Stimulation of negative magnetoresistance by an electric field and light in silicon doped with boron and manganese

It is experimentally ascertained that light stimulates the negative magnetoresistance observed in a high electric field in silicon doped with boron and manganese. The optimum conditions (the electric field, temperature, illumination, and resistivity of the material) for observation of the largest magnitude of negative magnetoresistance in (Si:B):Mn are determined. The dependence of the negative magnetoresistance on the concentration of compensating impurity is established.     

Automatic player position detection in basketball games

This paper presents us with a framework for the automatic player position detection (APPD) in the game of basketball. Court players are detected in the images broadcasted via television stations. In them, at any point of time, the view is from only one camera. This makes the detection process much more difficult. The player detection is based on the mixture of non-oriented pictorial structures. The detection of body parts is performed by the Support Vector Machine (SVM) algorithm. The results of these detections are combined together with constraints on their locations, which specify the position of one body part with respect to the parent body part. In order to train the whole model, we used a latent form of SVM called the latent SVM (LSVM). Such approach generated the statistical accuracy of about 82 %, which represents one of the best results in basketball player detection framework. Beside players, the algorithm detected a certain number of false positive objects. These are mostly people from the audience and the referees as well. This paper contains a simple and robust solution to remove them all, based on the play court boundaries and the histogram comparison. Separating players in different teams is done by k-means clustering. The inputs to this algorithm are saturation histograms calculated on the jerseys. A spatial transformation is determined by the detected play court boundaries and the actual court measures. Using this transformation, points representing the location of detected players in TV images are mapped to the actual location of players on the court, which was the main goal of our research. The proposed solution is sound and efficient. In addition, it is backed up by the experimental results obtained using the model of the actual footage of basketball games.     

Singularity-free time integration of rotational quaternions using non-redundant ordinary differential equations

A novel ODE time stepping scheme for solving rotational kinematics in terms of unit quaternions is presented in the paper. This scheme inherently respects the unit-length condition without including it explicitly as a constraint equation, as it is common practice. In the standard algorithms, the unit-length condition is included as an additional equation leading to kinematical equations in the form of a system of differential-algebraic equations (DAEs). On the contrary, the proposed method is based on numerical integration of the kinematic relations in terms of the instantaneous rotation vector that form a system of ordinary differential equations (ODEs) on the Lie algebra \(\mathit{so}(3)\) of the rotation group \(\mathit{SO}(3)\). This rotation vector defines an incremental rotation (and thus the associated incremental unit quaternion), and the rotation update is determined by the exponential mapping on the quaternion group. Since the kinematic ODE on \(\mathit{so}(3)\) can be solved by using any standard (possibly higher-order) ODE integration scheme, the proposed method yields a non-redundant integration algorithm for the rotational kinematics in terms of unit quaternions, avoiding integration of DAE equations. Besides being ‘more elegant’—in the opinion of the authors—this integration procedure also exhibits numerical advantages in terms of better accuracy when longer integration steps are applied during simulation. As presented in the paper, the numerical integration of three non-linear ODEs in terms of the rotation vector as canonical coordinates achieves a higher accuracy compared to integrating the four (linear in ODE part) standard-quaternion DAE system. In summary, this paper solves the long-standing problem of the necessity of imposing the unit-length constraint equation during integration of quaternions, i.e. the need to deal with DAE’s in the context of such kinematical model, which has been a major drawback of using quaternions, and a numerical scheme is presented that also allows for longer integration steps during kinematic reconstruction of large three-dimensional rotations.     

Spoken emotion recognition through optimum-path forest classification using glottal features

A new method for the recognition of spoken emotions is presented based on features of the glottal airflow signal. Its effectiveness is tested on the new optimum path classifier (OPF) as well as on six other previously established classification methods that included the Gaussian mixture model (GMM), support vector machine (SVM), artificial neural networks – multi layer perceptron (ANN-MLP), k-nearest neighbor rule (k-NN), Bayesian classifier (BC) and the C4.5 decision tree. The speech database used in this work was collected in an anechoic environment with ten speakers (5 M and 5 F) each speaking ten sentences in four different emotions: Happy, Angry, Sad, and Neutral. The glottal waveform was extracted from fluent speech via inverse filtering. The investigated features included the glottal symmetry and MFCC vectors of various lengths both for the glottal and the corresponding speech signal. Experimental results indicate that best performance is obtained for the glottal-only features with SVM and OPF generally providing the highest recognition rates, while for GMM or the combination of glottal and speech features performance was relatively inferior. For this text dependent, multi speaker task the top performing classifiers achieved perfect recognition rates for the case of 6th order glottal MFCCs.     

Elastic–plastic response of structural foams subjected to localized static loads

Structural foams are increasingly used in engineering applications where high strength and low weight are important. They are used also as energy absorbers. Sandwich structures are a typical area for application of structural foams (as core materials). In a sandwich structure, the core transfers the transverse forces as shear stresses and supports the face sheets against buckling and wrinkling. The structural foams are notoriously sensitive to failure by the application of localized surface loads. Thus, the proper design requires an understanding of the mechanical response of the foam materials to localized external loads.In this paper, the elastic–plastic behavior of closed-cell cellular foams subjected to point and line loads is investigated both experimentally and numerically. Two types of Divinicell foam (H60 and H100) are studied. A finite element modeling procedure is developed using the ABAQUS package. Both plane and axisymmetric formulations for local indentations by rigid bodies are considered. The plastic behavior is described using the *CRUSHABLE FOAM HARDENING material model. This model is calibrated using experimental curves from uniaxial compression tests. Geometrical non-linearity is also taken into account. Both indentation and unloading phases are modeled. Static indentation tests of foam panels and beams are performed using spherical and cylindrical indentors, respectively. A comparison of indentation response obtained from the numerical analysis and from the tests is carried out. A good agreement between the modeling and the experimental data is achieved. In perspective view, the present investigation can contribute towards the development of a damage tolerance methodology for rigid foams.     

