bluuebunny/crossref_metadata_2025 huggingface dataset:
Transient analysis of a single server queueing system with infinite buffer
Authors: Huo Huixia , Xu Houbao , Chen Zhuoqian , Win Thet Thet
Published: October 2020

As a typical single server queueing system, computer integrated manufacturing system (CIMS) has been widely used in the field of intelligent manufacturing. However, how to derive its instantaneous index is still an important issue. This paper investigates the transient behavior of the CIMS with spectral method. By constructing an asymptotic system and analyzing the spectral distribution, we derive the explicit transient solution of the asymptotic system. Trotter–Kato theorem is used to prove that the transient solution of the CIMS is just the limitation of explicit transient solution of the asymptotic system. At the end of the paper, numerical examples are shown to illustrate the effectiveness of the proposed approximation.
Chirurgische Therapie des Lungenkarzinoms: Argumente für die Behandlung in großen Zentren
Authors: Hoffmann H. , Passlick B. , Ukena D. , Wesselmann S.
Published: October 2020

Anhand der Daten der DRG-Statistik wurde untersucht, wie sich die Versorgungssituation bei der chirurgischen Behandlung des Lungenkarzinoms in Deutschland darstellt und ob ein möglicher Zusammenhang zwischen Behandlungsvolumen und Hospitalletalität besteht. Ausgewertet wurden alle Behandlungsfälle der Jahre 2005 bis 2015 mit der Hauptdiagnose Lungenkarzinom (ICD C34) und den Prozeduren (OPS-Schlüssel 5-323–5-328) für anatomische Lungenresektionen. Die Behandlungsfälle wurden Krankenhausgruppen zugeordnet, definiert nach der Anzahl der durchgeführten Eingriffe pro Jahr. Die Gesamtzahl der anatomischen Lungenresektionen bei der Diagnose Lungenkarzinom stieg um 24 % von 9376 Resektionen in 2005 auf 11614 in 2015. Im Jahr 2015 wurden 57 % der anatomischen Lungenresektionen bei Patienten mit Lungenkarzinom in 47 High-Volume-Kliniken (Kliniken mit ≥ 75 Resektionen/Jahr) durchgeführt, die restlichen 43 % der Resektionen verteilen sich auf 271 Kliniken, die jeweils weniger als 75 Resektionen pro Jahr durchführen. In Krankenhäusern, in denen weniger als 25 dieser Eingriffe pro Jahr vorgenommen werden, ist die Krankenhausletalität mit 5,7 % (Mittelwert bezogen auf die Gesamtzahl der Eingriffe 2005 – 2015) fast doppelt so hoch wie in großen Zentren mit ≥ 75 Resektionen pro Jahr (Mittelwert 2005 – 2015: 3,0 %). Zusammenfassend bestätigt die vorliegende Auswertung der DRG-Statistik die traditionelle Konzentration der Lungenkrebsbehandlungen in Deutschland auf relativ wenige Kliniken mit großen Fallzahlen. Darüber hinaus konnte hier erstmals aktuell und flächendeckend für Deutschland ein Zusammenhang zwischen dem Behandlungsvolumen der Krankenhäuser und der Hospitalletalität nach chirurgischen Lungenkarzinombehandlungen belegt werden.
Biomedical x-ray imaging with a GaAs photon-counting detector: A comparative study
Authors: Scholz J. , Birnbacher L. , Petrich C. , Riedel M. , Heck L. , Gkoumas S. , Sellerer T. , Achterhold K. , Herzen J.
Published: October 2020

Photon-counting detectors provide several potential advantages in biomedical x-ray imaging including fast and readout noise free data acquisition, sharp pixel response, and high dynamic range. Grating-based phase-contrast imaging is a biomedical imaging method, which delivers high soft-tissue contrast and strongly benefits from photon-counting properties. However, silicon sensors commonly used in photon-counting detectors have low quantum efficiency for mid- to high-energies, which limits high throughput capabilities when combined with grating-based phase contrast imaging. In this work, we characterize a newly developed photon-counting prototype detector with a gallium arsenide sensor, which enables imaging with higher quantum efficiency, and compare it with a silicon-based photon-counting and a scintillation-based charge integrating detector. In detail, we calculated the detective quantum efficiency (DQE) of all three detectors based on the experimentally measured modulation transfer function, noise power spectrum, and photon fluence. In addition, the DQEs were determined for two different spectra, namely, for a 28 kVp and a 50 kVp molybdenum spectrum. Among all tested detectors, the gallium arsenide prototype showed the highest DQE values for both x-ray spectra. Moreover, other than the comparison based on the DQE, we measured an ex vivo murine sample to assess the benefit using this detector for grating-based phase contrast computed tomography. Compared to the scintillation-based detector, the prototype revealed higher resolving power with an equal signal-to-noise ratio in the grating-based phase contrast computed tomography experiment.
Polarization engineering via InAlN/AlGaN heterostructures for demonstration of normally-off AlGaN channel field effect transistors
Authors: Li Lei , Yamaguchi Ryohei , Wakejima Akio
Published: October 2020

