Spatial Uniformity Research Articles

Electrochemically exfoliated phosphorene nanosheet thin films for wafer-scale near-infrared phototransistor array

Two-dimensional (2D) black phosphorus (BP), or phosphorene, has recently emerged as a promising 2D semiconductor because of its p-type charge transport behavior and near-infrared photoresponsivity. However, the application of BP in practical electronic and optoelectronic devices is hindered by challenges in producing high-quality BP films over large areas. In this manuscript, we present a facile solution-based process to create wafer-scale BP films for fabrication of p-channel field-effect transistors that are responsive to near infrared light. Few-layer BP nanosheets are first exfoliated from the bulk crystal via electrochemical intercalation of cationic molecules and then vacuum-filtered through an anodic aluminum oxide membrane. The resulting BP film can be transferred onto an SiO2-coated silicon substrate, thereby allowing for realization of field-effect transistors after electrode deposition and thermal annealing. The transistor array exhibits spatial uniformity in electrical performance with an average hole mobility of ~0.002 cm2 V−1 s−1 and on/off ratio of 130. Furthermore, gate-induced modulation of the BP channel allows for enhancement in the photoresponsivity for 1550-nm light illumination up to 24 mA W−1, which benefits the application of the phototransistor array for near infrared imaging.

A robust bacterial high-throughput screening system to evaluate single nucleotide polymorphisms of human homogentisate 1,2-dioxygenase in the context of alkaptonuria

Alkaptonuria (AKU) is a rare inborn error of metabolism caused by a defective homogentisate 1,2-dioxygenase (HGD), an enzyme involved in the tyrosine degradation pathway. Loss of HGD function leads to the accumulation of homogentisic acid (HGA) in connective body tissues in a process called ochronosis, which results on the long term in an early-onset and severe osteoarthropathy. HGD’s quaternary structure is known to be easily disrupted by missense mutations, which makes them an interesting target for novel treatment strategies that aim to rescue enzyme activity. However, only prediction models are available providing information on a structural basis. Therefore, an E. coli based whole-cell screening was developed to evaluate HGD missense variants in 96-well microtiter plates. The screening principle is based on HGD’s ability to convert the oxidation sensitive HGA into maleylacetoacetate. More precisely, catalytic activity could be deduced from pyomelanin absorbance measurements, derived from the auto-oxidation of remaining HGA. Optimized screening conditions comprised several E. coli expression strains, varied expression temperatures and varied substrate concentrations. In addition, plate uniformity, signal variability and spatial uniformity were investigated and optimized. Finally, eight HGD missense variants were generated via site-directed mutagenesis and evaluated with the developed high-throughput screening (HTS) assay. For the HTS assay, quality parameters passed the minimum acceptance criterion for Z’ values > 0.4 and single window values > 2. We found that activity percentages versus wildtype HGD were 70.37 ± 3.08% (for M368V), 68.78 ± 6.40% (for E42A), 58.15 ± 1.16% (for A122V), 69.07 ± 2.26% (for Y62C), 35.26 ± 1.90% (for G161R), 35.86 ± 1.14% (for P230S), 23.43 ± 4.63% (for G115R) and 19.57 ± 11.00% (for G361R). To conclude, a robust, simple, and cost-effective HTS system was developed to reliably evaluate and distinguish human HGD missense variants by their HGA consumption ability. This HGA quantification assay may lay the foundation for the development of novel treatment strategies for missense variants in AKU.

