Growth and microstructure of AlN whiskers and dendrites

AlN whiskers or dendrites were synthesized with a sublimation-recrytallization method by using Al,AlN powders and some additives as raw materials.Whiskers with different sizes that featured high purity and good crystallinity were obtained by controlling temperature and gas supersaturation in the reaction container,The whiskers were described as long and straight single crystals of approximately 1-30 um in diameter by the centimeter range in length.However,AlN dendrites were about 1mm in diameter by 0.5cm in length,and showed an obviously preferential growth orientation.i.e.,perpendicular to [211] and [1011] planes.It is concluded that the whiskers or dendrites grow via the vapor-solid mechanism.     

Electronic Structures and Chemical Bonds of Cobaltite and Ni-Doped

The relation among electronic structure, chemical bond and thermoelectric property of Ca3 Co2 O6 and Ni-doped was studied by density function theory and discrete variation method（DFT-DVM）. The results indicate that the highest valence band（ HVB ）attd the lowest conduction band（ LCB ） are mainly attribuled to Co3d, Ni3d and O2p atomic orbitals. The property of a semiconductor is shown from the gap between HVB and LCB. The gap of Ni-doped one is less than that of Ca3 Co2 O6. The non-metal bond or ceramic characteristic of Ni-doped one is weaker than that of Ca3 Co2 O6, but the metal characteristics of Ni-doped one are stronger than those of Ca3 Co2 O6. The thermoelectric property should be improved by adding Ni element into the system of Ca3 Co2 O6 .     

Magnetic properties and XPS of Dy-Y and Dy-Nd alloys

The magnetic properties and X-ray photoelectron spectroscopy (XPS) spectra in the Dy100-xYx and Dy100-zNdz rare-earth alloys are studied.The magnetism measurements show that the dhcp crystal-field influence in the Dy-Nd alloys,which tends to destroy the orbital moment,does not vanish even though a field of 6T is applied.With increasing Y (or Nd) content the temperature region corresponding to helical phase becomes wider (or narrower).The XPS records suggest that the property of the valence fluctuation in neodymium tends to increase the Fermi wave vector kF of the Dy-Nd alloys.This testifies that the abrupt dropping of the Neel temperature,as Nd is introduced,is not only due to a dilution effect of Nd.The introduction of light rare earths into heavy ones is favorable for suppressing the helical phase in the alloys and overcoming the negative magnetocaloric effect.This result will play a guiding role in designing composite magnetic refrigeration working substances.     

Pattern Recognition and Forecast of Coal and Gas Outburst

Coal and gas outburst is a complicated dynamic phenomenon in coal mines, Multi-factor Pattern Recognition is based on the relevant data obtained from research achievements of Geo-dynamic Division, With the help of spatial data management, the Neuron Network and Cluster algorithm are applied to predict the danger probability of coal and gas outburst in each cell of coal mining district. So a coal-mining district can be divided into three areas： dangerous area, minatory area, and safe area. This achievement has been successfully applied for regional prediction of coal and gas outburst in Hualnan mining area in China.     

Synthesis of Ni-Zn ferfite and its microstructure and magnetic properties

Nanometer Ni0.5Zn0.5Fe2O4 powders with spinel phase were prepared by the hydrothermal method using purified FeSO4 solution from sodium jarosite＇s slag as materials. The results show that the spinel phase of Ni0.5Zn0.5Fe2O4 powders begins to form at a relatively low temperature （130 ℃） and a shorter holding time （1 h） when pH=8. The crystallization kinetics equation at 200℃ is ln[-ln（1-x）] =-0.78＋0.951n t. The growth activation energy of Ni0.5Zn0.5Fe2O4 grains is 41.6 kJ/moL in hydrothermal synthesis process. With the increase of sintering temperature, the density and diameter shrinkage of ferrite circulus increase, whereas its pores decrease. The results of magnetic measurements show that saturation magnetic flux density Bs increases and the coercivity Hc decreases with the increase of their sintering temperature. Magnetic parameters of all the investigated samples satisfy the character demand of high Bs, low Br and low Hc of soft magnetic ferrite materials.     

Geodynamical features and geotectonic evolution of Kalimantan and adjacent areas

Kalimantan Island is located in the Southeast Asia continental marginal tectono-magmatic mobile zone in the West Pacific Ocean, where the lithosphere of Earth is one of the most complicated tectonic mobile regions on the Earth since Meso-Cenozoic. Based on the geophysical data of the basement and deep structures, the stress field of mantle flow, the maximum principal stress field and geothermal flux, the crustal nature and geodynamical features of Kalimantan Island and adjacent areas were analyzed. Researches on geotectonic movement and evolution of Kalimantan and adjacent areas show that Southeast Asia continental margin crustobody was formed at about middle-late Triassic. In addition, the geotectonic units of the Kalimantan area were subdivided, and characteristics of their geotectonic evolution were discussed.     

