Tilted Plane Research Articles

P‐50: Multi‐depth‐SGD Based Tilted Plane Diffraction Propagation for Holographic Near‐eye Displays

To facilitate the practical application of wearable holographic near‐eye displays, the propagation between non‐parallel planes is essential for the hologram generation of off‐axis projection onto the holographic‐optical‐element (HOE) based combiners. However, existing methods, particularly the angular spectrum rotation‐based approach for generating tilted plane holograms, encounter challenges such as gradient loss when integrated with the stochastic gradient descent (SGD) algorithm. In this paper, we present a novel method for generating a tilted plane hologram using multi‐depth‐SGD, effectively mitigating the gradient loss issue.

A coupled VOF/embedded boundary method to model two-phase flows on arbitrary solid surfaces

We present an hybrid VOF/embedded boundary method allowing to model two-phase flows in presence of solids with arbitrary shapes. The method relies on the coupling of existing methods: a geometric Volume of fluid (VOF) method to tackle the two-phase flow and an embedded boundary method to sharply resolve arbitrary solid geometries. Coupling these approaches consistently is not trivial and we present in detail a quad/octree spatial discretization for solving the corresponding partial differential equations. Modelling contact angle dynamics is a complex physical and numerical problem. We present a Navier-slip boundary condition compatible with the present cut cell method, validated through a Taylor–Couette test case. To impose the boundary condition when the fluid–fluid interface intersects a solid surface, a geometrical contact angle approach is developed. Our method is validated for several test cases including the spreading of a droplet on a cylinder, and the equilibrium shape of a droplet on a flat or tilted plane in 2D and 3D. The temporal evolution and convergence of the droplet spreading on a flat plane is also discussed for the moving contact line given the boundary condition (Dirichlet or Navier) used. The ability of our numerical methodology to resolve contact line statics and dynamics for different solid geometries is thus demonstrated.

Efficient and accurate intensity diffraction tomography of multiple-scattering samples.

Optical Diffraction Tomography (ODT) is a label-free method to quantitatively estimate the 3D refractive index (RI) distributions of microscopic samples. Recently, significant efforts were directed towards methods to model multiple-scattering objects. The fidelity of reconstructions rely on accurately modelling light-matter interactions, but the efficient simulation of light propagation through high-RI structures over a large range of illumination angles is still challenging. Here we present a solution dealing with these problems, proposing a method that allows one to efficiently model the tomographic image formation for strongly scattering objects illuminated over a wide range of angles. Instead of propagating tilted plane waves we apply rotations on the illuminated object and optical field and formulate a new and robust multi-slice model suitable for high-RI contrast structures. We test reconstructions made by our approach against simulations and experiments, using rigorous solutions to Maxwell's equations as ground truth. We find the proposed method to produce reconstructions of higher fidelity compared to conventional multi-slice methods, especially for the challenging case of strongly scattering samples where conventional reconstruction methods fail.

Efficient Dense Orbital Angular Momentum Demultiplexing Enabled by Quasi‐Wavelet Conformal Mapping

AbstractOrbital angular momentum (OAM) has recently attracted increasing interest in optical communications for capacity scaling by OAM mode‐division multiplexing (MDM). OAM (de)multiplexer is crucial to the success of OAM‐MDM communications. Scalable and efficient dense OAM demultiplexing is highly desired, but full of challenges. Here, a quasi‐wavelet conformal mapping method is proposed and demonstrated to implement scalable and efficient dense OAM demultiplexing. The OAM mode is divided at the input plane into multiple concentric rings, which are mapped to multiple tilted plane waves and arranged side by side in a line. The engineered transformed light beams with periodic extension and increased length enable narrow focused spot width, reduced beam overlap, and suppressed demultiplexing crosstalk. The quasi‐wavelet conformal mapping method is compared with conventional log‐polar transformation scheme and hybrid log‐polar and fan‐out technique, and the crosstalk matrix for OAM demultiplexing is measured. Efficient OAM demultiplexing is demonstrated for 15 OAM modes (OAM−7 to OAM+7) with a maximum crosstalk of −12.1 dB in the experiment. Moreover, the method is also applied to system‐level data‐carrying OAM‐MDM communications with favorable performance. The demonstrated quasi‐wavelet conformal mapping method may pave the way for future ultrahigh capacity dense OAM‐MDM communications with a large number of OAM modes.