Normally-off AlGaN channel heterostructure field effect transistors (HFETs) have been proposed and investigated numerically by taking advantage of the polarization engineering perspective in III-nitrides. The utilization of polarization-matched InAlN/AlGaN heterostructures shifted the threshold voltage to approximately 1.1 V for an Al0.3Ga0.7N channel HFET. Compared to the AlGaN/GaN HFEF with a low breakdown voltage, the normally-off InAlN/AlGaN HFETs show substantially enhanced breakdown characteristics. Besides, the two-dimensional electron gas (2DEG) mobility in the InAlN/AlGaN HFETs exhibits much less reduction with the increasing temperature than that in the AlGaN/GaN HFET, according to the calculation of electron mobility dominated by alloy disorder scattering and polar optical phonon scattering. As a result, the temperature dependences of the power figures of merit based on the conduction loss consideration in terms of 2DEG mobility variation and Johnson figure of merit show superior potential for polarization-matched InAlN/AlGaN HFETs in high-power and high-frequency electronics applications particularly operating at elevated temperatures. This work provides a useful way for demonstration of normally-off AlGaN channel HFETs and is also helpful for design of future devices, which can be beneficially exploited from polarized III-nitride heterostructures.
Core excitations with excited state mean field and perturbation theory
Authors: Garner Scott M. , Neuscamman Eric
Published: October 2020

We test the efficacy of excited state mean field theory and its excited-state-specific perturbation theory on the prediction of K-edge positions and x-ray peak separations. We find that the mean field theory is surprisingly accurate, even though it contains no accounting of differential electron correlation effects. In the perturbation theory, we test multiple core–valence separation schemes and find that, with the mean field theory already so accurate, electron-counting biases in one popular separation scheme become a dominant error when predicting K-edges. Happily, these appear to be relatively easy to correct for, leading to a perturbation theory for K-edge positions that is lower scaling and more accurate than coupled cluster theory and competitive in accuracy with recent high-accuracy results from restricted open-shell Kohn–Sham theory. For peak separations, our preliminary data show excited state mean field theory to be exceptionally accurate, but more extensive testing will be needed to see how it and its perturbation theory compare to coupled cluster peak separations more broadly.
A perspective on hybrid quantum opto- and electromechanical systems
Authors: Chu Yiwen , Gröblacher Simon
Published: October 2020

Quantum opto- and electromechanical systems interface mechanical motion with the electromagnetic modes of optical resonators and microwave circuits. The capabilities and promise of these hybrid devices have been showcased through a variety of recent experimental advances that demonstrated exquisite control over the quantum state of solid-state mechanical objects. In this perspective, we offer an overview of the current state, as well as an outlook of the future directions, challenges, and opportunities for this growing field of research. We focus, in particular, on the prospects for ground state cooling of mechanical modes and their use in quantum circuits, transducers, and networks.
Melting curve and phase diagram of ammonia monohydrate at high pressure and temperature
Authors: Zhang H. , Datchi F. , Andriambariarijaona L. M. , Zhang G. , Queyroux J. A. , Béneut K. , Mezouar M. , Ninet S.
Published: October 2020

The phase diagram and melting behavior of the equimolar water–ammonia mixture have been investigated by Raman spectroscopy, x-ray diffraction, and visual observations from 295 K to 675 K and up to 9 GPa. Our results show non-congruent melting behavior of ammonia monohydrate (AMH) solid below 324 K and congruent melting at higher temperatures. The congruent melting is associated with the stability of a previously unobserved solid phase of AMH, which we named AMH-VII. Another, presumably water-rich, hydrate has also been detected in the range 4 GPa–7 GPa at 295 K on decompression of the high pressure disordered ionico-molecular alloy (DIMA) phase. Comparing our melting data to the literature suggests that non-congruent melting extends from 220 K to 324 K and that the solid phase that borders the fluid between 220 K and 270 K, called AMH-III, is not a proper phase of AMH but a solid solution of ammonia hemihydrate and ice. These results allow us to propose a revised and extended experimental phase diagram of AMH.
Intermittent rearrangements accompanying thermal fluctuations distinguish glasses from crystals
Authors: Mizuno Hideyuki , Tong Hua , Ikeda Atsushi , Mossa Stefano
Published: October 2020

Glasses exhibit vibrational and thermal properties that are markedly different from those of crystals. While recent works have advanced our understanding of vibrational excitations in glasses in the harmonic approximation limit, efforts in understanding finite-temperature anharmonic processes have been limited. In crystals, phonon–phonon coupling provides an extremely efficient mechanism for anharmonic decay that is also important in glasses. By using extensive molecular dynamics simulation of model atomic systems, here we first describe, both numerically and analytically, the anharmonic couplings in the crystal and the glass by focusing on the temperature dependence of the associated decay rates. Next, we show that an additional anharmonic channel of different origin emerges in the amorphous case, which induces unconventional intermittent rearrangements of particles. We have found that thermal vibrations in glasses trigger transitions among numerous different local minima of the energy landscape, which, however, are located within the same wide (meta)basin. These processes generate motions that are different from both diffusive and out-of-equilibrium aging dynamics. We suggest that (i) the observed intermittent rearrangements accompanying thermal fluctuations are crucial features distinguishing glasses from crystals and (ii) they can be considered as relics of the liquid state that survive the complete dynamic arrest taking place at the glass transition temperature.
Improved accuracy hysteresis model based on hypergeometric functions
Authors: Herceg Dejana , Herceg Djordje
Published: October 2020

