bluuebunny/crossref_metadata_2025 huggingface dataset:
Size dependent charge separation and recombination in CsPbI3 perovskite quantum dots
Authors: Shang Qiongyi , Kaledin Alexey L. , Li Qiuyang , Lian Tianquan
Published: August 2019

CsPbI3 perovskite quantum dots (QDs) have shown great potential in light-harvesting and light-emitting applications, which often involve the transfer of charge carriers in and out of these materials. Here, we studied size-dependent charge separation (CS) and charge recombination (CR) between CsPbI3 QDs and rhodamine B (RhB) molecules, using transient absorption spectroscopy. When the average size decreases from 11.8 nm to 6.5 nm, the average intrinsic CS time constant decreases from 872 ± 52 ps to 40.6 ± 4.3 ps and the corresponding charge recombination time constant decreases from 3829 ± 51 ns to 1384 ± 54 ns. The observed trend of size-dependent CS and CR rates can be well explained by Marcus theory using the theoretically calculated CS and CR driving forces (ΔGCS and ΔGCR), molecular reorganization energy (λRhB), and electronic coupling strength between QD and RhB (HCS and HCR). Unlike the extensively studied more strongly quantum confined Cd chalcogenide QDs, the CsPbI3 QDs are in a weak quantum confinement regime in which size-dependent coupling strength plays a dominant role in the size-dependent charge transfer properties.
Super-shear evanescent waves for non-contact elastography of soft tissues
Authors: Pitre John J. , Kirby Mitchell A. , Gao Liang , Li David S. , Shen Tueng , Wang Ruikang K. , O'Donnell Matthew , Pelivanov Ivan
Published: August 2019

We describe surface wave propagation in soft elastic media at speeds exceeding the bulk shear wave speed. By linking these waves to the elastodynamic Green's function, we derive a simple relationship to quantify the elasticity of a soft medium from the speed of this supershear evanescent wave (SEW). We experimentally probe SEW propagation in tissue-mimicking phantoms, human cornea ex vivo, and skin in vivo using a high-speed optical coherence elastography system. Measurements confirm the predicted relationship between SEW and bulk shear wave speeds, agreeing well with both theoretical and numerical models. These results suggest that SEW measurements may be a robust method to quantify elasticity in soft media, particularly in complex, bounded materials where dispersive Rayleigh-Lamb modes complicate measurements.
Effects of interfacial ligand type on hybrid P3HT:CdSe quantum dot solar cell device parameters
Authors: Greaney Matthew J. , Joy Jimmy , Combs Blair A. , Das Saptaparna , Buckley Jannise J. , Bradforth Stephen E. , Brutchey Richard L.
Published: August 2019

A series of CdSe quantum dot acceptors possessing six different ligand frameworks (i.e., pivalic acid, pyridine, butylamine, tert-butylthiol, thiophenol, and tetrahydrothiophene) were used as platforms for investigating the influence of quantum dot surface chemistry on the performance of hybrid poly(3-hexythiophene-2,5-diyl) (P3HT):CdSe quantum dot bulk heterojunction (BHJ) solar cells. We confirm that the device parameters used to evaluate solar cell performance are significantly influenced by the nature of the quantum dot surface ligand. The dependence of short circuit current density (JSC) on the CdSe ligand type was probed using ultrafast time-resolved photoluminescence (PL) measurements, and good correlations between the ligand-dependent trends in JSC and excited state lifetime were found, in which the P3HT:CdSe quantum dot BHJs with the shortest PL lifetimes possess the largest device current densities. The frontier energy levels of the quantum dot acceptors are significantly influenced by surface ligands, wherein the device open circuit potentials (VOC) were found to linearly correlate with the energy difference (ΔEDA) between the HOMO of the P3HT donor and the electrochemically determined LUMO of the CdSe quantum dot acceptors over a range of 220 mV. This work demonstrates the versatility of quantum dot ligand engineering for tuning the device parameters and performance of hybrid solar cells.
Identification of the expressome by machine learning on omics data
Authors: Sartor Ryan C. , Noshay Jaclyn , Springer Nathan M. , Briggs Steven P.
Published: August 2019

Significance

Our new method uses only epigenomic patterns to classify the expression potential of annotated genes and identifies pseudogenes that are difficult to classify based solely on sequence. Genes were divided into those with protein expression, those with mRNA expression, and those that are silent. A large fraction of annotated genes are constitutively silent in one lineage but can be transcribed in others. We refer to the species-wide set of transcribed genes as the expressome and show that it is much larger than the expressible gene set in any individual. Additionally, we find that DNA methylation patterns within the gene body can differentiate between genes that express proteins and genes that express only RNAs.
Large-effect flowering time mutations reveal conditionally adaptive paths through fitness landscapes inArabidopsis thaliana
Authors: Taylor Mark A. , Wilczek Amity M. , Roe Judith L. , Welch Stephen M. , Runcie Daniel E. , Cooper Martha D. , Schmitt Johanna
Published: August 2019

