bluuebunny/crossref_metadata_2025 huggingface dataset:
Futuramas of the present: the “driver problem” in the autonomous vehicle sociotechnical imaginary
Authors: Braun Robert , Randell Richard
Published: December 2020

The visions surrounding “self-driving” or “autonomous” vehicles are an exemplary instance of a sociotechnical imaginary: visions of a future technology that has yet to be developed or is in the process of development. One of the central justifications for the development of autonomous vehicles is the claim that they will reduce automobility related death and injury. Central to this narrative is the assumption that more than 90% of road crashes are the result of “driver error.” This paper describes the process by which this statistic has been constructed within road safety research and subsequently accepted as a received fact. It is one of the principal semiotic components of the autonomous vehicle sociotechnical imaginary: if human drivers are responsible for ~90% of road crashes, autonomous vehicles should in principle be able to reduce road death and injury rates by a similar percentage. In this paper, it is argued that death and injury are not an aggregate of events that can be distributed across the three central variables of traditional road safety research: the driver, the vehicle, and the environment. The autonomous vehicle sociotechnical imaginary has embraced the central assumption of road safety research, that road violence is not an intrinsic property of automobility but is contingent because largely due to driver error. On the basis of this assumption it has been possible to configure autonomous vehicles as the solution to road violence. Although sociotechnical imaginaries are typically oriented towards the future, it is the significance of the autonomous vehicle sociotechnical imaginary in the present that is the focus of this paper. Autonomous vehicles are not the radically transformational technology their proponents claim but simply the most recent of a succession of automobility sociotechnical imaginaries. They are not transformational because their promotion ensures the continued reproduction of more of the same: namely, more automobility.
Cold sintering of yttria-stabilized cubic bismuth oxide: Conductivity and microstructural evolution of metastable grain boundaries with annealing
Authors: Tsuji Kosuke , Herisson de Beauvoir Thomas , Ndayishimiye Arnaud , Wang Ke , Randall Clive A.
Published: December 2020

Yttrium-doped bismuth oxide (BYO) is densified by the cold sintering process (CSP) at 300 °C. The relative density reached is ∼90% of the theoretical density. The as-sintered BYO ceramic shows a total conductivity of >1 mS/cm at 500 °C. The conductivity slightly increased after the annealing process. The scanning and transmission electron microscopy analysis revealed that a metastable secondary phase formed adjacent to BYO grains in the as-CSP specimens. Once annealed, the secondary phase recrystallized and there is an associated total conductivity improvement.
Backbone oriented anisotropic coarse grains for efficient simulations of polymers
Authors: Goujon Florent , Martzel Nicolas , Dequidt Alain , Latour Benoit , Garruchet Sébastien , Devémy Julien , Blaak Ronald , Munch Étienne , Malfreyt Patrice
Published: December 2020

Despite the fact that anisotropic particles have been introduced to describe molecular interactions for decades, they have been poorly used for polymers because of their computing time overhead and the absence of a relevant proof of their impact in this field. We first report a method using anisotropic beads for polymers, which solves the computing time issue by considering that beads keep their principal orientation alongside the mean local backbone vector of the polymer chain, avoiding the computation of torques during the dynamics. Applying this method to a polymer bulk, we study the effect of anisotropic interactions vs isotropic ones for various properties such as density, pressure, topology of the chain network, local structure, and orientational order. We show that for different classes of potentials traditionally used in molecular simulations, those backbone oriented anisotropic beads can solve numerous issues usually encountered with isotropic interactions. We conclude that the use of backbone oriented anisotropic beads is a promising approach for the development of realistic coarse-grained potentials for polymers.
Time-variant prediction of flow over an airfoil using deep neural network
Authors: Peng Jiang-Zhou , Chen Siheng , Aubry Nadine , Chen Zhi-Hua , Wu Wei-Tao
Published: December 2020

In this article, we propose an unsteady data-driven reduced order model (ROM) (surrogate model) for predicting the velocity field around an airfoil. The network model applies a convolutional neural network (CNN) as the encoder and a deconvolutional neural network (DCNN) as the decoder. The model constructs a mapping function between temporal evolution of the pressure signal on the airfoil surface and the surrounding velocity field. For improving the model performance, the input matrix is designed to further incorporate the information of the Reynolds number, the geometry of the airfoil, and the angle of attack. The DCNN works as the decoder for better reconstructing the spatial and temporal information of the features extracted by the CNN encoder. The training and testing datasets of flow fields under different conditions are obtained by solving the Navier–Stokes equations using the computational fluid dynamics method. After model training, the neural network based ROM shows accurate and dramatically fast predictions on the flow field of the testing dataset with extended angles of attack and Reynolds numbers. According to the current study, the neural network-based ROM has exhibited attractive potentials on ROM of the unsteady fluid dynamic problem, and the model can potentially serve on investigating flow control or optimization problems in the future.
Correction of the VIR-visible dataset from the Dawn mission at Vesta
Authors: Rousseau B. , De Sanctis M. C. , Raponi A. , Ciarniello M. , Ammannito E. , Scarica P. , Fonte S. , Frigeri A. , Carrozzo F. G. , Tosi F.
Published: December 2020