A new model of hysteresis based on hypergeometric functions is presented. The model is based on a class of parameterized functions with two free parameters, which contains the Takács model as a special case. With a suitable choice of the parameters, a model of hysteresis can be constructed, which shows improved conformance to experimental data, such as steep and narrow loops obtained from grain-oriented electric steel. The performance of our model was tested and verified on our measurement data, as well as data from other sources. It retains the advantages such as simple numerical implementation and parameter estimation while offering an increase in accuracy.
Cell type-specific lipid storage changes in Parkinson’s disease patient brains are recapitulated by experimental glycolipid disturbance
Authors: Brekk Oeystein Roed , Honey Jonathan R. , Lee Seungil , Hallett Penelope J. , Isacson Ole
Published: October 2020

Significance

Recently, the field of Parkinson’s disease biology has shifted attention away from pure proteinotoxic hypotheses to emphasize primary cellular insults, including glycolipid disturbances. In this work, dopaminergic neurons in the Parkinson’s disease-vulnerable region of substantia nigra were found to accumulate neutral lipids, whereas in the same tissues, astrocytes have reduced lipid content, and resident microglia (a form of brain macrophage) show overall accumulation of lipids associated with inflammation. These changes were reproduced experimentally by blocking a specific lysosomal hydrolase in mice, generating a glycolipid accumulation in the animals. Based on these findings, it is reasonable to propose that restoring lipid homeostasis between neurons, astrocytes, and microglia could potentially influence PD pathogenesis and disease progression.
Formation of global self-beliefs in the human brain
Authors: Rouault Marion , Fleming Stephen M.
Published: October 2020

Significance

Momentary feelings of confidence accompany many of our actions and decisions. In addition to such “local” feelings of confidence, we also construct “global” confidence estimates about our skills and abilities (global self-performance estimates or SPEs). Distorted SPEs may have a pervasive impact on motivation and self-evaluation, for instance affecting estimates of our competitiveness at work or in a sports team. Here, we found that components of a brain network previously implicated in the tracking of local confidence was additionally modulated by SPE level, whereas ventral striatum tracked SPEs irrespective of confidence. Our findings of a neurocognitive basis for global SPEs lay the groundwork for understanding how distorted SPEs arise in educational and clinical settings.
Immigration in science
Authors: Casanova Jean-Laurent , Holtzman David M. , Kaech Susan M. , Lanier Lewis L. , Nathan Carl F. , Rudensky Alexander Y. , Tuveson David , Wolchok Jedd D.
Published: October 2020

The advance of science is dependent upon collaboration, which does not have a visa attached to it. Indeed, over 40% of all American-based Nobel Prize winners are immigrants, and data from the National Science Foundation show that 49% of postdocs and 29% of science and engineering faculty in the US are foreign-born. However, restrictive new immigration policies in the US have left many scientists deeply concerned about their future and many American-based laboratories worried about attracting the best talent. At JEM, we’re celebrating immigration by sharing the experiences of immigrant and nonimmigrant scientists on our editorial board. Alexander Rudensky and Jean-Laurent Casanova give their firsthand perspective on immigrating to the US, while Jedd Wolchok, Carl Nathan, David Holtzman, Susan Kaech, Lewis Lanier, and David Tuveson reflect on how immigration has affected their laboratories.
A non-contact calibration system for step gauges using automatic collimation techniques
Authors: Yujiu Sun , Shiqing Xu , Feng Qian , Yongqian Li , Zili Zhou
Published: October 2020

To calibrate transfer standards for length calibration, a non-contact calibration system for step gauges and gauge blocks has been developed, in which a laser interferometer was equipped to obtain the length displacement and dual-stage driving-position techniques were used to carry step gauges to approach the measuring location. A non-contact collimation technique combined with an optoelectronic microscope was proposed for achieving identification. The optoelectronic microscope eliminates both the contact deformation resulting from the mechanical force and motion deviations. The combination of dual-stage driving-position techniques and the non-contact collimation technique can ensure that the collimation repeatability is less than 20 nm. The experimental tests and comparison results indicated that the non-contact strategy and dual-stage position techniques can provide a reliable method for building a length calibration system for gauges, industrial line scales, and end bars.
Energy relaxation in disordered lattice ϕ
4 system: The combined effects of disorder and nonlinearity*
Authors: Wang Jianjin , Zhang Yong , Xiong Daxing
Published: October 2020

We address the issue of how disorder together with nonlinearity affect energy relaxation in the lattice ϕ
4 system. The absence of nonlinearity leads such a model to only supporting fully localized Anderson modes whose energies will not relax. However, through exploring the time decay behavior of each Anderson mode’s energy–energy correlation, we find that adding nonlinearity, three distinct relaxation details can occur. (i) A small amount of nonlinearity causes a rapid exponential decay of the correlation for all modes. (ii) In the intermediate value of nonlinearity, this exponential decay will turn to power-law with a large scaling exponent close to –1. (iii) Finally, all Anderson modes’ energies decay in a power-law manner but with a quite small exponent, indicating a slow long-time tail decay. Obviously, the last two relaxation details support a new localization mechanism. As an application, we show that these are relevant to the nonmonotonous nonlinearity dependence of thermal conductivity. Our results thus provide new information for understanding the combined effects of disorder and nonlinearity on energy relaxation.
Artificial neural network potential for gold clusters*
Authors: Cao Ling-Zhi , Wang Peng-Ju , Sai Lin-Wei , Fu Jie , Duan Xiang-Mei
Published: October 2020