Significance

Mutations are often assumed to be largely detrimental to fitness, but they may also be beneficial, and mutations with large phenotypic effects can persist in nature. One explanation for these observations is that mutations may be beneficial in specific environments because these conditions shift trait expression toward higher fitness. This hypothesis is rarely tested due to the difficulty of replicating mutants in multiple natural environments and measuring their phenotypes. We did so by plantingArabidopsis thalianagenotypes with large-effect flowering time mutations in field sites across the species’ European climate range. We quantified the adaptive value of mutant traits, finding that certain mutations increased fitness in some environments but not in others.
The TLCΦ satellite phage harbors a Xer recombination activation factor
Authors: Midonet Caroline , Miele Solange , Paly Evelyne , Guerois Raphaël , Barre François-Xavier
Published: August 2019

Significance

Cholera toxin, the principal virulence factor of
Vibrio cholerae
, is encoded in the genome of an integrative mobile element exploiting Xer (IMEX), CTXΦ. Nontoxigenic strains generally lack a suitable CTXΦ attachment site. In addition, CTXΦ integration is intrinsically irreversible. Nevertheless, new epidemic clones carrying potentially more potent toxins are constantly created by CTXΦ excision and reintegration cycles. Previous studies suggested that these cycles depended on another IMEX, TLCΦ, whose integration corrected the attachment site of nontoxigenic strains and whose excision promoted the joint elimination of CTXΦ copies. Our work brings molecular understanding to the role played by TLCΦ and suggests how similar IMEXs might participate in the evolution of other pathogenic bacteria.
The RNA demethylase FTO is required for maintenance of bone mass and functions to protect osteoblasts from genotoxic damage
Authors: Zhang Qian , Riddle Ryan C. , Yang Qian , Rosen Clifford R. , Guttridge Denis C. , Dirckx Naomi , Faugere Marie-Claude , Farber Charles R. , Clemens Thomas L.
Published: August 2019

Significance

Like other complex disorders, such as diabetes and obesity, osteoporosis is strongly influenced by genetic factors. In this study, we explored the function of the fat mass and obesity-associated gene (FTO), an RNA demethyase that has been strongly linked by genome-wide association studies to obesity and bone density. We show that loss of
Fto
in mouse osteoblasts leads to age-related bone loss with increased susceptibility of osteoblasts to cell death. RNA profiling of osteoblasts lacking
Fto
prioritized FTO targets that are members of the DNA repair pathway, which are activated in response to genotoxic stimuli. Our results identify an epigenetic pathway in which FTO normally functions in bone to enhance the stability of mRNA-encoding proteins that protect osteoblasts from genotoxic damage.
Topological phases and pumps in the Su–Schrieffer–Heeger model periodically modulated in time
Authors: Lü Xiao-Long , Xie Hang
Published: August 2019

By the Floquet theory, we transform the Su–Schrieffer–Heeger model with the periodically modulated nearest-neighbor (NN) and next-nearest-neighbor (NNN) interactions into an effective 2D model, which holds the total Chern number of  ±1 modulated by the parameter θ. Under a staggered electric potential, the topological phase diagrams of the effective 2D model are reshaped and similar to the well-known Haldane model. While under a staggered Zeeman field, the topological phase diagram has the same shape as the former case, but with different Chern numbers, such as the spin and valley Chern numbers. With the combination of the staggered Zeeman field and the electric field, the effective 2D model holds even richer topological phases. At last, we find some types of topological pump, which can generate the time-averaged current without any bias voltage. The current depends on their different Chern numbers. In other words, we can modulate the parameters to obtain various Chern numbers to control the topological pump.
Reemergence of superconductivity by 4d transition-metal Pd doping in over-doped 112-type iron pnictide superconductors Ca0.755La0.245FeAs2
Authors: Xing Xiangzhuo , Li Zhanfeng , Veshchunov Ivan , Yi Xiaolei , Meng Yan , Li Meng , Lin Bencheng , Tamegai Tsuyoshi , Shi Zhixiang
Published: August 2019

In 112-type iron-based superconductors (IBSs), rare earth (e.g. La) doping enhanced antiferromagnetic (AFM) order and 3d transition-metal (e.g. Co, Ni) doping induced reemergence of superconductivity (SC) in the over-doped regime (non-SC) are of particular interest, providing a significant opportunity to further understand the relationship between SC and AFM order in IBSs. Recently, 4d transition-metal Pd-doped 112-type Ca1-y
La
y
Fe1-x
Pd
x
As2 (x > 0.2, 0 ≤ y ≤ 0.3) compounds, which crystallized in new orthorhombic and tetragonal structures, have been identified (Inorg. Chem. 56 3030 (2017)). However, none of them exhibit SC, probably due to the oversubstitution of Pd for Fe. Here, to reveal the impact of slight Pd doping on the over-doped Ca1-y
La
y
FeAs2 and compare to 3d Co/Ni doping series, single crystals of Ca0.755La0.245Fe1-x
Pd
x
As2 with 0 ≤ x ≤ 0.08 are successfully grown using the self-flux method. We find that, upon only a small amount of Pd doping (x = 0.013), bulk SC with a maximum T
c of 28.5 K is reemerged, in contrast to the case with high Pd doping level. Moreover, based on the electrical resistivity and magnetization data, we construct the temperature-composition (T–x) phase diagram, the shape of which, particularly for the region where the AFM and SC phases coexist microscopically, is almost identical to that of Ca0.76La0.24Fe1-x
Ni
x
As2, but is distinctly different from that of Ca0.74La0.26Fe1-x
Co
x
As2, presumably due to the presence of complex doping mechanism in 112-type IBSs. Finally, for one selected single crystal with x = 0.013, superconducting properties including critical current density, vortex pinning mechanism, and vortex diagram are systematically studied by magnetization, magneto-optical imaging, and magneto-resistivity measurements. Our work provided more insight into the phase diagrams and superconducting properties of 112-type IBSs, allowing better understanding of its superconducting mechanism and developing the potential applications.
Students’ ability to analyse empirical data in practical work
Authors: Pols C F J
Published: August 2019