This work describes the correction method applied to the dataset acquired at the asteroid (4) Vesta by the visible channel of the visible and infrared mapping spectrometer. The rising detector temperature during data acquisitions in the visible wavelengths leads to a spectral slope increase over the whole spectral range. This limits the accuracy of the studies of the Vesta surface in this wavelength range. Here, we detail an empirical method to correct for the visible detector temperature dependency while taking into account the specificity of the Vesta dataset.
Development of a rigid suspended micro-island device and robust measurement method for thermal transport measurements
Authors: Nguyen Anh Tuan , Jones Casey , Lee Woochul
Published: December 2020

One of the most versatile techniques to study thermal transport in low dimensional materials utilizes a suspended micro-island device integrated with resistance thermometers. Advancements in experimental techniques with suspended micro-island devices resulted in increasing capabilities such as enhancing temperature resolution and expanding a measurable range of sample thermal conductance. In this work, we further improve the suspended micro-island based technique. Specifically, we present a rigid structure of the suspended micro-island device and robust measurement method for sequential heating. The rigid structure enabled by T-shaped beams prevents the displacement of suspended micro-islands, thus increasing the success rates of sample transfer especially for samples with a large cross-sectional area and short length. Besides, thermal isolation of micro-islands is maintained at a similar level through the T-shaped beams compared to conventional flat beams. Next, we introduce an advanced experimental approach that enables sequential heating to measure sample thermal conductance. Sequential heating in micro-islands can be used either to measure accurate sample thermal conductance even under unexpected asymmetric supporting beam configuration or to study thermal transport dependence on heat flow directions. Using a switch matrix for sequential heating eliminates the need for experimental reconfigurations during the experiment. We demonstrate the experimental method with thermal conductivity measurements of the Si nanowire under both the ideal symmetric beam configuration and replicated asymmetric beam configuration scenarios. The results show that the developed experimental method effectively eliminates potential experimental errors that can arise from the asymmetry in beam configurations.
Sessile drop response to a single wave electrokinetic excitation
Authors: Marin Quintero Juan S. , Waghmare Prashant R.
Published: December 2020

The response time for maximum drop deformation and its comparison with different time scales is established and verified with experiments. The applied fluctuation is achieved by applying a single wave perturbation of electrowetting with desired amplitude and frequency. To pinpoint the importance of the initial actuation conditions, the variance in the maximum drop deformation for a single wave perturbation is studied. The focus of this study was to analyze the maximum deformation of a drop for a wide range of actuation mechanism with a varied drop or surrounding medium viscosities. The drop response to this cyclic actuation is compared with the equivalent mass–spring–dampener system, and limitations of this approach are identified. Interestingly, the qualitative results were similar between the air and liquid medium cases, but the attainment of equilibrium configuration was dissimilar. As anticipated, the higher actuation magnitude and frequency deformed the drop significantly and thus altered the drop configuration. Higher viscosity of drops and the surrounding medium delayed the time to achieve the maximum deformation. Accurately predicting the time required for a drop to attain the maximum deformation is paramount for optimizing processes and based on microfluidics technology.
Picowatt calorimeter for optical absorption spectroscopy
Authors: Roshanzadeh B. , Boyd S. T. P. , Rudolph W.
Published: December 2020

An optical picowatt calorimeter at 4 K is demonstrated to measure absorption spectra from 330 nm to 1700 nm of optical samples. The minimum detectable absorbed power is 10 pW, resulting in absorption sensitivities of 0.3 ppm for 30 µW of incident power from a tunable source and 0.6 ppb for 15 mW laser excitation. Active temperature stabilization of main components of the cryogen-free cryostat and the use of paramagnetic temperature sensors with superconducting quantum interference device readout provided a low noise environment (700 nK temperature rms) and nK temperature resolution.
Calculation of spin–orbit couplings using RASCI spinless one-particle density matrices: Theory and applications
Authors: Carreras Abel , Jiang Hanjie , Pokhilko Pavel , Krylov Anna I. , Zimmerman Paul M. , Casanova David
Published: December 2020

This work presents the formalism and implementation for calculations of spin–orbit couplings (SOCs) using the Breit–Pauli Hamiltonian and non-relativistic wave functions described by the restricted active space configuration interaction (RASCI) method with general excitation operators of spin-conserving spin-flipping, ionizing, and electron-attaching types. The implementation is based on the application of the Wigner–Eckart theorem within the spin space, which enables the calculation of the entire SOC matrix based on the explicit calculation of just one transition between the two spin multiplets. Numeric results for a diverse set of atoms and molecules highlight the importance of a balanced treatment of correlation and adequate basis sets and illustrate the overall robust performance of RASCI SOCs. The new implementation is a useful addition to the methodological toolkit for studying spin-forbidden processes and molecular magnetism.
Doping and fabrication of polar-plane-free faceted InGaN LEDs with polychromatic emission properties on (1¯1¯22¯) semipolar planes
Authors: Matsuda Yoshinobu , Funato Mitsuru , Kawakami Yoichi
Published: December 2020

