An approach for cross-modality guided quality enhancement of liver image

<p><span>A novel approach for multimodal liver image contrast enhancement is put forward in this paper. The proposed approach utilizes magnetic resonance imaging (MRI) scan of liver as a guide to enhance the structures of computed tomography (CT) liver. The enhancement process consists of two phases: The first phase is the transformation of MRI and CT modalities to be in the same range. Then the histogram of CT liver is adjusted to match the histogram of MRI. In the second phase, an adaptive histogram equalization technique is presented by splitting the CT histogram into two sub-histograms and replacing their cumulative distribution functions with two smooths sigmoid. The subjective and objective assessments of experimental results indicated that the proposed approach yields better results. In addition, the image contrast is effectively enhanced as well as the mean brightness and details are well preserved.</span></p>

An Inverse Procedural Modeling Pipeline for SVBRDF Maps

Procedural modeling is now the de facto standard of material modeling in industry. Procedural models can be edited and are easily extended, unlike pixel-based representations of captured materials. In this article, we present a semi-automatic pipeline for general material proceduralization. Given Spatially Varying Bidirectional Reflectance Distribution Functions (SVBRDFs) represented as sets of pixel maps, our pipeline decomposes them into a tree of sub-materials whose spatial distributions are encoded by their associated mask maps. This semi-automatic decomposition of material maps progresses hierarchically, driven by our new spectrum-aware material matting and instance-based decomposition methods. Each decomposed sub-material is proceduralized by a novel multi-layer noise model to capture local variations at different scales. Spatial distributions of these sub-materials are modeled either by a by-example inverse synthesis method recovering Point Process Texture Basis Functions (PPTBF) [ 30 ] or via random sampling. To reconstruct procedural material maps, we propose a differentiable rendering-based optimization that recomposes all generated procedures together to maximize the similarity between our procedural models and the input material pixel maps. We evaluate our pipeline on a variety of synthetic and real materials. We demonstrate our method’s capacity to process a wide range of material types, eliminating the need for artist designed material graphs required in previous work [ 38 , 53 ]. As fully procedural models, our results expand to arbitrary resolution and enable high-level user control of appearance.

Ion energy distribution and non-linear ion dynamics in BP-HiPIMS and ACBP-HiPIMS discharge

Investigating the ion dynamics in the emerging bipolar pulse high power impulse magnetron sputtering (BP-HiPIMS) discharge is necessary and important for broadening its industrial applications. Recently, an optimized plasma source operating the BP-HiPIMS with an auxiliary anode and a solenoidal coil is proposed to enhance the plasma flux and energy, named as ACBP-HiPIMS (‘A’－anode, ‘C’－coil). In the present work, the temporal evolutions of the ion velocity distribution functions (IVDF) in BP-HiPIMS and ACBP-HiPIMS discharges are measured using a retarding field energy analyser (RFEA). For the BP-HiPIMS discharge, operated at various positive pulse voltages U+, the temporal evolutions of IVDFs illustrate that there are two high-energy peaks, E1 and E2, which are both lower than the applied U+. The ratio of the mean ion energy Ei,mean to the applied U+ is around 0.55－0.6 at various U+. In ACBP-HiPIMS discharge, the IVDF evolution shows three distinguishable stages which has the similar evolution trend with the floating potential Vf on the RFEA frontplate: (i) the stable stage with two high-energy peaks (E2 and E3 with energy respectively lower and higher than the applied U+ amplitude) when the floating potential Vf is close to the applied positive pulse voltage; (ii) the transition stage with low-energy populations when the Vf drops by ~20 V within ~10 μs; and (iii) the oscillation stage with alternating E2 and E3 populations and ever-present E1 population when the Vf slighly descreases unitl to the end of positive pulse. The comparison of IVDFs in BP-HiPIMS and ACBP-HiPIMS suggests that both the mean ion energy and high-energy ion flux have been effectively improved in ACBP-HiPIMS discharge. The formation of floating potential drop is explored using the Langmuir probe which may be attributed to the establishment of anode double layer structure.