Although students in upper secondary education are often asked to carry out practical work independently to a large extent, it is questionable whether they already have the knowledge to do so successfully. This study looks into the data analysis skills students aged 15 should possess according to various curriculum documents and investigates whether this is the case. To do so, the 51 students involved carried out two practicals using worksheets with questions in which they ought to apply each of the ten identified data analysis skills at least once. The analysis of their work shows that students master the skill of visualising data in graphs. In applying each of the other skills, students make many mistakes or do not know what to do or how to proceed. Students do not have a preconceived plan but work mostly ad hoc. They are able to draw valid but superficial conclusions which could have been drawn without an extensive 50 minute practical. Their lack in data analysis skills may result in not attaining the learning goals set in other practicals. Students thus should be taught how to analyse empirical data, the practicals used in this study may serve as a basis for this.
Relativity of simultaneity in secondary school: an analysis based on the Theory of the Conceptual Fields
Authors: Otero María Rita , Arlego Marcelo , Muñoz Edwin
Published: August 2019

In this paper, we present results about the conceptualization of the relativity of simultaneity and the operational invariants used by high school students. The Theory of Conceptual Fields is adopted to design, analyse and evaluate a didactic sequence to teach the basic aspects of the Theory of Special Relativity in secondary school. Only the situations related to the relativity of simultaneity are analysed here. An inductive categorization is constructed from 256 protocols generated in the implementations carried out in four 11th grade courses (15-16 years) (N = 128) in a public school of Colombia. The categorization identifies the resolutions of the students and the operative invariants that they use in each situation. The results indicate that the proposed situations would produce the emergence and awareness of the operational invariants linked to the relativity of Galileo, which would open the way to the conceptualization of the relativity of simultaneity in secondary school.
Navigating four dimensions – upper secondary students’ understanding of movement in spacetime
Authors: Kersting Magdalena
Published: August 2019

In contrast to classical physics, general relativity (GR) interprets gravity as geometry. Objects follow geodesic curves in four-dimensional spacetime and curvature creates the illusion of a gravitational force. Despite the scientific relevance of this theory, educational research in the domain of GR is scarce. This study contributes to a growing body of knowledge concerning secondary students’ understanding of GR. Based on a thematic analysis of audio records of student discussions of 97 Norwegian physics students (18-19 years), we present results on students’ understanding of geodesic movement in spacetime. Our findings can give guidance to improve learning and instruction of a key concept of GR at the upper secondary school level.
Embedding Diagrams - a Hands-on Activity for Understanding Spatial Curvature
Authors: Ryston Matěj
Published: August 2019

Even the basics of General Relativity are considered difficult for students due to its abstract nature and the lack of concrete demonstrations suitable for a typical classroom. One area that offers some possibility of hands-on activities for students are embedding diagrams, the curved surfaces that we use to illustrate spatial curvature. Plastic models of these surfaces can easily be made using a 3D printer, which is a piece of equipment that is rapidly becoming more and more available to schools and even students themselves. In this contribution, we will propose a chain of activities, with some of which the reader might already be familiar, meant for students to help them understand what spatial curvature is and how it relates to the motion of planetary bodies (not only) in our Solar System.
Infrared vision of artworks based on web cameras: a cross-disciplinary laboratory of optics
Authors: Daffara Claudia , De Manincor Nicole , Perlini Luca , Bozzo Giacomo , Sapia Peppino , Monti Francesca
Published: August 2019

Applied optics offers a way to teach fundamental concepts of light properties and radiation-matter interaction through interdisciplinary experimental activities. In this framework, we designed a cross-disciplinary laboratorial activity on optics applied to artworks based on DIY instrumentation for the secondary school level. The teaching sequence includes inquiry-based seminars and laboratorial activities on imaging, spectrometry, infrared applications to conservation science.
Collaborative Learning vs. Lecture for Introductory Physics Students: A One-Year Longitudinal Study
Authors: Feldman G , Schiltz G , Vaterlaus A
Published: August 2019

A collaborative group-learning classroom was implemented on a trial basis at ETH Zürich in the Spring 2017 semester. Data on conceptual understanding, problem-solving ability, and student feedback were collected from the class and compared to a parallel large lecture class. In addition, a comprehensive Final Exam was given in January 2018 to assess the overall learning achievements of the students in both sections. These comparative data will be presented in order to gauge the effectiveness of the collaborative pedagogical approach.
Highly precise analytic solutions for classic problem of projectile motion in the air
Authors: Chudinov Peter , Eltyshev Vladimir , Barykin Yuri
Published: August 2019

