bluuebunny/crossref_metadata_2025 huggingface dataset:
Metallic sandwich panels subjected to high-intensity air-blast: Real-gas effects in modeling fluid–structure-interaction
Authors: Ghoshal Ritwik
Published: September 2020

This paper investigates the influence of real-gas effects in fluid–structure-interaction while estimating high-intensity air-blast loads and its subsequent implications on the crushing of metallic sandwich panels. It is well known that at high pressure and temperature, nitrogen and oxygen molecules present in the air undergoes ionization and dissociation, which may, in turn, lead to higher stagnation pressure upon reflection from a wall. However, almost all fluid–structure-interaction models use the ideal-gas assumption even at very high pressure and temperature in estimating air-blast loads to simulate core compression of sandwich panels. In the present work, a new method is proposed to predict air-blast loads on free-standing metallic sandwich panels considering electronic excitation, ionization, and dissociation of the constituents in the air during fluid–structure-interaction. One-dimensional dynamic response of free-standing sandwich panels due to air-blast loads, which is computed based on the proposed method, is investigated and compared with other existing theories based on ideal-gas. The interaction of the panel with the fluid beyond, i.e., air-backed and water-backed conditions, is also studied. Real-gas effects in the air at the backside are also investigated and compared with the ideal-gas based backing condition. The study reveals that using ideal-gas based fluid–structure-interaction models in predicting high-intensity air-blast loads on sandwich panels leads to an under-prediction in core compression and plastic dissipation for the same “crushing strength to incident over-pressure ratio.” Therefore, ignoring real-gas effects in the fluid–structure-interaction phase while designing the low-density core of a sandwich panel for high-intensity air-blast mitigation can be detrimental and may lead to catastrophic failure.
Maximum expected ramp rates using cloud speed sensor measurements
Authors: Wang Guang Chao , Kurtz Ben , Bosch Juan Luis , de la Parra Íñigo , Kleissl Jan
Published: September 2020

Large ramps and ramp rates in photovoltaic (PV) power output are of concern and sometimes even explicitly restricted by grid operators. Battery energy storage systems can smooth the power output and maintain ramp rates within permissible limits. To enable PV plant and energy storage system design and planning, a method to estimate the largest expected ramps for a given location is proposed. Because clouds are the dominant source of PV power output variability, an analytical relationship between the worst expected ramp rate, cloud motion vector, and the geometrical layout of the PV plant is developed. The ability of the proposed method to bracket actual ramp rates is assessed over 10 months under different meteorological conditions, demonstrating an average compliance rate of 98.9% for a 2 min evaluation time window. The largest observed ramp of 29.7% s−1 is contained with the worst case estimate of 34.3% s−1. This method provides a convenient yet economical approach to worst-case PV ramp rate modeling and is compatible with solar irradiance measured at coarse temporal resolution.
Linear and nonlinear optical properties of RbTiOPO4–KTiOPO4 alloys studied from first principles
Authors: Ghoohestani Marzieh , Hashemifar S. Javad , Arab Ali.
Published: September 2020

We investigate the linear optical properties of RbxK1−xTiOPO4 alloy crystals (x = 0, 0.25, 0.5, 0.75, 1) in the framework of the Bethe–Salpeter approach and the second-order optical response of these crystals within the independent particle approximation. The independent particle spectrum of KTiOPO4 (KTP) shows that this crystal absorbs light in the near-UV region. By solving the full Bethe–Salpeter equation, it is seen that the excitonic effects lead to an overall increase of the intensity and a redshift of about 1.6 eV in the absorption onset from the near-UV region to the visible region, reflecting the significant role of the electron–hole (e)–(h) coulomb interaction. It is shown that the spatial distribution of the e–h pair dominating the absorption onset is very localized around the titanium atoms. The absorption spectra at different Rb substitutions indicate an insignificant variation in the energy of the absorption onset due to the small differences in the corresponding bandgaps. The second-harmonic susceptibility tensor components of KTP/RbTiOPO4 (RTP) alloys at λ=1064 nm are evaluated and compared with experimental results. We show that Rb substitution modifies the maximum values of deff in Rb0.5K0.5TiOPO4 and RTP. Our results provide a valuable theoretical framework for tuning the optical properties of the KTP based crystals through doping for optoelectronic applications.
Whose role is it? Primary care and the provision of emotional support for women experiencing miscarriage: a pilot qualitative Australian study
Authors: Sumarno Vellyna , Temple-Smith Meredith J. , Bilardi Jade E.
Published: September 2020

