bluuebunny/crossref_metadata_2025 huggingface dataset:
Six-Dose Intravenous Tranexamic Acid Regimen Further Inhibits Postoperative Fibrinolysis and Reduces Hidden Blood Loss following Total Knee Arthroplasty
Authors: Zhang Shaoyun , Xie Jinwei , Cao Guorui , Lei Yiting , Huang Qiang , Pei Fuxing
Published: August 2019

There is no consensus regarding the ideal dosages and times of multiple-dose intravenous tranexamic acid (IV-TXA) administration in total knee arthroplasty (TKA). This study aimed to assess the effect of six-dose IV-TXA with the total dosage more than 6 g on postoperative fibrinolysis and hidden blood loss (HBL) after primary TKA. A total of 175 patients were randomized into three groups to receive placebo (group A), or a single preoperative dose of 20 mg/kg IV-TXA (group B), or six-dose IV-TXA from the beginning of the procedure to subsequent 24 hours with the total dosage more than 6 g (group C). The calculated HBL, maximum hemoglobin (Hb) drop, transfusion rate, and the incidence of thromboembolic events were compared among groups. The levels of fibrinolysis parameters in plasma including fibrin(-ogen) degradation products (FDP) and D-dimer were measured at six time points from preoperatively to 3-month postoperative period. The mean HBL and maximum Hb drop in group C (515.51 ± 245.79 mL, and 2.06 ± 0.73 g/dL, respectively) were significantly lower than those in groups B (756.06 ± 226.79 mL, p < 0.001; and 2.77 ± 0.78 g/dL, p < 0.001, respectively) and A (987.65 ± 275.38 mL, p < 0.001; and 3.49 ± 0.86 g/dL, p < 0.001, respectively). Such differences were also detected between groups A and B (p < 0.001 and p < 0.001, respectively). The levels of FDP and D-dimer in plasma were lower in group C than those in groups B and A on postoperative 24, 48, 72 hours (p < 0.001 for all). No episode of transfusion occurred, and the incidence of thromboembolic events were similar among groups (p > 0.05). The administration of six-dose IV-TXA during the first 24 hours resulted in reduced HBL following TKA without a measured increase in thromboembolic events.
Photovoltaic effect in m-plane orientated ZnOS epitaxial thin films
Authors: Chen Jian , Pei Weijie , Wang Yang , Ding Yali , Zhang Qingfeng , Li Mingkai , Lu Yinmei , Chen Hong , He Yunbin
Published: August 2019

We report on the photovoltaic (PV) effect in nonpolar (10 1¯ 0) orientated ZnO1-xSx (i.e., m-ZnOS) epitaxial thin films. The m-ZnOS films were epitaxially grown on m-sapphire using pulsed laser deposition. Photovoltaic devices were made by evaporating two parallel Au electrodes on the epitaxial m-ZnOS films. The best PV performance was achieved involving the film deposited at 5.5 Pa oxygen pressure with an open-circuit voltage of 0.694 mV and a short-circuit current density of 122.3 μA/cm2. The internal spontaneous electric field along the polar c-axis of m-ZnOS, which lies in parallel to the film surface and perpendicular to the Au electrodes, is the driving mechanism for the separation and transport of the photogenerated carriers. Complementary to conventional solar cells that operate under visible-light, such transparent PV devices can be installed on various windows to generate electricity using ultraviolet light, thereby efficiently extending the deployment of PV technology and the usable wavelength range of the solar spectrum.
Band evolution of two-dimensional transition metal dichalcogenides under electric fields
Authors: Chen Peng , Cheng Cai , Shen Cheng , Zhang Jing , Wu Shuang , Lu Xiaobo , Wang Shuopei , Du Luojun , Watanabe Kenji , Taniguchi Takashi , Sun Jiatao , Yang Rong , Shi Dongxia , Liu Kaihui , Meng Sheng , Zhang Guangyu
Published: August 2019

Band engineering of two-dimensional transition metal dichalcogenides (2D TMDCs) is of great significance with regard to both fundamental exploration and practical application. Here we report on a study of the band evolution of monolayer and bilayer TMDCs (WS2, WSe2, and MoS2) under vertical electric fields. Our results show that the electric field has a negligible influence on the bandgaps of monolayer TMDCs. For bilayer TMDCs, our results show that their intralayer direct bandgaps are also immune to the electric field. However, the indirect bandgaps of bilayer TMDCs can be effectively tuned by a vertical electric field. Interestingly, we find that the field tunability of the bandgap in bilayer WSe2 is much larger than those in bilayer WS2 and MoS2.
Experimental comparisons between AM and BW modulation heating excitation of ELF/VLF waves at EISCAT
Authors: Yang Jutao , Wang Jianguo , Li Qingliang , Wu Jian , Che Haiqin , Ma Guanglin , Hao Shuji
Published: August 2019