Here is studied a classic problem of the motion of a projectile thrown at an angle to the horizon. The number of publications on this problem is very large. The air drag force is taken into account as the quadratic resistance law. An analytic approach is used for the investigation. Equations of the projectile motion are solved analytically. All the basic functional dependencies of the problem are described by elementary functions. There is no need to study the problem numerically. The found analytical solutions are highly accurate over a wide range of parameters. The motion of a baseball and a badminton shuttlecock is presented as examples.
Visual and gestural metaphors for introducing energy to student teachers of primary school and kindergarten levels
Authors: Corni Federico , Fuchs Hans U. , Landini Alessandra , Giliberti Enrico
Published: August 2019

The linguistic expressions scientists and educators use for energy are in most cases expressions of the principal metaphor of substance, although energy is an imponderable concept. The substance metaphor is embodied and familiar to students, so we can rely on it as useful for helping them develop a productive framework for understanding energy.

In this paper we will introduce a laboratory course for student teachers of primary school and kindergarten levels using visual and gestural metaphors for introducing energy,
TSPK and beliefs about teaching and learning electricity in lower secondary: A comparison between teacher students and first year teachers
Authors: Schubatzky Thomas , Haagen-Schützenhöfer Claudia , Krumphals Ingrid
Published: August 2019

The relationship between teachers’ beliefs, topic specific professional knowledge (TSPK) and their teaching practice has driven research in the field of teachers’ professional knowledge for the last decades. Currently in Austria teacher education programmes and induction phases are reformed. In the course of the development of new curricula and courses knowledge about their quality and effectiveness is essential. Therefore, appropriate test-instruments are needed. This contribution presents results of a pilot study focusing on teacher students and first-year teachers TSPK and beliefs. In order to investigate whether and to what extent TSPK varies between teacher students and fully educated teachers, the presented study focuses on the comparison of TSPK-test results of pre-service teachers and first year teachers in Austria. Additionally, the relationship between TSPK, beliefs and knowledge of the Nature of Science was investigated.
Teaching Critical Thinking in the physics classroom: High school students think about antimatter
Authors: Sadidi Farahnaz , Pospiech Gesche
Published: August 2019

Teaching students the skills that they need for everyday life like Critical Thinking (CT) is the goal of education. Embedding Critical Thinking skills within a content-specific instruction is expected to improve students’ critical-thinking skills. In this article, we present our content-specific instructional design for promoting students’ critical-thinking skills. The target group comprises German high school students of grades 11 and 12. The specific topic of learning modules is antimatter. To design the instruction, we combined the model of “First Principles of Instruction” with our domain-specific interpretation of Halpern’s general definition of Critical Thinking skills. To develop and optimize our instructional design, we use Design-Based Research cycle.
Science Club activity at Székely Mikó High School
Authors: Pető M
Published: August 2019

The aim of the Science Club is to organize workshops that improve the technical and IT competence and skills of students. These transcurricular activities are based on STEM topics, Arduino applications, robotics and space research, which are not included in the school curricula. Through these activities, students are acquainted with the latest results of science and technology, which they can apply in practical workshops. The achievements of the Science Club (Arduino controlled meteorological station, minisatellite, rescue and fire robot, etc.) show that these activities can motivate students to participate more effectively at classroom activities in order to learn theoretical subjects and later choose a career in this field.
Numerical Study on Enhancing Heat Transfer of the Belt-type Resistance Heater in the Hypersonic Wind Tunnel
Authors: Mao Qing , Chen Jiufen , Xu Xiaobin , Fan Xiaohua
Published: August 2019

Numerical studies of Heat transfer enhancement of belt-type Electric-resistance Heater is reported in this paper. The effect of different kinds of belt arrangements is studied in detail. Results show that, for changing m and n, which is the spacing between adjacent belts both in vertical and horizon, the comprehensive Performance Evaluation Criterion(PEC) increases as belt spacing decreases; For the case of model adding several baffles, the PEC reaches 1.6, with Nu/Nuo and f / f0
comes to 3.38 and 9.51; For the staggered arrangement belt geometry, the PEC attains 1.18 and the flow field uniformity improves significantly compared with the aligned arrangement one.
Optimization of duct structure and analysis of its impact on temperature inside the shelter
Authors: Lu Jiawei , Wang Tao , Wang Liangmo , Chen Wei , Chen Yandong
Published: August 2019

The flow field of the air duct in a shelter was studied using the computational fluid dynamics (CFD) and experiment methods. The improvement methods of vortexes at the bends were analysed. It was found that the corner chamfer and the installation of guide plates have significant effect on improving the vortex. The optimized scheme expanded the inlet and outlet area of the air duct and chamfered the inner bends, then the uniformity of velocity at outlets on both sides of the straight duct was increased by 47% and 42% respectively. The duct was placed in the shelter for simulation. The results showed that the total air volume of the air duct has increased, so the cooling effect is better. The temperature distribution in the shelter is more uniform after optimization, especially in the front part due to the improvement of vortexes.
Comparative Study of Free Vortex and Random Vortex in the Design of Wind Tunnel Axial Fan
Authors: Geng Zihai , Cai Jinsheng , Huang Zhilong
Published: August 2019

