bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulation of Penning Gas Discharge in 2D/3D Setting
Authors: Rokhmanenkov A S , Kuratov S E
Published: July 2019

This work presents a numerical simulation of the Penning discharge in 2D/3D formulation. The simulation is based on the electrostatic particle method in cells using structured rectangular grids and implemented in the VSim software package. To simulate the kinetic processes in a gas-discharge plasma, the Monte-Carlo collision method was used. The calculations were carried out for several sets of chemical kinetics reactions, and their comparison is given. Various characteristics of the Penning discharge in 2D and 3D formulation were calculated, such as anodic/cathodic currents, the distribution of charged particles in space and energies, etc. A comparison of the simulation results with experimental data was observed.
Numerical Simulation of Electrodynamic Structure of Penning Discharge in Large Volume Discharge Chamber with Annular Anode
Authors: Dikalyuk A S
Published: July 2019

In the study numerical simulation of electrodynamic structure of Penning gas discharge formed in large volume discharge chamber with annular anode is performed. For numerical modelling computer code implementing two dimensional axisymmetric electrostatic particle-in-cell method on unstructured grids is used. Computer simulation results of the Penning gas discharge in He under pressure 3·10−4 - 9·10−4 mbar, anode voltage 1-2 kV in the presence of external magnetic field B∼0.1 T are provided. Comparison of numerical and experimental results is performed.
Calculation of the Fraction of Atomic Hydrogen in the Penning Discharge Plasma using the PIC-MCC Method
Authors: Gumennov V O , Dikalyuk A S
Published: July 2019

In this paper, the process of dissociative ionization is incorporated into the existing model of Penning discharge in molecular hydrogen. The analysis of studies for the selection of effective cross-sections for this process is performed. The results of calculations with the following parameters are given: working gas - H2, p = 0.8 mTorr, V = 600 V, B = 200-500 G. Comparison of calculated relative shares of atomic and molecular ions with experimental data obtained at the University of California, Berkeley has been performed.
Abnormal Glow Discharge between Two Electrodes on Plane with Transverse Magnetic Field
Authors: Surzhikov S T
Published: July 2019

Surface glow discharge in the abnormal mode of its burning at pressure 5 Torr is numerically studied at a voltage drop of ∼650 V between electrodes, located on plate surface at a distance of 2 cm. The drift-diffusion two-dimensional model of gas discharge plasma is used for the description of electrodynamic parameters of the discharge. It is shown that external transverse magnetic field of induction about 0.2 T occurs significant influence on the gas discharge plasma configuration, squeezing or expanding electric current channel between electrodes depending on the magnetic field polarization. Two-dimensional fields of electrodynamic functions, such as the volume concentrations of charged particles, electric potential and the force lines of electric field strength without and with external magnetic field are presented and analyzed.
Burning rate of solid homogeneous energetic materials with a curved burning surface
Authors: Rashkovskiy S.A. , Krupkin V.G. , Marshakov V.N.
Published: July 2019

We study experimentally the combustion of a double-based solid propellant NB at a pressure of p = 1 bar, and show that combustion occurs in the cellular-oscillating mode: combustion occurs in the form of separate cells that periodically appear on the burning surface, move along it and disappear. We show that in this mode, a carbonized skeleton is formed on the burning surface, consisting of products of incomplete decomposition of propellant. This skeleton is associated with the burning surface and plays an important role in maintaining the cellular-oscillating mode of combustion of the double-based propellant. To explain the experimental data, we consider a combustion model with a curved burning surface. We show that the burning rate depends on the curvature of the burning surface: with increasing curvature of the burning surface, the local burning rate decreases and combustion becomes impossible if the nondimensional radius of curvature (Michelson-Markstein criterion) of the burning surface becomes less than some critical value. The calculated critical value of the Michelson-Markstein criterion is in good agreement with that obtained in experiments. Using the developed model of combustion of solid homogeneous energetic materials (SHEMs) with a curved burning surface, we calculate the critical combustion diameter of various SHEMs and the shape of stationary cells on the burning surface. The critical combustion diameters of various SHEMs calculated in this way we compare with the available experimental data. A good agreement between the theory and experiments was obtained.
Numerical testing of the similarity conditions for the induction plasmatrons
Authors: Vasilevskii S A , Kolesnikov A F , Bryzgalov A I , Yakush S E
Published: July 2019

Detailed comparison of numerical results obtained for IPG−4 plasmatron (base case), IPG − 3H hypothetical plasmatron and IPG − 3 real plasmatron is provided to estimate the accuracy of the similarity conditions and the applicability of that conditions for the pair of IPG − 4 and IPG − 3 plasmatrons. IPG − 3H hypothetical plasmatron is geometrically similar to IPG − 4 one and has twice larger dimensions. The operating regime of IPG − 3H is obtained from the IPG − 4 operating regime with use of the similarity conditions for the operating parameters. The operating regime of IPG − 3 real plasmatron is the same as for IPG − 3H. Vortical electric field generated by the inductor coils with high frequency current around the discharge channel is calculated with use of 2D model with far field boundary conditions. This calculation is integrated with the solver for Navier-Stokes equations for plasma flow. The comparison of IPG − 4 and IPG − 3H results shows about 4÷7% accuracy of the similarity conditions for main plasma parameters. The comparison of IPG − 4 and IPG − 3 results shows that application of the similarity conditions for this case provides a qualitative agreement but the quantitative difference in some parameters may be large, up to 35÷40%.
Experiment Study on Sound Properties of Carbon Fiber Composite Material
Authors: Yan Zhong , Pu Zhou , Haijun Feng , Yi Zhang
Published: July 2019