Experimental and numerical study of swirl impingement cooling for turbine blade leading edge with internal ridged wall and film extraction holes

This paper presents a comparative experimental and numerical study of the internal heat transfer and pressure loss of swirl impingement cooling for turbine blade leading edge with internal ridges and film extraction holes. The leading edge cooling study includes a typical impingement cooling with centerline normal jets, a swirl impingement cooling with offset jets, and a swirl impingement cooling with offset jets and ridged wall. The normal jets are arranged at the impingement plate centerline, and the offset jets adopt a staggered arrangement alternatively on the lateral sides of the impingement plate. The ridged concave wall features two small semi-circular ridges symmetrically on opposite sides under the offset jets. Three rows of film holes are arranged symmetrically on the leading edge cavity, and another two rows of film holes are arranged on the opposite cavity wall behind. Transient thermochromic liquid crystal (TLC) experiments are conducted to obtain the detailed heat transfer distributions on the internal surface of the leading edge cavities with different cooling configurations. The results show that in the swirl impingement cooling, the swirling flow induced by the offset jets impinging onto the concave wall improves the streamwise heat transfer uniformity on the leading edge internal wall, which overcomes the limitation of large heat transfer non-uniformness between jet stagnation region and surrounding regions in typical normal jet impingement cooling. In the swirl impingement cooling with ridged wall, the near-wall jet interacts with the ridges on the concave wall and develops more widely along the spanwise directions, which greatly improves the spatial heat transfer uniformity. In addition, the ridges on the wall can also induce near-wall jets to separate from the wall and attach to the opposite concave wall, which produces low-velocity recirculation in the leading edge cavity and improves the capability and uniformity of coolant outflow through the film holes. Compared to the normal jet impingement cooling, the heat transfer of swirl impingement cooling with smooth and ridged wall can be increased respectively by 10.8%–14.0% and 10.9%–23.6% for the jet Reynold number from 20,000 to 50,000. In addition, the pressure loss is also reduced slightly by less than 5% in the swirl impingement cooling. As supplements to the experiments, numerical computations provide more insights into the turbulent flow structure in the leading edge cooling configurations.

Theoretical Study of the Spatial Resolution Characteristics of Magnetic Focusing Framing Tubes

Three magnetic focusing framing tubes are designed based on short magnetic lenses, long magnetic lenses, and hybrid lenses consisting of short and long magnetic lenses, and the spatial resolution characteristics of these framing tubes are theoretically studied. The excitation current of the short magnetic lenses is 0.15 A, the imaging magnification ratio is 1:1, and the spatial resolution is better than 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> . The spatial resolution difference is 23.08% within the 30-mm off-axis. The spatial resolution of the long magnetic lens framing tube is better than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20~\mu \text{m}$ </tex-math></inline-formula> , and the spatial resolution difference is 10.71%. However, the long magnetic lenses require a large excitation current of 26.25 A. For the hybrid magnetic lenses, the excitation current of 0.15 A is used to achieve a spatial resolution of better than 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and a spatial resolution difference of 8.11%. The simulation results show that the hybrid magnetic lenses are the best imaging method among these three lenses. A high spatial resolution and spatial resolution uniformity can be simultaneously obtained by using a small excitation current in the hybrid magnetic lens framing tube.

Light intensity and uniformity in commercial broiler houses using lighting programs derived from Global Animal Partnership (GAP) lighting standards

Global Animal Partnership (GAP) is an organization that has created alternative standards for raising commercial broilers, including elevated light intensity and provisions for natural light. The objectives of this study were to compare light intensity levels and spatial uniformity in the following treatments derived from GAP lighting standards: 1) light intensity from natural and artificial sources greater than 50 lx (NL 1% +LED), and 2) natural light only provided through an opening equal or greater than 1.0% of total floor area (NL 1% ). Light intensity was also measured in a house using a traditional LED lighting program (LED) for comparison. Light intensity was spatially measured at a fixed point in time (static) for the NL 1% +LED, NL 1% , and LED treatments and then temporally measured in three house sections (pad, mid, and fan) over a 24 h period. Overall static mean light intensity was significantly higher (P < 0.05) in the NL 1% +LED and NL 1% treatments than the LED treatment, and most dissimilar in the mid house section (LED=2.8 lx, NL 1% +LED=95.4 lx, NL 1% =77.1 lx). Seventy-nine percent and 53% of the floor area in the NL 1% +LED and NL 1% treatments were above 50 lx, the target light intensity set by GAP. Light uniformity was best in the pad and mid sections of the LED treatment. Temporal testing showed at mid house that light intensity was most influenced by natural light and that daily averages were 23 times higher in the NL 1% treatment (NL 1% =46.0 lx; LED = 2.0 lx). GAP derived lighting programs resulted in markedly different lighting environments compared to traditional programs.