In this paper, the experimental results of the extremely/very low frequency (ELF/VLF) radiation from the ionosphere by amplitude modulation (AM) mode and dual-beam beat-wave (BW) mode modulation heating using the European Incoherent Scatter Scientific Association (EISCAT) heating facility are presented. By comparing the dependence of the ELF/VLF radiation sources formed by AM and BW models on the geomagnetic field disturbance and the differences in different periods, this paper aims to examine some issues such as source regions and mechanisms addressed in the theoretical study of ionospheric high frequency modulated heating. The results show that (1) in the AM mode, the intensity of the ELF/VLF radiation source depends on the intensity of geomagnetic disturbance and thus on the magnitude of natural currents in the ionosphere, while in the BW mode, the intensity of the ELF/VLF radiation source is less dependent on the intensity of geomagnetic disturbance; (2) during the relatively quiet period of geomagnetic disturbance, the intensity of the ELF/VLF radiation source formed by AM mode modulation heating decreases and by BW mode modulation, heating increases when the ionization of the lower ionosphere decreases. The results of our EISCAT modulation experiments presented in the current paper and the earlier one by Yang et al. [“The polarization characteristics of ELF/VLF waves generated via HF heating experiments of the ionosphere by EISCAT,” Phys. Plasmas 25, 092902 (2018)] support that the BW mode heating mechanism mainly results from the ponderomotive nonlinearity, and the modulation region is located in the F layer.
Hydrogel-mediated semiconductor wafer bonding
Authors: Kishibe Kodai , Tanabe Katsuaki
Published: August 2019

The concept of hydrogel-mediated semiconductor wafer bonding was proposed and demonstrated in this work. The unique property of hydrogels was utilized to simultaneously realize high mechanical stability, electrical conductivity, and optical transparency in semiconductor interfaces. The high applicability of this method for rough surfaces to be bonded was also demonstrated, owing to the soft, deformable interfacial contact agent to be solidified in the bonding process. Furthermore, the bonding experiments were carried out in ambient air at room temperature, which, therefore, provides cost and throughput advantages in device production. In addition, the developed bonding technique was used for demonstrating the fabrication and operation of solar cell devices, with current paths across the bonded interfaces, which verified the method's practical applicability. Our semiconductor bonding and interfacial engineering scheme are expected to open up a pathway for simple, handy, and low-cost, but flexible and high-performance optoelectronic material integration.
Gaseous 3He nuclear magnetic resonance probe for cryogenic environments
Authors: Fan X. , Fayer S. E. , Gabrielse G.
Published: August 2019

Normal nuclear magnetic resonance (NMR) probes cannot be used to make high frequency resolution measurements in a cryogenic environment because they lose their frequency resolution when the liquid sample in the probe freezes. A gaseous 3He NMR probe, designed and constructed to work naturally in such cryogenic environments, is demonstrated at 4.2 K and 5.3 T to have a frequency resolution better than 0.4 ppb. As a demonstration of its usefulness, the cryogenic probe is used to shim a superconducting solenoid with a cryogenic interior to produce a magnetic field with a high spatial homogeneity and to measure the magnetic field stability.
Planar collapse of a submerged granular column
Authors: Pinzon G. , Cabrera M.
Published: August 2019

Submerged mass flows are commonly considered a natural geohazard that interacts with terrestrial and submarine infrastructure and communities and are linked to the generation of tsunamis. Previous studies have investigated submerged mass flows by means of the benchmark case of a granular column collapse. This study explores the mobility and collapse dynamics of submerged granular columns within a planar configuration as a function of the column aspect ratio a. The use of a planar configuration allows the monitoring of the moving mass and its deformation patterns and provides a novel insight into the particle-fluid interactions at release and during collapse not possible before. Special attention was devoted to the column saturation and release mechanism. The column mobility is observed to be directly controlled by a and is linked to a clear distinction between triangular and trapezoidal deposits. The column collapse is found to be described by two characteristic times, marking transition points through the collapse stages. The associated deformation patterns reflect both at a column scale and at localized particle groups during collapse, reflecting in the velocity scaling of a deformable and moving granular mass and the occasional ejection of particles at its surface. We observed that the area of the released portion decreases during collapse and converge toward an equivalent portion of surface particles with little influence by a. The experimental results provide a novel insight into the study of submerged mass flows and set a reference behavior for future numerical validations.
A novel experimental setup for in situ optical and X-ray imaging of laser sintering of polymer particles
Authors: Hejmady Prakhyat , Cleven Lucien C. , van Breemen Lambèrt C. A. , Anderson Patrick D. , Cardinaels Ruth
Published: August 2019

We present a unique laser sintering setup that allows real time studies of the structural evolution during laser sintering of polymer particles. The device incorporates the main features of classical selective laser sintering machines for 3D printing of polymers and at the same time allows in situ visualization of the sintering dynamics with optical microscopy as well as X-ray scattering. A main feature of the setup is the fact that it provides local access to one particle-particle bridge during sintering. In addition, due to the small scale of the device and the specific laser arrangement process, parameters such as the temperature, laser energy, laser pulse duration, and spot size can be precisely controlled. The sample chamber provides heating up to 360 °C, which allows for sintering of commodity as well as high performance polymers. The latter parameters are controlled by the use of a visible light laser combined with an acousto-optic modulator for pulsing, which allows small and precise spot sizes and pulse times and pulse energies as low as 500 μs and 17 μJ. The macrostructural evolution of the particle bridge during sintering is followed via optical imaging at high speed and resolution. Placing the setup in high flux synchrotron radiation with a fast detector simultaneously allows in situ time-resolved X-ray characterizations. To demonstrate the capabilities of the device, we studied the laser sintering of two spherical PA12 particles. The setup provides crucial real-time information concerning the sintering dynamics as well as crystallization kinetics, which was not accessible up to now.
Effects of bulk viscosity on compressible homogeneous turbulence
Authors: Chen Song , Wang Xiaoning , Wang Jianchun , Wan Minping , Li Hui , Chen Shiyi
Published: August 2019

