Contact size-dependent switching instabilities in HfO2 RRAM

Journal of Materials Science: Materials in Electronics - A comprehensive understanding of the resistive switching mechanisms that activate REDOX-based random access memory devices is necessary to...     

Estimation of heart rate signals for mental stress assessment using neuro fuzzy technique

This paper presents the evaluation of mental stress assesment using heart-rate variability (HRV). The activity of the autonomic nervous system (ANS) is studied by means of time-frequency analysis (TFA) of the heart-rate variability signal. Spectral decomposition of the heart-rate variability before smoking and after smoking was obtained. Mental stress is accompanied by dynamic changes in ANS activity. HRV analysis is a popular tool for assessing the activities of autonomic nervous system. The approach consists of (1) monitoring of heart rate signals, (2) signal processing using wavelet transform (WT) (different wavelets), (3) neuro fuzzy evaluation techniques to provide robustness in HRV analysis, (4) monitoring the function of ANS under different stress conditions. Our experiment involves 20 physically fit persons under different times (before smoking and after smoking). Nero fuzzy technique have been used to model the experimental data.     

A semantic approach to a framework for business domain software systems

In enterprise firms, enormous amounts of electronic documents are generated by business analysts and other business domain application users. Applications that use these documents are often driven by business logic that is hard-coded together with application logic. One approach to the separation of business logic from applications is to create and maintain business and information extraction rules in an external, user-friendly format. The drawback of such an externalization is that the business rules, usually, do not have machine interpretable semantics. This situation often leads to misinterpretation of domain analysis documents, which can inhibit the productivity of computer-assisted analytical work and the effectiveness of business solutions. This paper proposes an ontology and rule-based framework for the development of business domain applications, which includes semantic processing of externalized business rules and to some extent externalization of application logic. The creation of external information extraction rules by the business analyst is a cumbersome and time consuming task. In order to overcome this problem, the framework also includes a rule learning system to semi-automate the generation of information extraction rules from source documents with the help of manual annotations. The main idea behind the work presented in this paper is to re-engineer very large enterprise information systems to adapt to Semantic Web computing techniques. The work presented in this paper is inspired by an industrial project.     

An experimental investigation on oil mist characterization used in MQL milling process

In this study, a method is developed to determine the oil mist characteristics for the minimal quantity lubricant process. The oil mist is characterized by the size, velocity, and volume flow rate of its particles. In each case, a specific measurement process is used: the laser diffraction granulometry method, the particle image velocimetry, and the gravimetric method. These methods are used in the case of static and simple models with different inner channels. Experimental tests have been done with the same inner channel as the existing spindle inner channel. Different output models with different inner canalizations have been tested, using these experimental processes. The main goal is to control the characteristics of output oil mist as a function of the input oil mist device parameters.     

Experimental flame speed in multi-layered nano-energetic materials

This paper deals with the reaction of dense Metastable Intermolecular Composite (MIC) materials, which have a higher density than conventional energetic materials. The reaction of a multilayer thin film of aluminum and copper oxide has been studied by varying the substrate material and thicknesses. The in-plane speed of propagation of the reaction was experimentally determined using a time of- flight technique. The experiment shows that the reaction is completely quenched for a silicon substrate having an intervening silica layer of less than 200 nm. The speed of reaction seems to be constant at 40 m/s for silica layers with a thickness greater than 1 μm. Different substrate materials such as glass and photoresist were also used.     

Computational fluid dynamics modeling of gas dispersion in multi impeller bioreactor

In the present study, experiments have been carried out to identify various flow regimes in a dual Rushton turbines stirred bioreactor for different gas flow rates and impeller speeds. The hydrodynamic parameters like fractional gas hold-up, power consumption and mixing time have been measured. A two fluid model along with MUSIG model to handle polydispersed gas flow has been implemented to predict the various flow regimes and hydrodynamic parameters in the dual turbines stirred bioreactor. The computational model has been mapped on commercial solver ANSYS CFX. The flow regimes predicted by numerical simulations are validated with the experimental results. The present model has successfully captured the flow regimes as observed during experiments. The measured gross flow characteristics like fractional gas hold-up, and mixing time have been compared with numerical simulations. Also the effect of gas flow rate and impeller speed on gas hold-up and power consumption have been investigated.     

Nitrogen redistribution, microstructure, and elastic constant evaluation using ultrasonics in aged 316LN stainless steels

The presence of even dilute concentrations of nitrogen (0.08 mass pct) is found to have a strong influence on the microstructure of a nuclear grade 316LN austenitic stainless steel, thermally aged at 1123 K. High-resolution transmission electron microscopy (TEM) evidence of pre-precipitation reactions involving formation of Cr-N rich clusters prior to Cr₂N precipitation has been presented. A tendency for cellular precipitation has been observed on continued aging above 500 hours. Beyond 1000 hours, chi precipitates are the most frequently seen phase. The observed microstructural variations correlate well with ultrasonic velocity and attenuation measurements. The present study reveals that nitrogen in solid solution decreases all the elastic constants, namely longitudinal modulus, elastic modulus, shear modulus, and bulk modulus in this steel but has a negligible effect on Poisson’s ratio. The stages associated with the precipitation of intragranular coherent Cr₂N are, however, associated with an increase in all the elastic constants including Poisson’s ratio.     

Thermodynamic modelling of the spontaneous vitrification process using transformation diagrams

Spontaneous vitrification is a phenomenon where a crystalline phase transforms to the amorphous phase on annealing at low temperatures. It has been reported to occur in several binary alloy systems. This phenomenon has been widely investigated in the Ti–Cr system through experiments as well as thermodynamic modeling. The models reported in literature suffer from several drawbacks. They are not consistent with experimental observations. These models treat this non-equilibrium process as an essentially equilibrium process albeit involving two meta-stable phases. The thermodynamics of the “spontaneous vitrification” process has been modeled using the concept of Transformation Diagrams. This method considers the thermodynamics of non-equilibrium phase transformation and does not involve assumptions of equilibrium at any stage. A significant conclusion derived from the present model is that it is the close-packed hcp structure that transforms to the amorphous phase whereas the transformation of the relatively open bcc structure to the amorphous phase is forbidden thermodynamically. These conclusions are in contrast with the predictions of the earlier models.