Origin of Local Structures of U-Co Melts: A First-Principles Study

The local structures of U-Co melts have been studied by first-principle calculations. Two sub-peaks are observed in the first peaks of U-U pair distribution functions. The Voronoi polyhedral analyses also show two separate core-shell U-U distances. Therefore, the calculated results propose that U atoms will play dual roles, “chemical” and “topological”, in the local structures of U-Co melts. In addition, the chemical effect of U atoms will be strengthened when containing more U atoms. The interaction of Co and U atoms is slightly affected by the compositions. The Co-centered clusters are mostly prism-like or antiprism-like polyhedral, which can be predicted by the solute-solvent model. The distribution of the coordinated numbers of Co atoms is much narrower than that of U atoms, showing relatively stable Co-centered clusters. The chemical and topological roles of U atoms are intuitively observed in the electron density of U-Co melts, which presents both metallic and covalent bonding characteristics for U-U bonds. In the end, we conclude that the partial localization of U 5f-electron is responsible for the dual roles of U atoms. The present results provide a theoretical understanding of the origin of the local structures of U-Co melts.

Formation and destruction of striation plasmas in helium glow discharge at medium pressures

The striation plasmas are usually generated in positive column of glow discharge, in which abundant and complex physics are involved, especially, in medium or high pressures. This paper was aimed at investigating the formation and deformation of helium striation plasmas at kPa level pressures. The characteristics of helium striation plasmas, especially, the optical emission characteristics were investigated. The emission lines of 706.52 nm and 391.44 nm related to energetic electrons and high energy metastable helium atoms were focused on during the discharge process. Formation of striation plasmas in helium glow discharge, is mainly associated with the instability resulting from stepwise ionization vis high energy metastable state atoms, Maxwellization of electron distribution functions and gas heating. The deformation effect of helium striation plasmas is very significant when a small amount of nitrogen or oxygen is mixed into the discharge plasmas. The reduction of mean electron energy and the consumption of high energy metastable helium atoms are the potential reasons for deformation of striation plasmas.

Adsorption Sites on Pd Nanoparticles Unraveled by Machine-Learning Potential with Adaptive Sampling

Catalytic properties of noble-metal nanoparticles (NPs) are largely determined by their surface morphology. The latter is probed by surface-sensitive spectroscopic techniques in different spectra regions. A fast and precise computational approach enabling the prediction of surface–adsorbate interaction would help the reliable description and interpretation of experimental data. In this work, we applied Machine Learning (ML) algorithms for the task of adsorption-energy approximation for CO on Pd nanoclusters. Due to a high dependency of binding energy from the nature of the adsorbing site and its local coordination, we tested several structural descriptors for the ML algorithm, including mean Pd–C distances, coordination numbers (CN) and generalized coordination numbers (GCN), radial distribution functions (RDF), and angular distribution functions (ADF). To avoid overtraining and to probe the most relevant positions above the metal surface, we utilized the adaptive sampling methodology for guiding the ab initio Density Functional Theory (DFT) calculations. The support vector machines (SVM) and Extra Trees algorithms provided the best approximation quality and mean absolute error in energy prediction up to 0.12 eV. Based on the developed potential, we constructed an energy-surface 3D map for the whole Pd55 nanocluster and extended it to new geometries, Pd79, and Pd85, not implemented in the training sample. The methodology can be easily extended to adsorption energies onto mono- and bimetallic NPs at an affordable computational cost and accuracy.

Safety and Risk of Operating Facilities: Rapid Assessment Methodology

Two methods for methodology uses “risk indices” (dam condition index I), as well as “fuzzy logic methods” to combine the original quantitative and qualitative (expert) information on the operated dam condition. The approach applied is in accordance with the recommendations of IEC 31010: 2019. Risk Management — Risk Assessment Techniques. Deterministic assessments of the condition in the form of “risk indices” were also used as input data in assessing the probability of the failure and in developing a probabilistic risk assessment methodology. The original database, as well as the damage assessment scale, modified in the course of the research, summarize the experience of surveys and examination of safety declarations of more than 180 hydraulic works in Russia. A description is given of the methods of initial assessment and digitization (quantification) of the condition index I, as well as combining the initial quantitative and qualitative (expert) information about various damages. The practical feasibility and the possibility of categorizing (with fuzzy boundaries) conditions and levels of damage to hydraulic structures are shown. With regard to various conditions and levels of damage, proposals are made for practical actions to ensure the safety of dams in the process of monitoring, inspection, development of a reconstruction project and its expertise. As a result of the research, the dependence of the probability of the failure pfailure on the average value of the Iср index has been established and the graph “pfailure – Iср” is presented, which is well described by the exponential and is convenient for practical application. The value of I ср is determined according to the data of visual and instrumental control of the dam condition of the as well as according to expert estimates. The methodology for creation the indicated graph is presented. The creation of this graph became possible on the basis of: statistical processing, proof of the “normality” of the distribution of the I indices and the estimation (according to the distribution functions constructed for each level of damage) the probability of the failure pfailure, as well as during the survey and examination of the dam project. Proposals are formulated for the practical application of the proposed methods for assessing the risk of operating dams, and the near-term prospect of research in the field of risk assessment and ensuring dam safety is formulated.