Early-season plant-to-plant spatial uniformity can affect soybean yields

Increased soybean (Glycine max L. Merril) seed costs have motivated interest in reduced seeding rates to improve profitability while maintaining or increasing yield. However, little is known about the effect of early-season plant-to-plant spatial uniformity on the yield of modern soybean varieties planted at reduced seeding rates. The objectives of this study were to (i) investigate traditional and devise new metrics for characterizing early-season plant-to-plant spatial uniformity, (ii) identify the best metrics correlating plant-to-plant spatial uniformity and soybean yield, and (iii) evaluate those metrics at different seeding rate (and achieved plant density) levels and yield environments. Soybean trials planted in 2019 and 2020 compared seeding rates of 160, 215, 270, and 321 thousand seeds ha−1 planted with two different planters, Max Emerge and Exact Emerge, in rainfed and irrigated conditions in the United States (US). In addition, trials comparing seeding rates of 100, 230, 360, and 550 thousand seeds ha−1 were conducted in Argentina (Arg) in 2019 and 2020. Achieved plant density, grain yield, and early-season plant-to-plant spacing (and calculated metrics) were measured in all trials. All site-years were separated into low- (2.7 Mg ha−1), medium- (3 Mg ha−1), and high- (4.3 Mg ha−1) yielding environments, and the tested seeding rates were separated into low (< 200 seeds m−2), medium (200–300 seeds m−2), and high (> 300 seeds m−2) levels. Out of the 13 metrics of spatial uniformity, standard deviation (sd) of spacing and of achieved versus targeted evenness index (herein termed as ATEI, observed to theoretical ratio of plant spacing) showed the greatest correlation with soybean yield in US trials (R2 = 0.26 and 0.32, respectively). However, only the ATEI sd, with increases denoting less uniform spacing, exhibited a consistent relationship with yield in both US and Arg trials. The effect of spatial uniformity (ATEI sd) on soybean yield differed by yield environment. Increases in ATEI sd (values > 1) negatively impacted soybean yields in both low- and medium-yield environments, and in achieved plant densities below 200 thousand plants ha−1. High-yielding environments were unaffected by variations in spatial uniformity and plant density levels. Our study provides new insights into the effect of early-season plant-to-plant spatial uniformity on soybean yields, as influenced by yield environments and reduced plant densities.

Pore-Scale Saturation and Liquid Water Pathways in PEFCs: Insights from Correlative 2D and 3D X-Ray Imaging

Improving the efficiency of polymer electrolyte fuel cells (PEFCs) through high power density operation necessitates liquid water management in the cathode gas diffusion layer (GDL), where liquid water saturation inhibits oxygen diffusivity. To this end, there have been numerous efforts aimed at understanding liquid water transport behaviour to guide GDL design improvements. X-ray imaging of representative in-operando miniaturized PEFC samples has been instrumental to much of recent progress [1–4] in understanding liquid water distribution patterns. Radiographic two-dimensional (2D) images have enabled visualization of liquid water dynamics [3] while three-dimensional (3D) computed tomography images have provided pore-scale information of liquid water saturation states in the GDL [2] and of its transport mechanism [4]. However, how liquid water pathways are formed and the likelihood for preferential pathways remain unclear.In this work, we investigate factors that influence liquid water distribution and pathway definition using correlative rapid 2D and long duration 3D operando X-ray datasets which enable a visualization of liquid water breakthrough dynamics and the corresponding pore-scale interactions in the GDL. The correlated images together with GDL pore structure visualization are used to identify three characteristic pore-scale saturation behaviour with sample regions highlighted in Fig. 1. These regions include locations with restricted liquid water breakthrough, locations with apparent large breakthrough porous pathways where breakthrough liquid water is observable at least in the 2D images, and similarly porous regions where no liquid water breakthrough is observed. It is found that the behaviour shown in the identified regions are strongly linked to local pore-scale structural characteristics and capillary pressure distribution in the GDL. Investigating the 3D virtual GDL from around the microporous layer through to the channel interface, it is shown that liquid water pathways get increasingly defined with a decrease in spatial uniformity towards the flow channels. Pore-scale analysis and observed flow mechanisms show that the defined pathways are locally accessible paths of least capillary resistance dictated by pore radius and associated hydrophobicity. These findings highlight the important role that pore scale topology plays in addition to pore size distribution for future GDL design aimed at improving water management. Keywords— operando, fuel cell, water, pore structure, X-ray imaging Acknowledgments Funding for this research was provided by the Natural Sciences and Engineering Research Council of Canada, Ballard Power Systems, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, Western Economic Diversification Canada, and Canada Research Chairs.