The bulk viscosity appearing in the Navier-Stokes equations is generally assumed to be zero for dilute monatomic gases or incompressible fluids. With the growing interest in compressible flows, it is necessary to have a more clear understanding of the role of bulk viscosity and its effects on the properties of flow fields. In the present study, the effects of bulk viscosity on statistically stationary compressible homogeneous turbulence are studied by numerical simulations at the turbulent Mach number range 0.1–0.6. The results of compressible isotropic turbulence and compressible shear turbulence are compared and discussed for three bulk to shear viscosity ratios, i.e., μb/μ=0, 10, and 30. The compensated spectrum of the velocity component shows that a better Mt4 scaling is obtained with a higher bulk to shear viscosity ratio. This observation is confirmed by the one-point statistics of normalized compressible kinetic energy, Kc/Ks, which retains the Mt4 scaling that is predicted by pseudosound theory at turbulent Mach numbers up to 0.6 when μb/μ increases to 30. The analysis of small scale properties reveals that the compressibility of the flow is significantly reduced when bulk viscosity is involved, and the flow fields approach the nearly incompressible state, which is the reason that the Mt4 scaling is observed at a much higher turbulent Mach number compared to the previous studies on the compressible homogeneous turbulence without the bulk viscosity.
Stress banding in compressed quasi-two-dimensional aqueous foams
Authors: Behera Bigyansu , Kalelkar Chirag , Raj M Kiran
Published: August 2019

We present results from a study of the compression of a quasi-two-dimensional aqueous foam in a Hele-Shaw cell. Our results show that during compression, the spatially averaged normal-stress difference localizes in bands with a wavelength of the order of the mean diameter of a bubble. Stress field colormaps are constructed by image analysis and used to visualize the bands. We investigate the phenomenon by varying the mean bubble diameter and polydispersity. We quantify the extent of (global) compression by measuring the average of an anisotropy ratio for the eigenvalues of the statistical strain tensor and find the probability distribution of the angle between corresponding eigenvectors of the statistical stress and strain tensors. We show that these stress bands are ruptured in regions in which avalanches of neighbor-switching T1 events occur, which suggests local stress relaxation in these regions.
Physical and chemical strains co-tuned magnetic properties of double perovskite PrBaMn2O5.5+δ epitaxial films
Authors: Chen Mingfeng , Bao Shanyong , Zhang Yang , Wang Yujia , Liang Yuhan , Wu Jialu , Huang Tongtong , Wu Liang , Yu Pu , Zhu Jing , Lin Yuanhua , Ma Jing , Nan Ce-Wen , Jacobson A. J. , Chen Chonglin
Published: August 2019

Different layered perovskite-related oxides are known to exhibit important electronic, magnetic, and electrochemical properties including metal-insulator transition, colossal magnetoresistance, excellent mixed ionic/electronic conductivity, and especially their flexible tunability by external or internal stimuli. Here, we show that the microstructure and magnetic properties of double perovskite PrBaMn2O5.5+δ (PBMO) epitaxial films can be co-tuned by the physical strain via a proper choice of substrate and film thickness and the chemical strain from the concentration of oxygen vacancies. It is surprisingly found that the films with more oxygen vacancies reveal more Mn4+ formed along with Mn2+ under the influence of interface strain, and meanwhile, Mn4+ exhibits a thickness-dependent distribution with a high amount at the interface. Consequently, the increased proportion of Mn4+ diminishes the saturation magnetization and decreases the Curie temperature of PrBaMn2O5.5+δ epitaxial films, revealing the availability of physical and chemical strains tuning the properties of highly epitaxial double perovskite films.
The permeability of tag questions in a language contact situation
Authors: Carvalho Ana M. , Kern Joseph
Published: August 2019

In this paper, we utilize negative polarity tag questions in order to assess to what extent discourse-pragmatic variables are susceptible to language contact induced changes. Based on a comparison of forms and functions of negative tags in the varieties spoken by Portuguese-Spanish bilinguals in a community on the Uruguayan-Brazilian border with the one spoken by monolinguals in the Uruguayan capital, we aimed at assessing to what extent any differences in this variable behavior may be affected by contact with Portuguese. Our results indicate that, despite the high permeability of discourse-pragmatic features in contact situations attested in the literature and the presumed tendency for cognate languages to converge, the forms and functions of negative tags in bilingual Spanish did not radically differ from the monolingual variety. We found, instead, an intricate pattern of convergences and divergences that challenges the presupposed assumptions about extreme permeability of cognate discourse pragmatic systems in contact.
The Aggregate Dynamics of Lower Court Responses to the US Supreme Court
Authors: Masood Ali S. , Kassow Benjamin J. , Songer Donald R.
Published: August 2019