Zonal reconstruction of surfaces from gradient fields

A method is given to reconstruct a surface from measured surface gradient values located on a two-dimensional, square grid using a zonal method. Reconstruction is done square by square, using a surface elevation value calculated when processing the previous neighboring square as a reference elevation value and then calculating the difference from that value for the other three locations of the square. The curved surface area element defined by a grid square is, in general, a tilted, toric surface that is decomposed into four component surfaces; a tilted plane, a surface of revolution, and two cross-cylinder surfaces. Only the tilted plane and the oblique cross-cylinder surface contribute to elevation differences at the square corners so only they need to be included in the calculations. This unique use of available information allows the surface to be reconstructed without the iterative steps that are generally needed in zonal reconstruction methods. Methods to deal with boundary conditions and with measurement noise are also included in the implementation of the method.

Control of Néel Vector with Spin-Orbit Torques in an Antiferromagnetic Insulator with Tilted Easy Plane.

Injecting spin currents into antiferromagnets and realizing efficient spin-orbit-torque switching represents a challenging topic. Because of the diminishing magnetic susceptibility, current-induced antiferromagnetic dynamics remain poorly characterized, complicated by spurious effects. Here, by growing a thin film antiferromagnet, α-Fe_{2}O_{3}, along its nonbasal plane orientation, we realize a configuration where the spin-orbit torque from an injected spin current can unambiguously rotate and switch the Néel vector within the tilted easy plane, with an efficiency comparable to that of classical ferrimagnetic insulators. Our study introduces a new platform for quantitatively characterizing switching and oscillation dynamics in antiferromagnets.

Optimal Design and Techno-Economic Analysis of a Grid-Connected Photovoltaic and Battery Hybrid Energy System

The application of green energy technologies (GETs) has been accepted universally due to the industrial revolution, increasing energy demand, high standard of living, population growth and fluctuation of crude oil prices. In view of this, GETs have been recognized on a global note as a promising and significant alternative to meet ever increasing power demand. This research work is aimed at optimal operation and design of hybrid renewable energy system (HRES) to enhance the performance of the power system while taking into consideration the energy produced, levelized cost of energy (LCOE), return on investment (ROI), solar fraction (SF), net present value (NPV), payback period and saved CO2 emissions based on the photovoltaic (PV) orientation. This is due to the fact that the solar panel generates more electrical output when its surface is perpendicular to the solar radiation. The PV orientation significantly affects the output of a solar farm, for this reason, fixed tilted plane, vertical axis tracking system and two axes tracking system are proposed in this research work to estimate their effects on the technical, economic and environmental performance of HRES. This paper presents a grid-connected HRES that comprises utility grid, PV, battery system (BS) and load. The modelling and simulation of HRES are implemented by using PVsyst.7 energy tools in conjunction with the meteorological data made available by the National Aeronautics and Space Administration (NASA). The research outputs show that the two axes tracking system is more techno-economic feasible when compared with the fixed tilted plane and vertical axis tracking system based on the following results: Energy obtained from the grid of 4.657 MW/yr, LCOE of 0.075 ZAR/kWh, ROI of 862.7%, SF of 0.6781, NPV of 828,881.74 ZAR, payback period of 3.5 years and carbon balance of 732.240 tons. The outcomes of the study can be used by the power system planners and designers as benchmarks to utilize the prospect of solar resources for power sector reform and the industrial revolution.