In cluster science, it is challenging to identify the ground state structures (GSS) of gold (Au) clusters. Among different search approaches, first-principles method based on density functional theory (DFT) is the most reliable one with high precision. However, as the cluster size increases, it requires more expensive computational cost and becomes impracticable. In this paper, we have developed an artificial neural network (ANN) potential for Au clusters, which is trained to the DFT binding energies and forces of 9000 Au
N
clusters (11 ≤ N ≤ 100). The root mean square errors of energy and force are 13.4 meV/atom and 0.4 eV/Å, respectively. We demonstrate that the ANN potential has the capacity to differentiate the energy level of Au clusters and their isomers and highlight the need to further improve the accuracy. Given its excellent transferability, we emphasis that ANN potential is a promising tool to breakthrough computational bottleneck of DFT method and effectively accelerate the pre-screening of Au clusters’ GSS.
Super-resolution filtered ghost imaging with compressed sensing*
Authors: Meng Shao-Ying , Shi Wei-Wei , Ji Jie , Tao Jun-Jie , Fu Qian , Chen Xi-Hao , Wu Ling-An
Published: October 2020

A filtered ghost imaging (GI) protocol is proposed that enables the Rayleigh diffraction limit to be exceeded in an intensity correlation system; a super-resolution reconstructed image is achieved by low-pass filtering of the measured intensities. In a lensless GI experiment performed with spatial bandpass filtering, the spatial resolution can exceed the Rayleigh diffraction bound by more than a factor of 10. The resolution depends on the bandwidth of the filter, and the relationship between the two is investigated and discussed. In combination with compressed sensing programming, not only high resolution can be maintained but also image quality can be improved, while a much lower sampling number is sufficient.
Synaptic plasticity and classical conditioning mimicked in single indium-tungsten-oxide based neuromorphic transistor*
Authors: Liu Rui , He Yongli , Jiang Shanshan , Zhu Li , Chen Chunsheng , Zhu Ying , Wan Qing
Published: October 2020

Emulation of synaptic function by ionic/electronic hybrid device is crucial for brain-like computing and neuromorphic systems. Electric-double-layer (EDL) transistors with proton conducting electrolytes as the gate dielectrics provide a prospective approach for such application. Here, artificial synapses based on indium-tungsten-oxide (IWO)-based EDL transistors are proposed, and some important synaptic functions (excitatory post-synaptic current, paired-pulse facilitation, filtering) are emulated. Two types of spike-timing-dependent plasticity (Hebbian STDP and anti-Hebbian STDP) learning rules and multistore memory (sensory memory, short-term memory, and long-term memory) are also mimicked. At last, classical conditioning is successfully demonstrated. Our results indicate that IWO-based neuromorphic transistors are interesting for neuromorphic applications.
Close-coupled nozzle atomization integral simulation and powder preparation using vacuum induction gas atomization technology*
Authors: Wang Peng , Li Jing , Wang Xin , Liu Heng-San , Fan Bin , Gan Ping , Guo Rui-Feng , Ge Xue-Yuan , Wang Miao-Hui
Published: October 2020

We simulate the gas-atomization process of a close-coupled annular nozzle for vacuum induction gas atomization at a three-dimensional scale. Moreover, the relationship between the simulated droplet type and experimentally metallic powder is established by comparing the morphology of droplets with powders. Herein, the primary atomization process is described by the volume-of-fluid (VOF) approach, whereas the prediction of powder diameter after secondary atomization is realized by the VOF-Lagrangian method. In addition, to completely reflect the breaking and deformation process of the metallic flow, we employ the VOF model to simulate the secondary atomization process of a single ellipsoidal droplet. The results show that the primary atomization process includes the formation of surface liquid film, appearance of serrated ligaments, and shredding of ligaments. Further, gas recirculation zone plays an important role in formation of the umbrella-shaped liquid film. The secondary atomization process is divided into droplet convergence and dispersion stages, and the predicted powder diameter is basically consistent with the experiment. In general, the four main powder shapes are formed by the interaction of five different typical droplets.
Effects of heat transfer in a growing particle layer on microstructural evolution during solidification of colloidal suspensions*
Authors: You Jia-Xue , Zhang Yun-Han , Wang Zhi-Jun , Wang Jin-Cheng , Liu Sheng-Zhong
Published: October 2020