Miscarriage can cause significant psychological morbidity. Women frequently report dissatisfaction with healthcare professionals’ support following miscarriage. This pilot study aimed to explore the views and practices of GPs in providing emotional support to women experiencing miscarriage. Eight GPs participated in semi-structured interviews. GPs considered women’s physical care their top priority at the time of miscarriage; however, acknowledged miscarriage could result in significant emotional sequelae. Most GPs felt it was their role to provide emotional support, including expressing empathy, listening and normalising miscarriage to mitigate guilt and self-blame. GPs preferred an individualised approach to emotional support and mostly offered follow-up appointments if a patient requested it or was considered ‘high risk’ for mental health issues. Some GPs believed miscarriage support was within the scope of primary care practice; however, others felt it was the role of social networks and pregnancy loss support organisations. GPs identified several structural and external barriers that precluded enhanced emotional support. Further tools and resources to enhance support care may be of benefit to some GPs. The feasibility of GPs providing follow-up support remains uncertain. Further research is required to determine whether support is best placed within primary care or better served through external organisations.
Soil type, bulk density and drainage effects on relative gas diffusivity and N2O emissions
Authors: Rousset Camille , Clough Tim J. , Grace Peter R. , Rowlings David W. , Scheer Clemens
Published: September 2020

Nitrous oxide (N2O), a greenhouse gas, contributes to stratospheric ozone depletion. Agricultural fertiliser use and animal excreta dominate anthropogenic N2O emissions. Soil relative gas diffusivity (Dp/Do) has been used to predict the likelihood of soil N2O emissions, but limited information exists about how soil N2O emissions vary with soil type in relation to Dp/Do. It was hypothesised that, regardless of soil type, the N2O emissions would peak at the previously reported Dp/Do value of 0.006. Four pasture soils, sieved and repacked to three different bulk densities, were held at nine different soil matric potentials between near saturation and field capacity. Soil nitrate and dissolved organic matter concentrations were adequate for denitrification at all soil matric potentials. Increasing soil bulk density and soil matric potential caused Dp/Do to decline. As Dp/Do declined to a value of 0.006, the N2O fluxes increased, peaking at Dp/Do ≤ 0.006. This study shows that the elevation of N2O fluxes as a Dp/Do threshold of 0.006 is approached, holds across soil types. However, the variability in the magnitude of the N2O flux as Dp/Do declines is not explained by Dp/Do and is likely to be dependent on factors affecting the N2O:(N2O + N2) ratio.
Stiffness of the interface between a colloidal body-centered cubic crystal and its liquid
Authors: Hwang Hyerim , Weitz David A. , Spaepen Frans
Published: September 2020

Significance

This paper reports the experimental determination of the stiffness of the interface between a body-centered cubic crystal and its liquid using colloids controlled by dielectrophoresis in an electric bottle. That the measured value is lower than that of alternative interfaces supports the phenomenological explanation invoked for a long-standing observation in phase transformations: the preferential nucleation of body-centered cubic crystals in the solidification of metal alloys.
Soft x-ray irradiation induced metallization of layered TiNCl
Authors: Kataoka Noriyuki , Tanaka Masashi , Hosoda Wataru , Taniguchi Takumi , Fujimori Shin-ichi , Wakita Takanori , Muraoka Yuji , Yokoya Takayoshi
Published: September 2020

We have performed soft x-ray spectroscopy in order to study the photoirradiation time dependence of the valence band structure and chemical states of layered transition metal nitride chloride TiNCl. Under the soft x-ray irradiation, the intensities of the states near the Fermi level (E
F) and the Ti3+ component increased, while the Cl 2p intensity decreased. Ti 2p–3d resonance photoemission spectroscopy confirmed a distinctive Fermi edge with Ti 3d character. These results indicate the photo-induced metallization originates from deintercalation due to Cl desorption, and thus provide a new carrier doping method that controls the conducting properties of TiNCl.
Energy spectra of coupled Su-Schrieffer-Heeger chains with



-symmetric imaginary boundary potentials
Authors: Kong Ze-Xuan , Zhang Yu-Feng , Hao Hai-Xing , Gong Wei-Jiang
Published: September 2020

We theoretically investigate the eigenenergies of coupled Su-Schrieffer-Heeger (SSH) chains with




-symmetric imaginary potentials. It is found that the direct coupling between two SSH chains leads to the splitting of the topological edge states accompanied by the destruction of their original natures. If the two SSH chains are indirectly coupled via an impurity, additional nontopological isolated states are allowed to come up. Next when the




-symmetric potentials are incorporated, the topological zero-energy states undergo the simple




-symmetry breaking. However, the nontopological isolated states exhibit complicated variations. For the directly-coupled case, the phase transition of these states can be seen. Alternatively, in the indirectly-coupled SSH system, the partial




-symmetry breaking occurs in the presence of broken particle-hole symmetry. We believe that these findings can be helpful for understanding topological properties of coupled non-Hermitian SSH systems.
Impacts of dark energy on constraining neutrino mass after Planck 2018
Authors: Zhang Ming , Zhang Jing-Fei , Zhang Xin
Published: September 2020

Considering the mass splittings of three active neutrinos, we investigate how the properties of dark energy affect the cosmological constraints on the total neutrino mass

∑

m

ν

using the latest cosmological observations. In this paper, several typical dark energy models, including ΛCDM, wCDM, CPL, and HDE models, are discussed. In the analysis, we also consider the effects from the neutrino mass hierarchies, i.e. the degenerate hierarchy (DH), the normal hierarchy (NH), and the inverted hierarchy (IH). We employ the current cosmological observations to do the analysis, including the Planck 2018 temperature and polarization power spectra, the baryon acoustic oscillations (BAO), the type Ia supernovae (SNe), and the Hubble constant H
0 measurement. In the ΛCDM+

