Electrochemical intercalation in NiOx thin films

In this work we investigated the mechanism of the electrochemical intercalation reactions in rf sputtered nickel oxide thin films electrodes by two techniques: mechanical stress change measurements by means of an optical technique and mass changes using an electrochemical quartz microbalance (EQCM). The experiments were performed in alkaline electrolytes containing cations of the first column of the periodic table. Reversible mass and volume changes were observed. In order to explain these experimental results, an exchange reaction is proposed, in which the oxidation process is accompanied by the deinteractional of a relative large number of “light” cations, simultaneously with the intercalation of a smaller number of heaviest cations.     

Longitudinal elastic waves in columns due to earthquake motion

An analysis is presented of longitudinal waves in a thin elastic column. Velocity is specified at one end, and the boundary condition at the other end is expressed in terms of a range of effective impedances of an attached structure. Propagation, reflection and interference of the waves are followed by the method of characteristics. Integration of differential equations along characteristics yields the wave-induced stress, which is then applied to problems of earthquake excitation. Numerical examples are given for recorded updown ground motion of the Kobe Earthquake.     

外加剂混凝土动态与静态坍落度损失的流变特性

本文对动、静态下混凝土坍落度损失的规律进行了研究,并从流变学的角度分析了外加剂对动、静态下混凝土坍落度损失的影响坍落度损失存在差别的原因.     

Evolution of the capillary network in a reactive powder concrete during hydration process

Ultrasonic waves in echographic mode, combined with autogenous shrinkage measurements, were used to study the evolution of the capillary network of reactive powder concrete (RPC) from the time after the mixing. Two characteristic porous classes have been identified: the first, between 10 and 20 nm, begins when the material reaches its solid hyperstatic state, and the second about 1 or 2 nm. The first class is associated with the porous space between the C-S-H hydrate clusters and the second with the internal porosity of the hydrate. The evolution of the active capillary radius as a function of the degree of hydration allows us to understand the strong interaction between the capillary network size and the chemical activity given by the dissipated calorimetric power curve. Indeed, the maximum point of the chemical activity marks the transition of the first class of pores to the second one. Finally, measurements of electrical conductivity through RPC samples show that after the maximum of the dissipated power, the curve of this electrical conductivity presents the same evolution as the capillary radius. As the electrical conductivity clearly depends on the evolution of the capillary network, the similarity between the results confirms our analysis in pore classes.     

Integrating scheduling and control functions in computer integrated manufacturing using artificial intelligence

Proper integration of scheduling and control in Flexible Manufacturing Systems will make available the required level of decision-making capacity to provide a flexibly-automated, efficient, and quality manufacturing process. To achieve this level of integration, the developments in computer technology and sophisticated techniques of artificial intelligence (AI) should be applied to such FMS functions as scheduling. In this paper, we present an Intelligent Scheduling System for FMS under development that makes use of the integration of two AI technologies. These two AI technologies — Neural Networks and Expert Systems — provide the intelligence that the scheduling function requires in order to generate goodschedules within the restrictions imposed by real-time problems. Because the system has the ability to plan ahead and learn, it has a higher probability of success than conventional approaches. The adaptive behavior that will be achieved contribute to the integration of scheduling and control in FMS.     

Neutron Stress Measurement of W‐Fiber Reinforced Cu Composite

Stress measurement methods using neutron and X‐ray diffraction were examined by comparing the surface stresses with internal stresses in the continuous tungsten‐fiber reinforced copper‐matrix composite. Surface stresses were measured by X‐ray stress measurement with the sin²ψ method. Furthermore, the sin²ψ method and the most common triaxal measurement method using Hooke's equation were employed for internal stress measurement by neutron diffraction. On the other hand, microstress distributions developed by the difference in the thermal expansion coefficients between these two phases were calculated by FEM. The weighted average strains and stresses were compared with the experimental results. The FEM results agreed with the experimental results qualitatively and confirmed the importance of the triaxial stress analysis in the neutron stress measurement.     

CONSTRUCTION OF ADMISSIBLE OPERATION CONDITION DOMAIN FOR WELL-STIRRED REACTORS DURING THEIR DESIGN AND CONTROL STAGES

The work examines the problem of constructing an admissible operation condition domain for a well-stirred reactor which would satisfy restrictions in conversion, selectivity, heat removal and stability. The domain is very important and must be known during the reactor design and control stages because it yields visual information for analyzing the reactor operations and makes it possible to find the variation intervals of decision variables, necessary to calculate and optimize the reactor. Being known, the admissible operation condition domain makes it possible to estimate the limiting restrictions and to choose the necessary reserves. The domain has completely been studied analytically for chemical processes with arbitrary kinetics.     

The fracture stress of chemical vapour deposited diamond

The factors which control the fracture stress of chemical vapour deposited diamond have been studied using the 3-point bend geometry. Fracture stress values of 300–800 MPa for the growth side and 600–1200 MPa for the nucleation side were recorded for samples of thickness 0.4–2.4 mm. A Weibull modulus of 23 was calculated for the growth surface data, showing that the fracture stress variability was low for a brittle material. A theory based on these results demonstrates that the material behaviour is remarkably simple, depending only on the grain size and the sample thickness, regardless of wide variations in other parameters such as optical transmission and stress state. The paper also contains a possible explanation for this well-defined behaviour based on microstress variations resulting from differences in defect density in different growth sectors within a grain.     

Application of boundary element method to 3-D problems of coupled thermoelasticity

This paper deals with a new boundary element method for analysis of the quasistatic problems in coupled thermoelasticity. Through some mathematical manipulation of the Navier equation in elasticity, the heat conduction equation is transformed into a simpler form, similar to the uncoupled-type equation with the modified thermal conductivity which shows the coupling effects. This procedure enables us to treat the coupled thermoelastic problems as an uncoupled one, A few examples are computed by the proposed BEM, and the results obtained are compared with the analytical ones available in the literature, whereby the accuracy and versatility of the proposed method are demonstrated.