We argue that given finite resources to review the large number of lower court decisions, Supreme Court justices should primarily be interested in aggregate responses to their precedents. We offer a theory in which the US Supreme Court drives aggregate responses to its decisions by signaling the utility of its precedents to judges on the lower courts. Specifically, we argue that lower court judges have a greater propensity to rely on a Supreme Court decision when the justices explicitly direct a lower court to consider a formally argued decision in its summary decisions. Our results demonstrate that such signals significantly increase the frequency with which the lower courts adopt the precedents of the US Supreme Court. We corroborate the causality of these links through qualitative analyses, distance matching methods, and simultaneous sensitivity analysis. Our study offers new and important insights on judicial impact and decision-making behavior in the American courts.
The stability of a skyrmion in a nanotube
Authors: Huo Xiaohong , Liu Yan
Published: August 2019

We study the stability of a skyrmion in a nanotube by using micromagnetic simulations. We find that skyrmions can exist stably in a nanotube within a moderate magnetic field range when the magnetic field is perpendicular to the center axis of the nanotube. In nanotubes the shape of the skyrmion is elliptical. The semimajor and semiminor axes of the ellipse depend on the magnetic field and the angular position of skyrmion. When the skyrmion has an angular displacement from the direction of magnetic field, its shape and size change greatly with the angular position of skyrmion. Also the topological number is dependent on the angular position of skyrmion. When the angular position of skyrmion reaches a critical value, the skyrmion annihilates. The critical angle that skyrmion can survive is not affected by the circular current density, but depends on the radius of nanotube and the strength of magnetic field.
Mimicking the cochlea with an active acoustic metamaterial
Authors: Rupin Matthieu , Lerosey Geoffroy , de Rosny Julien , Lemoult Fabrice
Published: August 2019

The human ear is a fascinating sensor, capable of detecting pressures over ten octaves of frequency and twelve orders of magnitudes. Here, following a biophysical model, we demonstrate experimentally that the physics of a living cochlea can be emulated by an active one-dimensional acoustic metamaterial. The latter solely consists on a set of subwavelength active acoustic resonators, coupled to a main propagating waveguide. By introducing a gradient in the resonators’ properties, we establish an experimental set-up which mimics the dynamical responses of both the dead and the living cochleae: the cochlear tonotopy as well as the low-amplitude sound amplifier are reproduced.
Teaching quantum mechanics in high-school ─ Discipline-Culture approach
Authors: Weissman E Y , Merzel A , Katz N , Galili I
Published: August 2019

This study presents a new approach to teaching quantum mechanics in high school physics courses facing the extremely deficient and fragmented treatment of quantum mechanics at present. The suggested curriculum adopts the new paradigm of discipline-culture in representing physics knowledge. In accordance, the curriculum is structured in nucleus-body-periphery emphasizing the principles (nucleus), their illustration (body) and their contrast with the alternative pictures in classical mechanics (periphery). The new curriculum for 30 teaching hours is presented. The results of an experimental application to 46 12th grade students in four groups shows a positive impact on students’ conceptual knowledge and students’ nature-of-science understanding. The benefits of the applied approach and limitations of the study are presented.
Colours in your pocket: smartphone-based spectrometers to investigate the quantum world
Authors: Malgieri Massimiliano , De Ambrosis Anna , Rosi Tommaso , Onorato Pasquale , Gratton Luigi M. , Oss Stefano
Published: August 2019

We designed a low cost spectrometer to be used by groups of students with an inquiry approach. This simple equipment allows to investigate the additive and subtractive models of colour formation, to study the selective absorption of a material and explain it from a microscopic point of view. The home made apparatus was used in several experiments showing the quantum nature of the absorption and production of light with the aim of bridging optics and modern physics.
Physics for skills development in preschool in Mexico.
Authors: Ramírez Díaz Mario Humberto
Published: August 2019

Physics has historically been a goal and as a media to reach out for other educational skills. Unfortunately, in Mexico preschool teachers lack tools to develop science in their little students. To help in this situation, we propose the use of “Einstein Box,” a set of toys where the kids can select and play with, then teachers explain the general physics concepts involved in the working of the toys. The results for the kids are amazing because they not only learn about basic physics, furthermore, mathematical thinking, social skills and verbal abilities, all around physics concepts.
Combining strategies to make General Physics lectures more attractive and to improve students’ performances
Authors: López G A , Alonso I , Sáenz J , Leonardo A , González-Rojí S J , González de Arrieta I , Echániz T , Unzueta I , Lafuente-Bartolome J , de la Pinta N , García-Goiricelaya P , Martinez-Perdiguero J , Gurtubay I G
Published: August 2019