Mechanical and Thermal Properties of Polysiloxanes and NBR Blend Elastomer

A series of elastomers , based on NBR , polysiloxanes （PS） were prepared and characterized by tensile tests, thermogravimetry （ TG ） and differential scanning calorimetry （ DSC ）. Two kinds of vulcanizing agent, DMDBH （2,5-dimethyl- 2,5-di （ t- butyl perory ） hexane ） and DCP （ dicumylperoxide ） were used to investigate the influence of different vulcanizing agents on properties of PS/ NBR. The addition of PS to NBR was found to improve the thermal stability and decrease the tensile strength of NBR. The tensile strength decreased conshterably while the elongation at break increased obviously with the increase of PS content. The series using DMDBH as vulcanizing agent showed a higher tensile strength and elongation at break than the series using DCP as vulcanizing agent. Simultaneity the thermal stability increased with the increase of PS content.     

Decomposition and reconstitution principle for complex surfaces and its applications

Though there are already a variety of models for complex surfaces, they are not so convenient as needed in practice. A hierarchical model and the principle of decomposition and reconstitution for complex surfaces have been proposed, which have the potential to enhance the support of automated design systems on creative work intelligently Then the progress made is discussed involving the applications of the new principle in the following three areas:conjugation surface calculation, tool path generation in numerically controlled machining, and machining process innovation by re-recognition     

Synthesis of Ni-Zn ferrite and its microstructure and magnetic properties

1 INTRODUCTION Ni-Zn ferrite with spinel structure is a versatile technological material due to their high-resistivity and low-eddy current losses, particularly suitable for high-frequency applications. Ni-Zn ferrites have been commercially used in recording heads, antennas rods, loading coils, microwave devices and telecommunication applications fields, and so on[1?2]. Ni-Zn ferrites are usually prepared by the conventional ceramic method[3] and the wet-chemical method[4?16]. The cerami…     

nstruction Science and TechnologyJ

my of Educational ScienceJournal of Tianjin Academy of Educational ScienceJournal of Tianjin Academy of Educational ScienceJournal of Tianjin Academy of Educational ScienceJournal of Tianjin Academy of Educational ScienceJournal of Tianjin Academy of Educational Science     

Preparation of High Impermeable and Crack-resistance Chemical Admixture and Its Mechanism

A kind of high impermeable and crack-resistance chemical admixture ( HICRCA ) was prepared, which is a compound chemical admixture composed of an expansion ingredient, density ingredient, and organic hydrophobic poreblocking ingredient. The results of the experiments indicate that the addition of HICRCA improves mortar and concrete in the following performances: ( 1 ) perfect workability: slump is more than 22cm, the slump after 3 h is about 16cm; (2) high impermeability.for the mortar, the pervious height under a water pressure of 1.5MPa is 1.5cm,for the concrete, the pervious height under a water pressure of 5.0MPa is 2.2cm; (3) high crack-resistance:there is a micro-expansion at the age of 9Od ; ( 4 ) high compressivestrength : compared with the controlled concrete, the compressive strengths at the age of 3d and 28d are improved by 66.4% and 62.0%, respectively. At the same time, the effects of different curing condigon on mortar and concrete expansive and shrinkage performance were studied. In addition, the impermeable and crack-resistance mechanism was investigated in the present paper.     

Comparison of Conventional and Microwave-assisted Synthesis and Characteristics of Aluminum-pillared Rectorite

The synthesis and characterization of aluminum-pillared rectorite were studied. The synthesis was conducted with both conventional heating and microwave irradiation. Microwave irradiation was found to enhanee the intercalation and ion-exchange during synthesis, and to be able to produce the rectorite with a larger d001 aad a better uniformity. The specific surface area is 180 m^2 / g and basal spacing is 3.2 nm.The texture change and thermal and hydrothermal stability of cross- linked rectorite were examined using XRD, FTIR, nitrogen-adsorption and TGA. The experimental results show that the aluminum-pillared rectorite, after calcined at 800℃ for 3 hours, can keep the basal aluminum-silicate texture and would not disperse in water at room or an elevated temperature. The alumimum-pillared rectorite shows a high specific surface area, good thermal and hydrothermal stability, and is promising in applications as catalyst carriers and adsorbents for waste treatment.     

Thermal Decomposition Behavior and Kinetics of Composites from Coal and Polyethylene

A thermogravimetric analysis （TG） was conducted to study the thermal decomposition behavior and kinetics of composites from coal and high density polyethylene （HDPE）, linear low density polyethylene （LLDPE） or low density polyethylene （LDPE）. The results show that coal facilitates melting of the polyethylene before temperatures reach 700 K in nitrogen due to the exothermic effect of coal. Above 700 K, adding coal into the polyethylene will result in smaller maximum rates of mass loss and higher initial mass loss temperatures of the composites. Hence, some chemical interactions, occurring between liquid compounds released in the pyrolysis of the coal and polymer, depend on several factors, such as coal rank and the molecular structure of polymers. Synergetic effects in coal and polymers were also found. Both chemical interactions and synergetic effects control the entire thermal decomposition behavior of composites. The larger the amount of coal in the composites, the greater the decomposition temperature spans and the higher the maximum decomposition temperature, the smaller the devolatilization rates. The effect of coal on the thermal stability of composites lies in the hydrogen acceptor effect of the coals. Thermal decomposition of the coals, the polymers and related composites can be modelled via first order parallel reactions between 563 K and 763 K.     