Coaccretion + Giant-impact Origin of the Uranus System: Tilting Impact

Abstract The origin of the Uranian satellite system remains uncertain. The four major satellites have nearly circular, coplanar orbits, and the ratio of the satellite system to planetary mass resembles Jupiter’s satellite system, suggesting the Uranian system was similarly formed within a disk produced by gas coaccretion. However, Uranus is a retrograde rotator with a high obliquity. The satellites orbit in its highly tilted equatorial plane in the same sense as the planet’s retrograde rotation, a configuration that cannot be explained by coaccretion alone. In this work, we investigate the first stages of the coaccretion + giant-impact scenario proposed by Morbidelli et al. (2012) for the origin of the Uranian system. In this model, a satellite system formed by coaccretion is destabilized by a giant impact that tilts the planet. The primordial satellites collide and disrupt, creating an outer debris disk that can reorient to the planet’s new equatorial plane and accrete into Uranus’ four major satellites. The needed reorientation out to distances comparable to outermost Oberon requires that the impact creates an inner disk with ≥1% of Uranus’ mass. We here simulate giant impacts that appropriately tilt the planet and leave the system with an angular momentum comparable to that of the current system. We find that such impacts do not produce inner debris disks massive enough to realign the outer debris disk to the post-impact equatorial plane. Although our results are inconsistent with the apparent requirements of a coaccretion + giant-impact model, we suggest alternatives that merit further exploration.

Technical Performance Prediction and Employment Potential of Solar PV Systems in Cold Countries

Power distribution to decentralized and remote communities secluded from centralized grid connections has always been a problem for utilities and governments worldwide. This situation is even more critical for the isolated communities in Russia due to the vast nature of the country. Therefore, the Russian government is formulating and implementing several strategies to develop its renewable energy sector. However, very little information is available on the possible performance of solar photovoltaic (PV) modules under Russian weather conditions for all year round. Thus, this study has been designed to fill that research gap by assessing the performance ratio (PR), degradation, energy loss prediction, and employment potential of PV modules in the Sverdlovsk region of Russia using the PVsyst simulation model. A side-by-side comparison of the fixed tilted plane and tracking horizontal axis East–West were analyzed. According to the results, the annual production probability (P) for the fixed PV module for a P50, P75, and P90 is 39.68 MWh, 37.72 MWh, and 35.94 MWh, respectively, with a variability of 2.91 MWh. In the case of the tracking PV module, the annual production probability for the P50, P75, and P90 is 43.18 MWh, 41.05 MWh, and 39.12 MWh, respectively, with a variability of 3.17 MWh. A PR of 82.3% and 82.6% is obtained for the fixed and tracking systems, respectively, while the PV array losses for the fixed and tracking orientations are 15.1% and 14.9%, respectively. The months of May to August recorded the highest array losses due to the high temperatures that are usually recorded within that period.

Optimization of Solar Panel Tilt and Azimuth Angle for Maximum Solar Irradiation and Minimum Loss for Rural Electrification

Abstract: The earth receives solar power at a rate of 120 petawatts, meaning that the energy obtained from the sun in a single day could satisfy the world’s energy needs for almost twenty years. Africa is often considered and referred as the "Sun continent" or the continent where the Sun's influence is the greatest, yet over 600 million people in sub-Saharan Africa live without electricity. This inexhaustible, untapped, abundant, and environmentally friendly solar energy potential encouraged solar power generation technologies to flourish faster than any other renewable energy technology most especially in Africa. The amount of electricity generated by a fixed-tilt solar PV system depends on the orientation of the PV panel (tilt and azimuth angle) relative to the sun. The panel of a solar PV system collect solar radiation more efficiently when the sun's rays are perpendicular to the panel: when the sun hits it directly at a 90o degree angle; but the sun is a moving target. Not only does it move across the sky throughout the day, but it is higher in the sky in the dry season (winter) from October to March and lower in the sky in the wet season (summer) from April to September. Since the climate is usually characterized into two seasons, the system optimization presented in this paper was carried out based on: yearly irradiation yield (fixed tilted plane) to guarantee optimum solar irradiation throughout the year, with 0.0% loss with respect to optimum. The system eliminates the challenges associated with changing the solar panel orientation every season, or using the expensive and inefficient sun tracker in tracking sun energy; while guaranteeing higher energy production, better system performance, lower system losses, and low operational cost. The system optimization was carried out with the “PVsyst simulation software” made for PV system designers and researchers to predict the performance of different solar system configurations, evaluate the results, and identify the best approach for maximum energy production. This paper investigated the optimal tilt and azimuth angle for solar panel orientation techniques for a typical rural community in Nigeria (Ndikelionwu) to advance rural electrification. After series of simulation and optimization processes; the best yearly irradiation yield was recorded when the solar panel is at 40o tilt and 0o Azimuth angle; with 0.0% loss with respect to optimum. Keywords: Optimization, PVsyst, Solar Irradiation, Tilt and Azimuth Angle, Global on Collector Plane, Fixed Tilted Plane, Rural Electrification, Solar Panel Orientation And Yearly Irradiation Yield.

