Effects of Spherical Aggregates Addition on Properties of Al2O3-SiO2 System Castables

Compared with traditional aggregates,spherical aggregates with high flowability,easy control of particle size distribution and favor of dense packing and so on,are expected to replace traditional aggregates as important raw materials for future high performance refractories. Therefore,investigation of effects of spherical aggregates addition on properties of refractories becomes very meaningful. Using A70 mullite traditional aggregates and A70 mullite spherical aggregates, bauxite homogenization powder,microsilica,and calcium aluminate cement as raw materials,different AlO-SiOsystem low cement castables were prepared by replacing conventional aggregates with spherical aggregates. The effect of spherical aggregates addition on workability and mechanical properties of castables after heated at different temperatures was researched,and microstructure of the specimen was analyzed by SEM. Compared with traditional irregularly shaped aggregates,spherical aggregates endow castables with better flowability and easy pump ability. By introduction of spherical aggregates into the castables,flowability and pumpability are significantly improved,and water addition and ball completely sunk time are reduced. The introduction of spherical aggregates is favorable to density and cold crushing strength of castables,but unfavorable to CMOR. The effect of spherical aggregates addition on HMOR at1 400 ℃ can be negligible. Microstructure analysis showsthat the boundary bonding between spherical aggregates and matrix is strong,similar to the traditional aggregates.

Obstacle avoidance method of three-dimensional obstacle spherical cap

Focusing on obstacle avoidance in three-dimensional space for unmanned aerial vehicle(UAV), the direct obstacle avoidance method in dynamic space based on three-dimensional velocity obstacle spherical cap is proposed, which quantifies the influence of threatening obstacles through velocity obstacle spherical cap parameters. In addition, the obstacle avoidance schemes of any point on the critical curve during the multi-obstacles avoidance are given. Through prediction, the insertion point for the obstacle avoidance can be obtained and the flight path can be replanned. Taking the Pythagorean Hodograph(PH) curve trajectory re-planning as an example, the three-dimensional direct obstacle avoidance method in dynamic space is tested. Simulation results show that the proposed method can realize the online obstacle avoidance trajectory re-planning, which increases the flexibility of obstacle avoidance greatly.

Synthesis of Lightweight Spherical Forsterite Aggregates and Research on Their Application in Mgo Based Castables

Magnesite fine powder, natural silica powder,light-burned magnesia fine powder, silica fume and middle grade magnesia fine powder were used as the starting materials,and silica sol as binder to get high purity lightweight spherical forsterite aggregates. The mixture was granulated on a disc pelletizer and then calcined at 1 400 ℃ for 3h. The synthesized spherical forsterite aggregates were added in Mg O based castables with MgO-SiO2-H2O binding system to replace equaldensity high purity common forsterite aggregates. Effect of spherical forsterite aggregates addition on properties of MgO based castables was investigated. The results show that: compared with common aggregates,lightweight spherical forsterite aggregates can improve castables ’flow ability and decrease water addition; addition of spherical aggregates has little effect on cold strength of castables; with the increase of spherical aggregate addition,shrinkage of specimens after drying and heating at intermediate temperatures decreases,but the expansion of specimens after heating at high temperatures increases,bulk density decreases and apparent porosity increases,and thermal conductivity declines.

Influence of Kyanite Content on Microstructures and Properties of Castables Containing Spherical Lightweight Mullite Aggregates

Five lightweight mullite castables were prepared using the lightweight mullite aggregate（M45A） with narrow particle size distribution and spherical shape,mullite powder（M45P）,kyanite powder,microsilica and Secar 71 cement as raw materials. After the specimens fired at 1100 ℃,1200 ℃ and 1300 ℃ for 3h,respectively,the effects of kyanite contents（ 8%,10%,12%,14%,16% by mass） on the physical properties,phase composition and microstructures were investigated through an X-ray diffractometer（ XRD）,a scanning election microscopy（ SEM） and a microscopy measurement method,etc. The results show that,for the specimens fired at 1300 ℃ with the kyanite content from 8%to16%, the bulk densities and apparent porosities change little,but the cold modulus of rupture and the crushing strengths decrease significantly,and the linear change rates increase from-0.87% to 0.64%. The most apposite mode is the specimen containing 12% kyanite fired at 1300 ℃, which has a high crushing strength of 29.3 MPa,a low linear change of 0.18%,an apparent porosity of 36.8% and a bulk density of 1.73 g/cm^3.