In this paper, the sound absorption coefficient and transmission loss of carbon fiber composite material are tested by stand wave tube equipment, and the factors affecting the performance of the carbon fiber composite material are analyzed. The results show that the sandwich structure can effectively improve the sound absorption coefficient and transmission loss; increasing material thickness appropriately can also improve acoustic performance of the carbon fiber composite material. The carbon fiber composite material with reasonable structure design can be used as acoustic material in the field of vibration and noise reduction.
Calculating optimum gear ratios of a two-stage helical reducer with first stage double gear sets
Authors: Pi Vu Ngoc , Thi Hong Tran , Thi Phuong Thao Tran , Khac Tuan Nguyen , Hung Le Xuan , Anh Tung Luu
Published: July 2019

This paper presents a study on the determination of the optimum gear ratios of a two-stage helical reducer with first stage double gear sets. In the study, an optimization problem was built in order to find the optimum gear ratios of the reducer. In the optimization problem, the objective function was the reducer cross section area. Also, the influence of the input factors including the total reducer ratio, the wheel face width coefficient, the allowable contact stress and the output torque were evaluated. In order to investigate the effects of these factors on the optimum gear ratios, a simulation experiment was designed and conducted. In addition, equations for calculating the optimum gear ratios were introduced. By using these equations, the gear ratios can be determined accurately in a simple way.
Study on Film Characteristics of Piston-Cylinder Interface of High-Pressure Common Rail Radial Piston Pump with Micro Motion
Authors: Qi Bo , Zhang Yong , Meng Guoyou , Ding Yao , Ye Ming
Published: July 2019

When the high-pressure common rail radial piston pump works, the piston is subjected to film pressure and cam driving force, resulting in some micro-motion such as offset and inclination. A large number of theoretical studies have shown that the micro-motion of piston has an important effect on the film characteristics of piston-cylinder interface. In this paper, according to the theory of hydrodynamic lubrication, Reynolds equation and film thickness equation of piston micro-motion are established, and solve the problem of the lubricant film of the piston-cylinder interface under different working conditions. The results show that the working pressure and cam speed have great influence on the film characteristics of piston-cylinder interface with micro-motion. The research results provide theoretical support for the optimization of the film parameters of the piston-cylinder interface.
Advantages of using virtual reality and building information modelling when assessing suitability of various heat sources, including renewable energy sources
Authors: Chudikova B , Faltejsek M
Published: July 2019

The pace of changes in the construction industry is constantly accelerating. It includes 3D modeling, utilization of drones, 3D printing and virtual or augmented reality. Augmented reality combines something real, such as existing buildings, with expanded 2D or 3D digital information about individual technologies or planned changes, and the actual projection of individual elements into a given (even hidden) space. It can be a key for improving project engineering processes, subsequent maintenance or more efficient renovation procedures. Virtual and augmented realities need 3D building models, i.e. incorporation of building information modelling. Building information modelling (BIM) is a modern and efficient solution process that incorporates the entire building life cycle, based on a realistic model and information. Individual building technical equipment, i.e. including heat sources, to a certain extent influence the internal structure of individual buildings, particularly in the case of a more complex structures. The article describes some of the modern technologies that can be applied to the administration, maintenance and implementation of building technical equipment. Such technologies can also help when deciding about the most suitable heat source for a given building. The article points out the benefits of incorporating these modern technologies.
Simulation of heavy-duty engine based on flexible multi-body dynamics
Authors: Li Wen , Chen Lei , Liu Jintao , Liu Zhenxing , Zhuang Baotang
Published: July 2019

For heavy-duty diesel engine, the structural flexibility of the crankshaft and the engine block has an important influence on the dynamic characteristics of the engine. The deformation and modal resonance generated at work must be considered. Therefore, the multi-body dynamic analysis of the crankshaft and the body structure is based on the flexible body model of the crankshaft and the body. In this paper diesel engine dynamics behaviour is analysed based on flexible multi-body method. The dynamic substructure condensation method is used to reduce the he shaft and the bearing block, obtain the flexible body model of the crankshaft and the body, reduce the computational solution scale, and improve the computational efficiency.
Simulation of nozzle position optimization based on single-phase flow
Authors: Chen Guang , Zhou Yuancong , Qian Xuelin , Wu Wenmin , Zhao Yifan , Hu Yumei
Published: July 2019