Electrically driven polar-plane-free faceted InGaN light-emitting diodes (LEDs) are demonstrated on semipolar (1¯1¯22¯) GaN substrates. The doping properties on the (1¯1¯22¯) plane are investigated using planar LED structures. After establishing the doping conditions, three-dimensional faceted LED structures composed of semipolar and nonpolar planes are fabricated by regrowth on the (1¯1¯22¯) GaN substrates with dielectric masks. The fabricated LEDs exhibit a clear rectifying property and a polychromatic emission derived from facet-dependent emission colors, which can be tuned by altering the mask geometry. These observations suggest that polar-plane-free LED structures may lead to highly radiative polychromatic light emitters.
Phase and amplitude dynamics of coupled oscillator systems on complex networks
Authors: Woo Jae Hyung , Honey Christopher J. , Moon Joon-Young
Published: December 2020

We investigated locking behaviors of coupled limit-cycle oscillators with phase and amplitude dynamics. We focused on how the dynamics are affected by inhomogeneous coupling strength and by angular and radial shifts in coupling functions. We performed mean-field analyses of oscillator systems with inhomogeneous coupling strength, testing Gaussian, power-law, and brain-like degree distributions. Even for oscillators with identical intrinsic frequencies and intrinsic amplitudes, we found that the coupling strength distribution and the coupling function generated a wide repertoire of phase and amplitude dynamics. These included fully and partially locked states in which high-degree or low-degree nodes would phase-lead the network. The mean-field analytical findings were confirmed via numerical simulations. The results suggest that, in oscillator systems in which individual nodes can independently vary their amplitude over time, qualitatively different dynamics can be produced via shifts in the coupling strength distribution and the coupling form. Of particular relevance to information flows in oscillator networks, changes in the non-specific drive to individual nodes can make high-degree nodes phase-lag or phase-lead the rest of the network.
Practitioner observations of oral nicotine use in elite sport: You snus you lose
Authors: Kasper Andreas M. , Close Graeme L.
Published: December 2020

The elite sport environment is one where athletes strive to find a competitive edge, through improved recovery modalities, cognitive performance or physical capacity. Due to this, non‐scientifically evidenced and/or pseudo‐scientific alternative remedies are ever popular. Snus (an oral tobacco based product containing the highly addictive compound nicotine) is one alternative ‘physical and psychological performance enhancer’, purported to act as a ‘mental and physical booster’, ‘relaxative’ and even as an ‘appetite suppressor’. Despite snus having serious adverse health effects, along with no proven benefit to physical or mental performance, observations by the authors working in professional sport, along with several reports in the mainstream media, would suggest that the use of snus in elite sport appears to be increasing. Perhaps most worrying, the use of snus has been reported to be prevalent within younger athletes. It is crucial that athletes are fully educated with regards to the health implications of snus and other oral tobacco‐based products, whilst practitioners should be aware of its growing prevalence in sport with strategies in place to discourage its use.
More of the bulk from extremal area variations
Authors: Bao Ning , Cao ChunJun , Fischetti Sebastian , Pollack Jason , Zhong Yibo
Published: December 2020

It was shown recently in (Bao N et al 2019 Class. Quantum Grav.
36 185002), building on work of Alexakis, Balehowksy, and Nachman (Alexakis S et al 2017 arXiv:1711.09379), that the geometry of (some portion of) a manifold with boundary is uniquely fixed by the areas of a foliation of two-dimensional disk-shaped surfaces anchored to the boundary. In the context of AdS/CFT, this implies that (a portion of) a four-dimensional bulk geometry can be fixed uniquely from the entanglement entropies of disk-shaped boundary regions, subject to several constraints. In this note, we loosen some of these constraints, in particular allowing for the bulk foliation of extremal surfaces to be local and removing the constraint of disk topology; these generalizations ensure uniqueness of more of the deep bulk geometry by allowing for e.g. surfaces anchored on disconnected asymptotic boundaries, or HRT surfaces past a phase transition. We also explore in more depth the generality of the local foliation requirement, showing that even in a highly dynamical geometry like AdS-Vaidya it is satisfied.
The effect of Cu additions in FePt–BN–SiO2 heat-assisted magnetic recording media
Authors: Streubel Robert , N’Diaye Alpha T , Srinivasan Kumar , Kalitsov Alan , Jain Shikha , Ajan Antony , Fischer Peter
Published: December 2020

Structural and chemical order impact magnetic properties of solids, which are governed by spin–orbit coupling and exchange interaction. The ordered L10 phase of FePt is a key material to heat-assisted magnetic recording; to enable high storage density, a solid understanding is needed of structural and chemical disorder at small length scales, as well as associated modifications of the electronic band structure. Here, we investigate the effect of boron and copper additions (≲6 mol% Cu) on structural and magnetic properties of L10 FePt granular media. Two copper-driven mechanisms, although competing, can lead to improvements in both structural and magnetic properties. In particular, the Cu substitution on the Fe-site leads to a degradation of magnetic properties due to the delocalized electron orbitals originating from a larger Cu d-orbital occupancy. At the same time, Cu substitution leads to an enhanced crystallographic order and consequently magneto-crystalline anisotropy, which offsets the former effect to a large extent. Our study is based on magnetometry, x-ray absorption spectroscopy, ab-initio calculations and a phenomenological theory of disordered FePt granular media. We do not observe a sizable modification to Fe moments and electronic configuration; Cu reveals two different resonances associated with the presence and absence of Cu–B bonds that vary with total Cu concentration.
Quantum numbers of the pentaquark states