Heat transfer is the foundation of freezing colloidal suspensions and a key factor for the interface movement. However, how the thermal conductivity of particles affects freezing microstructural evolution remains unknown. Here in this work, a mathematical model is built up to investigate thermal interactions among a growing particle layer, pulling speeds, and the freezing interface under a thermal gradient. Experiments are conducted to confirm the tendency predictions of the model. With the increase of pulling speeds, the drifting distance of the freezing interface increases and the time to finish drifting decreases. When the thermal conductivity of particles (k
p) is smaller than that of the surrounding (k
w), the freezing interface tends to go forward to the warm side. Contrarily, the freezing interface tends to go back to the cold side when the thermal conductivity of particles is larger than that of the surrounding (α = k
p/k
w > 1). It originates from the shape of the local freezing interface: convex (α < 1) or concave (α > 1). These morphological changes in the local interface modify the premelting drag force F
f. When α < 1, F
f decreases and the freezing morphology tends to be the frozen fringe. When α > 1, F
f increases and the freezing morphologies tend to be ice spears. These understandings of how the thermal conductivity of particles affect microstructural evolution may optimize the production of freeze-casting materials and their structural-functional properties.
Isgur-Wise function in Bc
decays to charmonium with the Bethe-Salpeter method *
Authors: Geng Zi-Kan , Jiang Yue , Wang Tianhong , Zheng Hui-Wen , Wang Guo-Li
Published: October 2020

The heavy quark effective theory vastly reduces the weak-decay form factors of hadrons containing one heavy quark. Many works attempt to directly apply this theory to hadrons with multiple heavy quarks. In this paper, we examine this confusing application by the instantaneous Bethe-Salpeter method from a phenomenological perspective, and give the numerical results for

decays to charmonium where the final states include

,

,

, and

. Our results indicate that the form factors parameterized by a single Isgur-Wise function deviate substantially from the full ones, especially when excited states are involved. The relativistic corrections (

corrections) require the introduction of more non-perturbative universal functions, similar to the Isgur-Wise function, which are the overlapping integrals of the wave functions with the relative momentum between the quark and antiquark.
Effects of a contusive spinal cord injury on cortically-evoked spinal spiking activity in rats
Authors: Borrell Jordan A , Krizsan-Agbas Dora , Nudo Randolph J , Frost Shawn B
Published: October 2020

Objective. The purpose of this study was to determine the effects of spinal cord injury (SCI) on spike activity evoked in the hindlimb spinal cord of the rat from cortical electrical stimulation. Approach. Adult, male, Sprague Dawley rats were randomly assigned to a Healthy or SCI group. SCI rats were given a 175 kDyn dorsal midline contusion injury at the level of the T8 vertebrae. At 4 weeks post-SCI, intracortical microstimulation (ICMS) was delivered at several sites in the hindlimb motor cortex of anesthetized rats, and evoked neural activity was recorded from corresponding sites throughout the dorsoventral depths of the spinal cord and EMG activity from hindlimb muscles. Main results. In healthy rats, post-ICMS spike histograms showed reliable, evoked spike activity during a short-latency epoch 10–12 ms after the initiation of the ICMS pulse train (short). Longer latency spikes occurred between ∼20 and 60 ms, generally following a Gaussian distribution, rising above baseline at time L
ON, followed by a peak response (L
p), and then falling below baseline at time L
OFF. EMG responses occurred between L
ON and L
p( 25–27 ms). In SCI rats, short-latency responses were still present, long-latency responses were disrupted or eliminated, and EMG responses were never evoked. The retention of the short-latency responses indicates that spared descending spinal fibers, most likely via the cortico-reticulospinal pathway, can still depolarize spinal cord neurons after a dorsal midline contusion injury. Significance. This study provides novel insights into the role of alternate pathways for voluntary control of hindlimb movements after SCI that disrupts the corticospinal tract in the rat.
The parallel & distributed code for numerical simulation of relativistic magnetohydrodynamics simulation
Authors: Kulikov Igor , Chernykh Igor , Karavaev Dmitry , Sapetina Anna , Prigarin Vladimir , Protasov Victor , Ulyanichev Ivan
Published: October 2020

A new code for modeling relativistic magnetohydrodynamic flows is described in the paper. The developed program code is based on a combination of adaptive nested grids. Magnetic hydrodynamics of the process is simulated using nested grids. Subgrid processes are simulated using regular grids. In the paper, we will outline the main components of program code building. These steps are common to other program codes for magnetized flows simulation.
The Supercomputing Simulation of Instability and Shock Waves in Gas Giant
Authors: Gornova Alisa , Kulikov Igor , Chernykh Igor
Published: October 2020

The research of the gas giant atmosphere behavior during its interaction with a stellar wind is given in paper. The various case of interaction of atmosphere with the dense gas current are considered. The numerical model based on gravitational hydrodynamics equations was used. The combination of operator splitting approach, Godunov’s and HLL methods, and the piecewise parabolic method on local stencil is used for the solution of equations. The computing experiments were made on the supercomputer equipped with Intel Xeon Phi accelerators.
Calculation of the expansion dynamics of evaporated tungsten under the action of a laser pulse
Authors: Arakcheev A S , Lazareva G G , Maksimova A G , Popov V A , Ivashin N E
Published: October 2020

The paper is devoted to the numerical implementation of a model of the dynamics of the tungsten vapors flow evaporating from the sample surface. To calculate the speed and mass flow rate of the substance evaporating from the sample surface, a system of gas dynamics equations is numerically solved. The boundary conditions for the gas velocity and density on the heated surface have a great influence on the solution of the problem. Boundary conditions for temperature are obtained as a result of solving the two-phase Stefan problem in a cross-section of the sample. The aim of the study is to model the erosion of the sample surface and penetration of heat flow into the material.
Ontological approach to formalization of knowledge in computational plasma physics
Authors: Snytnikov A V , Glinskiy B M , Zagorulko G B , Zagorulko Y A
Published: October 2020