The numerical simulation on the lubrication of the complex gearbox was studied and an optimization for its injection lubrication system was carried out. Firstly, a pair of high speed gear test bench was built and related experiments were completed. The experimental results verified the correctness of the numerical simulation modeling method. Then the numerical model of the injection lubrication of the complex gear box was established, the simulation analysis was carried out. The results show that the overlong injection distance, the angle of the end face and the arrangement of the nozzle in the out of mesh side are not good for lubrication. And there is a trace in the center plane of the two meshing gear, along which the ejected oil will be under the least impact of the high speed airflow that driven by the rotating gears. When the nozzle axis is in the direction of the trace, the gear lubrication condition is the best.
Study and comparison on mechanical properties of various polymers reinforced with ground tires rubber (GTR)
Authors: Marín-Genescà M , García-Amorós J , Bordes-Arroyo J , Mujal-Rosas R , Vidal Ll Massagués
Published: July 2019

The recycling of worn tires is a big challenge nowadays and it is necessary for environmental and economic reasons: mass production of tires, as well as the difficult storage or elimination is a real environmental problem. Various methods for recycling tires are currently used, such as mechanical grinding, which puts vulcanized rubber, steel and fibers apart. The rubber may be used in several industrial applications as flooring, insulations, footwear, etc. The aim of this paper focuses on finding a new application for the old used tires (GTR). Tires dust and 7 different polymers have been mixed, and we have checked the maximum accepted values of GTR that can be admitted while keeping mechanical properties within acceptable values, as well as initial polymer microstructure. This would allow including GTR in industrial applications of recycled polymers. The recycled tire dust which results from the industrial milling processes has been divided by categories according to the size of the particles. This has been mixed with different polymers, in different GTR concentrations in order to establish its conduct through mechanical test. With the present study it is intended to give a second outlet to the tires out of use, demonstrating the feasibility of the mechanical properties analyzed.
Orthogonal Experimental Study on Two Side-direction Burrs of Grind-hardening Workpiece Based on Transverse Feed
Authors: Gao Shunxing , Liu Judong , Jin Jiawei , Xu Zhilong , Yang Xiaofan
Published: July 2019

Based on the orthogonal experiment, the influences of grinding depth (a
p), the workpiece feeding rate (v
w) and the transverse regrinding value (C
r) on two side-direction burr of 40Cr steel large-plane grind-hardening workpiece were investigated. The results show that, under the coupling of heat and force in the grind-hardening process, the surface metal of the workpiece metal flows toward the unconstrained direction on both sides, resulting in the formation of the burr. The grinding depth and the workpiece feeding rate become leading factors affecting the size of the burr. Moreover, the significance of three factors to the size of the burrs is as follows: the grinding depth (a
p) > the workpiece feeding rate (v
w) > the transverse regrinding value (C
r). The result showed that the maximum size of the first-pass and the second-pass burr would increase with the increasing of the grinding depth and the transverse regrinding value in grind-hardening processes, but it decreases with the workpiece feeding rate. The optimal process parameters are a
p=0.1mm, v
w=0.8m/min, and C
r=1mm under the experiment conditions.
Development of a 3-y-old Pediatric Cervical Spine Finite Element Model
Authors: Li Na , Wei Wei , Wu Siwen , Du Xian ping , Liu Yin , Rong Pengfei
Published: July 2019

A 3-year-old pediatric cervical spine finite element (FE) model with detailed anatomical and material properties was developed and validated against cadaver tests under both quasi-static loadings. First, bone geometry was reconstructed based on high-resolution computed tomography (CT) scans, and elastic-plastic material was defined to simulate the cortical and cancellous bones. To simulate various ligament tears during dynamic tensile, ligament failure was defined using force versus displacement curves, which had a sigmoidal shape governed by three control points. To better represent the complicated structure of the disc, nucleus pulposus, annulus fibrosus substrate and four pairs of reinforced fiber lamina, intervertebral discs were defined using composite materials combined with viscoelastic material, hill foam material and four pairs of reinforced fiber lamina, respectively. This FE model could be utilized in prediction of cervical spine fracture, ligament and disc tear underlying pediatric cervical injuries.
Finite Element Analysis of Fatigue Crack of Square Bird-Beak X-joints Under Brace Axial Loading
Authors: Adhikari P , Huang F , Cheng B
Published: July 2019

This paper presents a numerical study of the fatigue crack propagation of square bird-beak hollow section welded X-joints. A pair of axial forces were applied at the brace ends, while the chord ends were free. Finite element modelling was done in ABAQUS while FRANC3D was used for the computation of stress intensity factor and crack propagation. The initial crack inserted at the site of maximum stress concentration. Paris’ law was used to compute the fatigue life. The results obtained from the finite element analysis compared with the experimental data, and the predicted crack growth was found to be in good agreement with the test observations. For such joints, the surface cracks length vs. fatigue crack growth curve proposed to ensure practicability in real applications.
Response Surface Methodology for Optimization Studies of Microwave-assisted hydrodistillation of essential oil from Vietnamese Citrus aurantifolia (Lemon fruit)
Authors: Hien Tran Thien , Duc Lam Tri , Tien Nguyen Van , Phat Dao Tan , Hong Nhan Le Thi , Quoc Toan Tran , Vo Dai-Viet N. , Anh Vy Tran , Bui Le Minh
Published: July 2019