∑

m

ν

model, we obtain the upper limits of the neutrino mass

∑

m

ν

<
0.123

eV

(DH),

∑

m

ν

<
0.156

eV

(NH), and

∑

m

ν

<
0.185

eV

(IH) at the 95% C.L., using the Planck+BAO+SNe data combination. For the wCDM+

∑

m

ν

model and the CPL+

∑

m

ν

model, larger upper limits of

∑

m

ν

are obtained compared to those of the ΛCDM+

∑

m

ν

model. The most stringent constraint on the neutrino mass,

∑

m

ν

<
0.080

eV

(DH), is derived in the HDE+

∑

m

ν

model. In addition, we find that the inclusion of the local measurement of the Hubble constant in the data combination leads to tighter constraints on the total neutrino mass in all these dark energy models.
3D Relativistic MHD Simulations of Pulsar Bow Shock Nebulae
Authors: Bucciantini Niccolò , Olmi Barbara , Zanna Luca Del
Published: September 2020

Pulsars out of their parent SNR directly interact with the ISM producing so called Bow-Shock Pulsar Wind Nebulae, the relativistic equivalents of the heliosphere/heliotail system. These have been directly observed from Radio to X-ray, and are found also associated to TeV halos, with a large variety of morphologies. They offer a unique environment where the pulsar wind can be studied by modelling its interaction with the surrounding ambient medium, in a fashion that is different/complementary from the canonical Plerions. These systems have also been suggested as the possible origin of the positron excess detected by AMS and PAMELA, in contrast to dark matter. I will present results from 3D Relativistic MHD simulations of such nebulae. On top of these simulations we computed the expected emission signatures, the properties of high energy particle escape, the role of current sheets in channeling cosmic rays, the level of turbulence and magnetic amplification, and how they depend on the wind structure and magnetisation.
Coupled MHD – Hybrid Simulations of Space Plasmas
Authors: Moschou S. P. , Sokolov I. V. , Cohen O. , Toth G. , Drake J. J. , Huang Z. , Garraffo C. , Alvarado-Gómez J. D. , Gombosi T.
Published: September 2020

Heliospheric plasmas require multi-scale and multi-physics considerations. On one hand, MHD codes are widely used for global simulations of the solar-terrestrial environments, but do not provide the most elaborate physical description of space plasmas. Hybrid codes, on the other hand, capture important physical processes, such as electric currents and effects of finite Larmor radius, but they can be used locally only, since the limitations in available computational resources do not allow for their use throughout a global computational domain. In the present work, we present a new coupled scheme which allows to switch blocks in the block-adaptive grids from fluid MHD to hybrid simulations, without modifying the self-consistent computation of the electromagnetic fields acting on fluids (in MHD simulation) or charged ion macroparticles (in hybrid simulation). In this way, the hybrid scheme can refine the description in specified regions of interest without compromising the efficiency of the global MHD code.
Comparative study of high order methods for subsonic turbulence simulation with stochastic forcing
Authors: Kritsuk Alexei G. , Yee H. C. , Sjögreen Björn , Kotov Dmitry
Published: September 2020

A class of spatially seventh-order nonlinear filter methods with adaptive dissipation control developed by Yee & Sjögreen [1, 2] is tested on three-dimensional subsonic turbulence simulations with stochastic forcing. The Euler equations are solved using the Strang operator splitting of the homogeneous part of the equations and the stochastic forcing term, with an ODE solver used to integrate the latter. Both Ducros et al. and Kennedy-Gruber skew-symmetric split formulations of the inviscid flux derivatives are considered to minimize the use of numerical dissipation. The nonlinear filter methods are shown to be numerically stable for this application at least up to an rms Mach number of 0.6. The performance and accuracy of this numerical approach are compared with those of second order TVD and fifth and seventh order WENO methods. The nonlinear filter methods are shown to be substantially more computationally efficient, delivering a superior spectral bandwidth compared to the standalone TVD and WENO methods.
Inverse transfer of magnetic helicity in supersonic magnetohydrodynamic turbulence
Authors: Teissier J.-M. , Müller W.-C.
Published: September 2020

The inverse transfer of magnetic helicity is studied through a fourth-order finite volume numerical scheme in the framework of compressible ideal magnetohydrodynamics (MHD), with an isothermal equation of state. Using either a purely solenoidal or purely compressive mechanical driving, a hydrodynamic turbulent steady-state is reached, to which small-scale magnetic helical fluctuations are injected. The steady-state root mean squared Mach numbers considered range from 0.1 to about 11. In all cases, a growth of magnetic structures is observed. While the measured magnetic helicity spectral scaling exponents are similar to the one measured in the incompressible case for the solenoidally-driven runs, significant deviations are observed even at relatively low Mach numbers when using a compressive driving. A tendency towards equipartition between the magnetic and kinetic fields in terms of energy and helicity is noted. The joint use of the helical decomposition in the framework of shell-to-shell transfer analysis reveals the presence of three distinct features in the global picture of a magnetic helicity inverse transfer. Those are individually associated with specific scale ranges of the advecting velocity field and commensurate helical contributions.
thornado-transport: Anderson- and GPU-accelerated nonlinear solvers for neutrino-matter coupling1
Authors: Paul Laiu M , Harris J Austin , Chu Ran , Endeve Eirik
Published: September 2020