Computational plasma physics is a wide area of research, which includes a certain set of physical phenomena, mathematical equations, numerical methods, programming strategies, and hardware architectures that directly follow each other. To design an efficient code for solving a computational plasma physics problem, the researcher should have a clear understanding of the relationships between the concepts of physics, mathematics, computer science, and computer architecture. Ontology is one of the effective ways to realize (provide) such an understanding. Authors propose an approach to design an ontology which will show how physical phenomena determine mathematical equations being used, how the equations define numerical methods, and how methods enable programming strategies to form an architecture-efficient implementation of problem solution.
Performance improvement of particle-in-cell method for numerical modelling of open magnetic system
Authors: Boronina M.A. , Chernykh I.G. , Genrikh E.A. , Vshivkov V.A.
Published: October 2020

The work is connected with numerical simulation of plasma dynamics in open magnetic trap in diamagnetic regime. The hybrid particle-in-cell model we develop allows to perform numerical experiments for the high ratio of Larmor radius of the ions and the one of the electrons due to the combining of the kinetic description for the ions and MHD description for the electron plasma component. The disadvantage of the model is the stability condition and the corresponding requirements for the time step. In practice a doubling of the grid nodes in each direction leads to the decrease of the time step x6 times. For the characteristic times of the plasma processes 102 reciprocal ion cyclotron frequencies the computations required few days for grids 100x500. The processing of the particle data takes more than 85% of the total computation time, thus its effective realization yields significant gain in performing. In our algorithm we combine the dynamic load balance and vectorized computations of densities and current densities. We present the results of numerical experiments on its basis including the highly non-uniform particle distribution in the domain and the increasing of the particle number due to the beam injection.
Cross-platform implementation of Particle-In-Cell method for simulation of high-temperature and fusion plasma by means of hybrid supercomputers equipped with GPU or Intel Xeon Phi accelerators
Authors: Romanenko Alexey A , Snytnikov Alexey V , Boronina Marina A
Published: October 2020

A new Python-based Particle-In-Cell code is presented. The code uses leapfrog particle pusher. The important feature of our code is that all the particles are pushed at once, thus the code is vectorized to improve performance. Electric field is given by Poisson equation with Least squares solver. The code involves collision simulation by PIC-MC method. Both large-scale (MPI) and fine-grain parallelization are being used. The implementation is based on the efficient NumPy library in Python language with the help of Dask package to improve Numpy performance. GPU implementation involves PyCUDA and the performance with Intel Xeon processors and Intel Xeon Phi accelerators is supported by high-performance Intel Python.
GPU-native gas dynamic solver on octree-based AMR grids
Authors: Menshov I , Pavlukhin P
Published: October 2020

GPU implementation of the Godunov-type gas dynamic solver on three-dimensional octree-based grids is proposed. In this implementation, all dynamic adaptive mesh refinement (AMR) procedures are performed entirely on GPU as opposed to most of other implementations where grid metadata is transferred to CPU for further updating. Conducted bench tests show that eliminating regular CPU–GPU grid data transferring in the proposed parallel AMR algorithms makes it possible to reduce the grid modification overhead to lower than 2% on Nvidia Tesla V100. The results concerned with both CUDA and OpenMP implementation performance are also presented.
An adaptive multigrid on block-structured grids
Authors: Feodoritova O B , Zhukov V T
Published: October 2020

An implementation of the multigrid method on conformal block-structured grids is proposed. The algorithm is intended to solve a boundary-value problem for elliptic PDEs. Each block is discretized using a structured hexahedron grid.The set of multilevel grids are arranged in hierarchical levels. In each block the discrete finite volume scheme is constructed on the fine level grid. The coarse level equations are formed by the Galerkin procedure. The presence of the irregular block connections leads to irregular stencils in the nodes which adjoin of several blocks. Instead of a special irregular node treatment we propose to find the solution in these nodes in additive manner. Such an opportunity is provided by the use of the explicit iterative procedures for both the smoothers and the coarsest grid solver. We also present an adaptive technique which adjusts these procedures for achieving the prescribed multigrid convergence rate. The proposed approach enhances the potential of the multigrid method in ultra-parallel computing.
Facile manufacturing of fused-deposition modeled composite scaffolds for tissue engineering—an embedding model with plasticity for incorporation of additives
Authors: Manjunath Kamath S , Sridhar K , Gopinath V , Sankar KrishnaKumar , Sundaram A , Gupta Nilkantha , Shiek Ahmed S S J , Shantanu Patil S
Published: October 2020