Source Rock Classification and the Basic Structare of Coal and Kerogen

In accordance with the confusion on classification of source rocks, the authors raised a source rock classification for its enriched and dispersed organic matter types based on both Aipern‘s idea^[1] and maceral genesis/composition. The determined rock type is roughly similar to paiynofacies of Combaz^[2], whereas it is “rockmaceral facies (for coal viz. coal facies)“ in strictly speaking. Therefore, it is necessary to use the organic ingredients classification proposed by the authors so that it can be used for both maceral analysis and environment research^[3]. This source rock classification not only shows sedimentology and diagenetic changes but also acquires organic matter type even if hydrocarbon potential derived from maceral‘s geochemical parameters. So, it is considered as genetic classification. The “rock-maceral facies“ may be transformed to sedimentary organic facies^[3], which is used as quantitative evaluation means if research being perfect. Now, there are many models in terms of structure either for coal or for kerogen. In our opinion, .whatever coal or kerogen ought be polymer,then we follow Combaz‘s thought^[2] and study structure of amorphous kerogens which are accordance with genetic mechanism showing biochemical and geochemical process perfectly, Here. we use the time-of-flight secondary ion mass spectrometry (TOFSIMS) to expand Combaz‘s models from three to five, They are also models for coal.     

Asking and Giving Clarification

In a conversation,the speaker may sometimes not give you enoughexact information.To get additional and detailed information,you maywant to ask him or her to clarify what has been said.1.Sorry,I’m not quite clear about what you meant by UFO.2.Um…um…um…I don’t quite understand what you meant byUFO.     

Optimization principle of combined surface and underground mining and its applications

The pit limit optimization is discussed, which is one of the most important problems in the combined mining method, on the basis of the economic model of ore-blocks. A new principle of the limit optimization is put forward through analyzing the limitations of moving cone method under such conditions. With a view to recovering as much mineral resource as possible and making the maximum profit from the whole deposit, the new principle is to maximize the sum of gain from both open-pit and underground mining. The mathematical models along the horizontal and vertical directions and modules for software package (DM&MCAD) have been developed and tested in Tonglushan Copper Mine. It has been proved to be rather effective in the mining practice.     

Analysis of Physical and Chemical Characteristics and Influence Factors of UCG

Based on the UCG (underground coal gasification) theory, the “three zones“ which are oxidization zone,reduction zone, and drying zone, were divided; physical and chemical properties of each zone were analyzed. Factors, such as temperature, rate of water pouring, quanzity of air blast, thickness of coal seam, and the operation pressure were discussed. Among the influencing factors, the temperature is the most important one.     

Chemisorption-facilitated dislocation emission and motion, and induced nucleation of brittle nanocrack

Using a special TEM constant deflection device, the change in dislocation configuration ahead of a loaded crack tip before and after adsorption of Hg atoms and the initiation of liquid metal-induced nanocracks (LMIC) have been observed. The results show that chemisorption of Hg atoms can facilitate dislocation emission, multiplication and motion. Nanocracks will be initiated in the dislocation-free zone (DFZ) or at the crack tip when chemisorption-facilitated dislocation emission, multiplication and motion reach a critical condition. On the basis of the available experimental evidence concerning liquid metal embnttlement (LME), a new mechanism for this phenomenon is considered. This involves the fact that the decrease in surface energy induced by chemisorption of Hg atoms results in a reduction in the critical stress intensity factors for dislocation emission and the resistance for dislocation motion. On the other hand, the plastic work and KIC will decrease with the decrease in the surface energy.     

Review:Mg and Its Alloy——Scope, Future Perspectives and Recent Advancements in Welding and Processing

镁/镁合金焊接与加工的最新进展与未来展望

Sachin Kumar,武传松

（山东大学 材料科学与工程学院,济南 250061）

中文说明：

该文非常详细地综述了镁及镁合金的生产、加工及焊接的研究现状。尤其是在镁合金焊接部分,作者比较详细地阐述了熔化焊、激光焊、固相焊及钎焊等方法在镁合金焊接中的研究现状、存在问题与发展动向。该文对于镁合金焊接研究人员具有重要的参考价值。

关键词：镁;镁合金;加工;焊接;连接;最新进展

     

The Perfect Recursive Least Square Algorithm and Applications to Tracking and Prediction

Based on the theory of generalized inverse, the perfect recursive least square (PRLS) algorithms for the cases of general weighted, optimal weighted and exponetial weighted are derived in this paper. The PRLS algorithms give the least square estimal (LSE) without the requrirnent of a priori statistical knowledge of the initial state to be estimated. Further, with the FRLS algorithms, we provide the deadbeat and unbiased state estimators for some linear systems, and present the multimodel tracking and prediction (MMTP) algorithms for maneuvering targets