the most influential characteristics as it is difficult to evaluate. In this study, experiments were performed to assess the time-of-flight (TOF) of critically refracted longitudinal (Lcr) waves traveling in different regions of a unidirectional carbon-epoxy sample with allowable manufacturing non-uniformities using transducers of 1 MHz and 3.5 MHz to vary the depth of propagation. A phased array system (PAS) with transducers of 5 and 10 MHz was used to identify the regions with non-uniformities in the structure through the signal-to-noise ratio (SNR) and B-Scan images. The material under test is a unidirectional composite bar made of carbon fibers (HexTow® AS4) pre-impregnated with epoxy matrix (HexPly® 8552). The investigation shows that the TOF of the Lcr wave and the SNR results can be linearly related, for an optimized configuration. Therefore, the influence of non-uniformities can be removed from TOF using SNR values. Based on the results, a coupled PAS-Lcr ultrasonic system is proposed to measure stress in composites, including those with non-uniformities.

A new method for analytical modeling of microfluidic extraction

Despite single-phase parallel flows for which analytical solutions are available for species conservation equation in its most general form, little progress has been made in analytical modeling of cross-stream diffusion in stratified multiphase flows. The main reason is that solute concentration and fluid properties are discontinuous at the interface of phases. In the present study, a new method of solution is presented for the analytical treatment of solute transport in stratified multiphase flows. The solution methodology starts with developing separate species conservation equations for the phases, which, upon non-dimensionalization, are replaced with a single equation for which series solutions are obtained utilizing the variational calculus. Using the method proposed, analytical solutions are obtained for mass transport in microfluidic two-phase extraction by taking the influences of the non-uniform velocity and the axial diffusion effects into account. The inclusion of the non-uniform velocity effects, which leads to 3D solutions, enables us to capture the heterogeneous transport of solutes, a phenomenon that is ignored by the available simple 2D solutions. The results indicate that axial diffusion in stratified multiphase flows is significantly more important than in single-phase flow and is not characterized solely by the Peclet number. It is also found that the only parameter controlling the length required for a complete extraction is the solvent-to-solution viscosity ratio.

Incorporating global multiplicative decomposition and local statistical information for brain tissue segmentation and bias field estimation

Medical image is a cornerstone of modern healthcare providing unique diagnostic. However, intensity nonuniformity is quite often found in medical images and unavoidably poses many challenges for precise image segmentation. In this paper, we present an incorporating global multiplicative decomposition and local statistical information level set technique for tissue segmentation and bias estimation that handles both high noise and intensity nonuniformity. An image can be factored into two multiplicative parts (namely, bias-free image and bias field), which are used to capture global intensity statistics. At the same time, our technique considers statistical information with not only the mean but also the variance. Pixel intensity generally fluctuates around its mean in a local region. The variance can adjust the disagreement of each pixel to its mean, and is explored to overcome the effects of intensity nonuniformity. Finally, the level set energy formulation is in the form of the global multiplicative decomposition and local statistical information. To verify the availability of our technique, we have thoroughly experimented on composite and real images. Our techniques are also applied to the lesion regions of brains. Experimental results display that our technique can segment different kinds of images with high noise and intensity nonuniformity more accurately, and outperforms other solutions in comparison.

Non-uniform Effects of Nociceptive Stimulation to Motoneurones during Experimental Muscle Pain

Nociceptive stimulation is predicted to uniformly inhibit motoneurone pools of painful muscles and those producing painful movements. Although reduced motoneurone discharge rate during pain provides some evidence, recent data show evidence of increased excitability of some motoneurones. These observations suggest non-uniform effects of nociception on motoneurone excitability. More direct measures are required, but this is difficult to assess as few measures enable in vivo evaluation of motoneurone excitability in humans. We investigated changes in motoneurone excitability during experimental pain using two methods in separate experiments: (i) estimation of the time-course of motoneurone afterhyperpolarization (AHP) from interval death rate analysis of interspike intervals of single motor unit discharge; and (ii) probability of early motoneurone discharge to a descending volley excited using transcranial magnetic stimulation (TMS). Tibialis anterior motor units were recorded with fine-wire electrodes before, during and after painful infusion of 5% hypertonic saline into the muscle. Activation of 17 units (16 participants) could be used for AHP analysis. Data show shortened (n = 11) and lengthened (n = 6) AHP time-course. Increased (n = 6) and decreased (n = 6) probability of early motoneurone discharge were observed in the TMS experiment. These convergent observations suggest non-uniform effects of nociceptive stimulation on motoneurone pools. This does not support the hypothesis that nociceptive input induces uniform inhibition of painful muscle. Instead, interpretation of results implies redistribution of activity between motor units, with possible benefit for unloading painful tissues. This finding supports an interpretation that differs from the generally accepted view in pain physiology regarding adaptation to motor function in pain.