Pc+

via symmetry analysis
Authors: Chen Chong-yao , Chen Muyang , Liu Yu-Xin
Published: December 2020

We investigate the quantum numbers of the pentaquark states

P

c

+

, which are composed of 4 (three flavors) quarks and an antiquark, by analyzing their inherent nodal structure in this paper. Assuming that the four quarks form a tetrahedron or a square, and the antiquark is at the ground state, we determine the nodeless structure of the states with orbital angular moment L ≤ 3, and in turn, the accessible low-lying states. Since the inherent nodal structure depends only on the inherent geometric symmetry, we propose the quantum numbers J

P
of the low-lying pentaquark states

P

c

+

may be

3

2

−

,

5

2

−

,

3

2

+

and

5

2

+

, independent of dynamical models.
Edge- and strain-induced band bending in bilayer-monolayer Pb2Se3 heterostructures*
Authors: Fan Peng , Qian Guojian , Wang Dongfei , Li En , Wang Qin , Chen Hui , Lin Xiao , Gao Hong-Jun
Published: December 2020

By using scanning tunneling microscope/microscopy (STM/STS), we reveal the detailed electronic structures around the sharp edges and strained terraces of lateral monolayer-bilayer Pd2Se3 heterostructures. We find that the edges of such heterostructures are well-defined zigzag type. Band bending and alignment are observed across the zigzag edge, forming a monolayer-bilayer heterojunction. In addition, an n-type band bending is induced by strain on a confined bilayer Pd2Se3 terrace. These results provide effective toolsets to tune the band structures in Pd2Se3-based heterostructures and devices.
Molecular beam epitaxy growth of iodide thin films*
Authors: Cai Xinqiang , Xu Zhilin , Ji Shuai-Hua , Li Na , Chen Xi
Published: December 2020

Study of two-dimensional (2D) magnetic materials is important for both fundamental research and application. Here we report molecular beam epitaxy growth of iodides, candidates for exhibiting 2D magnetism. Decomposition of CrI3 is utilized to produce stable gaseous I2 flux. Growth of MnI2, GdI3, and CrI2 down to monolayer is successful achieved by co-depositing I2 and corresponding metal atoms. The thin films of the three materials are characterized by scanning tunneling microscope and found to be insulators with bandgaps of 4.4 eV, 0.6 eV, and 3.0 eV, respectively. The film growth paves the way for further study of magnetic properties at the 2D limit.
Ground-state structure and physical properties of YB3 predicted from first-principles calculations*
Authors: Chu Bin-Hua , Zhao Yuan , Wang De-Hua
Published: December 2020

Using the calypso algorithm with first-principles calculations, we have predicted two orthorhombic Cmmm and Pmmm structures for YB3. The new structures are energetically much better than the previously proposed WB3-type, ReB3-type, FeB3-type, and TcP3-type structures. We find that the Cmmm phase transforms to the Pmmm phase at about 31 GPa. Subsequent calculations show that the Cmmm phase is mechanical and dynamical stable at ambient conditions. The analysis of the chemical bonding properties indicates that there are strong B–B bonds that make considerable contributions to its stability.
Theoretical analysis and numerical simulation of acoustic waves in gas hydrate-bearing sediments*
Authors: Liu Lin , Zhang Xiu-Mei , Wang Xiu-Ming
Published: December 2020

Based on Carcione–Leclaire model, the time-splitting high-order staggered-grid finite-difference algorithm is proposed and constructed for understanding wave propagation mechanisms in gas hydrate-bearing sediments. Three compressional waves and two shear waves, as well as their energy distributions are investigated in detail. In particular, the influences of the friction coefficient between solid grains and gas hydrate and the viscosity of pore fluid on wave propagation are analyzed. The results show that our proposed numerical simulation algorithm proposed in this paper can effectively solve the problem of stiffness in the velocity–stress equations and suppress the grid dispersion, resulting in higher accuracy compared with the result of the Fourier pseudospectral method used by Carcione. The excitation mechanisms of the five wave modes are clearly revealed by the results of simulations. Besides, it is pointed that, the wave diffusion of the second kind of compressional and shear waves is influenced by the friction coefficient between solid grains and gas hydrate, while the diffusion of the third compressional wave is controlled by the fluid viscosity. Finally, two fluid–solid (gas-hydrate formation) models are constructed to study the mode conversion of various waves. The results show that the reflection, transmission, and transformation of various waves occur on the interface, forming a very complicated wave field, and the energy distribution of various converted waves in different phases is different. It is demonstrated from our studies that, the unconventional waves, such as the second and third kinds of compressional waves may be converted into conventional waves on an interface. These propagation mechanisms provide a concrete wave attenuation explanation in inhomogeneous media.
Reputational preference and other-regarding preference based rewarding mechanism promotes cooperation in spatial social dilemmas*
Authors: Pei Huayan , Yan Guanghui , Wang Huanmin
Published: December 2020

