Computational Work Research Articles

Theoretical investigations of structural, electronic, magnetic, and optical properties of group V (X = V, Nb, Ta) added CeO2-X materials for optoelectronic applications.

Depletion of natural resources, responsible for energy production, is a serious concern for researchers to develop alternate energy resources or materials. Scientists have proposed various energy materials which are based on semiconductors and their underlying physics. Cerium oxide (CeO2) is a versatile energy material which receives much attention owing to excellent photocatalytic, photonic, thermal stability, and optoelectronic applications. Even though CeO2 exhibited remarkable physical properties, but yet, they can be enhanced upon suitable doping. Focus on current research is to dope group V elements into CeO2 in order to enhance its electronic and optical response. The density of states (DOS) and band gaps of proposed materials are calculated, and significant improvement is noted after applying TB-mbj method. Optical absorption spectra of V/Nb/Ta-doped CeO2 show blueshift and decrease in reflectivity along with the presence of magnetism illustrate potential uses of these materials in future UV optoelectronics, spintronics, sensing, and energy harvesting devices. This research is based on computational work carried using Wien2k code where PBE-GGA approximation is used to approximate exchange and correlation potentials. Supercells of vanadium/niobium/tantalum-doped CeO2 are constructed, and spin-polarized density of states (DOS) along with optical constant are calculated. TB-mbj method is used to bring improvements in DOS and band gaps of proposed materials. Iterations are conducted using convergence criterion, and non-relativistic calculations are performed.

BEB-based models for ionisation cross sections of electron and positron impact with diatomic molecules

The ionising interactions of high-energy particles with molecules have applications in many areas. Despite this, some areas, including positron scattering, lack experimental data due to difficulties in performing experiments. Here, quick and simple methods for computing direct electron and positron impact ionisation cross sections are presented. These calculations, performed using the open-source software RAPID-CS, can provide a complete data set as a first approximation for when experimental, or more detailed computational work is not available. The cross-sectional data set includes the total, partial/fragment-specific, single-differential, average secondary electron energy and stopping power cross sections. The molecules N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}, O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} and CO were chosen to study due to the availability of positron scattering data. An overall good agreement with experimental and other computational results is presented.Graphical abstractDirect electron (left) and positron right) impact partial ionisation cross sections for N2. Total cross section: red, N2+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N^{+}_{2}$$\\end{document} partial cross section: blue, N+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{+}$$\\end{document} partial cross section: green.electron: solid lines: BEB, experimental measurements by Lindsay and Mangan [36]:Ürosses, Straub et al. [37]: stars, Opel et al. [39]: squares. Positron: solid lines: BEB0, Dashed lines: BEBA, Marler and Surko [23]: red crosses, Bluhme et al. [24]: stars

Prevalence of dry eye disease among IT students in Pakistan.

Dry eye disease (DED) is a common tear film disorder caused by decreased tear production or increased tear evaporation. The increased use of computers in the workplace has brought about the development of ocular health concerns, including dry eye disease. Therefore, this study was designed to determine the prevalence of DED associated with computer work and recommend preventing or reducing its development. This study investigated the prevalence of DED among IT students in Dera Ghazi Khan. A cross-sectional descriptive study was conducted among 327 undergraduate students of the IT department in the district of Dera Ghazi khan over 5months from September 2021 to January 2022. DED was assessed subjectively with Ocular Surface Disease Index. Data were analysed using SPSS version 21. The quantitative analysis was presented as mean and standard deviation, and qualitative variables were introduced in frequency and percentages. The chi-square test (Fisher's exact test) was used to study the significance of associations between dependent and independent variables. The mean age of the participants was 20.25 ± 1.305years (range 17-25). The prevalence of DED among computer programmers was 47.7%. This study showed that gender (p = 0.31), contact lens usage (p = 0.64), and duration of time spent on computer display units (p = 0.47) were not significant determinants of DED among computer programmers. DED is prevalent among IT students, along with different symptoms. However, further studies are required to adequately measure the prevalence of DED during longer exposure time to computer screens and explore environmental risk factors.