Generalized chromatic aberrations in non-rotationally symmetric optical systems–Part I: mathematical approach

In non-rotationally symmetric optical systems, chromatic aberrations must be defined in a generalized way with reference to the optical axis ray and optimal tilted parabasal image plane of the central wavelength. In this paper, the definition of generalized chromatic aberrations is clarified. The mathematical calculation in optical systems with arbitrary symmetry and surface shape is realized by ray- and wavefront-based methods, respectively, that are originally identical. The additivity of wavefront after each surface ensures the surface decomposition of chromatic aberrations. In the end, the influence of pupil aberration, which is of a higher order, is discussed. The consistency of our methods with Seidel aberrations in the lowest aberration order of the rotationally symmetric system and the application of our methods in diverse non-rotationally symmetric refractive systems will be addressed in detail in Part II.

Quantifying end-face quality of cleaved fibers: Femtosecond laser versus mechanical scribing

A femtosecond laser-based scribing procedure has been investigated for cleaving silica optical fiber. As a proof of concept, SMF 28 fiber was scribed by 1030 nm femtosecond laser pulses at 10 kHz and then placed under tension to initiate cleaving. The resulting end faces were measured using a noncontact optical interferometer, but the subsequent analysis identified deficiencies in the conventional “cleave angle” parameter. This was partly due to the difficulty of aligning the longitudinal axis of the fiber with the optical axis of the optical profilometer, but also because the end faces generally did not resemble a simple tilted plane. As an alternative metric, we therefore evaluated the probability density function of the local tilts over the central portion of the cleaved end faces (0.9 fraction of the fiber radius) after subtracting the global best fit plane. This provided a median tilt value of 0.17° for laser scribing and 0.55° for mechanical scribing (averaged over five samples of each). The laser-scribed fibers had a total height variation of 12 µm versus 17 µm for the mechanically-scribed fibers, and they were free of rounding and melting around the edges. Thus the cleaved end face produced by femtosecond laser scribing has superior quality in terms of flatness, smoothness and symmetry compared to mechanical scribing. The technique also has important potential advantages compared to laser cleaving based on CO2 lasers, where the glass is machined by melting. With further development of the technique, it has the potential to be used for automated cleaving of specialty fibers and multi fiber arrays with comparable cleave quality.

Flaw Detection on a Tilted Particleboard by Use of the Spec-Radiation Method

Herein, we present a novel approach to the spec-radiation method (a method of acoustical holography) for determining the sound distribution on a tilted particleboard by calculating a single plane and rotation in the frequency domain. The tilted particleboard allows testing without standing waves between the transmitter and the particleboard. This eliminates the need to evaluate several parallel planes and to search for values belonging to the tilted particleboard. The numerical requirements can be optimally exploited through a combination with a flaw detectability enhancement method. The results are supported by experiments on a wooden particleboard with flaw imitations. Finally, we showed, through a comparison with the usual procedure of identifying a flaw (calculating many parallel planes and then selecting the data belonging to the tilted plane), that the calculation of the tilted plane is up to 98.5% faster and improves the detectability of flaws in a tilted particleboard.