To study the incentive mechanisms of cooperation, we propose a preference rewarding mechanism in the spatial prisoner’s dilemma game, which simultaneously considers reputational preference, other-regarding preference and the dynamic adjustment of vertex weight. The vertex weight of a player is adaptively adjusted according to the comparison result of his own reputation and the average reputation value of his immediate neighbors. Players are inclined to pay a personal cost to reward the cooperative neighbor with the greatest vertex weight. The vertex weight of a player is proportional to the preference rewards he can obtain from direct neighbors. We find that the preference rewarding mechanism significantly facilitates the evolution of cooperation, and the dynamic adjustment of vertex weight has powerful effect on the emergence of cooperative behavior. To validate multiple effects, strategy distribution and the average payoff and fitness of players are discussed in a microcosmic view.
Magnetic anisotropy in 5d transition metal–porphyrin molecules*
Authors: Zhang Yan-Wen , Ge Gui-Xian , Sun Hai-Bin , Yang Jue-Ming , Yan Hong-Xia , Zhou Long , Wan Jian-Guo , Wang Guang-Hou
Published: December 2020

Single molecule magnets (SMMs) with large magnetic anisotropy energy (MAE) have great potential applications in magnetic recording. Using the first-principles calculations, we investigate the MAE of 5d transition metal–porphyrin-based SMMs by using the PBE and PBE + U with different U values, respectively. The results indicate that W–P, Re–P, Os–P, and Ir–P possess the considerably large MAE among 5d TM–P SMMs. Furthermore, the MAE of 5d TM–P can be facilely manipulated by tensile strain. The reduction of the absolute value of MAE for Ir–P molecule caused by tensile strain makes it easier to implement the writing operation. The decreasing of the occupation number of minority-spin channels of Ir-d
x
2 – y
2
orbital leads the MAE to decrease when the tensile strain increases.
General M-lumps, T -breathers, and hybrid solutions to (2+1)-dimensional generalized KDKK equation*
Authors: Yuan Peisen , Qi Jiaxin , Li Ziliang , An Hongli
Published: December 2020

A special transformation is introduced and thereby leads to the N-soliton solution of the (2+1)-dimensional generalized Konopelchenko–Dubrovsky–Kaup–Kupershmidt (KDKK) equation. Then, by employing the long wave limit and imposing complex conjugate constraints to the related solitons, various localized interaction solutions are constructed, including the general M-lumps, T-breathers, and hybrid wave solutions. Dynamical behaviors of these solutions are investigated analytically and graphically. The solutions obtained are very helpful in studying the interaction phenomena of nonlinear localized waves. Therefore, we hope these results can provide some theoretical guidance to the experts in oceanography, atmospheric science, and weather forecasting.
Parameter accuracy analysis of weak-value amplification process in the presence of noise*
Authors: Qiu Jiangdong , Li Zhaoxue , Xie Linguo , Luo Lan , He Yu , Ren Changliang , Zhang Zhiyou , Du Jinglei
Published: December 2020

We theoretically introduce the statistical uncertainty of photon number and phase error to discuss the precision of parameters to be measured based on weak measurements. When the photon counting scheme is used, we discuss the relative accuracy of the system in the presence of phase error by using the orthogonal and nonorthogonal pre- and post-selected states, respectively. When using the measurement scheme of pointer shift, we discuss the measurement accuracy in the presence of phase error, pointer resolution, and statistical uncertainty. These results give a guide way to get the smallest relative precision and deepen our understanding about weak measurement.
Characterization and application in XRF of HfO2-coated glass monocapillary based on atomic layer deposition*
Authors: Li Yan-Li , Wang Ya-Bing , Lu Wei-Er , Kong Xiang-Dong , Han Li , Zhao Hui-Bin
Published: December 2020

Coating a glass monocapillary x-ray optics with high-density film is a promising way to improve transmission characteristics. For a long time, it has been a challenge to coat a high-density film in the inside of monocapillary with an extremely high length-to-diameter ratio. In this work, HfO2 film is deposited on the inner wall of a tapered glass monocapillary with length 9.9 cm, entrance diameter 596.4 μm, and exit diameter 402.3 μm by atomic layer deposition. The coated and uncoated monocapillaries are studied by the transmission process of x-rays with energy from 5 keV to 100 keV and the x-ray fluorescence (XRF) spectra of a Mo sample are detected. Improved transmission characteristics have been obtained for the HfO2-coated monocapillary. The energy upper limit of focused x-rays increases from 18.1 keV to 33.0 keV and the ‘penetration halo’ is suppressed to some extent. The XRF spectrum presents two stronger peaks at ∼ 17.4 keV and ∼ 19.6 keV which are considered as the characteristic x-rays of Mo K
α
and Mo K
β
. These results reveal that more higher energy x-rays from the W x-ray tube are totally reflected on the inner wall of the HfO2-coated glass monocapillary due to the increase of total reflection critical angle. This work is significant for more applications of monocapillary in higher energy x-ray field.
Continuous-wave operation of InAs/InP quantum dot tunable external-cavity laser grown by metal-organic chemical vapor deposition*
Authors: Wang Yan , Luo Shuai , Ji Haiming , Qu Di , Huang Yidong
Published: December 2020