Stimulated microbial growth for permeability reductions in granular soils

The controlled production of microbial growth has the potential to reduce groundwater flow in seepage and dewatering systems. Stimulating the growth of indigenous bacteria could clog the pore space and result in a substantial permeability reduction. This study investigated the spatial distribution of permeability reduction under different nutrient stimulation treatments of indigenous bacteria across 16 cm columns of Ottawa 50–70 sand. Spatially uniform permeability reductions of up to an order of magnitude were achieved using both a high glucose (50 mg/l) and a low glucose (10 mg/l) nutrient formulation. The overall permeability began to decrease by day 2 and approached a minimum permeability by day 14. There was no noticeable difference in the final permeability nor the rate of permeability reduction between high and low glucose formulations. Upscaling of experiments is highly recommended for future studies on the spatial uniformity of microbial growth and biologically induced permeability reductions.

Non-cuboid iterative room optimizer

The growing processing power of desktop and distributed cloud cluster computing is playing a larger role providing computational architectural acoustic solutions. This presentation will provide a status update on the Non-cuboid Iterative Room Optimization software called NIRO. It offers an iterative approach to full bandwidth optimization of critical listening rooms. The program uses a finite element method (FEM), image source model (ISM), and non-dominating sorting genetic algorithm (NSGA) to simultaneously optimize the room geometry of any shaped room, including boundary admittances, for any number of listeners and loudspeakers. It minimizes the weighted sum of the modal response and speaker boundary interference response, the spatial uniformity around the mix position and reflections in the reflection free zone (RFZ). With an optimal room setup, acoustical diffusors and absorbers with a specified resonant frequency, bandwidth, and efficiency are added to the model to optimize the acoustic properties. A combination of FEM, ISM, and an additional geometrical acoustics model is used to generate full bandwidth impulse responses. The RFZ, envelopment, reverberation time, low-frequency response, and temporal decay are optimized and evaluated. Following the addition of HRTFs, stereo auralization can be generated. Proof of performance and application examples will be presented.

Flexible Metamaterial Wrap for Improved Head Imaging at 3 T MRI With Low-Cost and Easy Fabrication Method.

Magnetic resonance imaging (MRI) requires spatial uniformity of the radiofrequency (RF) field inside the subject for maximum signal-to-noise ratio (SNR) and image contrast. Bulky high permittivity dielectric pads (HPDPs) focus magnetic fields into the region of interest (ROI) and increase RF field uniformity when placed between the patient and RF coils in the MR scanner. Metamaterials could replace HPDPs and reduce system bulkiness, but those in the literature often require a complicated fabrication process and cannot conform to patient body shape. Proposed is a flexible metamaterial for brain imaging made with a scalable fabrication process using conductive paint and a plastic laminate substrate. The effects of single and double-sided placement of the metamaterial around a human head phantom were investigated in a 3 T scanner. When two metamaterial sheets were wrapped around a head phantom (double-sided placement), the total average signal in the resulting image increased by 10.14% compared to placing a single metamaterial sheet underneath the phantom (single-sided placement). The difference between the maximum and minimum signal intensity values decreased by 57% in six different ROIs with double-sided placement compared to single-sided placement.

