Determination of porosity of reduced hematite by stereologic methods

The stereologic analysis of a solid grain has been applied for determination of its porosity. The investigations were carried out on a natural hematite grain reduced to magnetite at 723 K. Stereologic analysis enabled the porosity of this material to be determined on the basis of independently measured grain contours and volume fractions of grain components: hematite, magnetite and pores. A conformity criterion has been formulated, regarding determination of grain volume on the basis of known densities of components and their measured volume fractions in the grain, and on the basis of weight and apparent grain density measurements. The volume increase accompanying reduction of hematite to magnetite, determined from these independent measurements, was in the range 7–19%. By measuring Ferets diameter, the volume of the convex envelope of the grain increased as a result of phase transformation by about 11%. Simultaneously, the volume of the solid phase was found to decrease by 1.5%. The total porosity of the reduced grain, determined by stereologic analysis amounted to 17.5%; 7.7% of which was related to cracks and large pores, and 9.8% to small pores in the magnetite phase. The porosity value determined by the classical mercury method was approximately the same.     

Controlling patterns of geospatial phenomena

Modeling spatially distributed phenomena in terms of its controlling factors is a recurring problem in geoscience. Most efforts concentrate on predicting the value of response variable in terms of controlling variables either through a physical model or a regression model. However, many geospatial systems comprises complex, nonlinear, and spatially non-uniform relationships, making it difficult to even formulate a viable model. This paper focuses on spatial partitioning of controlling variables that are attributed to a particular range of a response variable. Thus, the presented method surveys spatially distributed relationships between predictors and response. The method is based on association analysis technique of identifying emerging patterns, which are extended in order to be applied more effectively to geospatial data sets. The outcome of the method is a list of spatial footprints, each characterized by a unique “controlling pattern”—a list of specific values of predictors that locally correlate with a specified value of response variable. Mapping the controlling footprints reveals geographic regionalization of relationship between predictors and response. The data mining underpinnings of the method are given and its application to a real world problem is demonstrated using an expository example focusing on determining variety of environmental associations of high vegetation density across the continental United States.     

Michell cantilevers constructed within a half strip. Tabulation of selected benchmark results

The paper delivers the benchmark results for the Michell cantilevers constructed within a half strip, for selected values of the σ _T /σ _C ratio, σ _T , σ _C being the admissible stresses in tension and compression, respectively.     

TSV constraints related to temperature excursion, pressure during molding, materials used and handling loads

The current paper focuses on several mechanical aspects of a waferlevel packaging approach using a direct face-to-face Chip-to-Wafer (C2W) bonding of a MEMS device on an ASIC substrate wafer. Requirements of minimized inherent stress from packaging and good decoupling from forces applied in manufacturing and application are discussed with particular attention to the presence of through-silicon vias (TSV) in the substrate wafer. The paper deals with FEM analysis of temperature excursion, pressure during molding, materials used and handling load influence on mechanical stress within the TSV system and on wafer level, which can be large enough to disintegrate the system.     

Vocal-based emotion recognition using random forests and decision tree

This paper proposes a new vocal-based emotion recognition method using random forests, where pairs of the features on the whole speech signal, namely, pitch, intensity, the first four formants, the first four formants bandwidths, mean autocorrelation, mean noise-to-harmonics ratio and standard deviation, are used in order to recognize the emotional state of a speaker. The proposed technique adopts random forests to represent the speech signals, along with the decision-trees approach, in order to classify them into different categories. The emotions are broadly categorised into the six groups, which are happiness, fear, sadness, neutral, surprise, and disgust. The Surrey Audio-Visual Expressed Emotion database is used. According to the experimental results using leave-one-out cross-validation, by means of combining the most significant prosodic features, the proposed method has an average recognition rate of \(66.28\%\), and at the highest level, the recognition rate of \(78\%\) has been obtained, which belongs to the happiness voice signals. The proposed method has \(13.78\%\) higher average recognition rate and \(28.1\%\) higher best recognition rate compared to the linear discriminant analysis as well as \(6.58\%\) higher average recognition rate than the deep neural networks results, both of which have been implemented on the same database.     