The design methods of axial flow fan mainly include free vortex design method and random vortex design method. The random vortex design method and free vortex design method were used to design aerodynamic parameters of two fan systems, and then the performance of these two fan systems was compared by numerical simulation. In the numerical simulation, the random vortex method and free vortex method are applied, respectively, based on the fan design parameters given by the acoustically guided wind tunnel fan section, and the physical model was established, the numerical simulation comparison study was conducted for the two sets of fan systems. The comparative analysis of the numerical simulation results shows that compared with the free vortex method, the fan designed by the random vortex method can reduce the local separation of tip and root of the blade, and the axial velocity distribution of fan blade and fan section outlet can be more uniform, and there is a certain increase in fan blade efficiency. These results verify that the design method of random vortex fan is feasible in large wind tunnels, especially in wind tunnels with aerodynamic noise reduction requirements, and can provide powerful conditions for optimizing aerodynamic and acoustic performance of the fan.
Research on the temperature field model of plate hot rolling process based on CUDA
Authors: Liu Wenhong , Guo Siying , Zhang Siyu
Published: August 2019

The current temperature field model of plate rolling process is generally based on CPU programming, due to the influence of computer performance, the accuracy and speed of the model can not be improved at the same time. To solve this problem, this paper studies the temperature field model with particle swarm optimization to modify the heat transfer coefficients, and the parallel program of this model is written under CUDA architecture, on premise of ensuring the accuracy of the model, the computation speed of the model is improved. To get the best acceleration, this paper analyzes the factors affecting GPU performance, the accuracy and speed of the temperature field model before and after modification are compared under the best acceleration configuration. Final temperature field model calculation error reduced to an average of 15.57 °C, better than the model based on the empirical formula, the computing speed is also improved, which is 1.78 times that of CPU.
Clothing Design Model for High Temperature Work based on Heat Conduction
Authors: Wang Zhenzhen , Feng Shaofen , Chen Hongyu , Chen Xueyue , Zhou Shijie , Pan Wenwen
Published: August 2019

By analyzing the temperature changes of the three-layer high-temperature clothing and the air layer of the fourth layer, according to the calculation of the temperature distribution of the high-temperature clothing, the temperature changes of the high-temperature clothing are related to the heat, ignoring the heat transfer of heat radiation in the clothing and the internal heat sources between the layers, defining three variables of time, temperature and thickness, according to the law of conservation of energy and Fourier’s law of heat transfer. The law obtains the heat conduction equation. The forward difference method in the finite difference method is used to solve the equation, and the numerical model is obtained. Then, the relationship diagrams of temperature, time and thickness are drawn. The experimental results show that the heat absorbed by the outside is consumed layer by layer in the process of heat transfer, and finally the air layer contacted with human body tends to 48 C. Finally, according to the formula Q = cm Delta U of heat absorption in physics, further analysis is carried out, and the optimal thickness of Layer II and Layer IV is obtained by using the optimization algorithm.
Study on Flow Field Optimization for SCR System of Coal-fired Power Plants
Authors: Liu Xiuru , Sun Yiqing , Xue Fangming , Su Jingcheng , Chen Feng
Published: August 2019

Coal-fired power plants are undergoing ultra-low emission retrofits. When the flue structure of the SCR denitrification system of the existing unit is fixed, the internal baffles and static mixers need to be optimized to ensure the flow field uniformity, thus ensuring the denitrification efficiency and controlling the ammonia escape rate. For a 660 MW SCR system, numerical simulation of flue gas flow uniformity and cold state test of physical model were carried out. The results show that the uniformity of the flow field distribution and the mixing effect of ammonia and gas in the SCR denitrification system are effectively improved by adding deflectors and optimizing the static mixers. The research in this paper provides reference for similar engineering design and construction in the future.
Radiative Heat Flux of a Burning Crude Oil Tank to the Adjacent Tank under the Conditions of Varied Wind Flows
Authors: Zhou Feng
Published: August 2019

Simulation about the large-scale crude oil tank fire is conducted. By utilizing the FDS to simulate the 105m3 crude oil tank fire and gaining the feature of the flame under four different wind conditions, the incident radiation distribution of the flame on the adjacent tank is acquired. The cylindrical flame radiation model is used to simplify the flame and the radiation simulation is conducted with COMSOL software. It suggests that the wind condition influence the incident radiation distribution as well as the radiation intensity. In the same wind condition, the position and the incidence angle hold different effect on radiation distribution. Finally, according to the characteristics of incident radiation, some suggestions are proposed for firefighting.
The stall of different ice accretion airfoil
Authors: Feng Yupeng
Published: August 2019