Continuum soft tissue models from upscaling of arrays of hyperelastic cells

Constitutive models for soft tissue mechanics are typically constructed by fitting phenomenological models to experimental measurements. However, a significant challenge is to rationally construct soft tissue models that encode the properties of the constituent cells and their extracellular matrix. This work presents a framework to derive multiscale soft tissue models that incorporate properties of individual cells without assuming homogeneity or periodicity at the cell level. We consider a viscoelastic model for each cell (which can deform, grow and divide), that we couple to form a network description of a one-dimensional line of cells. We use a discrete-to-continuum approach to form (nonlinear) continuum partial differential equation models for the tissue. These models elucidate the contrasting role of the two forms of dissipation: substrate dissipation localizes the deformation to the neighbourhood of the free boundary and inhibits morphoelastic growth, whereas internal cell dissipation promotes spatial uniformity and does not influence the elongation length. Furthermore, cell division is shown to increase the rate of elongation of the array compared with growth alone, provided the substrate dissipation is proportional to the cell surface area.

High-Throughput Nanopore Fabrication and Classification Using Xe-Ion Irradiation and Automated Pore-Edge Analysis.

Large-area nanopore drilling is a major bottleneck in state-of-the-art nanoporous 2D membrane fabrication protocols. In addition, high-quality structural and statistical descriptions of as-fabricated porous membranes are key to predicting the corresponding membrane-wide permeation properties. In this work, we investigate Xe-ion focused ion beam as a tool for scalable, large-area nanopore fabrication on atomically thin, free-standing molybdenum disulfide. The presented irradiation protocol enables designing ultrathin membranes with tunable porosity and pore dimensions, along with spatial uniformity across large-area substrates. Fabricated nanoporous membranes are then characterized using scanning transmission electron microscopy imaging, and the observed nanopore geometries are analyzed through a pore-edge detection and analysis script. We further demonstrate that the obtained structural and statistical data can be readily passed on to computational and analytical tools to predict the permeation properties at both individual pore and membrane-wide scales. As an example, membranes featuring angstrom-scale pores are investigated in terms of their emerging water and ion flow properties through extensive all-atom molecular dynamics simulations. We believe that the combination of experimental and analytical approaches presented here will yield accurate physics-based property estimates and thus potentially enable a true function-by-design approach to fabrication for applications such as osmotic power generation and desalination/filtration.

Enhancing optoacoustic mesoscopy through calibration-based iterative reconstruction

Optoacoustic mesoscopy combines rich optical absorption contrast with high spatial resolution at tissue depths beyond reach for microscopic techniques employing focused light excitation. The mesoscopic imaging performance is commonly hindered by the use of inaccurate delay-and-sum reconstruction approaches and idealized modeling assumptions. In principle, image reconstruction performance could be enhanced by simulating the optoacoustic signal generation, propagation, and detection path. However, for most realistic experimental scenarios, the underlying total impulse response (TIR) cannot be accurately modelled. Here we propose to capture the TIR by scanning of a sub-resolution sized absorber. Significant improvement of spatial resolution and depth uniformity is demonstrated over 3 mm range, outperforming delay-and-sum and model-based reconstruction implementations. Reconstruction performance is validated by imaging subcutaneous murine vasculature and human skin in vivo. The proposed experimental calibration and reconstruction paradigm facilitates quantitative inversions while averting complex physics-based simulations. It can readily be applied to other imaging modalities employing TIR-based reconstructions.