Algorithms in the Margins: Organized Community Resistance to Port Automation in the Los Angeles Harbor Area

Public deliberations on artificial intelligence and machine learning (AI/ML) provoke strong interest in automation, or the perceived displacement of human labor due to general technological advances. Social science scholarship on well-compensated technology workers and a growing global underclass suggests automation remains largely a myth, with emerging technologies generating new forms of computational and emotional work. But little research has examined automation from the vantage point of community members at perceived greatest risk of displacement, such as those sustained by generations of logistics labor and physically located in racialized, underserved areas. In the United States and around the globe, logistics work is directly targeted by “automation engineers” to reduce labor costs on behalf of industry interests, posing a severe threat to port workers and their respective communities. This article examines organized community resistance to automation within the Los Angeles Harbor Area, drawing on four public hearings following the Port of LA’s planned integration of autonomous vehicles for the movement of cargo (i.e., automated straddle carriers). We find community mobilizations widely sought to enlarge public consideration of AI/ML to encompass matters of societal well-being and the collective good. These include shifting from the legality of AI integration to underscore public morality in light of anticipated harm, in addition to emphasizing the invisible social arrangements surrounding the Port and nearby community life. Our research reveals how lay people may reassert their own importance when confronted by technoscientific injustice, such as by reframing the future of work toward an insistence on “the future of our communities.”

Finite difference approximations of the spatially homogeneous Fokker–Planck–Landau equation

Finite difference methods are developed for approximating the spatially homogeneous Fokker–Planck–Landau equation for Coulomb collisions. The numerical methods apply the Fast Fourier Transform to improve time efficiency. Computational work is then done to compare the numerical approximations using FFT with the numerical method of Wollman (2017). In addition, some computations are done to verify the theoretical rate of convergence of the FPL equation proved in Strain and Guo (2008).

Fast random vector transforms in terms of pseudo-inverse within the Wiener filtering paradigm

We propose two techniques for the fast numerical implementation of a random vector transform within Wiener filtering paradigm. In signal processing terminology, the transform is interpreted as an optimal filter. The proposed transform aims to minimize the sum of distances between a reference random vector xi and its transformed counterpart yi, for all i=1,…,p. In contrast to known techniques where the transform consists of p matrices that minimize a difference between a single reference random vector and p observed random vectors, the proposed transform uses a single optimal matrix to transform p random vectors. It requires less computational work for the numerical implementation. Nevertheless, a direct numerical realization of the transform involves computation of the covariance matrix pseudo-inverse and the matrix square root which might be large, and then are computationally expensive. Proposed fast versions of the transform allow us to avoid that computation and, as a result, accelerate the numerical implementation. While the fast proposed techniques are approximate versions of the original transform, it is shown that their accuracies are very close to those of the original transform. An error analysis is provided. The effectiveness of the proposed transform is illustrated by numerical experiments in four real-world scenarios.

Research on High-performance Computing Network Search System based on Computer Big Data

An efficient computing system for massively parallel systems is established. The stochastic Petri net abstracts and models the high-performance computer work scheduling system. The IB switch is modeled. Stochastic Petri nets are used for performance analysis. Finally, the proposed method is combined with InfiniBand interconnection architecture to evaluate the system's delay. The experimental results prove the feasibility of this algorithm.

Impact of extended π-conjugated acceptor moieties on non-linear optical behavior in polar medium for designed 4,4-dimethyl-4H-indeno[1,2-b] thiophene based materials