Going one step further in the use and impact measurement of new strategies to improve the teaching-learning process during lecturing General Physics courses, the current contribution reports the last results/observations obtained by the authors on the combination of simple classroom experiments with active methodologies and new technologies (media). Cross-checking the answers in multiple choice questions done online during the lectures and in exams at the end of the term shows that this strategy has, at least partly, a positive effect on clarifying misconceptions. The overall opinion of the students was assessed and it showed that this lecturing approach is useful and motivating, making the lectures more attractive and stimulating eagerness to understand Physics.
Scaffolds to support the development of scientific skills in physics
Authors: Ferreira-Bautista J , Pifarré M
Published: August 2019

This paper responds to the social demand to equip learners with the skills capable to create solutions that are sustainable over time, to increasingly complex problems. To this end, this study designed implemented and evaluated an instructional process aimed to students’ development of scientific skills during the scientific inquiry process. A quasi-experimental study was designed in which participated 61 university students of physics university course participated in the study. The results show that the students of the experimental group developed higher level of scientific skills than the control group.
Physics in traditions: the ritual of the owners of the Mexican sky.
Authors: Espíndola. R. , Del Valle G. , Hernández G. , Muciño D. , Guijosa S. , Jiménez J. L. , Campos I.
Published: August 2019

Mexico is characterized by its immense cultural diversity, one culture of many is in the state of Veracruz where the Totonac culture lived. His developed of a ritual known as “The Papantla flyers”[1], which is related to fertility of the earth, this ritual consists of a group of five men who climb to the top of a 31-meter pole, tie a rope around their waist and throw themselves headlong into the void with open arms. A child, observing this ritual asks his father, “at the top, the pole has an engine that unrolls the rope and causes men to descend?”. In this work, we study the equations of motion associated to the trajectory of the men who are thrown into the void, through the design and construction of an experimental model. To compare the experimental results with the analytical solution obtained by proposing the analytical equation that describes its movement, at the same time emphasizing the use of computational tools for simulation of the model using Easy Java Simulation.
Teacher students’ beliefs about teaching physics and their teacher education
Authors: Krumphals I , Hopf M , Haagen-Schützenhöfer C
Published: August 2019

It is beyond doubt that teacher education plays a crucial role in the development of the educational system. Following the educational reconstruction for teacher education model [1], a clarification of teacher students’ beliefs seems mandatory in order to improve the education of future physics teachers. The main aim of this research project was to determine beliefs of physics teacher students about high quality physics instruction at school. Therefore, interviews with 23 physics teacher students and an additional case study with six teacher students were conducted. Several beliefs of teacher students’ such as experiments rise students’ interest and with the help of experiments physical contents can be memorized better were found.
The use of history of science on physics teaching as a social representation from pre-service teachers
Authors: Rodrigues E V , Borges A , Pietrocola M
Published: August 2019

In this work we used the Social Representation theory and one of its methods for investigating social representations of a group of undergrad physics students (N = 77), taking teaching credential, regarding the usage of History of Science as teaching strategy. Our empirical data showed a social representation with a nucleus consisting of elements from History of Science more as a contextualization tool and pragmatics science products than as a human process. The lack of a representation of science as process point out the need of rethinking the undergrad curriculum in order to expand students views on the nature of science.
Enhancing Scientific Inquiry by Mathematical Reasoning: Case of Applying Limits to Model Motion of a System of Objects
Authors: Sokolowski Andrzej
Published: August 2019

Mathematics and physics constitute parts of STEM that are widely recognized as a leading platform in contemporary education. While the effects of the methods of mathematics on discoveries in physics are unquestionable, using mathematical reasoning to enhance understanding of physics is still being researched. This study is posited to contribute to that research, and it investigates students’ skills to apply limiting the analysis to determine the acceleration of two objects connected by a massless string. Twenty-five (N=24) first-year students enrolled in the algebra-based college physics course took part in this case study. While the pretest showed that the students did not consider limits to answer questions that required limiting analysis, designed instructional unit whose goal was to bring forth the technique helped apply limits and made the solution process more explicit. Posttests results supported the study thesis that integrating more sophisticated mathematical apparatus into the analysis of physical systems opens a gate not only for advancing students’ scientific inquiry skills, but also their general STEM disposition.
A perspective on Interactive Lecture Demonstrations as a computer supported collaborative learning (CSCL) activity
Authors: Chaudhury S. Raj , Canatsey Sarah , Ward Phillip J.
Published: August 2019

Active learning designs that leverage the power of information and computer technologies (ICT) can vary tremendously in how they engage students – individuals, small groups or whole class. Interactive lecture demonstrations (ILDs) are instructor-led activities which engage the whole class and are designed address students’ mental models of core concepts in the discipline. The use of ICT allows for real time experiments conducted using sensors, simulations and even data analysis as the core of the activity. In this perspectives paper, we analyze the features of traditional ILDs through the lens of the field of computer supported collaborative learning (CSCL).
The Physics and the Chemistry of Michael Faraday to form for citizenship
Authors: Nogueira S R A , Cardoso F S , Carvalho F L C , Marinelli M O , Bezerra A S , Senra P R
Published: August 2019