In this study, microwave-assisted hydrodistillation extraction technique was applied to extract the essential oil from Vietnamese Citrus aurantifolia (Lemon fruit). The optimal conditions for microwave-assisted extraction of lemon fruit oil was determined by response surface methodology. A central composite design (CCD) was used to estimate the effects of three independent variables plant material to extraction time (B: 30, 60, 90 min), microwave power (C: 300, 450, 600 W), and solvent ratio (A: 2, 3, 4 mL/g)., and on the extraction yield of Lemon fruit oil. The optimal extraction conditions of Citrus aurantifolia oil was plant material to solvent ratio 2.80 mL/g, extraction time 63.29 min and microwave power 477.82W. The maximum Lemon fruit oil yield was 2.427%. Under the extraction condition, the experimental values matched with the anticipated results by analysis of variance. It showed high fitness of the model used and the benefit of response surface methodology for optimizing and indicate the expected extraction condition.
Application of Box–Behnken design with Response Surface Methodology for Modeling and Optimizing Microwave-assisted Hydro-distillation of Essential Oil from Citrus reticulata Blanco Peel
Authors: Hien Tran Thien , Phat Dao Tan , Chinh Nguyen Duy , Duc Lam Tri , Trung Do Sy , Quoc Toan Tran , Thanh Huong Nguyen Thi , Vo Dai-Viet N. , Giang Bach Long , Duy Nguyen Trinh
Published: July 2019

In this research, microwave-assisted hydro-distillation and Response Surface Methodology were selected for optimizing factors affecting the yield of essential oil from Citrus reticulate Blanco peels. This combined process was successfully modeled and optimized using a Box–Behnken design with response surface methodology (RSM). The effects of the material and water ratios, extraction time and microwave power on the extraction essential oils, efficiency of Citrus reticulata Blanco Peel were investigated. The optimal conditions for the Citrus reticulate Blanco peels oils yield were found to be a material and water ratios were 3.1:1mL/g, extraction time was 91.24 min, microwave power at 478 (W). Furthermore, analysis of variance indicated that the proposed quadratic model successfully interpreted the experimental data with coefficients of determination of the predicted R2 of 0.9909 concurred with the adjusted R2 of 0.9826. A confirmation test of the optimal conditions verified the validity of the model, yielding an essential oil efficiency of 5.5
Preparation and High Temperature Tensile Mechanical Properties of Multilayer Metal Hot Forging Die Specimens
Authors: Wang Huajun , Gao Ye , Yao Liang , Qi Zhenzhen , Zhu Chundong , Liu Qingyang
Published: July 2019

The bonding strength of cladding is the key to the normal use of multilayer metal hot forging die. This paper presents a method of multilayer metal specimens prepared by PTAW. The specimens are selected H13 steel as the substrate, M2 steel as the transition layer, Ni60A alloy as the high temperature cladding, and the high temperature tensile test is performed on the Gleeble 3500 machine. The research results show that the substrate and cladding have good metallurgical bonding and the cladding hardness is higher than the substrate. Compared with H13 specimens, tensile strength of cladding metal specimens increase, elongation and yield strength decrease. All tensile fractures appeared on the H13 substrate during the experiment. It indicates that the cladding strength and bonding strength are higher than the substrate and the high temperature strength of cladding metal hot forging die is overall superior to H13 hot forging die.
Thermal and hydraulic performance of micro pin fin heat sinks with different pin fin shapes
Authors: Wang Peng , Chen Liang
Published: July 2019

Efficient cooling of high heat flux devices has promoted the development of micro pin fin heat sinks. In this study, four micro pin fin heat sinks (MPFHSs) with different pin fin shapes, i.e., circular, square and diamond and streamline ones are fabricated by laser micromilling methods. Their single-phase heat transfer and fluid flow performance are explored to assess the pin fin shape effect. Convective flow tests are conducted at Reynolds number of 150-750 at two heat fluxes using deionized water as the coolants. It was found that the streamline MPFHS presented the best heat transfer performance. On the contrary, the diamond fin pin heat sink presented the worst heat transfer performance, whereas it featured the smallest pressure drop among the four MPFHSs. The diamond micro pin fins showed the smallest thermal resistance at a certain pressure drop, and should be selected as the optimum one for the MPFHS applications when the overall thermal and hydraulic performance is considered.
Synthesized BiVO4 was by the co-precipitation method for Rhodamine B degradation under visible light
Authors: Duy Nguyen Trinh , Cao Vu Dai , Huu Nguyen Vinh , Xuan Nong Linh , Duy Luu Tuan , Vo Dai-Viet N. , Do Sy Trung , Duc Lam Tri
Published: July 2019

Recently, BiVO4 photocatalysts has been received much attention in field of catalysts. Because it can be used to degrade harmful organic catalysts in visible light, irradiation produces CO2, H2O and less harmful organic matter. In this study, we have successfully synthesized a BiVO4 photocatalysts via co-precipitation method in the presence of urea and different calcined temperatures. The survey calcined temperatures as 300°C; 350°C; 400°C and 450°C. The obtained materials were characterized by Scanning electron microscope (SEM) and X-ray diffraction (XRD). The photocatalytic activity was evaluated by the photocatalytic degradation of rhodamine B (RhB) degradation under visible compact Philip lamp (40W) light irradiation. The result indicates that all samples calcined are monoclinic scheelite structure of BiVO4. The BiVO4-350°C sample performed the best in the photodegradation of RhB.
Research Progress of Blade Coatings in Wwind Turbines
Authors: Tang Meiling , Huang Lizhe , Wang Jianyu , Guan Duojiao
Published: July 2019