Most relevant input parameters selection for 10-min global solar irradiation estimation on arbitrary inclined plane using neural networks

ABSTRACT This paper propounds the use of ‘Weights’ method to assess the relative importance of input features for estimating 10-min global solar irradiation on an arbitrary tilted plane, using artificial Neural Networks (ANNs). Two different data sources are exerted: satellite data, including different inclinations, are used for learning, while ground data, measured at Bouzaréah radiometric station (Algeria), are used for testing. ‘Weights’ method allowed to identify the relative importance of input variables and rank them according to their order of contribution, thus significantly improving the performance of the model by eliminating the parameters that are poorly correlated with the network output. The results show that the most relevant input data are in the following order: the global horizontal irradiation 35.9%, extraterrestrial irradiation 25.08%, declination 15.81%, elevation of the sun 12.60% and inclination 10.61%. The optimal configuration includes 16 neurons in the hidden layer with nRMSE = 6.37% and R 2 = 0.992.

Distinctive structural properties of THB11, a pentacoordinate Chlamydomonas reinhardtii truncated hemoglobin with N- and C-terminal extensions

Hemoglobins (Hbs) utilize heme b as a cofactor and are found in all kingdoms of life. The current knowledge reveals an enormous variability of Hb primary sequences, resulting in topological, biochemical and physiological individuality. As Hbs appear to modulate their reactivities through specific combinations of structural features, predicting the characteristics of a given Hb is still hardly possible. The unicellular green alga Chlamydomonas reinhardtii contains 12 genes encoding diverse Hbs of the truncated lineage, several of which possess extended N- or C-termini of unknown function. Studies on some of the Chlamydomonas Hbs revealed yet unpredictable structural and biochemical variations, which, along with a different expression of their genes, suggest diverse physiological roles. Chlamydomonas thus represents a promising system to analyze the diversification of Hb structure, biochemistry and physiology. Here, we report the crystal structure, resolved to 1.75 Å, of the heme-binding domain of cyanomet THB11 (Cre16.g662750), one of the pentacoordinate algal Hbs, which offer a free Fe-coordination site in the reduced state. The overall fold of THB11 is conserved, but individual features such as a kink in helix E, a tilted heme plane and a clustering of methionine residues at a putative tunnel exit appear to be unique. Both N- and C-termini promote the formation of oligomer mixtures, and the absence of the C terminus results in reduced nitrite reduction rates. This work widens the structural and biochemical knowledge on the 2/2Hb family and suggests that the N- and C-terminal extensions of the Chlamydomonas 2/2Hbs modulate their reactivity by intermolecular interactions.

Robot assisted versus laparoscopic suturing learning curve in a simulated setting

BackgroundCompared to conventional laparoscopy, robot assisted surgery is expected to have most potential in difficult areas and demanding technical skills like minimally invasive suturing. This study was performed to identify the differences in the learning curves of laparoscopic versus robot assisted suturing.MethodNovice participants performed three suturing tasks on the EoSim laparoscopic augmented reality simulator or the RobotiX robot assisted virtual reality simulator. Each participant performed an intracorporeal suturing task, a tilted plane needle transfer task and an anastomosis needle transfer task. To complete the learning curve, all tasks were repeated up to twenty repetitions or until a time plateau was reached. Clinically relevant and comparable parameters regarding time, movements and safety were recorded. Intracorporeal suturing time and cumulative sum analysis was used to compare the learning curves and phases.ResultsSeventeen participants completed the learning curve laparoscopically and 30 robot assisted. Median first knot suturing time was 611 s (s) for laparoscopic versus 251 s for robot assisted (p < 0.001), and this was 324 s versus 165 (sixth knot, p < 0.001) and 257 s and 149 s (eleventh knot, p < 0.001) respectively on base of the found learning phases. The percentage of ‘adequate surgical knots’ was higher in the laparoscopic than in the robot assisted group. First knot: 71% versus 60%, sixth knot: 100% versus 83%, and eleventh knot: 100% versus 73%. When assessing the ‘instrument out of view’ parameter, the robot assisted group scored a median of 0% after repetition four. In the laparoscopic group, the instrument out of view increased from 3.1 to 3.9% (left) and from 3.0 to 4.1% (right) between the first and eleventh knot (p > 0.05).ConclusionThe learning curve of minimally invasive suturing shows a shorter task time curve using robotic assistance compared to the laparoscopic curve. However, laparoscopic outcomes show good end results with rapid outcome improvement.