Solvent Effect on the Synthesis of Oleylamine Modified Au Nanoparticles and Their Self-Assembled Film for SERS Substrate

The preparation and self-assembling of monodisperse gold nanoparticles (Au NPs) is of great significance for its SERS application. According to the oleylamine-reduced method, oleylamine (OAm) serves as the reducing agent and stabilizing agent, and the effects of different reaction parameters such as solvent and temperature on the size and dispersity of Au NPs have been evaluated. The Au NPs synthesized with toluene as the solvent have the best dispersity and narrowest particle size distribution with adjustable sizes. The particle size gradually increases with the increase in reaction temperature. The highly ordered self-assembly film of Au NPs was employed as surface-enhanced Raman scattering (SERS) substrate for the probing molecule of rhodamine 6G. The Au substrate exhibits excellent spatial uniformity and SERS reproducibility, which indicates its practicability as a substrate. This study provides a simple synthesis strategy of highly ordered monodispersed Au NPs, which can serve as a SERS substrate with excellent spatial uniformity and SERS re-producibility.

A Feasibility Study of an Optimization-Based Active Field Uniformity Compensation Method for Superconducting Magnets

In order to enhance the quality of measurement results of various scientific instruments, such as magnetic property measurement systems, magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR) and others, a spatially uniform magnetic field is required at the magnetic center. However, the measured field uniformity is usually worse than that in the design result due to the manufacturing errors of a superconducting magnet system. Therefore, spatial field uniformity compensation is needed to reduce the effects of manufacturing errors on field uniformity. Conventional field compensation methods require recursive routines of field mapping and compensation coil current adjustments, which lead to a less effective time-consuming process. In this study, a recently developed active field compensation algorithm employing pattern search, an optimization theory, will be introduced. A MATLAB code for active compensation coil current calculations with pattern search was developed, and six compensation coil designs and field distribution calculations with and without the proposed method were also carried out to compare the results. The test results demonstrate the feasibility of the proposed field compensation method for superconducting magnets.

Characterization of vertical and longitudinal gusts generated by twin pitching airfoils

An experimental investigation is performed to characterize vertical and longitudinal gusts generated by a gust generator device in a low-speed water tunnel. The device is composed of two pitching airfoils with adjustable motion modes, namely, in-phase and out-of-phase. Phase-locked two-dimensional particle image velocimetry is used to measure the velocity field downstream of the airfoils. When the two airfoils pitch in phase, periodic vertical gusts dominate the flow field, while periodic longitudinal gusts dominate when the two airfoils pitch out of phase. A waveform similarity coefficient is proposed to quantify the spatial uniformity of the gust fields, which measures how similar gust profiles are at different spatial locations. For the two types of gusts, various airfoil spacings, pitching amplitudes, and reduced frequencies are considered to examine the effects of parameters on the downstream gust characteristics. The results show that a smaller airfoil spacing produces a larger gust amplitude; however, the region with a better uniformity is reduced. As the pitching amplitude increases, the gust amplitude increases linearly, and the uniformity of the measurement region improves. The slope between the gust amplitude and pitching amplitude increases with a reduced frequency, but further larger reduced frequencies could result in poor gust uniformity. Excluding the cases with poor uniformity, this device delivers a vertical gust amplitude up to 6.7% of the free-stream velocity with reduced frequencies of k = 0.2–0.6 and a longitudinal gust amplitude of 10% of the free-stream velocity with reduced frequencies of k = 0.2–0.8.

Spatial uniformity of action potentials indicates base-to-apex depolarization and repolarization of rainbow trout (Oncorhynchus mykiss) ventricle.