The fused-deposition modeling (FDM) process is carried out at an elevated temperature, preventing the addition of biological factors, drugs, bioactive compounds, etc, during fabrication. To overcome this disadvantage, a 3D interlinked porous polylactic acid (PLA) scaffold was fabricated by FDM, followed by the embedding of a polycaprolactone (PCL) scaffold into the pores of the PLA at room temperature, yielding a PLA-PCL scaffold. In addition, PLA-PCL scaffolds with nanohydroxyapatite (PLA-PCL-nHAP) and multiwalled carbon nanotubes (PLA-PCL-MWCNT) were also fabricated. Here, the FDM-fabricated PLA scaffold functions as the structural component, whereas the embedded PCL scaffold acts as the functional component, which provides a the ability to functionalize the scaffolds with the desired chemical or biological materials. The embedding process is straightforward, cost effective, and does not require sophistication. A mechanical characterization of the scaffolds suggests that the Young’s modulus of the PLA-PCL scaffold (16.02 MPa) was higher than that of the FDM-fabricated PLA (9.98 MPa) scaffold, by virtue of embedded PCL matrix. In addition, finite element analysis showed that the von Mises stress on a mandible with scaffolds was 4.04 MPa, whereas for a mandible with a defect, it was 6.7 MPa, confirming the stress distribution efficiency and mechanical stability of these scaffolds. Furthermore, field emission-scanning electron microscope analysis implied the presence of interlinked porous structures with pore diameters of 50 µm to 300 µm. X-ray diffraction results revealed an increased crystallinity (%) in the embedded models (PLA-PCL, PLA-PCL-nHAP and PLA-PCL-MWCNT), compared to a PLA printed scaffold. Additionally, Raman analysis revealed that the embedding process did not cause chemical alterations in the polymeric chains. In vitro analysis with human osteoblasts demonstrated the osteoconductive nature of the scaffold, which supported mineralization. In brief, the advantage of our model is that it helps to overcome the difficulties of manufacturing a filament with the desired additives for FDM, and offers the ability to incorporate the desired concentrations of heat-labile bioactive molecules during the embedding process at ambient temperatures.
Automaticity and delegation in climate targets
Authors: Frame David , von Stein Jana
Published: October 2020

The problem of dynamically inconsistent preferences is common in domestic and international politics. A country’s—or indeed the world’s—future health (economic, social, environmental, etc.) often requires policy adjustments that are costly and unpopular. Governments face formidable pressures to underinvest today in policies whose consequences are optimal in the future. This challenge may be particularly acute when leaders face accountability mechanisms that induce frequent policy responsiveness such as elections. Policies that automatically adjust in response to other changes are a common proposed solution to these types of problems. To be successful, index-based approaches typically also require delegation to an independent authority. In the realm of climate mitigation, we argue that a combination of automaticity and delegation can provide a promising combination for policymakers to consider as they attempt to develop enduring solutions to climate change.
Emission Characteristic of a Dual fuel Compression Ignition Engine Operating on Diesel + Hydrogen & Diesel + HHO gas with same Energy Share at Idling Condition
Authors: Subramanian Balaji , Venugopal T , Feroskhan M , Sivakumar R
Published: October 2020

Clean burning nature and renewability of hydrogen makes it viable and alternative / supplementary fuel for utilization in IC engine. In the past two decades, researchers have gained interest in using hydrogen in Internal combustion (IC) engines. Electrolysis is the widely used technique for production of hydrogen. The effect on emission parameters of using hydrogen and HHO gas in a dual fuel engine at idling condition was focused in this research work. HHO gas was synthesized from stored cylinders of hydrogen & oxygen in 2:1 ratio. The mixture of H2 and O2 are produced in stoichiometric ratio similar to electrolysis of water. Effect of introduction of hydrogen gas and stimulated HHO gas on emission characters such as unburnt hydrocarbon (UHC), carbon dioxide (CO2), oxides of nitrogen (NOx) and smoke of the engine were noted at idling condition (1700 rpm). Engine was supplied with 6, 12, 18, 24, 30, 36 LPM of hydrogen and 9, 18, 27, 36, 45, 54 LPM of HHO gas where the composition of mixture was maintained in the ratio of 2:1 and energy supplied by Hydrogen and HHO gas remains same. Introduction of hydrogen and HHO gas has reduced the total diesel fuel consumption and formation of CO2 at all operating condition than neat diesel operation. There was slight increase in UHC emission with hydrogen and by substituting HHO gas the UHC emission was reduced.
Effects of butanol blending ratio in biogas-biodiesel dual fuel engine
Authors: Neeraj Bandi Raj , Tharundeep K , Dinesh Kumar M , Deveshwaran S , Bommisetty Ankith , Gobinath N , Feroskhan M
Published: October 2020

By the rise in population, the usage of non-renewable fuels is increasing. It led to the depletion of fossil fuels and other environmental issues. Reducing the usage of fossil fuel, enhancing performance and reducing emissions are the key areas in this research. In this experiment, a conventional single cylinder CI engine is used in dual fuel mode. In dual fuel mode, biogas is used as primary fuel and biodiesel (Palm oil) with various butanol blending ratios (10%, 20% and 30%) is used as pilot fuel. Various properties like flash and fire point, cloud and pour point, viscosity, density, calorific values are measured. Biogas flow rate and applied load are varied for each blending ratio. The effects of load, butanol blending ratio and biogas flow rate on BTE, BSFC, HC, CO and NOx emissions are analyzed and compared with diesel-only mode. Biodiesel with 30% butanol blend in dual fuel mode shows better brake thermal efficiency at 12 lpm flow rates. All test cases prove 12 lpm is better than 16 lpm biogas flow rates. Increase in biogas flow rate reduces NOx emissions. However, it increases HC and CO emissions. And this investigation proposes to intervene in the dual fuel biogas-biodiesel engine at 12 lpm biogas rate of flow.
Community Energy Sharing in a Microgrid Architecture with Energy Storage and Renewable Energy Support
Authors: Karthikeyan R. , Parvathy A.K. , Priyadarshini S.
Published: October 2020