Ice along the leading edge of upper surfaces have detrimental effects on performance and control of an aircraft. Various icing shapes airfoil have various influence on aerodynamic characteristics and stall phenomenon. The mechanics model, of which ice accretion zone is on the leading edge, is produced by the assembly of various ice shapes (rime ice and mixed ice) and NACA0012 airfoil, In order to analyse the cause of stall phenomenon. The Reynolds averaged Navier-Stokes (N-S) equations are solved using Spalart-Allmaras (S-A) turbulence models the entire flow field. The results show: 1) the stalling angle of attack is various in case of various ice shapes on the leading edge. The stalling angle of attack is 15.5° in case of none ice, about 9° in case of rime ice and about 7.8° in case of mixed ice. 2) The way of airflow separation is different in case of various ice shapes on the leading edge. The vortex zone is expanded from the trailing edge to the leading edge in case of rime ice. Both vortex zones at the leading edge and the trailing edge are expanding meanwhile into one vortex zone in case of mixed ice.
Airflow Inclination Sensor Based on Temperature Field
Authors: Zheng Yonghong , Peng Shiliu , Xiao Wei
Published: August 2019

It is the temperature field of the closed cavity that plays a decisive role in sensitive inclination. With numerical simulation of ANSYS, the temperature field was analyzed separately under the environmental temperature and heat source temperature unchanged. When the temperature difference between environment and heat source remains constant, the temperature gradient of flow field remains invariant. A circuit can be designed so that the temperature difference between the environment and the heat source does not change during the operation of the inclination sensor, and improving the stability of sensor performance further with the circuit.
Study on the influence of pumping system on the hydrodynamic performance of air tanker
Authors: Xiao Zhijian , Wang Lili , Huang Miao , Jiang Rong , Wan Yuxiang
Published: August 2019

The influence of the pumping system on the hydrodynamic performance of the air tanker were investigated in this paper. The hydrodynamic performance of the air tanker with different displacements under the different Froude numbers was studied by experimental method. RANS methods and overset mesh were used to compute the viscous flow field of an air tanker under three conditions at different Froude numbers. Numerical method adopted in this paper was verified and validated by comparing the experimental results with the simulation results. The experimental results showed that the total resistance and the heave amplitude of air tanker with different displacements increased, while the pitch angle decreased, as the speed increased. And the larger the displacement, the greater the total resistance, pitch angle and heave amplitude. The simulation results showed that the drainage efficiency, the load of the baler and the additional pitching moment showed non-linear growth with increasing speed. As the baler lowered, the total resistance and heave amplitude of the aircraft increased, but the pitch reduced. The effect on the hydrodynamic performance of air tanker was not obvious as the baler closed.
Simultaneous determination of size and velocity of microspheres in flow by polarization analysis of the scattered light
Authors: Huang Xiaoqun , Bailly Yannick , Lepiller Valérie
Published: August 2019

A particle sizing method based on the analysis of polarization status of light scattered by targeted particles is introduced, with the polarization ratio of scattered light obtained through particle image processing. The optical setup was combined with PIV (Particle Image Velocimetry) for the simultaneous determination of particle velocity field. The presented granulometry and velocimetry method was applied to determine the size distribution of DEHS particles dispersed in ambient air generated by an aerosol generator. With the particle velocity field acquired simultaneously, the size distributions of DEHS particles under different operating pressures obtained from the presented method were compared with standard values provided by the manufacturer and showed a good correspondence, which proved it to be a promising flow field diagnostic technique.
Aerodynamic Characteristics of a Ducted Fan System Based on Momentum Source Method
Authors: Cai Hongming , Ma Guoliang , Li Zhongxin
Published: August 2019

Ducted fan systems have received a considerable attention due to their potential for wide application in both civil and military missions. Compared with isolated fans, the presence of duct can substantially weaken the contraction of fan wake and gives the potential to fly efficiently with high security, compact structure and low noise. Based on the momentum source method (MSM) and the S-A turbulence model, a computational fluid dynamics (CFD) simulation model is established and validated as a reliable tool by comparing with calculation results based on sliding mesh technique. The effect of the revolution speed, flight velocity and angle of attack on the aerodynamic characteristics of the ducted fan system is evaluated in detail. The calculation results show that the thrust of the ducted fan system shows an approximate quadratic increase with the increasing revolution speed; As the vertical velocity increases, the thrust of the ducted fan system increases first and then decreases; As the forward velocity increases, the lift and drag of the ducted fan system increase; As the angle of attack increases, the drag of the ducted fan system increases and the lift first increases and then decreases.
Optimal Design and Flow-field Simulation of a Dual Fluid Atomizer
Authors: Yu Minghao , Wang Rui , Liu Kai , Liu Kang
Published: August 2019

Two-dimensional turbulent flow-field properties of two types dual fluid atomizers which are currently popular in the market were numerically simulated and studied by using the commercial fluid dynamics software FLUENT. The present paper summarized their atomization characteristics respectively after studying the distribution rules of internal pressure, streamline and turbulent kinetic energy of the two kinds of dual fluid atomizers at different air flow rates. Finally, the conclusion was reached that the water absorption of the Type B atomizer is better than that of the Type A atomizer, but the secondary atomization effect of the Type B atomizer is not as good as the Type A’s.
Improved finite volume method for solving 1-D advection equation
Authors: Zhao Siyuan , Zhou Junjie , Jing Chongbo , Li Lingquan
Published: August 2019