With the expansion of wind turbine capacity, blade technology is evolving. Correspondingly, the preparation of the surface coatings of the blade should develop rapidly. Since most of the wind farms in China are built in deserts and oceans, the protection of the blades is particularly important. Blade coatings protect the blade’s normal operation and extend its service life. The work discussed the preparation materials for wind turbine blade coatings and the difficulties faced by the development of coatings in China.
Study on Base Resin of Fire-proof and Anticorrosive Steel Structure Coatings
Authors: Shi Jun , Yang Yuan quan
Published: July 2019

Study on the effect of waterborne epoxy resin on coating properties. The experimental results show that the basic and mechanical properties of the paint film will be enhanced with the appropriate increase of curing agent. When the amount of waterborne epoxy resin: curing agent = 1:1.25, the film performance is the best. When the curing agent content continues to increase, it will affect the performance of the coating; The amount of distilled water in waterborne epoxy resin also affects the performance of the paint film. When the amount of waterborne epoxy resin: distilled water consumption = 1:1.25, the film performance is the best, When the amount of distilled water continues to increase, the viscosity, impact strength and hardness of the paint film begin to decrease.
Analysis of the Correlation Degree between Safety Condition and Influencing Factors of Heavy Machinery
Authors: Luo Hongqi , Liu Xia
Published: July 2019

It is important to research the relationship of safety condition and its influencing factors in heavy machinery industry. The influence level of factors on the death toll in ten thousand special equipment is analysed, which includes the main business income of heavy machinery, standard quantity, operators of special equipment, number of safety supervision organization and accident frequency. The correlation degree between the accident frequency and the death toll in ten thousand special equipment is 0.699, while the correlation degree for standard number, special equipment operators and safety supervision organization is 0.540, 0.514 and 0.512, respectively. The accident frequency has the most significant impact on the death toll in ten thousand special equipment, followed by the standard number, special equipment operators and safety supervision organization, while the main business income has the least impact. It shows that promoting local legislation and standards are conducive to improving the safety condition of heavy machinery in China.
Development of solar-light-driven photocatalyst for energy and environmental application
Authors: Liu Na , Zhu Qi , Zhang Nan , Wang Jiayun , Yang Yingnan
Published: July 2019

Efficient utilization of solar energy could relieve many energy and environmental problems. Overall photocatalytic water-splitting using solar energy has received enormous attention for production of renewable hydrogen from water. Recently, a novel Ag3PO4 photocatalyst with band gap of 2.43 eV, possessing remarkable photocatalytic ability for organic dye degradation has been reported. In this work a highly efficient photocatalyst P/Ag/Ag2O/Ag3PO4/TiO2 has been synthesized and characterized by SEM, TEM, XRD, EDS, XPS, UV-vis and PL respectively. The results suggest that a highly efficient photocatalyst P/Ag/Ag2O/Ag3PO4/TiO2 has been synthesized successfully and performed strong absorption band in visible-light region, high separation efficiency of photo excited electron-hole pairs and small band gap (approximately 2.2 eV). On the other hand, Rodamine B (RhB) and methanol are representative organic compounds that can be used as sacrificial reagent for increasing water-splitting efficiency. For the purpose of identifying the possibility of generating oxygen and hydrogen by the as-prepared P/Ag/Ag2O/Ag3PO4/TiO2 under simulated solar irradiation, the accumulated amount of oxygen and hydrogen was evaluated. The results showed that the optimal conditions of water-splitting process by using the mixture of RhB and methanol under solar light is 20% of methanol, 1.0 ppm of RhB and 0.100 g/L of catalyst dosage. In summary, as-prepared P/Ag/Ag2O/Ag3PO4/TiO2 composite has the potential for environmental and energy application under solar light.
Influence of the Pressure of Open-Close Water-Cooled Moulds on Casting/Mould Interface Heat Transfer and Casting Solidification Process
Authors: Yao Q H , Zeng Y D , He L T , Zhang J
Published: July 2019

In this paper, the experimental model for a self-designed open-close water-cooled mould was utilized to measure the temperature curves of various points inside the casting and mould under different mould pressure. The Interface heat transfer coefficient(IHTC) of the casting/water-cooled mould interface was calculated by using the Beck nonlinear estimation back-calculation method, and on this basis, the rule of how pressure affects heat transfer coefficient was obtained. Then the coefficient can be defined as the boundary condition(BC) to simulate the solidification process of the experimental casting. The results showed that the simulation outcome considering the influence of pressure was completely different from those of general water-cooled moulds, which can be proved by the about 35% solidification time decrease, visibly reduced shrinkage porosity area in the casting and more accurate simulation results. The anatomical results of the experimental casting also confirmed this.
Preparation and characterization of high-strength low-thermal-conductivity cement-based insulation materials
Authors: Zhang X X , Wang Z P , She A M , Wei Y Q , Zhu Z Y
Published: July 2019