Algorithms for neutrino-matter coupling in core-collapse supernovae (CCSNe) are investigated in the context of a spectral two-moment model, which is discretized in space with the discontinuous Galerkin method, integrated in time with implicit-explicit (IMEX) methods, and implemented in the toolkit for high-order neutrino-radiation hydrodynamics (thornado). The model considers electron neutrinos and antineutrinos and tabulated opacities from Bruenn (1985), which includes neutrino-electron scattering and pair processes. The nonlinear system arising from implicit time discretization of the equations governing neutrino-matter coupling is iterated to convergence using Anderson-accelerated fixed-point methods, which avoid formation of Jacobians and inversion of dense linear systems. Numerical experiments show that, for a given tolerance, a nested iteration scheme which aims to reduce opacity evaluations can lower the computational cost. Our initial port to GPUs, using both OpenMP and OpenACC, shows an overall speedup of up to ∼ 100× when compared to results using a single CPU core. These results indicate that the algorithms implemented in thornado are well-suited to GPU acceleration.
Relaxing Numerical Difficulties Arising from Discretization in the Cylindrical Coordinates
Authors: Hanawa Tomoyuki , Matsumoto Yosuke
Published: September 2020

The cylindrical coordinates, (r, ϕ, z), are often used in our numerical simulations, in particular, when gas accretes onto a central object. Although the cylindrical coordinates have several advantages in describing rotation, they have apparent singularity at r = 0. The singularity induces some difficulties in numerical simulations. First, it is difficult to solve the flow across the axis numerically. Second, the time interval between two successive time steps is restricted by the innermost cell size, resulting in large numbers of time steps to follow dynamics in the outer regions. Here, we present a new discretization scheme to overcome these difficulties. First, we evaluate the centrifugal force from the dynamical pressure working on the azimuthal cell surface. Our method of the evaluation is based on the vector analysis. Second, we reduce the angular resolution appreciably. Our examples demonstrate that the innermost circular region around the axis can be resolved by only six numerical cells. We increase the angular resolution with the increase in the radius so that each numerical cell has an aspect ratio close to unity. Then all the numerical cells have nearly the same size, and the CFL condition is relaxed. We show our application to an accreting protostar after showing a Sod shock tube problem and a uniform flow. The test problems demonstrate that the apparent singularity around the axis have no critical effects on the results.
Three-dimensional cylindrical Poisson solver with vacuum boundary conditions
Authors: Moon S
Published: September 2020

Self-gravity and rotation are two key ingredients in dynamics of astronomical disk systems such as galactic and protostellar disks. Despite its importance, there has not yet been so far an efficient algorithm to solve the Poisson equation in three-dimensional cylindrical coordinates under vacuum boundary conditions. By generalizing the James algorithm to cylindrical coordinates, we develop an accurate (second-order convergence) and efficient (faster than MHD) cylindrical Poisson solver that is scalable up to ∼ 104 cores. We develop a method to calculate the cylindrical discrete Green’s function, which is an essential element of the James algorithm to estabilish its second-order accuracy. We implement our cylindrical version of the James algorithm in Athena++ code and demonstrate its accuracy and efficiency by performing the convergence test and the weak scaling test.
The Castro AMR Simulation Code: Current and Future Developments
Authors: Zingale M. , Almgren A. S. , Sazo M. Barrios , Bell J. B. , Eiden K. , Harpole A. , Katz M. P. , Nonaka A. J. , Willcox D. E. , Zhang W.
Published: September 2020

We describe recent developments to the Castro astrophysics simulation code, focusing on new features that enable our simulations of X-ray bursts. Two highlights of Castro’s ongoing development are the new integration technique to couple hydrodynamics and reactions to high order and GPU offloading. We discuss how these features will help offset some of the computational expense in X-ray burst models.
Height–diameter allometry for the management of city trees in the tropics
Authors: Song Xiao Ping , Lai Hao Ran , Wijedasa Lahiru S , Tan Puay Yok , Edwards Peter J , Richards Daniel R
Published: September 2020