3041Wall shear stress measurement by ultrafast vector flow imaging for atherosclerotic carotid stenosis

Abstract Background Carotid plaque vulnerability assessment is an important factor in guiding the decision to treat significant carotid stenosis. Ultrafast Ultrasound Imaging (UF) offers the possibility of evaluating local flow velocities over an entire 2D image, allowing access to velocity measurements in contact with the arterial wall and to measure the wall shear stress (WSS). Purpose To evaluate the feasibility of WSS measurement in a prospective series of patients with carotid stenosis. Methods A 7.5 MHz linear probe of an Aixplorer scanner was used. UF acquisitions had 3 tilted plane waves transmits (−10; 0; 10°) and an effective frame rate of 5000Hz. We evaluated the flow velocity in 5 areas of the carotid wall: common carotid artery (1), plaque ascent (2), plaque peak (3), plaque descent (4), internal carotid artery (5) (Figure). WSS was computed with the vector field speed using the following formula, WSS=μ·δn·v with v the blood velocity, n the normal vector to the vessel wall and μ, the blood viscosity, calculated from the hematocrit value for each patient. WSS measurement method was first validated using a laminar flow phantom and known viscosity. And then, 33 patients were then prospectively evaluated, with a median carotid stenosis degree of 80% [75–85]. Results Significant correlation was found between in vitro measurement and the theoretical WSS values (R2=0.95; p&lt;0.001).In patients,the maximum WSS value over the cardiac cycle follows the shape of the plaque with an increase during the ascend, reaching its maximum value of 3.57 Pa [2.47–4.45] at the peak of the plaque, and a fall after passing the peak (0.99 Pa [0.8–1.32]) lower than the WSS values in the non-stenotic areas (1.55 Pa [1.13–1.90] for the common carotid artery) (Table). Table 1 Wall's area Wall shear stress (Pa) Min Max Delta 1. Common carotid artery 0.14 [0.05–0.27] 1.55 [1.13–1.90] 0.73 [0.55–0.96] 2. Plaque's ascent 0.39 [0.24–0.59] 2.63 [1.89–3.28] 1.20 [0.89–1.79] 3. Plaque's peak 0.60 [0.32–0.89] 3.57 [2.47–4.45] 1.78 [1.44–2.46] 4. Plaque's descent 0.16 [0.13–0.22] 0.99 [0.80–1.32] 0.52 [0.34–0.73] 5. Internal carotid artery 0.17 [0.13–0.35] 1.37 [1.04–1.75] 0.72 [0.50–0.87] Results are median [25th–75th percentile]. Figure 1 Conclusion UF provide reliable WSS values. High WSS was present at the peak of the plaque, whereas lowest WSS values were found at the post-stenotic zone. WSS evaluation may help to better characterize the carotid plaque vulnerability.