In the current study, the organic compounds (D2-D9) with D1–π–D2–π–A configuration were designed by structural modeling with various end-capped acceptor moieties for nonlinear optical (NLO) study. TD-DFT/DFT approaches at CAM-B3LYP/6-311G(d,p) level were accomplished to investigate the NLO behavior of these compounds. For this, various analyses: frontier molecular orbitals (FMOs), density of states (DOS), UV–Vis absorption, natural bond orbitals (NBOs), transition density matrix (TDMs) and non-linear optical (NLO) investigations were performed. These findings revealed that all designed chromophores exhibited comparable band gaps (3.962–4.182 eV) and absorption spectra (λmax = 441.6–460.7 nm) with reference chromophore (band gap = 4.008 eV). An efficient charge transfer from central core in HOMO was transferred towards terminal acceptors in LUMO that was also supported by DOS and TDM maps. Among all studied chromophores, the significant linear and nonlinear polarizability properties were examined in D5 (<α>=2.213 × 10-22esu), D6 (βtot = 3.339 × 10-28esu) and D4 (γtot = 3.068 × 10-33esu) chromophores. The NLO results indicated that the designed compounds (D5, D6 and D4) possess promising NLO behavior via effective charge delocalization. It is inferred that the current computational work might be helpful for further developments in non-linear optic field.

Low-Speed Space Launch System Computational Fluid Dynamics: A Comprehensive Overview

In this review paper, low-speed computational work from NASA Langley Research Center in support of the Space Launch System (SLS) is discussed. This information includes both historical and present efforts with the Kestrel computational fluid dynamics solver. The low-speed aerodynamics of SLS is highly complex, and the analysis of the unsteady flowfield requires significant computational efforts. The SLS mission profile varies from the vehicle static on the launch pad through high-speed ascent. This study focuses on the prelaunch as well as liftoff and transition portions of the flight both in proximity to the launch tower and in isolation. High-alpha conditions, as large as 90 deg, result in a flowfield dominated by massive, large-scale flow separation and asymmetric vortices. High-fidelity solutions require an unsteady computational formulation to accurately capture the aerodynamics of the vehicle. A detailed discussion of the computational approach is presented, followed by key efforts to support the program, both historic and present, including information that has been either published previously or that has never before been published external to NASA.

On the Motion Past a Slip-Stick Sphere and a Shear Free Sphere in a Viscous Fluid

The theoretical development of the complex fluid flows such as more than one obstacle with different shapes have great interest for scientists to understand flow phenomena and verify the model or approximate solution. The complex physical properties due to a uniform streaming motion past two fixed spheres is investigated having one with shear stress and another being shear stress-free. This study concerns analytical technique of a steady incompressible viscous fluid past to two fixed spheres. The Gegenbaur function and associated Legendre polynomials is used to derive the solution that simplify the process of the theoretical calculations. The mathematical expression for the flow fields are obtained in terms of stream functions by Gegenbaur function and associated Legendre polynomials. The physical properties of interest such as the Stokes stream function, the stress and its drag are calculated. It is understandable that for the uniform streaming motion around a sphere with the stress and its drag are affected owing to the presence of another stress-free are analyzed. The present result can be considered as a generalized by making other established results as a corollary of this solution. This theoretical study helps to the numerical or computational work for the verification of their approximated results of interest.

Nonlinear fractional-order differential equations: New closed-form traveling-wave solutions

Abstract The fractional-order differential equations (FO-DEs) faithfully capture both physical and biological phenomena making them useful for describing nature. This work presents the stable and more effective closed-form traveling-wave solutions for the well-known nonlinear space–time fractional-order Burgers equation and Lonngren-wave equation with additional terms using the exp ( − Φ ( ξ ) ) (-\Phi (\xi )) expansion method. The main advantage of this method over other methods is that it provides more accuracy of the FO-DEs with less computational work. The fractional-order derivative operator is the Caputo sense. The transformation is used to reduce the space–time fractional differential equations (FDEs) into a standard ordinary differential equation. By putting the suggested strategy into practice, the new closed-form traveling-wave solutions for various values of parameters were obtained. The generated 3D graphical soliton wave solutions demonstrate the superiority and simplicity of the suggested method for the nonlinear space–time FDEs.