The spatial pattern of electrical activation is crucial for a full understanding of fish heart function. However, it remains unclear whether there is regional variation in action potential (AP) morphologies and underlying ion currents. Because the direction of depolarization and spatial differences in the durations of ventricular APs set limits to potential patterns of ventricular repolarization, we determined AP morphologies, underlying ion currents and ion channel expression in four different ventricular regions (spongy myocardium; and apex, base and middle of the compact myocardium), and correlated them with in vivo electrocardiograms (ECGs) in rainbow trout (Oncorhynchus mykiss). ECGs recorded from three leads indicated that the depolarization and repolarization of APs propagate from base to apex, and the main depolarization axis of the ventricle is between +90 and +120deg. AP shape was uniform across the whole ventricle, and little regional differences were found in the density of repolarizing K+ currents or depolarizing Ca2+ and Na+ currents and the underlying transcripts of ion channels, providing compelling evidence for the suggested excitation pattern. The spatial uniformity of AP durations and base-to-apex propagation of activation with a relatively slow velocity of propagation indicates no special ventricular conduction pathway in the trout ventricle such as the His-Purkinje system of mammalian hearts. The sequence of repolarization is solely determined by activation time without being affected by regional differences in AP duration.

Simulation of Plasma Assisted Supersonic Combustion over a Flat Wall

This work presents a simplified methodology to couple the physics of a nanosecond pulsed discharge to the process of supersonic combustion in a flat wall combustor configuration. Plasma and supersonic combustion are separately simulated and then coupled by seeding plasma-generated radicals on the combustion domain. The plasma model is built assuming spatial uniformity and considering only the kinetic effects of the nanosecond pulsed discharge. Therefore, a zero-dimensional kinetic scheme accounting for the generation of plasma species is utilized. For the combustion model, the complete set of Favre-averaged compressible Navier Stokes equations along with finite rate chemistry is solved through a control-volume based technique via the commercial software Ansys Fluent. The computational results are compared against experimental studies showing that the proposed methodology can capture the main kinetic effects of the nanosecond pulsed discharge on supersonic combustion. OH concentration contours reveal the presence of an enhanced flame when the plasma is applied following the trends from experimental OH PLIF images. In addition, time evolving temperature and OH concentration contours show that the ignition delay time is reduced with the application of the discharge.

A novel design framework of synthetic radial aperture focusing for volumetric transrectal ultrasound imaging.

In this paper, we present a novel design framework of synthetic radial aperture focusing for three-dimensional (3D) transrectal ultrasound imaging (TRUS-rSAF), in which multiple transmittance/reception events at different scanning angles are synthesized to reconstruct a radial plane in the target volume, securing high spatial resolution and texture uniformity. A theory-based design approach has not been available to push the envelope of the 3D rSAF technique. Herein, a closed-form analytical description of the TRUS-rSAF method is presented for the first time, effectively delineating spatial resolution and grating lobe positions in the radial dimension of a TRUS transducer. We demonstrate a solid optimization workflow based on the theoretical foundation to improve its spatiotemporal resolution, grating lobe artifacts, and signal-to-noise ratio. A specific design criterion was considered to outperform a clinical 3D TRUS imaging as a reference (TRUS-REF), where each radial plane is reconstructed with a single transmittance/reception event using a motorized actuator. The optimized TRUS-rSAF method significantly enhanced spatial resolution up to 50% over the TRUS-REF method while providing clinically effective temporal resolution (2–8 volume/sec) with negligible grating lobe artifacts. The results indicate that the proposed design approach would enable a novel TRUS imaging solution in clinics.

Analysis of the energy distribution of iron nano-spheres for bit-patterned media

Improved magnetic memory systems belong to the main research topics in spintronics. Here we show micromagnetic simulations used to analyze the energy density of nano-scaled iron spheres. Layers of different thickness, partly coated with iron oxide, were tested in terms of spatial uniformity of the physical system energy. For a single non-coated or iron-oxide coated droplet, the spatial distribution of the total energy is not uniform and depends on the nano-droplet size. Additionally, for systems consisting of four objects, the relation between relative distance and the resultant magnetization distribution was analyzed. The mutual relation between droplet size and the underlying magnetization distribution as well as the character of local energy extrema was investigated. The size changes for the four-droplet system were compared with the single object behavior to obtain a criterion for the minimum distance between spheres to behave as a single object. The calculations revealed that the oxidized spheres could be placed closer to each other in comparison to the non-coated system. For the proposed oxide coated system, the increase of this maximum packing density is equal to about 12%, as compared to the non-coated system.