Trees are important components of urban greenery because of their large stature and longevity, and their ability to enhance the environmental quality of city landscapes. However, benefits and hazards associated with trees depend on their size, which changes over time and varies among species. While urban trees are often measured during routine management, the full value of these data is rarely realised. Our study uses nation-wide inspection records from Singapore to develop allometric models for 54 species grown in the urban tropics (n = 345 794), a region that is poorly represented in allometric literature. We use the height–diameter relationship to demonstrate how analyses of existing datasets can be used to support decisions on tree inspection and maintenance. The accuracy of models developed separately for each species (single-species models) and using the pooled data for all species (mixed-effects model) was compared. Model outputs and derived metrics were used to detect height outliers and priority regions that may require greater inspection effort, which we summarise using spatial visualisations and an online web application. Model parameters also varied according to each species’ pruning intensity and maximum height, and can thus provide a useful heuristic when selecting species to plant. Such data-driven approaches have the potential to support both management and research, though changes to workflows may be needed to take advantage of new sources of data. Integrating multiple datasets into decision-making will require expertise across multiple disciplines, and coordinated action among stakeholders. By sharing the code used to develop the allometric models in a new open-source R package ‘allometree’, we hope to promote reproducibility and facilitate the application of allometric equations to other tree parameters, study regions and management objectives.
Field test of a new type of lightning - dispelling rocket against cumulus electric field
Authors: Yang Weidong , Guan Yiying , Zhang Yang , Yang Fan , Jin Weiping , Yuan Yougen , Jing Xiaolei , Chen Nong , Guan Fushun , Liu Ying , Xiong Feng , Guan Tianyu
Published: September 2020

Based on the field test of 48 new lightning dissipating rockets launched by cumulonimbus and stratus, we preliminarily draw the following conclusion: the new lightning dissipating rockets can reduce the absolute value of the electric field inside and outside cumulonimbus; The greater the electric field value of cumulonimbus (the stronger the convection), the greater the influence of the new rocket on the electric field, and vice versa. The rocket has little effect on stratospheric electric field. This method can eliminate or reduce the lightning activity, so as to provide effective active lightning defense means for ships at sea, rocket launching and forest areas, and thus effectively reduce the disasters caused by lightning to human beings.
Research on fracture mechanism of blast wall on offshore platform under impulse loading
Authors: Luo Fang , Zhang Shilian
Published: September 2020

In this paper, the fracture mechanism of the corrugated blast wall on offshore platform is analyzed and studied. Based on the experimental results of the typical corrugated blast wall, the fracture state is calculated by incremental pressure loading and the ultimate state is analyzed.The cracked joints have been strengthened and the anti-explosion performance compared with the original model. Results show that reasonable strengthening of the weak parts can effectively improve the overall ultimate anti-explosion capability of the corrugated blast wall. This research could be a reference for the design of structure protection.
Combination of ERT and EM methods in the exploration of karst caves and foundation in the Nujiang airport survey of China
Authors: Yue Yunbao , Guo Ziming , Luo Wei , Zhang Gang , Chen Ning
Published: September 2020

Due to controls from karst cave, grike fissure zone, tectonic crushed zone and other defects in rock masses, the airfield runway in the karst region is easy to have collapse and leakage failure, thus resulting in runway deformation and buckling. Therefore, it is of important significance to detect rock defects in airfield runway accurately. In this study, electrical resistivity tomography (ERT) and electromagnetic (EM) were combined to detect stability of karst cave and foundation under the runway of Nujiang airport survey of China. Size, shape and scale of underground karst cave were detected accurately by setting 3 ERT measuring lines. Distribution of karst caves in shallow underground layer was disclosed and validated by drilling data. Electrical structures in deep underground layer were detected by setting 11 EM profiles. Based on 2D EM inversion and 3D modeling, it found that electrical structure in deep underground layers of the runway was dominated by high specific resistance, indicating that there’s relatively complete bed rock mainly composed of limestone. Hence, the foundation showed relatively satisfying overall stability, accompanied with local distribution of low-resistance anomalies which was attributed to crushed mudstone. Research results demonstrated that the combination of ERT and EM is feasible and applicable to detect geological structural stability in karst development and deep positions beneath the runway in karst areas.
Characteristics and risk assessment of debris flow in northeast tibetan plateau
Authors: Jing Hao , Yan Lihua , Li Youtai , Li Jie
Published: September 2020

Debris flow disasters frequently occur in northeast Tibetan plateau, especially, along section of the G-213 line from Ceke to Mohan highway in Longwu Gorge. This area is prone to debris flow disasters due to its special geological environment. In present study, we investigated the characteristics of 11 typical debris flow gullies and calculated the risk assessment by matter-element extension method. The matter-element model of debris flow hazard assessment was constructed and ten assessment factors were selected to evaluate the debris flow hazard. The results showed that the matter-element extension method was highly accurate for the risk assessment of debris flow gullies, which was in good agreement with the result of expert assessment, This method has obvious superiority, the risk assessment of debris flow gully was based on the grade, corresponding to the maximum of the comprehensive correlation degree.
Probabilistic analysis of tunnel excavation with spatially correlated Young’s modulus
Authors: Lu Anling , Yang Haoqing , Jin Dalong
Published: September 2020

Understanding the responses of tunnel excavation is essential in urbanization. Tunnel constructions are subject to uncertainties originated from complex geological conditions, including the spatial variability of soil properties. Therefore, it is necessary to adopt probabilistic methods that can analyse the spatial variability of geotechnical parameters in tunnel construction. Previously few studies considered plastic strain of tunnels considering the spatial variability of geotechnical properties. In this study, the effects of the statistics (correlation lengths and Coefficients of Variation (CoV)) of spatially correlated Young’s modulus on horizontal/vertical displacements and maximum plastic strain are studied. The mean and median values of the vertical displacement are insensitive to the correlation lengths, while the standard deviation is positively correlated with the correlation lengths. With the increase of CoV, the distribution of maximum plastic strain becomes dispersed, but the change is no longer significant when the CoV is small.
Inverse identification of gaseous pollutant sources in a mixed ventilation room with downwind scheme-based backward modeling
Authors: Liu Guizhi , Liu Di , Zhang Hongmei , Xu Zhouyun , Dong Xiaozhen
Published: September 2020