We demonstrate high-performance broadband tunable external-cavity lasers (ECLs) with the metal-organic chemical vapor deposition (MOCVD) grown InAs/InP quantum dots (QDs) structures. Without cavity facet coatings, the 3-dB spectral bandwidth of the Fabry–Perot (FP) laser is approximately 10.8 nm, while the tuning bandwidth of ECLs is 45 nm. Combined with the anti-reflection (AR) / high-reflection (HR) facet coating, a 92 nm bandwidth tuning range has been obtained with the wavelength covering from 1414 nm to 1506 nm. In most of the tuning range, the threshold current density is lower than 1.5 kA/cm2. The maximum output power of 6.5 mW was achieved under a 500 mA injection current. All achievements mentioned above were obtained under continuous-wave (CW) mode at room temperature (RT).
Exploring individuals’ effective preventive measures against epidemics through reinforcement learning*
Authors: Cui Ya-Peng , Ni Shun-Jiang , Shen Shi-Fei
Published: December 2020

Individuals’ preventive measures, as an effective way to suppress epidemic transmission and to protect themselves from infection, have attracted much academic concern, especially during the COVID-19 pandemic. In this paper, a reinforcement learning-based model is proposed to explore individuals’ effective preventive measures against epidemics. Through extensive simulations, we find that the cost of preventive measures influences the epidemic transmission process significantly. The infection scale increases as the cost of preventive measures grows, which means that the government needs to provide preventive measures with low cost to suppress the epidemic transmission. In addition, the effective preventive measures vary from individual to individual according to the social contacts. Individuals who contact with others frequently in daily life are highly recommended to take strict preventive measures to protect themselves from infection, while those who have little social contacts do not need to take any measures considering the inevitable cost. Our research contributes to exploring the effective measures for individuals, which can provide the government and individuals useful suggestions in response to epidemics.
GEANT4 simulation study of over-response phenomenon of fiber x-ray sensor*
Authors: Zhang Bin , Xie Tian-Ci , Qin Zhuang , Li Hao-Peng , Li Song , Zhao Wen-Hui , Chen Zi-Yin , Xu Jun , Lewis Elfed , Sun Wei-Min
Published: December 2020

The purpose of this article is to explore the cause of the over-response phenomenon of fiber x-ray sensor. The sensor is based on a length of PMMA fiber, whose end is filled with the scintillation material Gd2O2S:Tb. The Monte Carlo simulation software GEANT4 uses the phase space file provided by the International Atomic Energy Agency (IAEA), by irradiating the fiber x-ray sensor in the water phantom, counting the fluorescence signal of the optical fiber x-ray sensor after propagation through the fiber. In addition, the number of Cerenkov photons propagating through the fiber is also counted. Comparing this article with previous research, we believe that one of the reasons for the over-response of the fiber x-ray sensor is the non-linear response of the deposition energy of the scintillator to the fluorescence. By establishing a region of interest and counting the x-rays in this region, the simulation results show that the counted number of x-rays that may affect the fiber x-ray sensor is the biggest in the area of interest at a water depth of 5 cm. This result is close to the maximum dose point of the experimental and simulated percentage depth dose (PDD) curve of fiber x-ray sensor. Therefore, the second reason of the over-response phenomenon is believed to be fact that the inorganic materials such as Gd2O2S:Tb have larger effective atomic numbers, so the fiber x-ray sensors will cause more collisions with x-ray in a low energy region of 0.1 MeV–1.5 MeV.
Phase tracking with Hilbert transform and nonlinear wave-wave coupling analysis on the HL-2A tokamak
Authors: Zang L.G. , Ohshima S. , Qu Y.F. , Shi P.W. , Zhong W.L. , Hou Y.M. , Yan L.W. , Ji X.Q. , Li J.Q. , Yu D.L. , Shi Z.B. , Liu Yi , Yang Q.W. , Xu M.
Published: December 2020

A phase tracking method based on Hilbert transform algorithm is applied to the nonlinear wave-wave coupling analysis on HL-2A tokamak. Synthetic signal analysis is given to show the principle of phase analysis for the detection of nonlinear coupling. If the phase difference between two coherent modes is synchronized with the phase of a third mode, these three modes are nonlinearly coupled, vice versa. The time evolution of the phase of a coherent mode could be computed with Hilbert transform for experimental data, and a phase tracking flowchart is summarized. On HL-2A tokamak, the nonlinear coupling among two Alfvén modes (AMs) and a tearing mode (TM) has been confirmed with bicoherence analysis (Shi et al 2017 Phys. Plasmas
24 042509). With Hilbert transform, it is clearly observed that the phase difference between two AMs Δθ
12 is synchronized with the phase of the TM θ
TM. The synchronization is confirmed with normalized cross-correlation. An alternative to check this synchronization is to observe the histogram of the phase difference Δθ
12 − θ
TM.
Thinking styles and engineering: proposals for strengthening the professional training of engineers through physics courses
Authors: Gaete-Peralta C , Huincahue J
Published: December 2020