The increase in the number of installed renewable energy in a residential network needs an efficient energy management system (EMS) to store or sell the surplus energy back to the grid during the surplus generation. Selling of power back to the grid can affect the reliability of the traditional grid system, to avoid this energy sharing is proposed to share the surplus energy with close neighbours to avoid the transmission loss and increase the utilization rate of renewable energy. In this paper, we use the cyber-physical system (CPS) to coordinate the neighbours and to collect data from all the homes using the smart meters. The system’s objective is to reduce the grid cost and to benefit each home which shares the energy. This system reduces the need for a huge energy storage system (ESS) which is a major capital cost during the installation. We adopt a scheduling algorithm to manage the loads during the shortage of supply and flexibility in scheduling the loads helps to improve energy management without disturbing the user comfort. The whole model is validated with an experimental setup in the university as a part of the MNRE Funded Project.
Simulation of Electric Vehicle using Scilab for Formula Student Application
Authors: Dubey Manu , Bhardwaj Saksham , Harish R. , Shyam Kumar M.B
Published: October 2020

The principal objective of this research is development of a formula student electric vehicle and its performance analysis using model based simulation using Scilab. This project focuses on determining the technical parameters needed for electric vehicle designing using simulation tools currently available in market. Simulations are carried out using Optimum Lap and Scilab. Dynamic simulations of electric vehicles are conducted using this software for comparative study of different components which can affect the performance of the vehicle. Initially, lap simulation of vehicle is conducted based on various motors available in market using Optimum Lap to record speed, lap time, torque and energy consumption, this data is very crucial while selection of motor for the vehicle. Motors available in the market will be simulated and compared based on their energy consumption and voltage required. After selection of motor different battery cells will be compared based on their technical specifications to design a battery pack. Motor and battery will then be analysed using electric vehicle model created in Scilab to record the performance of the formula student electric vehicle. This project will guide students for selection of motor and battery for their car based on simulated data rather than actually buying and testing these components to save time and money.
Numerical Investigation of double pipe heat exchanger with different nanofluids
Authors: Naik Bharat , Soudagar Manzoore Elahi M , Thomas Merwyn , Dasurkar Kshitij , Alloli Omkar , Hussain Fayaz , Madlool N.A. , Alloli Mahalaxmi
Published: October 2020

The study represents an enhancement of heat transfer using different nanofluids containing nanoparticles (Al2O3, Cu, Ag, TiO2, SiO2, Fe) Volume fraction (0.02≤ϕ≤0.05). Numerical simulations are conducted using CFD (Computational Fluid Dynamics) and the model is generated using Solid works. The governing equations are solved using a SIMPLE technique and discretized using finite volume approach. The results show that the heat transfer rate increases with the increase of the flow rates, also it has been observed that heat transfer rate increases with increase of operating temperature and also by the concentration of nanoparticles.
Building bricks with PCM inserts for Passive cooling applications
Authors: Anfas Mukram T , Daniel Joseph
Published: October 2020

The vital predicament that mankind will face in near future is the deficiency of energy. Heavy dependency of fossil fuels for driving the systems make the problem too complex by adding the Green House Gas (GHG) emission also. Across the sphere, consumption pattern confirms the major role of building sector, mostly for space conditioning application. Passive cooling by Latent Heat Thermal Energy Storage is well-established method. In this work commercially available Phase Change Material (PCM) is used for latent heat storage. The PCM is inserted in the brick cavity. The performance of two types of PCM insert is compared, ie, macro encapsulation at the middle of the brick and microencapsulation near the outer wall of the brick. The results show that, the centrally encapsulated brick performs better in heating cycle, but during night time the heat entry into the living space is more. The micro encapsulation at offset to the wall side justifies for the night use.
Use of digital correlation techniques for investigating behaviour of geothermal driven piles
Authors: Sreelakshmi G , Asha M. N.
Published: October 2020

Geothermal energy has established its huge potential as renewable source of energy for general building establishments. A key feature here is the use of energy piles which serve as major energy exchange system which is sustainable and low-cost. Energy piles are basically driven precast piles employed to provide structural support to structures and act as heat exchange units to provide heating / cooling to buildings. The behaviour of energy piles is influenced by temperature, physical and engineering properties of soil. However, uncertainty still exists at pile soil interface irrespective of its heating or cooling conditions. The present study examines the suitability of using digital correlation technique (DIC) namely GeoPIV-RG software to study the soil deformation at pile soil interface in sandy soil. A rectangular test tank made of steel with a size of 60 × 20 × 45 cm is used for experimental studies. Hollow half section aluminum piles closed at the ends with two different pile length to outer pile diameter ratios viz., 10 and 15 of same flexural rigidity are used for the experimental studies. The piles are subjected to sustained loading simulated through Universal testing machine and movements of soil around the pile are captured using a digital camera. The image analysis software named GeoPIV-RG is used to determine the shear strains and soil displacements. Analysis of results indicated that this technique could capture deformation characteristics and surface heave formation in the surrounding infill medium.