Inverse computational fluid dynamics (CFD) modeling is an effective method to track indoor Pollutant sources. In this paper, heat transfer and instantaneous diffusion of contaminants in the mixed ventilation room have been investigated numerically. On the basis of the numerical simulation of indoor air flows, the reverse time modeling of diffusion-convection contaminant dispersions has been developed with the downwind scheme of the convection term. The program to implement the presented method is written in FORTRAN 90 and applied to the inverse time identification of the pollutant release history and source location. Direct simulation is conducted in the range of, Reynolds number (2×103 ≤ Re ≤ 5×104) and Grashof number (106 ≤ Gr ≤ 9×109). In addition, the streamfunction and heatfunction are expressed streamlines and heatlines respectively. It is shown that the flow structure, heat transfer level and potential will depend on the interactions of external forced flow and thermal buoyancy driven flows. The numerical results indicated the proposed source identification algorithm is effective and robust in indoor environment.
Drivers of energy-related CO2 emissions under structural adjustment in China
Authors: Li Xin , Yang Liyan , Qiang Ye
Published: September 2020

Taking the indicators related to structural adjustment from 1996 to 2015 as the factors, the influencing factors of national energy-related CO2 emissions was simulated based on the improved STIRPAT model. The findings include: (1) the five major industries, coal, steel, building materials, petrochemicals and non-ferrous metals, had the most significant positive driving effect on China’s energy-related CO2 emissions; (2) the real estate inventory indicators basically conformed to the Kuznets N-shaped curve, and indirectly drove energy-related CO2 emissions through the impact on the urbanization process or related industries; (3) the driving characteristics of carbon dioxide emissions from energy consumption were mainly determined by the features of socio-economic development, urbanization and industrialization in different stages. Thus, the key to ensure green coordinated development is to correctly handle the relationship between economic growth, urbanization, industrialization and carbon dioxide emission control of energy consumption in different stages of economic and social development.
The structure and sustainability of street srees in Changzhou, China
Authors: Wang Xinjun , Zhang Zhihong , Gao Jiaoyu , Cheng Jie , Dong Chao
Published: September 2020

Street trees provide essential ecosystem services and are important to local residents’ life, but there has not been much research on the structure of street trees in the city of Changzhou, China. This research surveys the structure of street trees in Changzhou with the aid of geospatial technologies and field sampling surveys. An investigation of the street trees on the 220 sampled transects of streets across the four districts of Changzhou reveals prominent problems with the species diversity, distribution, age structure, and density. Though street tree density in the city is approximately 177/Km, higher than many other cities in the world, with only 29 street tree species in 19 families and 27 genera, the diversity is lower. Among the tree species, only a limited few are planted widely. Young trees account for 43.2% of the total tree population, while large old trees decrease in number. Close spacing between trees, caused by unreasonably high density, results in enormous government expenses on pruning. These findings highlight the need for careful selection of appropriate tree species on the part of municipal administrators and planners. Suggestions are given on how to achieve a sustainable structure of street trees in Changzhou in the long run. Both the problems found and the corresponding suggestions are of referential meaning to the street tree development of other cities in China.
PM2.5 concentration prediction based on pseudo-F statistic feature selection algorithm and support vector regression
Authors: Liu Wenbo , Liang Shengnan , Yu Quan
Published: September 2020

Effective monitoring and prediction of PM2.5 concentration is of great practical significance to People’s Daily life and social development. In order to facilitate accurate prediction of the average daily concentration of PM2.5, a Feature Selection Algorithm Based on Pseudo F Statistic (FSPF) was proposed in this paper, and a PM2.5 concentration prediction model was combined with support vector regression. When constructing the model, all features are not selected into the model, and the pseudo-F statistic featu re selection algorithm is used to obtain more important feature variables related to PM2.5 concentration. On this basis, support vector regression based on different kernel functions is used to predict PM2.5 concentration. Through real data analysis, the hyperbolic tangent kernel support vector regression model (FSPF-SVR) selected by pseudo-F statistics features has the highest prediction accuracy when predicting the average PM2.5 concentration of Beijing in November and December 2017, with mean square errors of 1.441⋅10−3mg2/m6 and 1.307⋅10−3mg2/m6 respectively, which is better than the all-variable prediction model. At the same time, it is also better than random forest, weighted K nearest neighbor, Bagging regression, artificial neural network and other current mainstream machine learning regression prediction algorithms.
Spatio-temporal characteristics of land cover changes of Liangjiang new destrict in China during 2010-2018
Authors: Wang Xiaopan , Wang Chaolei , Wang Bing , Zhang Bin
Published: September 2020