In this paper we present a teaching-learning strategy based on the life of Faraday to provide knowledge of physics (electromagnetic induction) and chemistry (chemical bonds) and a wakening to citizenship. The strategy combined a film screening with experimentation and was applied with 4 classes of the first-grade secondary school in 2014 and 2016. In all classes the discussions about the movie and the student’s reports showed that they appropriated the specifics concepts, they got enchanted by Faraday’s life and became aware of their own capacity to build their future.
Numerical Simulation of Gas-Solid Two-Phase Flow and Deposition in a Novel Carbon Nanotubes Particles Trap
Authors: Geng Lei , Bai Wenjuan , Dong Fakui , Chu Dianming , Wang Lianlian , Zhou Yong , He Yan
Published: August 2019

The effects of gas-solid two-phase flow, flow velocity, model structure and temperature on deposition characteristics in Carbon nanotubes (CNTs) particles trap were simulated by Euler-Lagrangian model, adopt Realizable k–ε Model calculation of turbulent flow in trap, tracking of particle trajectories using stochastic orbital model. The simulated results are in good agreement with the experimental results, deposition of particles at orifice edge of baffle; The adhesion of particles to the wall surface is consistent with the phenomena presented by previous simulations. With the increase of temperature, the deposition rate of particles increases. The more the number of holes in baffle, the more particles are captured. At high wall temperature, the particle aggregation positions of concentric and heterocentric baffle trap are different. The deposition of the four wall particles in the concentric hole trap is obvious at the exit location, the particle deposition of heterocentric hole trap on baffle is obvious. For the vertical flow field, particles are preferentially deposited on the bottom baffle, and the heterocentric trap has a higher deposition rate than that of the concentric hole. The simulation reveals the difficult flow characteristics of particles in the trap, and the conclusions obtained are of great significance to improve the reliability of the design and amplification of the trap.
Shape Optimization and Analysis of a Low-resistance Mast
Authors: Xiang Chao , Li Baoren , Gong Yajun , Zeng Baoping
Published: August 2019

Aiming at the problem that the airfoil of WGN affects the motion resistance and noise, a set of general WEG airfoil design and optimization method is explored. First, the parameter design based on computational fluid dynamics computing method of WGN appearance is done. Then, the WGN appearance hydrodynamic characteristics was calculated with the airfoil design software XFOIL, and finally, the iterative optimization of the initial design of WGN appearance is done by the genetic algorithm, finally the fold down type SJZZWGN curve shape with low resistance and low noise is obtained to satisfy the mechanical properties. Finally, CFD software is used to analyse the optimization results and verify the rationality of the optimization results.
Numerical simulation of foam flow pressure drop in coiled tubing spiral section
Authors: Zhang Xiaoning , Sun Dongzhu , He Anle , He Zhenguo , Kong Lulin
Published: August 2019

A user-defined function and a numerical simulation method were used to analyze the pressure drop of foam flow in the coiled tubing spiral section, and the calculated pressure drop was compared with the simulated pressure drop. For foam flow in the straight section, as the influences of acceleration pressure drop and actual velocity profile were considered, the simulated pressure drop is higher than the calculated pressure drop. For foam flow in the spiral section, due to the compressibility, the foam physical properties change with pressure. Therefore, at different outlet pressures, the velocity profile and density profile are different at the same spot. Centrifugal force makes the velocity profile unsymmetrical. Outlet pressure, gas injection rate, and curvature have significant influence on pressure drop. During the hydraulics design for coiled tubing drilling with foam, the foam injection pressure should be as high as possible to decrease the pressure drop of foam flow in the spiral section.
Numerical Simulation of Heat and Moisture Transfer of Wall with Insulation
Authors: Wei Ming , Wang Bo , Liu Shunbo
Published: August 2019

This paper improves the heat-moisture coupling transfer model with temperature and relative humidity as the driving force, and regards the effective thermal conductivity and vapor permeability of the wall material as a function of temperature and relative humidity. The latent heat generated by steam diffusion was introduced into the model and the model was numerically calculated using the finite element software COMSOL Multiphysics. The calculation results show that as the thickness of the insulation increases, the heat transfer and moisture transfer inside the wall slow down. When the temperature gradient or the water vapor concentration gradient on both sides of the wall increases, the heat transfer rate will also increase. But they will gradually stabilize. After reaching a steady state, there will still be moisture and temperature transfer due to the existence of the gradient.
Experimental Study on the Effects of Pier Shape and Skew Angle on Pier Scour
Authors: Shahhosseini Mohammad , Yu Guoliang
Published: August 2019

