Papers by Keyword: Critical Condition

Abstract: Dynamic recrystallization behavior of Mg-8.0Gd-3.0Y-0.5Zr (wt.%) alloy and the critical conditions corresponding to the onset of dynamic recrystallization were investigated using uniaxial compression tests conducted at temperatures ranging from 350 °C to 500 °C and strain rates ranging from 0.001 s^-1 to 1 s^-1. Results show that increasing temperature and/or decreasing strain rate can enhance the process of dynamic recrystallization of Mg-8.0Gd-3.0Y-0.5Zr alloy and lower the peak stress and corresponding strain. However, decreasing temperature and/or increasing strain rate can promote the occurrence of twin dynamic recrystallization (TDRX) within the original grains at the cost of reducing the total volume fraction of dynamically recrystallized grains in the microstructure. Besides, the critical stress and strain corresponding to the onset of dynamic recrystallization of Mg-8.0Gd-3.0Y-0.5Zr at 400 °C and 0.1 s^-1 are 173MPa and 0.13, respectively.

Abstract: Based on the critical condition of fire liftoff about exhaust flow, the critical condition of fire liftoff caused by man-made interfering jet flow on the laminar flow condition was researched. The calculative formula for critical condition of fire liftoff caused by man-made interfering jet flow on the laminar flow condition was acquired. And the experiments were designed to validate the formula. The results show that the formula was accord with the experiments. It could be used for engineering application.

Abstract: This paper presents the global convergence theory of the discrete-time uniform pseudo projection anti-monotone network with the quasi–symmetric matrix, which removes the connection matrix constraints. The theory widens the range of applications of the discrete–time uniform pseudo projection anti–monotone network and is valid for many kinds of discrete recurrent neural network models.

Abstract: Due to the emergence of new asymmetric Water diversion and power generation system, the traditional computational formula for Thoma stable section area has been unable to meet the design requirement. The discriminant formula for stable section of surge tank is obtained in this paper by theoretical derivation. There is a great influence on the stable area of surge tank because of the head loss between surge tank and branch pipe. Based on the definition of k-degree symmetric diversion system, the critical condition of Water diversion and power generation system is obtained. The hydraulic parameters of k-degree symmetric Water diversion and power generation system can be optimized through the critical condition formula.

Abstract: In wet compression process water is injected at an inlet of compressor and continuous cooling occurs due to evaporation of water droplets during the compression process of air, which can save the compression work and enhance the performance of gas turbine system. In this work, performance analysis of the wet compression process is carried out under the critical conditions of water injection which are defined as the maximum water injection which can be evaporated completely inside the compressor. For various ambient conditions the important variables of wet compression process such as water injection ratio, temperature-averaged polytropic coefficient, compressor outlet temperature, and compression work are estimated under the critical injection conditions. Parametric studies show that compression work decreases with ambient temperature, however, the reduction ratio of compression work relative to dry increases with ambient temperature.

Abstract: A new approach to the consideration of the thermal explosion macrokinetic features for monomolecular reactions in homogeneous systems based on a strict accounting of burnout during the reaction process is proposed. It is established, that the qualitative changes of the phase trajectory structure (phase portrait) on the plane: heating rate-temperature determine the characteristic modes of reaction. This approach makes it possible to go beyond the Semenov theory and allows us to consider the variety of the reaction modes. From this point of view, the theory of Semenov is a special case which is valid only for reactions of zero order. The phase trajectories analyze on the parametrical plane Semenov criterion – Todes criterion gives an opportunity to define the regions of the thermal explosion degeneration, the transition regions and the region of the thermal explosion realization. With the use of such consideration, the necessary and sufficient conditions of the thermal explosion are found.

Abstract: As the deformation of chip increases with cutting speed, the morphology of chip changes from continuous to serrated type. It is supposed that serrated chips generate due to adiabatic shear instability in the primary deformation zone. A new analytical model for predicting adiabatic shear critical condition in orthogonal cutting is proposed by considering cutting conditions and properties of workpiece material. It is found that the influence of shear strain on the onset of adiabatic shear could be neglected. The shear strain rate and temperature, however, play a leading role on the onset of adiabatic shear. At lower cutting speed the shear strain rate plays a dominant role while at higher cutting speed the situation is just the reverse. With the increase of cutting speed, the yield stress, material characteristic constant and uncut chip thickness will facilitate adiabatic shear instability, while the coefficient of strain rate hardening, coefficient of strain hardening, coefficient of thermal softening, thermal diffusivity and tool rake angle have negative effect on adiabatic shear instability.

Abstract: The critical condition evaluation of BT mode is adopted to balance rights and benefits between government and investor. This paper aims to describe and analyze repurchasing radix design, yield design, and repurchasing mode design. Apply the fuzzy comprehensive evaluation to set the evaluation model, which includes 8 valuables factors reflected in the evaluation, and do the preliminary empirical research of the model and get the primary weighing of the 8 factors through the empirical research. By calculating and analyzing, the model truly reflects the interest relation between the government and the investor. Using this model, theoretical foundation to BT mode decision-negotiation is offered.

Abstract: It had been studied that thermal deformation properties of super-alloy Inconel690(IN690) by thermal simulation on Gleeble 3800 Simulator, which the ranges of temperature was 1000～1200°Cand strain rates was 1.0～80/s. According to the experiment data, the critical conditions of super-alloy Inconel690 had been researched by strain hardening rate. Zener-Hollomn parameters (Z) had been introduced into establish the critical conditions of dynamic recrystallization, such as critical strain and critical stress and peak strain. The results showed that the critical strain model which established using strain hardening rate was in good agreement with that of Sellar’s model.

Abstract: This paper carries out the research on the critical conditions of ferroelectric domain switch with different porosity and pressure. A micromechanics model is established with the influence of external electric field, stress load, domain wall energy and depolarization energy, etc. The results show that the domain switch critical dimension and nucleation energy decrease fastly in the initial stage and then decrease slowly as the reversed electric field evenly increases. The critical dimension and nucleation energy with different porosity and pressure are studied, too.