Effects of Spherical Light-weight Aggregates Additions on Workability and Mechanical Properties of Al_2O_3-SiO_2 System Castables

In order to clarify the effect of spherical light-weight aggregates addition on properties of A12 07 - Si02 system castables, adopting ATO mullite traditional light-weight aggregates and ATO mullite spherical light-weight aggre- gates, bauxite homogenization powder, microsilica , cal- cium aluminate cement as main raw materials, light- weight Al2 03 - SiO2 system castables were prepared by replacing conventional light-weight aggregate with spherical light-weight aggregates. The effects of spheri- cal light-weight aggregates addition on workability, me- chanical properties of castables after heated at different temperatures were researched; the microstructure of the aggregates was analyzed by SEM. The result shows that the introduction of spherical light-weight aggregates can significantly improve the flowability and reduce the water addition of the castables. Water demand of the castable is reduced from 18% with the conventional light-weight aggregates to 14% with spherical light-weight aggre- gates. In addition, light-weight castables prepared by spherical aggregates can keep the same workability with- in a wider range of water addition. Therefore, spherical aggregates are user-friendly. The introduction of spheri- cal light-weight aggregates is favorable to packing densi- ty and mechanical properties of castables, such as cold crushing strength, cold modulus of rupture, hot modulus of rupture at 1 200℃.

Properties of Castables Made of Spherical Lightweight Mullite Aggregates

The castables were prepared from spherical lightweight mullite aggregates,bauxite,SiO2 fine powder,α-Al2O3 fine powder and calcium aluminate cement.The performance changes of the castables were studied after heat treatment at 110℃for 24 h,1100℃for 3 h,1200℃for 3 h and 1300℃for 3 h.The results illustrate that the cold modulus of rupture and hot modulus of rupture of the castable increase with the rising heat treatment temperature.The cold crushing strength shows a“V”change trend when the heat treatment temperature rises from 1100 to 1300℃.After the specimen is heat treated at 1300℃,the thermal conductivity is 0.500 W·m-1·K-1,0.586 W·m-1·K-1,0.595 W·m-1·K-1 at 300,600 and 900℃,respectively.The SEM analysis explains the change trends of these properties.The prepared lightweight mullite castables can be applied as the working lining of hot-blast furnaces.

Generation of a novel spherical chaotic attractor from a new three-dimensional system

A new three-dimensional （3D） system is constructed and a novel spherical chaotic attractor is generated from the system. Basic dynamical behaviors of the chaotic system are investigated respectively. Novel spherical chaotic attractors can be generated from the system within a wide range of parameter values. The shapes of spherical chaotic attractors can be impacted by the variation of parameters. Finally, a simpler 3D system and a more complex 3D system with the same capability of generating spherical chaotic attractors are put forward respectively.

Using three-dimensional discrete spherical Fourier descriptors based on surface curvature voxels for pollen particle recognition

This paper presents a new method for extract three-dimensional （3D） discrete spherical Fourier descriptors based on surface curvature voxels for pollen particle recognition. In order to reduce the high amount of pollen information and noise disturbance, the geometric normalized curvature voxels with the principal curvedness are first extracted to represent the intrinsic pollen volumetric data. Then the curvature voxels are decomposed into radial and angular components with spherical harmonic transform in spherical coordinates. Finally the 3D discrete Fourier transform is applied to the decomposed curvature voxels to obtain the 3D spherical Fourier descriptors for pollen recognition. Experimental results show that the presented descriptors are invariant to different pollen particle geometric transformations, such as pose change and spatial rotation, and can obtain high recognition accuracy and speed simultaneously.

Apparent Accelerated Expansion of the Three-Dimensional Spherical Universe Observed during Its Contraction Phase

In recent years, it has been thought that the expansion of the universe has begun to accelerate. However, there are other views against this. Here we propose a new theory based on the three-dimensional spherical (S3) universe wherein the same observations as the present universe can also be found by the accelerated contraction of the universe. According to our theory, the expansion velocity of the S3 universe slowed down after the Big Bang, and all the kinetic energy was converted into potential energy to reach the great sphere. After that, accelerated contraction begins, and the universe finally converges to an original single point. In the S3 universe, the passage of time (referred to as “proper time”) changes depending on its expansion velocity. The frequency of light emitted from celestial bodies is determined by their proper time on emission, and when the light is observed by observers having different proper time, a redshift or blueshift is observed. Observers in the expansion phase observe redshifts, because the proper time of the observer progresses faster than that of emitted light, but observers in the contraction phase observe an accelerated delay of the proper time, so the progress of the proper time is reversed based upon its order from nearby celestial bodies, a blueshift is observed, and its range of observable distance increases. The results of this early contraction phase are consistent with the observations of the current universe. In conclusion, the S3 universe may be able to explain the geometrical structure of the current universe.