In the framework of the second-order finite volume method, a new improved finite volume method (FVM) for solving one-dimensional advection equations is proposed based on its conservation form. The new method first applies the scalar conservation law to the cells in the FVM, ensuring that it is conserved in time and space, and that the flat flow (ie, the transport physical quantity) is conserved. Secondly, the time integral values of adjacent grids boundary are equalized. Finally, by establishing an equation, numerical solution values are obtained. A strong discontinuity function was used in the paper to test the new method described in this paper and compare it to the central difference method (CDM) and traditional FVM. Without the limiter, the results show that the new method described in this paper has less dissipation and better stability than CDM and traditional FVM. In addition, after adjusting the convergence condition criterion number CFL to 2, the accuracy of the numerical solution can still be guaranteed.
Simulation and Research of CFD on Internal Pressure Parallel Hollow Fiber Membrane Module
Authors: Sun Xiaohan , Li Chunqing
Published: August 2019

Membrane bioreactor (MBR) has been widely used in sewage treatment, effectively solving many long-standing problems such as solid-liquid separation. In this paper, the internal pressure parallel type hollow fiber membrane module was taken as the research object. Based on the CFD theory and method, the solid-liquid separation of the flow entering the membrane module was simulated by FLUENT software. Firstly, the geometric model of the internal pressure parallel membrane module was established by the computational fluid dynamics (CFD) preprocessor and structured meshing was performed. Then the volume fraction of suspended solid (SS) at the exit of the model was calculated by Eulerian multi-phase flow model and Phase Coupled SIMPLE algorithm. The calculation results were presented as images in the CFD post processor. In this paper, the simulation calculation for different concentrations of suspended solid showed that the volume fraction of suspended solid at the exit of the model was zero, which was consistent with the actual MBR system operating data. The simulation results indicated that the model established in this paper had higher accuracy. The model can simulate and predict the separation effect of solid-liquid two-phase flow in wastewater treatment, which has certain reference value for MBR engineering design and research.
Numerical simulation technology and analysis of communication in flight simulator in storm environment
Authors: Xu Lingrui , Xiong Xiong
Published: August 2019

Based on the particle system and aerodynamic effects, the natural phenomena in the snowstorm environment are simulated in real time. Through the hydrodynamic model, a wind model is established. The motion of the snowstorm in the hurricane environment is regarded as the comprehensive motion of the wind and the free falling body of the snow. According to the natural attributes of snow particles and the actual visual requirements of flight simulation, the mathematical calculation is simplified, and the special weather of snow is simulated. Finally, the collision between particles is briefly evaluated and analyzed.
Modal optimization approach for composite aeroelastic wing model based on a derivative-free BFGS method
Authors: Lv Binbin , Lei Pengxuan , Guo Hongtao , Kou Xiping , Yu Li
Published: August 2019

The optimization problem of aeroelastic wing model may lead to highly coupled nonlinear equations whose Jacobian matrix is hard to be calculated, followed by adjusting the variable domain due to design variable importance in terms of their sensitivity. To overcome the problem, an optimization function for the modal frequency is established. And a suitable line search approach is combined with the BFGS method to improve its efficiency. Some numerical results are reported to show efficiency of the proposed method. An integrated modal optimization approach based on the BFGS is developed for the model design of a composite aeroelastic wing model. The stiffness of the key beams of the wing model is designed to be the optimization variables, bending frequency and torsional frequency are designed to be the optimization objective. Then the modal of CHN-T1 is optimized, it is shown that the method proposed is suitable for the optimization of composite aeroelastic wing model with a high efficiency.
Research on the Influences of Inertial Properties on Body Freedom Flutter for an Airfoil
Authors: Lei Pengxuan , Lv Binbin , Guo Hongtao , Kou Xiping , Yu Li
Published: August 2019

For some flying-wing aircraft with large aspect ratio, the pitching inertia is small, which makes the longitudinal short-period modal frequency higher. Structural flexibility makes the 1st bending mode frequency lower. This makes the pitching mode of rigid body easily coupled with the elastic mode, resulting in aeroelastic instability, which is called body freedom flutter. There are many factors affecting the body freedom flutter characteristics. The rigid body inertia and structural characteristics of the fuselage and wing all have an impact on it. Taking the flutter of an airfoil as an example, the structural dynamics model of the system is established. The flutter characteristics of the airfoil were solved by analytical method. The effects of pitching inertia and fuselage mass on the flutter speed, flutter frequency and flutter mode shape were studied.
Optimization design of flue gas temperature for Low-Low Temperature Electrostatic Precipitator
Authors: Sun Ke , Yan Yu , Jiang Jiahao , Deng Lei
Published: August 2019

Low temperature corrosion is one of the key issues in application of low-low temperature electrostatic precipitator. The concentration of SO3 affects the acid dew point temperature of flue gas. The exhaust temperature after the air preheater should be higher than the acid dew point temperature. The residual heat of flue gas is fully utilized by the low-temperature economizer. The efficiency of low-low temperature electrostatic precipitator is improved by the comprehensive effect of the condensation of SO3 on the surface of the fine particles, the decrease of the specific resistance of the particles and the agglomeration of the fine particles.
Numerical Simulation of Longitudinal Motion of High Speed Craft in Calm Water
Authors: Liu Jianmin , Yu Xiaoping
Published: August 2019