Scouring around the bridge piers is one of the reasons for their instability, and in the absence of a suitable solution, it will eventually lead to the destruction of the structure. Therefore, studying the mechanism of scouring and effective parameters on its value is essential. In this study, using a laboratory model, this scouring phenomenon was investigated, and the effect of bridge pier shape and the skew angle between water flow and bridge pier on scouring were investigated. Experiments for four pier shapes, including a rhombus 30° inner-angle, rhombus 60° inner-angle, a cylindrical and an oblong, and three velocities include 0.191, 0.30 and 0.380 m/s, in two modes: parallel and skew-angles between stream and piers. The results show that the depth of scouring depends on the shape of the bridge pier and the angle of its placement in the flow. The best shape of the piers, the smallest scouring around it, is the rhombus 30, rhombus 60, oblong and cylindrical respectively. When the rust-shaped pier was placed in running water, in addition to less flow turbulence, the amount of scouring is also reduced. Also, due to the test with an angle between the stream and the bridge pier, the turbulence of the stream and scouring around the pier of the rhombus30 is lower than the other piers. The shape factor can be used as 1.0 for circular and oblong, and 0.9 for the shape of the rhombus 30 and the rhombus60. By analyzing the experiments, a suitable form for the bridge pier, a rhombus 30° inner-angle was proposed.
Characterization of exchange flows within pressure exchanger device by Lattice Boltzmann method
Authors: Shi Yao , Liu Qingcha , Zhao Yiding
Published: August 2019

Seawater reverse osmosis (SWRO) with pressure exchanger (PX) been used widely on the earth for desalination to produce fresh water. Mixing due to exchange flow is considered to be dominant. In this paper, full-depth exchange flow is numerically simulated by Palabos, an open source program based on Lattice Boltzmann Method. GIF pictures and data produced by Palabos are analyzed to figure out how exchange flow processes. The velocity of the current front U=0.45 √(g(1 − γ)H is obtained from analysis. The results from the simulation are consistent with the Benjamin’s energy-conserving theory very well for full-depth exchange flow.
Research on sliding hydrodynamic performance of flying boat
Authors: Wang Xiaoxiang , Wu Bin , Li Xinying , Huang Miao
Published: August 2019

The towing tank test of a scaled flying boat model is designed to obtain it’s resistance, heaving and pitching characteristics as the speed changes in the sliding progress; then based on the secondary development of fluent; the global moving mesh and VOF methods are applied in the simulation; the calculation gives the fluid field around the boat, especially the wake flow, and also the pressure distribution of boat step. the results compared to the experiment date prove that using this method to study the hydrodynamic performance of a flying boat is feasible and precise.
Experimental study on a solenoid valve-based generator for droplet generation
Authors: Wang Liping , Kong Weiliang , Liu Hong , Wang Fuxin
Published: August 2019

An on-demand droplet generator is developed based on a high-speed and 2-way solenoid valve and studied experimentally in this paper. It is found that the valve-based droplet generator has good controllability, repeatability and stability. Under a suitable applied pressure, a single droplet can be generated by opening the valve with a short voltage pulse. Besides, the droplet size can be conveniently controlled by the applied liquid pressure and pulse width of the control signal. The results show that the present device successes to avoid the limitation of an appropriate outlet pressure required at nozzle tip for most droplet generators in the literature and is capable of producing droplets in a wide size range for a fixed nozzle diameter.
CFD Simulation of Two-Phase Flows in Anaerobic Digester
Authors: Chen Jianyuan , Chen Anpeng , Shaw Jiunnhaur , Yeh Chewei , Chen Shingder
Published: August 2019

In recent years, the study of Anaerobic Digestion (AD) has become one of the important technologies in the development of biogas production as renewable energy source. It can reduce the emissions of greenhouse gases and improve management of solid wastes. The production of biogas is influenced by many parameters including temperature, mixing, pH and hydraulic retention time etc. In this study, the mathematical model and numerical simulation of the turbulent, two-phase flow of liquid and gas in a Anaerobic Digester were conducted by Computational Fluid Dynamics. The hydrodynamic behaviours of the gas-lift and mechanical mixing digesters were investigated, such as velocity field, dynamic viscosity and optimal mixing type.
Dynamic Analysis of Torsional Vibration of Reed Damper of Diesel Engine
Authors: Li Yong
Published: August 2019

During the operation of diesel engine, there are many kinds of vibration modes in its shafting motion. Now the main explanation is torsional vibration. This kind of vibration may lead to the increase of shaft wear, even the fatigue damage of the shaft system or the damage of the diesel engine. During the operation of spring shock absorber, its components shear oil film continuously and interact with lubricating oil, which affects the change of fluid damping of the shock absorber, so as to better select effective methods to cope with the change. The fluid-solid coupling method is used to simulate the effect of lubricating oil and analyze the vibration absorption performance of shock absorber. Therefore, choosing elastic damped spring damper can respond to fluid-structure coupling analysis, through dynamic analysis, reduce torsional vibration of shafting and improve the safety of ship navigation, which has important significance and value.
Numerical study on the effect of rocket plume to the jet flow deflector in liquid rocket engine test stage
Authors: Ding Jiawei , Liu Yongwei , He Hong
Published: August 2019

Jet flow deflector is one of the most important facility in liquid rocket engine test stage. It is necessary to investigate the effect of rocket plume to the jet flow deflector. Based on the theory of computational fluid dynamics, the flow field of a rocket engine plume is simulated and analysed by numerical method. The velocity field and temperature field of the plume in rocket engine test are obtained. The structural characteristics of engine plume flow field and the impact effect on flow deflector are analysed. Finally, results are applied to the thermal protection design of the test stage.
Estimating an Optimal Multiple Savonius Wind Turbines Layout by CFD Velocity Pattern Analysis
Authors: Zakaria Ahmad , Nizam Ibrahim Mohd Shahrul
Published: August 2019