One way to contribute to the strengthening of professional training processes in Engineering is through teaching and evaluation methods physics courses that promote those thinking styles that should be preferred by an engineer to solve tasks of their profession. Based on the above, the objective of this research was to identify those thinking styles that ideally a graduate of industrial civil engineering from a certain Chilean university should prefer to perform their profession tasks. Responding to this objective, it will be possible to generate educational proposals in physics courses for that career. For this, a qualitative methodology called thematic analysis was used. The data sources were semi-structured interviews with academics with enough experience in the career, besides the analysis of the institutional graduation profile. From a deductive perspective, according to the thinking styles, the ideal preferences for the egislative, judicial, global, hierarchical, liberal and external styles emerged as a result. Finally, a discussion was held on some teaching and evaluation methods that can be carried out in the physics courses of this career in order to promote these thinking styles.
Phenomenology and scaling of optimal flapping wing kinematics
Authors: Gehrke Alexander , Mulleners Karen
Published: December 2020

Biological flapping wing fliers operate efficiently and robustly in a wide range of flight conditions and are a great source of inspiration to engineers. The unsteady aerodynamics of flapping wing flight are dominated by large-scale vortical structures that augment the aerodynamic performance but are sensitive to minor changes in the wing actuation. We experimentally optimise the pitch angle kinematics of a flapping wing system in hover to maximise the stroke average lift and hovering efficiency with the help of an evolutionary algorithm and in situ force and torque measurements at the wing root. Additional flow field measurements are conducted to link the vortical flow structures to the aerodynamic performance for the Pareto-optimal kinematics. The optimised pitch angle profiles yielding maximum stroke-average lift coefficients have trapezoidal shapes and high average angles of attack. These kinematics create strong leading-edge vortices early in the cycle which enhance the force production on the wing. The most efficient pitch angle kinematics resemble sinusoidal evolutions and have lower average angles of attack. The leading-edge vortex grows slower and stays close-bound to the wing throughout the majority of the stroke-cycle. This requires less aerodynamic power and increases the hovering efficiency by 93% but sacrifices 43% of the maximum lift in the process. In all cases, a leading-edge vortex is fed by vorticity through the leading edge shear layer which makes the shear layer velocity a good indicator for the growth of the vortex and its impact on the aerodynamic forces. We estimate the shear layer velocity at the leading edge solely from the input kinematics and use it to scale the average and the time-resolved evolution of the circulation and the aerodynamic forces. The experimental data agree well with the shear layer velocity prediction, making it a promising metric to quantify and predict the aerodynamic performance of the flapping wing hovering motion.
Fish-like three-dimensional swimming with an autonomous, multi-fin, and biomimetic robot
Authors: Berlinger F , Saadat M , Haj-Hariri H , Lauder G V , Nagpal R
Published: December 2020

Fish migrate across considerable distances and exhibit remarkable agility to avoid predators and feed. Fish swimming performance and maneuverability remain unparalleled when compared to robotic systems, partly because previous work has focused on robots and flapping foil systems that are either big and complex, or tethered to external actuators and power sources. By contrast, we present a robot—the Finbot—that combines high degrees of autonomy, maneuverability, and biomimicry with miniature size (160 cm3). Thus, it is well-suited for controlled three-dimensional experiments on fish swimming in confined laboratory test beds. Finbot uses four independently controllable fins and sensory feedback for precise closed-loop underwater locomotion. Different caudal fins can be attached magnetically to reconfigure Finbot for swimming at top speed (122 mm s−1 ≡ 1 BL s−1) or minimal cost of transport (CoT = 8.2) at Strouhal numbers as low as 0.53. We conducted more than 150 experiments with 12 different caudal fins to measure three key characteristics of swimming fish: (i) linear speed-frequency relationships, (ii) U-shaped CoT, and (iii) reverse Kármán wakes (visualized with particle image velocimetry). More fish-like wakes appeared where the CoT was low. By replicating autonomous multi-fin fish-like swimming, Finbot narrows the gap between fish and fish-like robots and can address open questions in aquatic locomotion, such as optimized propulsion for new fish robots, or the hydrodynamic principles governing the energy savings in fish schools.
Aspects of CFTs on real projective space
Authors: Giombi Simone , Khanchandani Himanshu , Zhou Xinan
Published: December 2020

We present an analytic study of conformal field theories on the real projective space

R

P

d

, focusing on the two-point functions of scalar operators. Due to the partially broken conformal symmetry, these are non-trivial functions of a conformal cross ratio and are constrained to obey a crossing equation. After reviewing basic facts about the structure of correlators on

R

P

d

, we study a simple holographic setup which captures the essential features of boundary correlators on