Reducing Protocol Analysis with XOR to the XOR-Free Case in the Horn Theory Based Approach

In the Horn theory based approach for cryptographic protocol analysis, cryptographic protocols and (Dolev?CYao) intruders are modeled by Horn theories and security analysis boils down to solving the derivation problem for Horn theories. This approach and the tools based on this approach, including ProVerif, have been very successful in the automatic analysis of cryptographic protocols. However, dealing with the algebraic properties of operators, such as the exclusive OR (XOR), which are frequently used in cryptographic protocols has been problematic. In particular, ProVerif cannot deal with XOR. In this paper, we show how to reduce the derivation problem for Horn theories with XOR to the XOR-free case. Our reduction works for an expressive class of Horn theories. A large class of intruder capabilities and protocols that employ the XOR operator can be modeled by these theories. Our reduction allows us to carry out protocol analysis using tools, such as ProVerif, that cannot deal with XOR, but are very efficient in the XOR-free case. We implemented our reduction and, in combination with ProVerif, used it for the fully automatic analysis of several protocols that employ the XOR operator. Among others, our analysis revealed a new attack on an IBM security module.     

Leftist Grammars and the Chomsky Hierarchy

Leftist grammars are characterized in terms of rules of the form a → ba and cd → d, without distinction between terminals and nonterminals. They were introduced by Motwani et al. [13], where the accessibility problem for some general protection system was related to these grammars. This protection system was originally proposed in [4] and [15] in the context of Java virtual worlds. The accessibility problem is formulated in the form "Can object p gain (illegal) access to object q by a series of legal moves (as prescribed by the policy)?" The membership problem for leftist grammar is decidable [13], which implies decidability of the accessibility problem for the appropriate protection system. We study relationships between language classes defined by various types of leftist grammars and classes of the Chomsky hierarchy. We show that general leftist grammars can define languages which arenot context free, answering in the negative a question from [13]. Moreover, we study some restricted variants of leftist grammars and relate them to regular, deterministic context-free, and context-free languages.     

ELECTROCHEMICAL MACHINING OF CURVILINEAR SURFACES

In this work a theoretical analysis of the ECM process of curvilinear surfaces has been presented. The purpose of this analysis is to predict the shape evolution of the machined object using: a shaping surface of small thickness (flat issue) and a blade of hydrodynamic machine (quasi-three dimensional issue). ECM modeling involves prediction of the machined surface shape evolution and distribution of physical-chemical parameters inside the interelectrode gap. The problem has been solved with the use of an equation of the electrolyte and hydrogen mixture (liquid and gas) flat flow inside the interelectrode gap. After introducing simplifying assumptions for the flow, void fraction distribution and the gap thickness, the equations were solved partly analytically, partly numerically. The obtained solutions for assigned parameters of the machining process are presented graphically in the form of distributions of: static pressure, the mixture flow rate, temperature, void fraction and evolution of the machined surface shape evolution.     

Damage and loading rate effects on the microfailure behaviour of Al2O3-ceramics studied by SEM

A scanning electron microscopy (SEM)-X-ray combined experimental approach to qualitative and semi-quantitative characterization of microfailure behaviour of an Al₂O₃-ceramic material in terms of induced damage is presented. The qualitative approach was based on representative fractographical images and data obtained by SEM whereas the semi-quantitative approach was based on a new technique of the X-ray electron probe microanalysis (X-ray EPMA) capable to detect the localized subsurface damage. The damage was induced by a simple rotary notch-cutting procedure where the associated damage parameters can be controlled by the cutting rate. By correlating certain characteristic macro- and microfractographic features/patterns with well-known microfailure mechanisms it was possible to make qualitatively, in an indirect way, evident the existence of induced damage which was assumed to be ideal brittle having only microcracking component. In the same correlating way the stimulating effect of internal pores on the damage development was deduced. Observed loading rate effects on the fractographic behaviour expressed by changes in fracture roughness and micromorphology were attributed to pore-assisted microcracking linkage. Low porosity under high loading rates tends to lower the fractographic roughness, a fact which can be related with a reduction in the ability of energy dissipation. On the other hand, high porosity under increasing loading rates leads to non observable changes in the fractographic roughness, a fact which is indicative of corresponding no appreciable changes in the dissipative character of the material. The measured local damage distribution ahead of the notch-tip shows a monotonic increasing of damaging effects toward the tip. By means of this distribution the total or average damage degree and process zone length ahead of the notch-tip were evaluated. The increase of these two damage parameters is not proportional to the increase in the cutting speed i.e. the rate of damage development. Finally, by assuming brittle damage an experimental approaching procedure for the estimation of the induced energy required for the microcracking damage was proposed.