Nonhomogeneity of phase state in a dusty plasma monolayer with nonreciprocal particle interactions

A monolayer—quasi-two-dimensional finite system—of Yukawa particles in a harmonic trap is under consideration. The effect of monolayer nonhomogeneity on dynamic properties and melting is studied. The results for two models of particle interactions are compared. The first model includes the reciprocal Yukawa potential and electrostatic harmonic trap. The second model additionally employs the point charge approximation of plasma wakes. It accounts for the nonreciprocity of interactions and anomalous heating of particle motion observed in dusty plasma experiments. It is demonstrated that in the point-wake model, both out-of-plane and in-plane kinetic energies of particles are radially dependent. This effect transforms the spatial distribution of dynamic characteristics in the monolayer. We show that the nonuniformity of monolayer properties might lead to several nonuniform melting scenarios and several scenarios of phase coexistence in the system. In the monolayer without nonreciprocal interactions, molten periphery coexists with a solid core. In the monolayer with plasma wakes, the opposite scenario is observed due to the joint effect of nonreciprocity and structural nonuniformity in the system. A perspective method to determine the position of the phase boundary is proposed.

Temporal Evolution of Scour at Submerged Circular Cylinders

Temporal evolutions of scour at submerged circular cylinders were investigated. Flow visualization was carried out around the cylinders over plane, under developed and equilibrium scour holes. Video analysis technique was used to formulate the equations for determining the diameter of the horseshoe vortex around the submerged cylinders, which is also verified from the vector diagrams drawn using the velocity measurements. The scour process similar to live bed scour was noticed around the downstream cylinder. The diameter of the horseshoe vortex is found to depend on the diameter of respective cylinder, submergence ratio, spacing between the cylinders and skew angle. This formulation along with the dislodgement and transportation of a single sediment particle is further incorporated in the proposed model for determining the time variation of scour around the submerged cylinders. It is evident from the results that the upstream cylinder shelters the downstream cylinder and thereby reduces the scour at the downstream cylinder. Proposed model is further extended to incorporate the effect of non-uniformity of the sediment particles on the time variation of scour depth. The results indicate significant reduction of scour depth of around 6% and 35% for upstream and downstream cylinders respectively due to the formation of the armor layer. The model is also compared with the local scour component of field data around cylindrical bridge piers to establish the differences in the scour process around a partially submerged cylinder and fully submerged tandem and skewed cylinders.

Non-uniform and volumetric effect on the hydrodynamic and thermal characteristic in a unit solar absorber

Experimental and numerical analyses on the thermal and hydrodynamic performance of volumetric solar receivers were conducted. Silicon carbide (SiC) absorbers with various pore structures were systematically investigated on a laboratory-scale test platform. A three-dimensional theoretical model coupling the fluid flow with internal heat transfer was presented. The major characteristics of the thermal and hydrodynamic behavior combining radiation, thermal conduction, and interphase convection in the absorber were presented. In addition, the key design parameters were systematically analyzed. The experimental results revealed that a small pore diameter significantly enhances the volumetric heat-transfer coefficient, which in turn increases the fluid temperature and subsequently leads to a high thermal efficiency. Under high local thermal non-equilibrium state, the non-uniform hydrodynamic characteristic significantly influenced due to the increase in the fluid viscosity at the hot spot, especially in the case of a small-pore-sized absorber, thereby increasing the risk of overheating. For absorbers with similar porosities (ϕ ∼ 0.85), dp decreased from 5.83 mm to 2.22 mm, and the thermal efficiency η increased by nearly 3%. Moreover, the simulation results revealed that the absorber unit with dp of 2.22 mm and ϕ of 0.95 exhibits the maximum thermal efficiency of 72.48%.

Advanced nanoscale characterization of aluminum nanoparticles with modified surface morphology via atmospheric helium and carbon monoxide plasmas

Aluminum nanoparticles (nAl) have the potential as energetic additives in explosive/propellant formulations. Scalable methodologies must be pursued to mitigate the inactive amorphous alumina shell surrounding the active aluminum (Al) core with modified surface morphology and chemistry for increased combustion effects. This paper explores the feasibility of making reactive core/shell nAl with thinned oxide shells and modified surface coatings via a two-step atmospheric plasma surface treatment process in a custom dielectric barrier discharge plasma reactor. The commercial nAl of nominal average size ∼40–60 nm was first treated with helium (He) followed by He/carbon monoxide (CO) plasmas for different durations. The resultant samples were characterized via high-resolution transmission electron microscopy (HRTEM) and Fourier transform IR (FTIR) spectra. HRTEM images revealed sporadic patchy γ-alumina deposits on particle surfaces and in gaps among particles for all samples, suggesting the non-uniform plasma effects of the He/CO glow. Nanoscale chemical analyses via scanning transmission electron microscopy elemental mapping and x-ray energy dispersive spectroscopy were further performed. Although no carbon-associated structure appeared in electron energy loss spectroscopy (EELS) spectra, the presence of carbonaceous materials was confirmed as a thin dispersive layer evenly distributed on the nAl surface suggesting either its amorphous nature or is present at a level insufficient to generate satisfactory EELS spectra. The trend of intensity profiles for key elements acquired by drawing lines across a single particle on the elemental maps confirmed that carbonaceous materials only existed on the surface and they were most likely carboxylates that increased with increased He/CO treatment duration, as evident by FTIR results. This work demonstrated the success of atmospheric plasma-treated reactive nAl with comprehensively characterized surface features via advanced microscopy and spectroscopy.