R

P

d

. The analysis is based on calculations of Witten diagrams on the quotient space

A
d
S

d
+
1

/

Z

2

, and leads to an analytic approach to two-point functions. In particular, we argue that the structure of the conformal block decomposition of the exchange Witten diagrams suggests a natural basis of analytic functionals, whose action on the conformal blocks turns the crossing equation into certain sum rules. We test this approach in the canonical example of ϕ
4 theory in dimension d = 4 − ϵ, extracting the CFT data to order ϵ
2. We also check our results by standard field theory methods, both in the large N and ϵ expansions. Finally, we briefly discuss the relation of our analysis to the problem of construction of local bulk operators in AdS/CFT.
Technocenosis paradigm sustainability management of a forest enterprise
Authors: Ansary M , Kuzminov A , Ternovsky O , Medvedskaya T , Panyavina E
Published: December 2020

The relevance of the study is associated with the need to provide an effective methodology for the implementation of information technologies in forestry management. The article substantiates for the first time the application of a technocenological approach to enterprise sustainability management in the forest industry. This approach is effective in a variety of products and equipment, provides an account of the important laws of their optimal construction and operation. The technocenological approach allows us to design the structural architecture of the main subsystems of the enterprise, describing it as a certain standard form of the statistical distribution of elements within the boundaries of mathematical stability. This allows using the model as a guide for various management decisions. It is assumed that the proposed formal model will not only increase the manageability of individual enterprises, but also accelerate the digitalization of the entire industry.
Microwave modification of wood: determination of mechanical properties of softwood
Authors: Aksenov A A , Malyukov S V
Published: December 2020

Studies of aspen and birch wood interaction with pulsed exposure to microwave energy have been carried out. A method for determining the effect of microwave energy on the temperature inside the test specimen has been developed. It includes experimental setup for studying heat and mass transfer during drying and heat treatment of wood with microwave energy. Moisture content inside wood specimens has been determined by a new method using a laboratory installation for studying the mechanical properties of wood under the influence of microwave energy. This energy influences on the drying speed of the tested wood specimens. The research enables to select the optimal mode of wood heating by pulsed exposure to microwave energy. The results of wood tests for strength and hardness, obtained under the influence of microwave energy, have revealed the effect of wood hardening. The research has shown that microwave treatment of specimens reduces drying time of aspen and birch wood by five times in comparison with convective treatment.
Forest fire extinguishing: theoretical study of the screw drum parameter influence on the efficiency of a forest fire soil-sweeping machine
Authors: Bartenev I M , Malyukov S V , Malyukova M A
Published: December 2020

Forest fires are studied and developed in all countries with forest resources. However, despite large number of studies, the problem is still far from being resolved and fires still cause great damage to forests. The article deals with research on the influence of the screw drum parameters on the quality of removing the surface soil layer from combustible materials and on the performance of the forest fires soil-sweeping machine. The geometric parameters of the screw drum of the forest fires soil-sweeping machine were optimized. As a result of optimization, the optimal values of the screw channel depth in the range of 7.5-8.7 cm and the screw pitch of 23-40 cm were obtained. At these optimal values, the ground cover content in the thrown soil stream will be less than 15 %, the productivity of the forest fires soil-sweeping machine will be more than 40 kg/s, and the power consumption will be less than 12 kW.
Current issues of the regional forestry planning on the example of the Sverdlovsk region (Russian Federation)
Authors: Theriou N , Pryadilina N , Zinovyeva I
Published: December 2020

The publication addresses the problematic issues of the regional forestry planning. The object of research is the forest sector of the Sverdlovsk region. The subject of research is the mechanism of regional forestry planning. The purpose of the work is to describe the current mechanism of regional forest planning and make individual proposals to improve its functioning. One decade of experience in applying the first forestry plans of the subjects of the Russian Federation have shown their failure. The new forestry plans, developed in the subjects of the Russian Federation using a unified methodology for the period from 2018 to 2029, do not inspire optimism either. The main reasons for the failure of forestry plans are the lack of a scientific concept and the usage of a forest management approach in their development. The conclusions are drawn on a number of organizational and methodological problems associated with the development and implementation of the existing regional forestry planning mechanism, as well as on the need to develop an up-to-date scientifically proven methodological basis for planning in the forest sector at the regional level.
Economic advantages of innovative technologies for accelerated forest regeneration in Russia
Authors: Sijacic-Nikolic M , Ivanova A , Sirotkina N
Published: December 2020

The article discusses the economic benefits of using new technologies for the production of planting material for creating forest plantations. The production costs of creating 1ha forest plantations are identified. A model of the technology of the process of creating forest plantations of fast-growing species, planting material obtained using innovative approaches in the form of contextual diagrams of the main processes is presented. The model organization of the process of creating forest plantations of fast-growing species was created in order to most efficiently use equipment and increase labour productivity. It is proved that the use of planting material obtained using nanotechnological approaches at the stage of microcloning can reduce production costs for creating forest plantations and thus significantly reduce the cost of planting material for plantation cultivation. It has been established that the developed innovative technology for obtaining planting material for creating forest plantations of fast-growing species has economic advantages over the traditional one.