Thermal insulation materials with high strength and ultra-low thermal conductivity are ideal construction ones for residential infrastructure. However, high strength of materials regularly means high thermal conductivity. To solve this problem, a novel thermal insulation material was prepared by using cement as the binder, silica fume as the mineral admixture, aerogel as the coarse filler and hollow SiO2 microsphere as the fine filler. The optimal proportion and preparation process were investigated by means of the orthogonal experiment and the single factor experiment method, respectively. On the other hand, their microstructures, in terms of aerogel particle size distribution and multi-scale composite structure were analysed by optical microscope, binarization image, scanning electron microscope. The results indicated that compared to conventional insulation materials, the produced materials in this study behaved much better performance in strength. The dry density, compressive strength and thermal conductivity reached 360 kg/m3, 4.55 MPa and 0.055 W/m·K, respectively. The incorporation of hollow SiO2 microsphere and silica fume led to the much thicker pore walls of the sample, and simultaneously the prolonging of stirring time resulted in the much smaller size of aerogel, which were considered as the two primary causes of its excellent mechanical performance.
Analysis of the causes of tube blocking in Jingbian gas field
Authors: Ye Congdan , Gou Shunchao , Feng Yuhan , Niu Buneng , Ma Yun
Published: July 2019

A large number of blockage appeared in gas wells and pipeline appeared, which caused plugging, corrosion and the increasing of wellbore pressure difference, and seriously affect the normal production of gas well of problems. In this paper, the water quality over the years and natural gas production of the JB1# well in the Jingbian gas field were analyzed, also include the composition of blockage with the chemical volumetric method (CVM), X-Ray Diffraction (XRD) and x-ray fluorescence (XFS) method. Meanwhile, the blockage powder was leached in simulated acid work solution, and then the leaching solution was analyzed with CVM. The experimental results show that the produced water in the JB1# well has unstable water quality, high salinity, high Cl- content, and low pH value, high H2S and CO2 content in natural gas, so easy to produce corrosion and carbonate scaling. The main component of the blockage is a mixture of corrosion product Fe2O3 and a small amount of CaCO3 scale. The corrosion product Fe2O3 is mainly generated by the mixture of dissolved oxygen, H2S, CO2 and other corrosion effects. The main cause of blockage in the JB1# well is the deposition of Fe2O3 and CaCO3 scales caused by the corrosive effects of dissolved oxygen, H2S and CO2.
Ultrasonic Evaluation of Young’s Modulus for Reduction of Brake Squeal Noise
Authors: Kim N
Published: July 2019

Elastic properties of friction materials in brake linings are important design parameters because modulus variations may lead to noise generation of braking systems. This paper is to describe about ultrasonic estimation of Young’s modulus of brake linings concerned with squeal noise problem for commercial trucks. Phase velocity of ultrasound propagating through brake lining was measured to calculate Young’s modulus based on elastic relations of acoustic waves with material properties. Two kinds of brake lining samples were produced with the same composition by different manufacturing process, one of which is a traditional product and the other is an advanced one developed for brake noise reduction. Five rectangular samples were cut out from each type of brake linings and machined for ultrasonic test. Acoustic pulse of 500KHz was applied to each sample to calculate the time-of-flight(TOF) for the measurement of wave velocity and Young’s modulus. The results of ultrasonic test indicate that the low noise brake samples have a less deviation of Young’s modulus than the traditional brake samples. This agrees with previous researches and FEM analysis that Young’s modulus variation of brake linings affects the squeal propensity and the instability of brake system.
Mechanical Design of Service Robot for Shuttlecock Sports
Authors: Chunlai Tian , Musheng Shen , Yixian Wang , Wei Gao
Published: July 2019

Shuttlecock ball is a popular sport in modern society which including entertainment, skills, mass, fitness, popularity and education. The current status artificial ball picking during the training and sports of the shuttlecock sports was reviewed in this paper. Based on the main structure and working principle of the picking robot, it was designed and presented here. It is designed by the three-dimensional CAD software. Through motion simulation analysis, the actual working process of the shuttlecock collection robot was shown. The structure design and motion simulation analysis of the whole machine were carried out and it verified the feasibility of the design. The shuttlecock collection robot is used of retrieving, sorting and placing the shuttlecock. It could effectively solve the inconvenience cause by the manual collecting in shuttlecock ball sports.
Research on dynamic characteristic of connecting rod with joint clearance
Authors: Li Shihua , Xu Jilong , Zhao Jie
Published: July 2019

In order to study the dynamic characteristics of revolving joint with clearance, the theoretical model of the revolving joint with clearance is established by using Newton Euler method and “contact-separation” state model. The kinetic equations are solved by using the Gear algorithm in MATLAB software. The change curves of the contact force and the center trajectory of the revolving joint shaft with clearance are obtained considering different clearance, contact stiffness, and rotational speed together. The research results have laid a theoretical foundation for improving the joint forces and the accuracy by using controller.
Mechanism analysis of bubbling corrosion caused by boiler flue gas on metal material
Authors: Zhang B Q , Wang S Z , Yang J Q , Cui C C , Jiang Z H , Wang D , Li J N
Published: July 2019