Implementation of a particle-in-cell method for the energy solver in 3D spherical geodynamic modeling

The thermal evolution of the Earth’s interior and its dynamic effects are the focus of Earth sciences.However,the commonly adopted grid-based temperature solver is usually prone to numerical oscillations,especially in the presence of sharp thermal gradients,such as when modeling subducting slabs and rising plumes.This phenomenon prohibits the correct representation of thermal evolution and may cause incorrect implications of geodynamic processes.After examining several approaches for removing these numerical oscillations,we show that the Lagrangian method provides an ideal way to solve this problem.In this study,we propose a particle-in-cell method as a strategy for improving the solution to the energy equation and demonstrate its effectiveness in both one-dimensional and three-dimensional thermal problems,as well as in a global spherical simulation with data assimilation.We have implemented this method in the open-source finite-element code CitcomS,which features a spherical coordinate system,distributed memory parallel computing,and data assimilation algorithms.

Micromorphological characterization and random reconstruction of 3D particles based on spherical harmonic analysis

The microscopic characteristics of skeletal particles in rock and soil media have important effects on macroscopic mechanical properties. A mathematical procedure called spherical harmonic function analysis was here developed to characterize micromorphology of particles and determine the meso effects in a discrete manner. This method has strong mathematical properties with respect to orthogonality and rotating invariance. It was used here to characterize and reconstruct particle micromorphology in three-dimensional space. The applicability and accuracy of the method were assessed through comparison of basic geometric properties such as volume and surface area. The results show that the micromorphological characteristics of reproduced particles become more and more readily distinguishable as the reproduced order number of spherical harmonic function increases, and the error can be brought below 5% when the order number reaches 10. This level of precision is sharp enough to distinguish the characteristics of real particles. Reconstructed particles of the same size but different reconstructed orders were used to form cylindrical samples, and the stress-strain curves of these samples filled with different-order particles which have their mutual morphological features were compared using PFC3D. Results show that the higher the spherical harmonic order of reconstructed particles, the lower the initial compression modulus and the larger the strain at peak intensity. However, peak strength shows only a random relationship to spherical harmonic order. Microstructure reconstruction was here shown to be an efficient means of numerically simulating of multi-scale rock and soil media and studying the mechanical properties of soil samples.

Spherical Linear Diophantine Fuzzy Sets with Modeling Uncertainties in MCDM

The existing concepts of picture fuzzy sets(PFS),spherical fuzzy sets(SFSs),T-spherical fuzzy sets(T-SFSs)and neutrosophic sets(NSs)have numerous applications in decision-making problems,but they have various strict limitations for their satisfaction,dissatisfaction,abstain or refusal grades.To relax these strict constraints,we introduce the concept of spherical linearDiophantine fuzzy sets(SLDFSs)with the inclusion of reference or control parameters.A SLDFSwith parameterizations process is very helpful formodeling uncertainties in themulti-criteria decisionmaking(MCDM)process.SLDFSs can classify a physical systemwith the help of reference parameters.We discuss various real-life applications of SLDFSs towards digital image processing,network systems,vote casting,electrical engineering,medication,and selection of optimal choice.We show some drawbacks of operations of picture fuzzy sets and their corresponding aggregation operators.Some new operations on picture fuzzy sets are also introduced.Some fundamental operations on SLDFSs and different types of score functions of spherical linear Diophantine fuzzy numbers(SLDFNs)are proposed.New aggregation operators named spherical linear Diophantine fuzzy weighted geometric aggregation(SLDFWGA)and spherical linear Diophantine fuzzy weighted average aggregation(SLDFWAA)operators are developed for a robust MCDM approach.An application of the proposed methodology with SLDF information is illustrated.The comparison analysis of the final ranking is also given to demonstrate the validity,feasibility,and efficiency of the proposed MCDM approach.

A new measuring method for maximal length, width and thickness dimensions of coarse aggregates

In order to establish a new method for measuring the dimensions of coarse aggregates, five different-size flat and elongated (F&E) coarse aggregates were glued into two specimens by epoxy resin, respectively, and slice images were obtained by X-ray CT, then the aggregates were extracted by the fuzzy c-means clustering algorithm. Attributions of the particle on different cross-sections were determined by the ‘overlap area method’. And unified three-dimensional Cartesian coordinate system was established based on continuous slice images. The coefficient values of spherical harmonics descriptor representing particles surface profile were gained, then each scanned particle was represented by 60×120 discrete points conformably with spherical harmonics descriptor. The chord length and direction angles were determined by the calculation. With the major axis (L) and orthogonal axis (W and T), the calculated results were compared with those measured by caliper. It is concluded that the new L, W, and T dimension measuring method is able to take the place of the present manual measurement.

IMAGING OF EEG BY SPHERICAL HARMONIC ANALYSIS

A new three dimensional imaging method for electroencephalogram(EEG) is suggested. It consists of the solution of an inward spherical harmonic continuation. The principle of the new method is introduced in Section II, then a few numerical simulation tests are shown and the feasibility of the new method is confirmed by the simulation results.