Based on WorldView-2 remote sensing images and other survey materials, we analysis the spatio-temporal characteristics of land cover change in Liangjiang New District during 2010 to 2018. The results are summarized as follows: 1) Land cover pattern changed dramatically, with the built-up increase, while the crop land, forest and grass land decrease. 2) Change in land cover types showed marked fluctuations over the three stages (2010-2012, 2012-2015, 2015-2018). Districts with the most obvious change of CL and FGS concentrated in the East and north of the Liangjiang New District. 3) There were significant differences in the intensity of land use dynamic degree change among different regions. The relative change land use dynamic degree of Lijia Street is the biggest, followed by Yuelai Street, Fusheng Town and Longxing Town.
Passive detection of carbon dioxide in the high temperature cement-kiln by FTIR
Authors: Gao Qiankun
Published: September 2020

Passive sensing by Fourier-transform infrared (FTIR) spectrometry allows detection and quantification of gas. In this work, the infrared radiation signal of the carbon dioxide in the cement-kiln was measured by FTIR. A new radiative transfer model was built to calculate transmittance from measured spectrum of the carbon dioxide in the cement-kiln. Based on the HITRAN database, the nonlinear least square fitting method was used to calculate the concentration of the carbon dioxide(CO2) from transmittance. The results show that this method of measuring the concentration of carbon dioxide and other gas in the high temperature cement-kiln is feasible and reliable. And this method is also applicable to the measurement of other gases, such as carbon monoxide(CO), sulfur dioxide(SO2), etc.
An improved semi-global matching method with optimized matching aggregation constraint
Authors: Huang Xu , Han Yilong , Hu Kun
Published: September 2020

Stereo dense image matching (DIM) is a key technique in generating dense 3D point clouds at low cost, among which semi-global matching (SGM) is one of the best compromise between the matching accuracy and the time cost. Most commercial or open-source DIM software packages therefore adopt SGM as the core algorithm for the 3D point generation, which computes matching results in 2D image space by simply aggregating the matching results of multi-directional 1D paths. However, such aggregations of SGM did not consider the disparity consistency between adjacent pixels in 2D image space, which will finally decrease the matching accuracy. To achieve higher-accuracy while keep the high time efficiency of SGM, this paper proposes an improved SGM with a novel matching aggregation optimization constraint. The core algorithm formulates the matching aggregation as the optimization of a global energy function, and a local solution of the energy function is utilized to impose the disparity consistency between adjacent pixels, which is capable of removing noises in the matching aggregation results and increasing the final matching accuracy at low time cost. Experiments on aerial image dataset show that the proposed method outperformed the traditional SGM method and another improved SGM method. Compared with the traditional SGM, our proposed method can increase the average matching accuracy by at most 11%. Therefore, our proposed method can applied in some smart 3D applications, e.g. 3D change detection, city-scale reconstruction, and global survey mapping.
Comparison of UAV-based multispectral sensors for detection of Solenopsis invicta Nests
Authors: Song Yuejun , Chen Feng , Liao Kaitao
Published: September 2020

The invasive red imported fire ant (Solenopsis invicta Buren) (Hymenoptera: Formicidae) has been continuing to expand its range in China, resulting in adverse ecological impacts to where it has invaded. As such, the reliable detection of Solenopsis invicta Buren nests is needed to effectively manage the species. In this paper, the spectral features of the Solenopsis invicta Buren nests were demonstrated using spectra samples obtained by ASD FieldSpec 4 during field surveys in Shanggao County, Jiangxi Province. Furthermore, channel reflectance estimations for three unmanned aerial vehicle (UAV)-based multispectral sensors were simulated correspondingly. Based on the channel reflectance from individual sensors, the detection of the Solenopsis invicta Buren nests was investigated. Generally, between-class differences in reflectance were relatively significant in both Green channel and Red channel, which suggests the importance of these two channels for the detection of Solenopsis invicta Buren nest. Minor between-sensor differences observed in both Green channel and Red channel suggest that detection results obtained from UAV-based multispectral observations could be comparable among the three sensors, considering only the spectral features. There are significant differences in reflectance between the soil of Solenopsis invicta Buren nests and ordinary soil over the longwave region of near infrared (NIR). It suggests the spectral measurement over the longwave region of NIR could be more useful in distinguishing the soil of Solenopsis invicta Buren nests from ordinary soil. Nevertheless, the multispectral sensors provided with channels covering visible and the shortwave region of NIR, possibly do not meet requirements completely for application. An effective method for detecting Solenopsis invicta Buren nests using UAV-based multispectral sensors is currently being evaluated.
Prediction of energy demand from China’s transportation sector: an empirical analysis from the perspective of the energy revolution
Authors: Fang Hai , Feng Zhenhua , Liu Fang , Cao Zilong
Published: September 2020