Hydrogen bubbling is a typical corrosion morphology caused by hydrogen sulfide corrosion. In order to explore hydrogen sulfide corrosion of iron, the composition of flue gas under actual conditions was simulated in this research. Hydrogen sulfide corrosion in flue gas of four kinds of materials selection of ground process pipeline and underground pipe string was researched experimentally. The pressure and temperature of hydrogen bubbling corrosion morphology under actual flus gas conditions were obtained. The electrochemical corrosion mechanism between iron and hydrogen sulfide was investigated.
A generalization of the theorems of Chevalley-Warning and Ax-Katz via polynomial substitutions
Authors: Baoulina Ioulia , Bishnoi Anurag , Clark Pete
Published: July 2019

We give conditions under which the number of solutions of a system of polynomial equations over a finite field

F

q

\mathbb {F}_q

of characteristic 

p
p

is divisible by

p
p

. Our setup involves the substitution

t
i

↦
f
(

t
i

)

t_i \mapsto f(t_i)

for auxiliary polynomials

f
1

,
…
,

f
n

∈

F

q

[
t
]

f_1,\dots ,f_n \in \mathbb {F}_q[t]

. We recover as special cases results of Chevalley-Warning and Morlaye-Joly. Then we investigate higher

p
p

-adic divisibilities, proving a result that recovers the Ax-Katz theorem. We also consider

p
p

-weight degrees, recovering work of Moreno-Moreno, Moreno-Castro, and Castro-Castro-Velez.
Stereoelectroencephalography: retrospective analysis of 742 procedures in a single centre
Authors: Cardinale Francesco , Rizzi Michele , Vignati Elena , Cossu Massimo , Castana Laura , d’Orio Piergiorgio , Revay Martina , Costanza Martina Della , Tassi Laura , Mai Roberto , Sartori Ivana , Nobili Lino , Gozzo Francesca , Pelliccia Veronica , Mariani Valeria , Lo Russo Giorgio , Francione Stefano
Published: July 2019

This retrospective description of a surgical series is aimed at reporting on indications, methodology, results on seizures, outcome predictors and complications from a 20-year stereoelectroencephalography (SEEG) activity performed at a single epilepsy surgery centre. Prospectively collected data from a consecutive series of 742 SEEG procedures carried out on 713 patients were reviewed and described. Long-term seizure outcome of SEEG-guided resections was defined as a binomial variable: absence (ILAE classes 1–2) or recurrence (ILAE classes 3–6) of disabling seizures. Predictors of seizure outcome were analysed by preliminary uni/bivariate analyses followed by multivariate logistic regression. Furthermore, results on seizures of these subjects were compared with those obtained in 1128 patients operated on after only non-invasive evaluation. Survival analyses were also carried out, limited to patients with a minimum follow-up of 10 years. Resective surgery has been indicated for 570 patients (79.9%). Two-hundred and seventy-nine of 470 patients operated on (59.4%) were free of disabling seizures at least 2 years after resective surgery. Negative magnetic resonance and post-surgical lesion remnant were significant risk factors for seizure recurrence, while type II focal cortical dysplasia, balloon cells, glioneuronal tumours, hippocampal sclerosis, older age at epilepsy onset and periventricular nodular heterotopy were significantly associated with seizure freedom. Twenty-five of 153 patients who underwent radio-frequency thermal coagulation (16.3%) were optimal responders. Thirteen of 742 (1.8%) procedures were complicated by unexpected events, including three (0.4%) major complications and one fatality (0.1%). In conclusion, SEEG is a safe and efficient methodology for invasive definition of the epileptogenic zone in the most challenging patients. Despite the progressive increase of MRI-negative cases, the proportion of seizure-free patients did not decrease throughout the years.
The Long-Term Impact of Early Life Stress on Orbitofrontal Cortical Thickness
Authors: Monninger Maximilian , Kraaijenvanger Eline J , Pollok Tania M , Boecker-Schlier Regina , Jennen-Steinmetz Christine , Baumeister Sarah , Esser Günter , Schmidt Martin , Meyer-Lindenberg Andreas , Laucht Manfred , Brandeis Daniel , Banaschewski Tobias , Holz Nathalie E
Published: July 2019

Early adversity has been related to brain structure alterations and to an increased risk of psychiatric disorders. The orbitofrontal cortex (OFC) is a key region for emotional processing, with structural alterations being described in several mental disorders. However, little is known about how its cortical thickness (CT) is affected by the long-term impact of life stress (LS) at different developmental stages. The present study aimed to investigate the effect of LS during infancy, childhood, and adolescence on CT alterations in the OFC and on psychopathology in 190 adults of an ongoing prospective cohort study. Chronic stressful life events were assessed in regular intervals. Participants rated depressive symptoms at the ages of 22 and 23 years. Morphometric data were collected at the participants’ age of 25 years. Chronic LS during infancy was associated with reduced CT in the right OFC and increased depressive symptoms. Moreover, the impact of chronic LS during infancy on OFC thickness was partially mediated by depressive symptoms in adulthood, suggesting an interplay of early LS, psychopathology, and CT alterations. Our findings highlight the long-term impact of early LS on an affective core brain structure and psychopathology later in life.
Outcomes after surgery for functional tricuspid regurgitation: a systematic review and meta-analysis
Authors: Veen Kevin M , Etnel Jonathan R G , Quanjel Thijs J M , Mokhles Mostafa M , Huygens Simone A , Rasheed Moniba , Oei Frans B S , ten Cate Folkert J , Bogers Ad J J C , Takkenberg Johanna J M
Published: July 2019

Aims 

This study aims to provide a contemporary overview of outcomes after tricuspid valve (TV) surgery for functional tricuspid regurgitation (TR).