In order to accurately estimate the hydrodynamic performance of high-speed crafts sailing in calm water, a numerical method based on CFD technology was established in this paper. The method included techniques such as cutting body mesh, overlapping mesh, two-phase flow, VOF model, and 6-DOF motion model. The numerical simulation of the craft’s heave and pitch coupling motion in hydrostatic water was carried out. The variation of the speed of the high speed craft with the change of the longitudinal angle and the center of gravity during the motion was analyzed. To prove feasibility and accuracy of numerical simulation method for hydrodynamic performance of longitudinal motion of high-speed crafts, the calculated results were compared with the experimental values of the ship model.
The Calculate Method of Flotation for Unbreakable Airplane
Authors: Jiang Ting , Wang Mingzhen , Zuo Zibin , Jiang Rong , He Chao
Published: August 2019

According to CCAR, the airplane which apply for cross ocean flight should do some airworthiness compliance on floatation after ditching. Because of the imperfect method in this area, we can not obtain the exact result which restrict the level promoted for airplane design. So an distinct and easy method is needed imminently. In this paper, we build a calculate method of attitude motion for flotation on hydrostatics, time domain and stepwise regression theories. Though decompose the yield of water into tiny part and make use of the relationship between float time and yield of water, we develop a software which is good at analyse the float time on the basic of CATIA If we study the flotation character in this way, we may save much time and simplify the complex question. In the end of this paper, we analyse the floatation for an airliner and the result shows that rhythms by calculate is good accord with that of experiment which declare the rationality of that method.
Heat dissipation analysis of electronic equipment based on CFD
Authors: Liu Xianlong , Tang Song , Feng Mei
Published: August 2019

In order to quantitatively analyze the heat dissipation of high-power devices, Icepak software is used for analysis. Comparing the effects of fans on heat dissipation, two models were established respectively (with fan and without fan). Combining the advantages of Icepak, the grid around the radiator is combined with structured and unstructured grid. Through the analysis, the maximum temperature decreases by 22.2°C and 36.6% when there is a fan (the flow rate is 0.003kg/s).
Numerical optimization design of vortex diode hydrodynamic cavitation reactor
Authors: Wang Jian , Chen Wei
Published: August 2019

Vortex diode is a novel hydrodynamic cavitation reactor, whose cavitation energy yield can be about 3∼8 times higher than the conventional ones. In this study, the numerical orthogonal experiment of the structure(Diameter of the chamber(D), Ratio of the diameter of the chamber to the diameter of axial tube(D/dc), and Ratio of the Diameter of the chamber to the height of the chamber(D/H) ) of vortex diode was carried out and the importance of the impedance ratio influence factor is: D>D/dc>D/H. The best performance was achieved when D=120mm; D/dc=5.0; D/H=5.0.Under the same conditions, the optimal value of D/H is in the range 5∼5.5 and the D/dc is in the range 4.0 ∼ 4.5.The impedance ratio was increased lightly and the flowrate was improved distinctly when we contracted the inlet and outlet of the axial and tangential tube.
Climate and soils at the Brazilian semiarid and the forest-Caatinga problem: new insights and implications for conservation
Authors: de Castro Oliveira Guilherme , Francelino Márcio Rocha , Arruda Daniel Meira , Fernandes-Filho Elpídio Inácio , Schaefer Carlos Ernesto Gonçalves Reynaud
Published: August 2019

This study aimed to test two hypotheses: (i) on the Brazilian semiarid territory, the climate has greater weight as a driver of vegetation than the soil and; (ii) the arboreal Caatinga is a vegetation whose environmental attributes are similar to the Dry Forest, in terms of soil and climate attributes. We analyzed attributes of the superficial horizon of 156 standardized profiles distributed throughout the Brazilian semiarid region. Bioclimatic variables were obtained from the WorldClim platform and extracted to profiles location. The main vegetation types in the region were considered: Caatinga, arboreal Caatinga, Dry Forest and Cerrado. Variable selection was performed with hierarchical correlation dendrogram and recursive feature elimination algorithm. Linear Discriminant Analysis and Random Forest (RF) algorithm were used for modeling the edaphic and climate niche and predict the vegetation with the selected variables. Climate and soil, individually, were able to separate the vegetation, but the climate was no better predictor than the soil. Therefore, we reject the first hypothesis. However, the better prediction was attained with the combined use of soil and climate attributes. The parsimonious RF model had good performance, with Kappa 0.61 ± 0.10 and 70.9% ± 7.7% accuracy. The combination of soil and climate predictors resulted in better separation of vegetation in the Brazilian semiarid region. Soil attributes are key variables in large-scale biogeographic modeling. The so-called arboreal Caatinga is distributed over a wide edaphic and climatic range, with strong similarity to the Dry Forest distribution, confirmed by the great overlap in the multivariate space, which confirms the second hypothesis. The results point towards an urgent review of the Atlantic Forest Law. The environments where the arboreal Caatinga and the Dry Forest occur are very similar, so that the former may represent a degraded phase of the Atlantic Forest, currently without the due legal protection.