Chaos in the inert Oort cloud

Context. Distant trans-Neptunian objects are subject to planetary perturbations and galactic tides. The former decrease with the distance, while the latter increase. In the intermediate regime where they have the same order of magnitude (the “inert Oort cloud”), both are weak, resulting in very long evolution timescales. To date, three observed objects can be considered to belong to this category. Aims. We aim to provide a clear understanding of where this transition occurs, and to characterise the long-term dynamics of small bodies in the intermediate regime: relevant resonances, chaotic zones (if any), and timescales at play. Methods. The different regimes are explored analytically and numerically. We also monitored the behaviour of swarms of particles during 4.5 Gyrs in order to identify which of the dynamical features are discernible in a realistic amount of time. Results. There exists a tilted equilibrium plane (Laplace plane) about which orbits precess. The dynamics is integrable in the low and high semi-major axis regimes, but mostly chaotic in between. From about 800 to 1100 astronomical units (au), the chaos covers almost all the eccentricity range. The diffusion timescales are large, but not to the point of being indiscernible in a 4.5 Gyrs duration: the perihelion distance can actually vary from tens to hundreds of au. Orbital variations are damped near the ecliptic (where previous studies focussed), but favoured in specific ranges of inclination corresponding to well-defined resonances. Moreover, starting from uniform distributions, the orbital angles cluster after 4.5 Gyrs for semi-major axes larger than 500 au, because of a very slow differential precession. Conclusions. Even if it is characterised by very long timescales, the inert Oort cloud mostly features chaotic regions; it is therefore much less inert than it appears. Orbits can be considered inert over 4.5 Gyrs only in small portions of the space of orbital elements, which include (90377) Sedna and 2012VP113. Effects of the galactic tides are discernible down to semi-major axes of about 500 au. We advocate including the galactic tides in simulations of distant trans-Neptunian objects, especially when studying the formation of detached bodies or the clustering of orbital elements.

Oblique-incidence, arbitrary-profile wave injection for electromagnetic simulations.

In an electromagnetic code, a wave can be injected in the simulation domain by prescribing an oscillating field profile at the domain boundary. The process is straightforward when the field profile has a known analytical expression (typically, paraxial Gaussian beams). However, if the field profile is known at some other plane, but not at the boundary (typically, nonparaxial beams), some preprocessing is needed to calculate the field profile after propagation back to the boundary. We present a parallel numerical technique for this propagation between an arbitrary tilted plane and a given boundary of the simulation domain, implemented in the Maxwell-Vlasov particle-in-cell code Smilei.

Big steps in advances of doppler ultrasound

Doppler Ultrasound is clinically important for evaluation of various hepatic vascular disease as well as hepatic vessel evaluation after liver transplantation. However, there are some limitations in conventional Doppler methods as follows: 1) time consuming and labor intensive and 2) limited slow flow sensitivity. There are two recently advanced Doppler signal-processing methods (i.e., UltraFast and superb microvascular imaging), which overcome those limitations. UltraFast Doppler ultrasound, which emerged with the advent of massive parallel computing (or processing) capabilities, transmits several tilted plane waves into the medium and coherently sums the backscattered echoes to reconstruct US images, leading to a marked increase in the frame rate, while conventional ultrasound imaging involves sequential medium insonification via focused beams and successive image reconstruction. A stored UltraFast Doppler clip contains information on both spectral analysis and color-coded flow imaging and could be retrospectively evaluated quantitative analysis, because UltraFast ultrasound has high spatio-temporal resolution. Superb microvascular imaging (SMI, Cannon Medical Systems Corporation, Tochigi, Japan) uses a different kind of adaptive wall filter, which could minimize the flash artifact and increased sensitivity to slow flow and improve the signal detection of flow from small vessels. Therefore, in clinical practice, UltraFast Doppler can be performed by anyone. If the exam protocol such as acquisition of clip by less experienced sonographer and evaluation by retrospective wave reconstruction by specialist can be established, efficient work force management can be possible. Superb Microvascular imaging can distinguish very slow portal flow by portal hyper tension and so forth from thrombus. Thrombus can be evaluated with almost the same resolution as CT. The weak flow of a small hepatic artery hiding by vigorous flow of portal vein after liver transplantation can be also distinguished. In conclusion, smart application of recent advanced Doppler technique will help comprehensive assessment of hepatic vascular abnormalities.