The morphology and crystallographic orientation of (a_2+γ) lamellar structure in duplex Ti--47.5Al--2.5V intermetallic compound have been studied by means of TEM,microdiffraction as well as 180°and non--180° rotation twinning analysis. A possible atomic model of the interface was suggested. Thus, approach was made to a mechanism on complex nucleation of α_2+γ two phases along α--Ti interface, and growth of α_2/γ/γ_t/α_2 or α_2/γ/α_2/γ as fundamental structural unit.
Abstract The surface electric field strength directly affects the accuracy of voltage measurement in DC voltage ratio standard devices. The auxiliary device known as the voltage regulation ring effectively reduces the surface electric field strength. Therefore, optimizing the voltage regulation ring’s structural characteristics is crucial for decreasing the electric field strength and enhancing the device’s accuracy. This study initially develops a functional engineering simulation model for the device that standardizes the ratio of DC voltages, employing finite element simulation software. Adjustments are made within a feasible range to compute the electric field strength along the surface of the voltage regulation ring, constructing a dataset. Subsequently, an FCC neural network model is constructed to capture the correlation between different parameters of the voltage regulation ring and the maximum surface electric field strength, yielding a relationship model. Finally, the design of the voltage regulation ring is optimized within a finite range using the constructed FCC neural network model to obtain parameters for minimum field strength. Experimental results indicate that under optimal conditions, the minimum electric field strength is 10051.4883 V/cm, effectively reducing the surface electric field strength of the DCVRS device, and provide a reliable and useful design methodology for equipment selection.
The structural and magnetic properties of MnBn clusters (n=1-7) have been investigated by using the generalized gradient approximation (GGA) in density functional theory. It was found that the ground state structures of Bn clusters aren’t modified by the encapsulation of the Mn atom in the MnBn (n4) clusters. However, starting from n ≥4, the strucutres of the host Bn clusters are changed due to the doping of the Mn atom, and the 3-D configurations become the ground state structures for MnBn clusters ( n ≥4). Comparison in the averaged binding energy of pure boron clusters and MnBn clusters revealed that dopant of the Mn atom somewhat reduces the stability of the MnBn clusters. The calculated results on the vertical ionization potentials and the fragmention energies indicated that the MnB2 and MnB6 clusters are more stable than their neighbors. The magnetic moment of the MnB5 is the biggest among all of the MnBn clusters. The total magnetic moment of MnBn (n=5 and 7) clusters is mainly provided by the Mn atom. Except for n=3 and 5, the magnetic moment of clusters not only attributes to Mn but also B atom. Mulliken population analysis result showed that the magnetic moment of MnBn clusters mainly comes from the localized d electron, due to its asymmetric densities of d orbital states.
Aggregates are granular materials used either as underlying materials for foundations and pavements or as skeleton structure and filling in Portland cement concrete and asphalt mixture. The physical properties, mechanical properties and gradation of aggregates have significant impacts on the performance of infrastructure. This chapter introduces the production, physical properties, mechanical properties and gradations of aggregates. The physical properties of aggregates include different densities, unit weight, void ratio, angularity, and fractured faces. The mechanical properties of coarse aggregates include crushing value, impact value, polished stone value, abrasion value, and soundness. The properties of fine aggregates mainly include different densities, unit weight, void ratio, angularity, fineness modulus and sand equivalency. By the end of the chapter, the sieve analysis, graduation curves, gradation theory and gradation designs methods are introduced.
Inorganic binding materials in civil engineering mainly include lime and Portland cement. They can be mixed with water to form pastes and then harden to obtain strength. This chapter starts by introducing the production, slaking, hardening, and properties of lime. It then introduces the production, hydration, properties, corrosion and supplementary materials of Portland cement. The hydration of cement including hydration products, hydration process and factors influencing hydration are discussed in detail. It then discusses the properties of cement including density, fineness, consistency, setting time, soundness, strength, hydration heat and voids. Different types of corrosions of cement including soft water corrosion, sulfate attack, magnesium corrosion, carbonation, and acid corrosion are also introduced. By the end of the chapter, the supplementary materials and properties of blended cement are discussed.
The experiential study has researched the question how blasting cone and the improvement of throwing crest change when concentrated charge has been prolonged to linear charge, and whether the theory of the concentrated charge can be used to replace the blasting crater design of linear charge and the parameter of blastiing cone and empitical method can be used in the designing work.
Virtual reality technology(VRT) is one which can produce a interchangeable,threedimensional environment system aided by computer graphics system,interface equipments to display and control synthetically.In this paper,the difinition,components,prospect of development and applications of VRT in mechanical engineering field are introduced.
The essay compares the cultural essence of the monotheism and polytheism,and analyzes the different influence of Monotheism and Poly theism upon religious culture and secular culture.
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