A comparison of neck and shoulder postures in symptomatic and asymptomatic female office workers in the actual work environment

ObjectiveThe present study aimed to compare the static and dynamic sitting posture during computer work among symptomatic and asymptomatic office workers in actual work environment. MethodsSeventy female office workers were divided into two groups: asymptomatic (n = 35) and symptomatic (n = 35). Subsequent to this classification, adjustments to their respective workstations were implemented in accordance with Occupational Safety and Health Administration (OSHA) guidelines. The assessment of neck (CV) and shoulder (FS) angles were conducted during both a typical seated posture and at intervals of 20 min over a duration of 3 h of computer work. ResultThe asymptomatic group had a range of age from 26 to 40 years, a BMI of 21.11 ± 2.14, and a working experience ranged from 1 to 16 years. In contrast, the symptomatic group had an age range from 24 to 40 years, a BMI of 21.12 ± 2.27, and a working experience ranged from 3 to 16 years. During static sitting posture, significant differences were observed in both CV (p = 0.01) and FS angles (p = 0.00) between the two groups. Additionally, during computer work sessions lasting for 3 h, a significant time effect (p = 0.00) was noted for the CV angle. Furthermore, the FS angle exhibited significant group (p = 0.00), time (p = 0.00), and interaction (p = 0.00) effects during work. ConclusionThis study underscores the development of neck flexion during prolong working in both groups. In addition, asymptomatic group experienced a progression more rounded shoulder during a 3-h working period. Prolonged periods of sitting and computer use appear to have adverse effects on neck and shoulder health, underlining the importance of implementing measures to mitigate these effects.

Scalable implicit solvers with dynamic mesh adaptation for a relativistic drift-kinetic Fokker–Planck–Boltzmann model

In this work we consider a relativistic drift-kinetic model for runaway electrons along with a Fokker–Planck operator for small-angle Coulomb collisions, a radiation damping operator, and a secondary knock-on (Boltzmann) collision source. We develop a new scalable fully implicit solver utilizing finite volume and conservative finite difference schemes and dynamic mesh adaptivity. A new data management framework in the PETSc library based on the p4est library is developed to enable simulations with dynamic adaptive mesh refinement (AMR), distributed memory parallelization, and dynamic load balancing of computational work. This framework and the runaway electron solver building on the framework are able to dynamically capture both bulk Maxwellian at the low-energy region and a runaway tail at the high-energy region. To effectively capture features via the AMR algorithm, a new AMR indicator prediction strategy is proposed that is performed alongside the implicit time evolution of the solution. This strategy is complemented by the introduction of computationally cheap feature-based AMR indicators that are analyzed theoretically. Numerical results quantify the advantages of the prediction strategy in better capturing features compared with nonpredictive strategies; and we demonstrate trade-offs regarding computational costs. The robustness with respect to model parameters, algorithmic scalability, and parallel scalability are demonstrated through several benchmark problems including manufactured solutions and solutions of different physics models. We focus on demonstrating the advantages of using implicit time stepping and AMR for runaway electron simulations.

An efficient constraint method for solving planning problems under end-effector constraints

Purpose In response to the challenge of reduced efficiency or failure of robot motion planning algorithms when faced with end-effector constraints, this study aims to propose a new constraint method to improve the performance of the sampling-based planner. Design/methodology/approach In this work, a constraint method (TC method) based on the idea of cross-sampling is proposed. This method uses the tangent space in the workspace to approximate the constrained manifold pattern and projects the entire sampling process into the workspace for constraint correction. This method avoids the need for extensive computational work involving multiple iterations of the Jacobi inverse matrix in the configuration space and retains the sampling properties of the sampling-based algorithm. Findings Simulation results demonstrate that the performance of the planner when using the TC method under the end-effector constraint surpasses that of other methods. Physical experiments further confirm that the TC-Planner does not cause excessive constraint errors that might lead to task failure. Moreover, field tests conducted on robots underscore the effectiveness of the TC-Planner, and its excellent performance, thereby advancing the autonomy of robots in power-line connection tasks. Originality/value This paper proposes a new constraint method combined with the rapid-exploring random trees algorithm to generate collision-free trajectories that satisfy the constraints for a high-dimensional robotic system under end-effector constraints. In a series of simulation and experimental tests, the planner using the TC method under end-effector constraints efficiently performs. Tests on a power distribution live-line operation robot also show that the TC method can greatly aid the robot in completing operation tasks with end-effector constraints. This helps robots to perform tasks with complex end-effector constraints such as grinding and welding more efficiently and autonomously.