The study re-defined the divisions of energy consumption in China transportation. By using the long-range energy alternatives planning system (LEAP), the analysis model for energy demand from China’s transportation sector is established. Five scenarios applicable to 2030 are set, involving a reference scenario, structural optimisation, technological advance, management improvement, and energy-use reform. The results show that the energy consumed by the transportation is limited to about 7 × 108 tons by 2030. Meanwhile, powerful polices and measures must be taken to guarantee that the inflection point of energy consumption appears in about 2045 with an energy consumption of about 8 × 108 tons. Structural optimisation is a key measure necessary to decrease total energy consumption before 2040, while technological advances will become a key approach in promoting the energy consumption revolution in the transportation after 2030. Strengthening urban spatial design and management can effectively reduce energy consumption.
The regulation of three gorges dam on lake Poyang: an assessment of the lake water level change during the dry season
Authors: Fan Hongxia , Wang Zhihuan , Wang Jianzhong , Chen Huai , Zhu Lijun
Published: September 2020

With a combination of field data analysis and numerical simulation on 2D river-lake hydrodynamics, this study focuses on the water level change in Lake Poyang regulated by the Three Gorges Dam (TGD) during the dry season. Based on the long-term measured water level series (1956-2012), after the completion of TGD, the dry season in Lake Poyang is promoted to start early, and its duration is extended. With the regulation of TGD during the impoundment period, more outflow from Lake Poyang pours into the Yangtze River, leading to the decrement of lake water level and an earlier occurrence (about 4-5 days forward) of the dry season. Besides, with the regulation of TGD during the flushing period, the water level in Lake Poyang is elevated, making a relief to the lake drought during the dry season.
The whole process test and analysis of flue gas SO3 in coal-fired power plant under variable load conditions
Authors: Hong Zhigang , Huang Quankai , Chen Wei , Liu Yongsheng
Published: September 2020

Under the current situation of ultra-low emission, it is of great significance to study the formation and removal of SO3 in various equipments of coal-fired power plants. At present, most researches on SO3 in coal-fired power plant focus on the influence of single equipment on flue gas SO3 under a certain load condition. In this research, a 300MW generating unit is tested under variable load conditions to explore the variation law of SO3 in various equipments under variable load conditions. The results show that SO3 is mainly generated in the boiler furnace and SCR denitrification device, and the total removal rate of SO3 is 84.6%. However, the removal efficiency of SO3 in electrostatic precipitators and the wet desulfurization systems shows great differences. Under full load condition, the removal rate of SO3 is 46.8% - 69.8%. When the load changes, the SO3 removal rate changes with the change of load, and the ESP is affected by the load most. The SO3 content in the ash increases from 11.267mg/g under 50% load to 14.763mg/g under 100% load, and such changes are mainly determined by flue gas temperature and flue gas flow.
Dynamic evolution assessing of Dongsha shoal of the Radial Sand Ridges in South Yellow Sea, based on the smallest enclosing rectangle centroids method
Authors: Liu Binglin , Jiang Shengnan , Zhang Zhenke , Wu Haotian , Wei Guoen , Shen Wei , Wang Qing
Published: September 2020

The smallest enclosing rectangle is an important parameter in the target features of geographic elements. Its centroid can indicate the general movement trend of geographic elements. Taking Dongsha in the radiant sandbar area off Jiangsu as an example, the shape was derived from long-period remote sensing images from 1973 to 2016, learning the concepts of the smallest enclosing rectangle and centroid, extract the Dongsha Shoal of each phase by ArcGIS. The smallest enclosing rectangle centroids compare the centroids of different periods to determine the overall movement trend of Dongsha Shoal in different periods. The study found that during the 43-year period, the overall movement direction of Dongsha shoal was north-north-east, specifically divided into five stages, each of which has a different direction and speed of movement. The smallest enclosing rectangle can be used as an useful method to study the dynamic change trend of marine sandbar.
A research on the seasonal difference of air pollution in Chengdu
Authors: Ma Chenwei , Ding Lijin
Published: September 2020

With the rapid development of Chengdu’s economy, the problem of air pollution has gradually drawn attention by scholars. Based on the time series data covers 2014 through 2019 of Chengdu, this research investigates the seasonal difference in air pollution and the possible influence of six pollutants on air pollution. The results indicated that there is a significant seasonal difference of air pollution in Chengdu and air pollutants are mainly fine particulate matter and ozone. Based on the findings, the government might consider achieve precise emission reductions for the pollution sources of PM2.5 and O3.
The ecological environment capacity of different functional zones in Lushan Scenic Area
Authors: Wen Li , Xie Dongming , Zhou Guohong , Qian Haiyan , Guo Ziwei
Published: September 2020

Eco-environment capacity assessment is to appraise the status of the ecoenvironment. Lushan Scenic Area is one of the global famous cultural landscapes in China. A multi-factor comprehensive analysis method and indicator weighting method are used to appraise the status of the eco-environment of different eco-function zones by building the ecoenvironmental capacity indicator system in Lushan Scenic Area. The results explain the different eco-function zones were various in the status of the eco-environment. The eco-protect zone was good status of eco-environment in middle and low hot tourism season, but it was bad status of eco-environment in high hot tourism season. However, the control developing zone, the natural landscape protect zone and eco-restoration zone were bad status of eco-environment in total tourism season. Many elements lead to the bad status of eco-environment, such as heavy tourist activity, high density buildings, water contaminating, and noise destroyed the eco-environment together.