Interaction between multiply charged manganese nanoclusters and sulfur atoms in silicon

We have studied the interaction of manganese nanoclusters with sulfur atoms in silicon. The results indicate that both simultaneous and sequential codoping with manganese and sulfur has little effect on the electrical properties (resistivity, carrier mobility, and conductivity type) of silicon. There is no extrinsic photoconductivity in the IR spectral region, and the material has only a small positive magnetoresistance. According to electron paramagnetic resonance data, the material contains only atomic manganese. Sulfur atoms in the silicon lattice are assumed to facilitate the capture of doubly charged manganese interstitials (Mn²⁺) at negatively charged vacancies, resulting in the formation of a multicomponent impurity cluster of composition Si₂S²⁺Mn²⁻ in the silicon lattice throughout the crystal. The optimal thermal annealing conditions for the formation of such clusters are determined. The ability to produce Si₂S²⁺Mn²⁻ clusters with controlled concentration allows one to tailor the main fundamental parameters of silicon and opens up new possibilities for such materials in nano- and microelectronic device development.     

Investigation of the phase composition of accretions formed into WHB under flash smelting of copper concentrate

The phase composition of the depositions formed in the radiation section of the waste heat boiler utilizer (RS of WHB) after injecting sulphatizing flow in the volume of the off-gases from the uptake of flash smelting furnace for copper sulphide concentrate smelting was studied. With the help of X-ray diffraction (XRD), Reflected-light microscopy and Electron probe microanalysis (EPMA) of samples from the accretions, it was established that the main crystalline phases in the accretions were spinel, delafossite, cuprite and tenorite. The results from EPMA have shown that the spinel phase is with variable composition from cuprospinel to solid solution into the system Fe₃O₄-CuFe₂O₄-ZnFe₂O₄ (magnetite-cuprospinel-franklinite). Calculated on the basis of XRD and EPMA approximate formulae for the phases, identified in the samples from the accretions were the following: of the cuprospinel-(Cu_0.85²⁺Zn_0.09²⁺Fe_0.06²⁺)(Fe_1.87³⁺Al_0.10³⁺Si_0.03⁴⁺)O₄; of the spinel solid solution—(Cu_0.32²⁺Zn_0.36²⁺Fe_0.32²⁺)(Fe_1.81³⁺Al_0.19³⁺)O₄; Delafossite—Cu_1.07Fe_0.93O₂; cuprite—Cu_1.99Fe_0.02Si_0.01O and tenorite—Cu_0.993Fe_0.008O. The influence of the temperature on the sulphate formation processes of copper and iron oxides in the dust-gas flow was evaluated, based on experimental data and thermodynamic analysis of phase equilibriums in the systems Cu-S-O and Fe-S-O for the conditions, typical of the radiation section of the waste heat boiler (RS of WHB).     

Mathematical programming synthesis of non-isothermal water networks by using a compact/reduced superstructure and an MINLP model

The synthesis problems of non-isothermal water networks, combining heat exchanger network and water network (WN), usually consist of a significant number of constraints and variables, namely, flow rates, contaminant concentrations, temperatures and a large number of non-linear terms. In most cases, solving medium and large-scale synthesis problems is computationally too expensive and challenging. In order to circumvent that problem, we propose a compact superstructure and mixed-integer non-linear programming model for the simultaneous synthesis of non-isothermal WNs. The proposed superstructure includes heat integration stages enabling direct and indirect heat exchanges with a manageable number of hot and cold streams. This reduces the models size enabling easier solutions of the synthesis problems using local solvers. In addition, a superstructure reduction strategy is proposed making the superstructure flexible and adaptable for different types of problems, namely, pinched and threshold, and providing additional reduction of connections within the proposed superstructure. The proposed model is solved using a two-step solution strategy including initialisation and design steps. The model is applied to the examples of different complexities including single and multiple contaminant problems, and water-using and wastewater treatment units. Using the proposed iterative strategy, the improved locally optimal solutions are identified for most examples, minimising the total annual cost of the overall network.     

Influence of mass transport on the performance of carbon gas-diffusion air electrodes in alkaline solution

The effect of mass transport on the electrochemical behaviour of carbon gas-diffusion air electrodes in alkaline solution was investigated on the basis of ΔE(i) curves. These curves are obtained by subtraction of potential values for an electrode operating with airE _air(i) from potential values for the same electrode operating with pure oxygenE _oxygen(i) at the same current densityi. Three different regions on these curves connected with different modes of mass transport are recognized. A model of the gas-diffusion air electrode which takes into account the diffusion of the gas, diffusion of the dissolved gas, electrochemical reaction and IR drop is used to explain the experimental results.     

Synthesis of regional networks for the supply of energy and bioproducts

This article presents a method for the synthesis of regional renewable energy supply chains, based on Mixed-Integer Linear Programming (MILP). This method addresses the challenges presented by biomass resources. The main challenges are the distributive and varied availabilities regarding both location and time. This work also aims to maximise the economically viable utilisation of resources, accounting for the competition between energy and food production. A four-layer supply chain superstructure has been developed, which includes the harvesting, preparation, core processing and distribution of products. This considered system’s boundaries involve a region, which is then divided into zones for optimising conversion operations and transportation flows. An MILP model has been formulated with profit maximisation as the optimisation criterion. The environmental impact is evaluated by the carbon footprint. The sensitivity of the optimal solutions is analysed for different regions’ sizes, transportation costs, pre-processing alternatives and the co-production of food and energy.