An improved three-dimensional spherical DDA model for simulating rock failure

In this paper, a discontinuous numerical model, namely SDDARF3D(three-dimensional spherical discontinuous deformation analysis for rock failure), is proposed for simulating the whole process of rock failure. Firstly, within the framework of the classical discontinuous deformation analysis(DDA) method, the formulation of three-dimensional spherical DDA(3D SDDA) is deduced; secondly, a bonding and cracking algorithm is constructed and the SDDARF3 D model is proposed; thirdly, corresponding VC++ calculation code is developed and some verification examples are calculated. The simulated results can intuitively reproduce the failure phenomena of rock mass, indicating that the proposed SDDARF3 D numerical model is correct and effective.

A Fuzzy PID Algorithm for a Novel Miniature Spherical Robots with Three-dimensional Underwater Motion Control

We proposed and developed a small bionic amphibious spherical robot system for tasks such as coastal environment monitoring and offshore autonomous search and rescue.Our third-generation bionic small amphibious spherical robots have many disadvantages,such as the lack of maneuverability and a small operating range.It is difficult to accomplish underwater autonomous motion control with these robots.Therefore,we proposed a fourth-generation amphibious spherical robot.However,the amphibious spherical robot developed in this project has a small and compact design,with limited sensors and external sensing options.This means that the robot has weak external information collection capabilities.We need to make the real time operation of the robot's underwater motion control system more reliable.In this paper,we mainly used a fuzzy Proportional-Integral-Derivative(PID)control algorithm to design an underwater motion control system for a novel robot.Moreover,we compared PID with fuzzy PID control methods by carrying out experiments on heading and turning bow motions to verify that the fuzzy PID is more robust and exhibits good dynamic performance.We also carried out experiments on the three-dimensional(3D)motion control to validate the design of the underwater motion control system.

Bounding box extraction from spherical hologram of elementary object to synthesize hologram of arbitrary three-dimensional scene with occlusion consideration(Invited Paper)

A novel method to extract a bounding box that contains the three-dimensional object from its spherical hologram is proposed. The proposed method uses the windowed Fourier transform to obtain the angular distribution of the quasi-collimated beams at each position in the spherical hologram and estimates the bounding box by accumulating the quasi-collimated beams in the volume inside the spherical hologram. The estimated bounding box is then used to realize occlusion effect between the objects in the synthesis of the three-dimensional scene hologram.

基于3D激光扫描技术的粗集料三维形态特征分析

为了能够建立精确的沥青混合料细观力学模型、优化混合料性能,需要先构建具有真实形态学特征的集料模型并计算分析集料形态参数,利用3D激光扫描技术采集了辉绿岩、石灰岩、玄武岩与卵石4种集料共500颗样本的三维点云数据,通过球谐函数简化集料模型,建立了三维集料样本库。归纳总结了现有集料的形态指标,通过皮尔逊相关性分析,选取F_(I)、A_(I)定量表征粗集料三维形态特征,对不同种类以及粒径集料的F_(I)、A_(I)进行统计分析。研究结果显示:当球谐序列阶数为10,三角形映射网格数为643时,简化后集料模型基本形状、体积与表面积均与真实集料非常接近;集料的F_(I)、A_(I)服从正态分布与对数正态分布,且随集料类型和粒径的变化而变化。

基于球谐函数的三维集料简化与重构方法

建立高效的三维集料重构方法是开展沥青混合料虚拟实验的必要前提。利用3D激光扫描仪采集500颗集料的点云数据,经正二十面体剖分简化后通过球谐函数表征其三维形态。分析集料的体积、表面积、形状指数FI、棱角性指数AI随点云数量与球谐阶数的变化规律,确定点云的简化标准。计算简化集料10阶球谐系数,得到121个球谐系数的累积分布曲线,根据分布特性采用Monte Carlo方法随机生成1 400组球谐系数,实现集料的几何重构,对比真实集料与虚拟集料AI、FI的分布特性,验证重构方法的有效性。结果表明:可采用642个数据点与10阶球谐函数实现集料的有效简化;虚拟集料的FIv、AIv分布范围均可包含真实集料的参数值。研究成果可以为沥青混合料的细观模型构建提供基础。

天然彩色盐制备方法的研究

文章介绍了一种具有球状结构的天然彩色盐及其喷雾制备方法,按重量百分计,所述彩色盐的主体成分氯化钠含量为80%~95%、彩色果蔬营养物质含量为5%~20%。文章所述方法获得彩色盐为球状团聚体,颗粒表面致密,彩色物质均匀分布、色泽稳定。该方法制备的产品颗粒超细,粒度分布均匀,平均粒径小,球形度高,流动性好,具有较好的抗结块性,该制备工艺简单、易于工业化生产。