Exploring for Route Preferences of Subway Passengers Using Smart Card and Train Log Data

As the mode share of the subway in Seoul has increased, the estimation of passenger travel routes has become a crucial issue to identify the congestion sections in the subway network. This paper aims to estimate the travel train of subway passengers in Seoul. The alternative routes are generated based on the train log data. The travel route is then estimated by the empirical cumulative distribution functions (ECDFs) of access time, egress time, and transfer time. The train choice probability is estimated for alternative train combinations and the train combination with the highest probability is assigned to the subway passenger. The estimated result is validated using the transfer gate data which are recorded on private subway lines. The result showed that the accuracy of the estimated travel train is shown to be 95.6%. The choice ratios for no-transfer, one-transfer, two-transfer, three-transfer, and four-transfer trips are estimated to be 53.9%, 37.7%, 6.5%, 1.5%, and 0.4%, respectively. Regarding the practical application, the passenger kilometers by lines are estimated with the travel route estimation of the whole network. As results of the passenger kilometer calculation, the passenger kilometer of the proposed algorithm is estimated to be 88,314 million passenger kilometer. The proposed algorithm estimates the passenger kilometer about 13% higher than the shortest path algorithm. This result implies that the passengers do not always prefer the shortest path and detour about 13% for their convenience.

Mori-Tanaka-based statistical methodology to compute the effective Young modulus of polymer matrix nano-composites considering the experimental quantification of nanotubes dispersion and alignment degree

This paper presents a Mori-Tanaka-based statistical methodology to predict the effective Young modulus of carbon nanotubes (CNTs)-reinforced composites considering three variables: weight content, reinforcement dispersion and orientation. Last two variables are quantified by two parameters, namely, free-path distance between nano-reinforcements and orientation angle regarding the loading direction. To validate the present methodology, samples of multi-walled CNTs (MWCNTs)-reinforced polyvinyl alcohol (PVA)-matrix composite were manufactured by mixing solution. The MWCNT/PVA Young modulus was measured by nano-indentation, while the MWCNTs Young modulus was quantified by micro-Raman spectroscopy. Both stretched and unstretched composite specimens were fabricated. Transmission electron microscopy (TEM) and in-plane image analysis were used to obtain fitting coefficients of log-normal frequency distribution functions for the free-path distance and orientation angle. It was evidenced that numerical results fit well to measured values of effective Young modulus of MWCNTs and MWCNT/PVA, with exception of some particular cases where significant differences were found. Microstructural heterogeneities, cluster formation, polymer chains alignment, errors associated with the dispersion, orientation and mechanical characterization procedures, as well as idealization and statistical errors, were identified as possible causes of these differences. Finally, using the proposed methodology and the dispersion and orientation distribution functions experimentally obtained, the effective Young modulus is estimated for three kinds of thermoplastic matrices (polyvinyl alcohol, polyethylene ketone, and ultra-high molecular weight polyethylene) with different kinds of nanotubes (single wall, double wall, and multi-walled), at different weight contents, finding the superior mechanical performance for double-walled CNTs-reinforced composites and the lower one for multi-walled CNTs-reinforced ones.

Single-spin asymmetry ATsin(2ϕ−ϕS) in π−p Drell-Yan process within TMD factorization

We study the single-spin asymmetry ATsin(2ϕ−ϕS) in the pion-induced Drell-Yan process within the transverse momentum dependent factorization (TMD factorization). The asymmetry can be expressed as the convolution of the Boer-Mulders function and the transversity function. We numerically estimate the asymmetry ATsin(2ϕ−ϕS) at the COMPASS kinematics with the model results for the pion meson distributions from the light-cone wave function approach and the available parametrization for the proton distributions. We also include the TMD evolution formalism both proton and pion parton distribution functions by using two different parametrizations on nonperturbative Sudakov form factor. We find that the asymmetry ATsin(2ϕ−ϕS) as functions of xp, xπ, xF and q⊥ is qualitatively consistent with the recent COMPASS measurement.