Proper arrangement of multiple VAWT turbines has been known to have increased the overall power efficiency. The challenge is how to optimally place each turbine within a given location such that the overall performance is improved. This paper presents a methodology by which the placement of individual turbine is determined by the location of vortices created by the upstream turbine. This analysis is carried out by using commercial CFD solver via sliding mesh approach. To clearly observe the creation of wake and vortices by an isolated Savonius turbine, the extra fine mesh was defined outside the rotating zone of the computational domain. The resulted velocity pattern generated shows an area of the high vortex created at the tip of advancing blade at a certain rotor angle. However, the returning blade generates a weaker vortex. The placement of consecutive Savonius wind turbine is, therefore, should be at an angle ranges between 20° to 90° with respect to the advancing blade of the upstream turbine. The analyses on two-turbine, three-turbines and nine turbines in V formation have shown an improvement up to 11% in the overall power efficiency.
Application of Computational Fluid Dynamics in Groundwater Pollution Remediation
Authors: Li Yan , Luo Yuhu
Published: August 2019

Computational fluid dynamics is widely used in scientific research in various fields. This paper introduces the basic principles of computational fluid dynamics numerical simulation calculation, and summarizes the simulation analysis of pollutant migration and diffusion in the surface underwater-groundwater recharge process, the mainstream fluid numerical model characteristics and the application of groundwater pollution control and restoration. It provides a reference for the selection of numerical models in groundwater pollution survey simulation and control restoration research.
Lead dust removal using electrostatic agglomeration
Authors: Wang Fang , Li Mingjun
Published: August 2019

PM2.5 (particulate matter smaller than 2.5 microns) emitted from non-ferrous metal smelting is a significant contribution to variety of heavy metals in the atmosphere. Previous studies found that, Pb, as and its oxide is mainly concentrated in PM2.5, or even PM1.0, which is seriously harmful to human health. The concern about fine particle emissions created a new problem to develop new methods to improve fine particle removal efficiency. Electrostatic agglomeration is one effective method to overcome the problem. In this study, chemical properties and size distribution of lead smelting dust was analyzed, and removal efficiency of fine particles in lead dust was tested using AC electrostatic agglomeration.
Natural frequency analysis of curved pipe conveying non-uniform axial flow
Authors: Wu Nan , Zhao Yuzhen , Liu Yongshou , Guo Qing
Published: August 2019

In this article, the natural frequencies of curved pipe conveying non-uniform axial flow are calculated. The non-uniformity of velocity distribution on the section is considered and the parabola fluid is adopted in the section. The Flügge curved beam is used to build the pipe model. The dynamic equation of pipe conveying non-uniform fluid is derived based on Hamilton principle. The wave propagation method is used to solve the equation. With different flow velocity, the natural frequency is computed in the assumption of non-uniform fluid and uniform fluid. Compared with the uniform fluid, the non-uniform fluid will have a higher frequency value.
The Pressure Pulsation and Spectrum Analysis of Ducted Propeller Based on SST k-ω model
Authors: Wang Yue , Ren Wanlong , Liu Gang , Liu Jin , Xu Juan , Hao Zongrui
Published: August 2019

The pressure pulsation and spectrum of the four-blade ducted propeller are numerical simulated by CFD method. The flow field inside and behind the propeller is analysed by using SST k-ω Model. On the basis of the flow field, an acoustic grid is built. By setting several monitoring points in the area behind the propeller, the pressure pulsation in these points are recorded. Time domain curves of pressure pulsation in different points show a similar changing circle. After Fast Fourier Transformation (FFT), the blade passing frequency is calculated. The pulsation value near the hub is smaller than that at the tip of the blade. The fundamental frequencies of the pressure pulsations of the wake field are the same at different axial positions. The rotation of the blade has a great influence on the pressure pulsation near the blade. The pressure pulsation amplitude is larger near the propeller, and the amplitude at a far distance is smaller.
Study on High Thermal Conductivity of X-ray Anode with Composite Diamond Substrate
Authors: Li Xinwei , Zhang Pingwei , Li Ye , Wang Xin
Published: August 2019

The thermal loading capacity of the anode of a micro-focus X-ray source is an important factor to limit the output power. In this paper, a composite reflective anode model with a thick film diamond layer as the target substrate of X-ray source was proposed. With the advantage of high thermal conductivity of the diamond film, the heat accumulated in a micro-focus area can be quickly output, to improve the thermal loading capacity of the anode. A composite anode with diamond substrate was modeled and simulated with the finite element analysis method. By studying the principle of high thermal conductivity of composite anode in the numerical simulation and comparing the composite anode with copper substrate anode, the essential causes of the high thermal conductivity of the anode with diamond substrate were identified. The relevant technical parameters were obtained in the simulation and comparison, which can be used for the design of anode of micro-focus X-ray sources.