Methods and results 

The literature was systematically searched for papers published between January 2005 and December 2017 reporting on clinical/echocardiographic outcomes after TV surgery for functional TR. A random effects meta-analysis was conducted for outcome variables, and late outcomes are visualized by pooled Kaplan–Meier curves. Subgroup analyses were performed for studies with a within-study comparison of suture vs. ring repair and flexible vs. rigid ring repair. Eighty-seven publications were included, encompassing 13 184 patients (mean age: 62.1 ± 11.8 years, 55% females). A mitral valve procedure was performed in 92% of patients. Pooled mean follow-up was 4.0 ± 2.8 years. Pooled early mortality was 3.9% (95% CI: 3.2–4.6), and late mortality rate was 2.7%/year (95% CI: 2.0–3.5), of which approximately half was cardiac-related 1.2%/year (95% CI: 0.8–1.9). Pooled risk of early moderate-to-severe TR at discharge was 9.4% (95% CI: 7.0–12.1). Late moderate-to-severe TR rate after discharge was 1.9%/year (95% CI: 1.0–3.5). Late reintervention rate was 0.3%/year (95% CI: 0.2–0.4). Mortality and overall (early and late) TR rate were comparable between suture vs. ring annuloplasty (14 studies), whereas overall TR rate was higher after flexible ring vs. rigid ring annuloplasty (6 studies) (7.5%/year vs. 3.9%/year, P = 0.002).

Conclusion 

This study shows that patients undergoing surgery for functional tricuspid regurgitation (FTR) have an acceptable early and late mortality. However, TR remains prevalent after surgery. The results of this study can be used to inform patients and clinicians about the expected outcome after surgery for FTR and can results serve as a benchmark for the performance of emerging transcatheter TV interventions.
The Piranha Genome Provides Molecular Insight Associated to Its Unique Feeding Behavior
Authors: Schartl Manfred , Kneitz Susanne , Volkoff Helene , Adolfi Mateus , Schmidt Cornelia , Fischer Petra , Minx Patrick , Tomlinson Chad , Meyer Axel , Warren Wesley C
Published: July 2019

The piranha enjoys notoriety due to its infamous predatory behavior but much is still not understood about its evolutionary origins and the underlying molecular mechanisms for its unusual feeding biology. We sequenced and assembled the red-bellied piranha (Pygocentrus nattereri) genome to aid future phenotypic and genetic investigations. The assembled draft genome is similar to other related fishes in repeat composition and gene count. Our evaluation of genes under positive selection suggests candidates for adaptations of piranhas’ feeding behavior in neural functions, behavior, and regulation of energy metabolism. In the fasted brain, we find genes differentially expressed that are involved in lipid metabolism and appetite regulation as well as genes that may control the aggression/boldness behavior of hungry piranhas. Our first analysis of the piranha genome offers new insight and resources for the study of piranha biology and for feeding motivation and starvation in other organisms.
Analysis of geomagnetic secular variation for the last 1.5 Ma recorded by volcanic rocks of the Trans Mexican Volcanic Belt: new data from Sierra de Chichinautzin, Mexico
Authors: Rodríguez-Trejo A , Alva-Valdivia L M , Perrin M , Hervé G , López-Valdés N
Published: July 2019

The great wealth of volcanism along the Trans Mexican Volcanic Belt (TMVB) and the need to improve the secular variation curve of the Earth magnetic field of the region is the aim of this research. 300 oriented cores from 33 sites and 21 individual cooling units were acquired from Sierra de Chichinautzin volcanic field (ChVF) and Sierra de Santa Catarina (SSC). Directional analysis and rock magnetic experiments were performed (e.g. thermal demagnetization, hysteresis loop, susceptibility vs temperature), achieving 21 new averaged palaeomagnetic directions. New results are consistent with the previous studies on the same cooling unit. We compiled all the palaeomagnetic studies performed on the ChVF, updating age and calculating an average direction per cooling unit and estimating an overall mean direction for the ChVF (Dec = 359.1°, Inc = 35.3°, N = 33, k = 21.6, α95 = 5.5°, Plat = 87.7° N, Plong = 227.4° E, K = 31.8, A95 = 4.5°).

Afterwards, we compiled all the previous palaeomagnetic studies along the whole TMVB with age ranging from 0 to 1.5 Ma, and constrained the directional analyses by specific quality criteria such as well-defined age, number of samples and quality of kappa) on the cooling unit consistency.

The mean direction and virtual geomagnetic pole (VGP) estimated for the TMVB, during the periods 0–40 ka and 0–1.5 Ma, are close to the geographic pole, supporting the validity of the geocentric axial dipole hypothesis. The directional results of this study also fit well with the predictions at Mexico City of the models SHA.DIF.14k and CALS10k2 calculated for the last 14 ka. The dispersion of the VGP's on the TMVB are also consistent with the expected values proposed by different models of palaeosecular variation. However, large gaps in the temporal record remain that should be filled by further palaeomagnetic studies.