Mechanistic Insight into Binding of Graphene Towards Multiple Therapeutic Target of SARS-CoV-2 by Molecular Docking and Dynamics Studies

Background: Even after more than three years of emergence of coronavirus diseases 2019 (COVID-19), it remains incurable, despite the use of emergency-approved vaccines. The impact of the emergency-approved vaccines against it is not highly certain. The entire world may face surge of new wave of the infection, and therefore, its reoccurrence cannot be denied. Causalities and economic losses may happen in the future. In this situation, it is need of the hour to explore some suitable therapeutic agents against this highly infectious and challenging disease. Organic molecules, inactivated virus etc were largely focused to derive the vaccines, however, nanomaterials still remain untested for it. Interaction of nanomaterials like graphene against proteins of the coronavirus to inhibit its activity is yet to be tested computationally. Method: In this computational research work, graphene is tested for interaction with the viral proteins, as the dimension of the novel coronavirus also belongs to nano-scale (diameter 65-125 nm). A detailed study ondocking structures and molecular dynamics between viral proteins and graphene, is undertaken. Autodock and Discovery Studio packages were used for docking calculations and interaction analysis, respectively. Molecular dynamics simulation was performed using NAMD software and obtained results were visualized using VMD software. Results: Range of proteins of the coronavirus including spike proteins (both open and closed form), Main Protease (MPRO), Receptor-Binding Domain (RBD), RNA-dependent RNA polymerase (RdRp), and Angiotensin Converting Enzyme 2 (ACE2) have been individually evaluated for their docking and dynamics with graphene, so as to inactivate the virus. Details of interacting amino acid residues of coronavirus with graphene is found in the study. Conclusion: Computationally, it is observed that most of these proteins were found interactive through their amino acid residues with graphene. Number of interacting amino acid residues is considerable enough to collectively acquire high binding energy. It can be envisaged that cumulative perturbations of all the interactions of each protein caused by graphene can lower down or inactivate the virus.

Predicting the effects of surgically determined parameters on exercise tolerance in Fontan patients

The Fontan physiology is a surgically created circulation for patients with a single functioning ventricle. Patients with this circulation tend to have lower exercise tolerance compared to those with a normal circulation. Important computational and experimental work has been done to investigate this reduction in exercise tolerance. However, there are few systematic modeling studies that focus on the effect of several surgically determined parameters within the same framework. We propose a mathematical model to describe the Fontan circulation under exercise. We then formulate a heuristic based on clinical data from Fontan patients to estimate exercise tolerance. The model is used to investigate the effect of three important surgically determined parameters on exercise tolerance: the systemic arterial compliance, the systemic-venous to pulmonary-venous fenestration, and the resistance of the total cavopulmonary connection.

Unexpectedly High Propylene/Propane Separation Performance of Asymmetric Mixed-Matrix Membranes through Additive-Assisted In Situ ZIF-8 Filler Formation: Experimental and Computational Studies.

Zeolitic-imidazolate framework-8 (ZIF-8), composed of a zinc center tetrahedrally coordinated with 2-methylimidazolate linkers, has garnered extensive attention as a selective filler for propylene-selective mixed-matrix membranes (MMMs). Recently, we reported an innovative and scalable MMM fabrication approach, termed "phase-inversion in sync with in situ MOF formation" (PIMOF), aimed at addressing the prevailing challenges in MMM processing. In this study, we intend to investigate the effect of additives, specifically sodium formate and 1,4-butanediol, on the modification of ZIF-8 filler formation within the polymer matrix in order to further improve the separation performance of the asymmetric MMMs prepared by the PIMOF. Remarkably, MMMs prepared with sodium formate as an additive in the coagulation bath exhibited an unprecedented C3H6/C3H8 separation factor of 222.5 ± 1.8 with a C3H6 permeance of 10.1 ± 0.3 GPU, surpassing that of MMMs prepared without additives (a C3 separation factor of 57.7 ± 11.2 with a C3 permeance of 22.5 ± 4.5 GPU). Our computational work complements the experimental investigation by studying the effect of ZIF-8 nanoparticle size on the specific surface interaction energy and apertures of ZIF-8. Calculations indicate that by having smaller ZIF-8 nanoparticles, stronger interactions are present with the polymer affecting the aperture of ZIF-8 nanoparticles. This reduction in aperture size is expected to improve selectivity toward propylene by reducing the permeability of propylene. These results represent a significant advancement, surpassing the performance of all previously reported propylene-selective MMMs and most high-quality polycrystalline ZIF-8 membranes. The notably enhanced separation performance primarily arises from the formation of exceedingly small ZIF-8-like particles with an amorphous or poorly crystalline structure, corroborated by our computational work.

Probing the Reactivity of ZnO with Perovskite Precursors.

To achieve more stable and efficient metal halide perovskite devices, optimization of charge transport materials and their interfaces with perovskites is crucial. ZnO on paper would make an ideal electron transport layer in perovskite devices. This metal oxide has a large bandgap, making it transparent to visible light; it can be easily n-type doped, has a decent electron mobility, and is thought to be chemically relatively inert. However, in combination with perovskites, ZnO has turned out to be a source of instability, rapidly degrading the performance of devices. In this work, we provide a comprehensive experimental and computational study of the interaction between the most common organic perovskite precursors and the surface of ZnO, with the aim of understanding the observed instability. Using X-ray photoelectron spectroscopy, we find a complete degradation of the precursors in contact with ZnO and the formation of volatile species as well as new surface bonds. Our computational work reveals that different pristine and defected surface terminations of ZnO facilitate the decomposition of the perovskite precursor molecules, mainly through deprotonation, making the deposition of the latter on those surfaces impossible without the use of passivation.

Benders decomposition for the energy aware task scheduling of constellations of nanosatellites

This paper describes a novel method for optimizing nanosatellite constellation scheduling based on Benders decomposition. The optimization of nanosatellite constellations is challenging due to the large number of variables and constraints involved, which increases the computational work required to get optimal solutions as the number of participating objects increases. Our strategy overcomes this obstacle by decomposing the complex problem into smaller, more manageable subproblems, rendering the original formulation scalable. The outcomes demonstrate that the Benders decomposition achieves the same optimal solutions obtained with the Gurobi solver applied to the baseline formulation while being significantly faster and more efficient, especially for larger constellation sizes. This method provides a valuable tool for decision-makers in the nanosatellite job scheduling process, highlighting the potential benefits of using decomposition methods such as the Benders decomposition for large-scale or challenging optimization problems in Offline Nanosatellite Task Scheduling (ONTS).

Size Isn't Everything: Geometric Tuning in Polycyclic Aromatic Hydrocarbons and Its Implications for Carbon Nanodots.

Recent developments in light-emitting carbon nanodots and molecular organic semiconductors have seen renewed interest in the properties of polycyclic aromatic hydrocarbons (PAHs) as a family. The networks of delocalized π electrons in sp2-hybridized carbon grant PAHs light-emissive properties right across the visible spectrum. However, the mechanistic understanding of their emission energy has been limited due to the ground state-focused methods of determination. This computational chemistry work, therefore, seeks to validate existing rules and elucidate new features and characteristics of PAHs that influence their emissions. Predictions based on (time-dependent) density functional theory account for the full 3-dimensional electronic structure of ground and excited states and reveal that twisting and near-degeneracies strongly influence emission spectra and may therefore be used to tune the color of PAHs and, hence, carbon nanodots. We particularly note that the influence of twisting goes beyond torsional destabilization of the ground-state and geometric relaxation of the excited state, with a third contribution associated with the electric transition dipole. Symmetries and peri-condensation may also have an effect, but this could not be statistically confirmed. In pursuing this goal, we demonstrate that with minimal changes to molecular size, the entire visible spectrum may be spanned by geometric modification alone; we have also provided a first estimate of emission energy for 35 molecules currently lacking published emission spectra as well as clear guidelines for when more sophisticated computational techniques are required to predict the properties of PAHs accurately.