Investigation of rubber–rubber blends miscibility

Polybutadiene rubber, poly(styrene‐co‐butadiene) rubber, natural rubber, and their blends were investigated to estimate the degree of miscibility of components in the blends. The morphology of a rubber–rubber blend controls its rheological properties and glass transition behavior. Therefore, two different measuring techniques were used: rheological characterization of blends by the rubber process analyzer (RPA) and temperature modulated differential scanning calorimetry (TMDSC). To study the dependence of complex viscosity on blend composition, two commonly used empirical mixing rules were applied: the log‐additivity mixing rule and the quadratic mixing rule. Viscoelastic properties of the examined samples were described by mechanical and relaxation spectra. Since the RPA measurements cannot be performed in a wide frequency range, the experimental results cannot offer a complete overview. Also, the quantitative analysis using the differential of the heat capacity, dC_p/dT, versus the temperature signal from TMDSC did not allow to calculate the weight fraction of the interface for all types of the blends under investigation. However, the combination of the two techniques applied provided complementary information on blend morphology and rubber–rubber miscibility. POLYM. ENG. SCI. 46:1649–1659, 2006. © 2006 Society of Plastics Engineers.     

PolyHIPEs from Methyl methacrylate: Hierarchically structured microcellular polymers with exceptional mechanical properties

Highly porous monoliths with excellent mechanical properties and porosity of up to 90% were prepared by the polymerisation of high internal phase emulsions (HIPE) containing methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA). Materials with open cellular morphology and cavity diameters between 0.6 and 4.5 μm are obtained using a homogenizer and between 0.8 and 25 μm using a standard overhead stirrer. Samples with 80% pore volume have E-moduli up to 180 MPa, while 75% porous samples exhibit E-moduli up to 211 MPa. A dependence of mechanical properties on cavity size distribution is identified, where a more hierarchically developed porous structure results in significantly better mechanical properties.     

IR Drying of Water-Based Acrylic PSA Adhesives

Results of infrared drying of an acrylic microsphere adhesive coating are presented. The effect of IR drying on adhesive coating was analyzed by Fourier transform infrared spectroscopy (FTIR). The adhesion strength was tested by peel adhesion measurement. Drying was experimentally carried out on materials dried to the same moisture extent at different operating conditions. The power of IR heating source, time of drying, and distance between adhesive coating and heating source were varied. The developed phenomenological model was compared with existing empirical models.     

Efficient Noise Robust Feature Extraction Algorithms for Distributed Speech Recognition (DSR) Systems

The evolution of robust speech recognition systems that maintain a high level of recognition accuracy in difficult and dynamically-varying acoustical environments is becoming increasingly important as speech recognition technology becomes a more integral part of mobile applications. In distributed speech recognition (DSR) architecture the recogniser's front-end is located in the terminal and is connected over a data network to a remote back-end recognition server. The terminal performs the feature parameter extraction, or the front-end of the speech recognition system. These features are transmitted over a data channel to the remote back-end recogniser. DSR provides particular benefits for the applications of mobile devices such as improved recognition performance compared to using the voice channel and ubiquitous access from different networks with a guaranteed level of recognition performance. A feature extraction algorithm integrated into the DSR system is required to operate in real-time as well as with the lowest possible computational costs.In this paper, two innovative front-end processing techniques for noise robust speech recognition are presented and compared, time-domain based frame-attenuation (TD-FrAtt) and frequency-domain based frame-attenuation (FD-FrAtt). These techniques include different forms of frame-attenuation, improvement of spectral subtraction based on minimum statistics, as well as a mel-cepstrum feature extraction procedure. Tests are performed using the Slovenian SpeechDat II fixed telephone database and the Aurora 2 database together with the HTK speech recognition toolkit. The results obtained are especially encouraging for mobile DSR systems with limited sizes of available memory and processing power.     

Motion design with Euler–Rodrigues frames of quintic Pythagorean-hodograph curves

The paper presents an interpolation scheme for G¹ Hermite motion data, i.e., interpolation of data points and rotations at the points, with spatial quintic Pythagorean-hodograph curves so that the Euler–Rodrigues frame of the curve coincides with the rotations at the points. The interpolant is expressed in a closed form with three free parameters, which are computed based on minimizing the rotations of the normal plane vectors around the tangent and on controlling the length of the curve. The proposed choice of parameters is supported with the asymptotic analysis. The approximation error is of order four and the Euler–Rodrigues frame differs from the ideal rotation minimizing frame with the order three. The scheme is used for rigid body motions and swept surface construction.     

Flow through packed bed reactors: 1. Single-phase flow

Single-phase pressure drop was studied in a region of flow rates that is of particular interest to trickle bed reactors . Bed packings were made of uniformly sized spherical and non-spherical particles (cylinders, rings, trilobes, and quadralobes). Particles were packed by means of two methods: random close or dense packing (RCP) and random loose packing (RLP) obtaining bed porosities in the range of 0.37–0.52. It is shown that wall effects on pressure drop are negligible as long as the column-to-particle diameter ratio is above 10. Furthermore, the capillary model approach such as the Ergun equation is proven to be a sufficient approximation for typical values of bed porosities encountered in packed bed reactors. However, it is demonstrated that the original Ergun equation is only able to accurately predict the pressure drop of single-phase flow over spherical particles, whereas it systematically under predicts the pressure drop of single-phase flow over non-spherical particles. Special features of differently shaped non-spherical particles have been taken into account through phenomenological and empirical analyses in order to correct/upgrade the original Ergun equation. With the proposed upgraded Ergun equation one is able to predict single-phase pressure drop in a packed bed of arbitrary shaped particles to within ±10% on average. This approach has been shown to be far superior to any other available at this time.     

Future trends of bioethanol co-production in Serbian sugar plants

Due to the reduction of the economic support for refined sugar efforts have been made to find new ways of using sugar beet outside food industry. This paper investigates the possibilities of introducing bioethanol co-production in Serbian sugar plants. Research shows current state of Serbian sugar industry and technical aspects of bioethanol co-production in sugar plants. These results represent important step toward mass production of bioethanol in Serbian factories. The main goals of introducing the concept of sugar and bioethanol coproduction would be efficient use of available resources for the production of energy, reduction of greenhouse gases emission, decreased dependence on import and creation of new jobs. Besides that, it would provide flexibility in terms of variation of produced quantities of sugar and ethanol, depending on the conditions prevailing on the market.     

Distributed Jacobi Joint Diagonalization on Clusters of Personal Computers

A new algorithm is described for distributed joint diagonalization of real symmetric or complex Hermitian matrices. The approach, which is based on the Jacobi diagonalization, utilizes distribution of the computational power and memory space, minimizes the communication costs, and runs on clusters of personal computers. It further combines two-step load balancing algorithm with a standard Kalman filter to enable quick but low-cost adaptation to resource varying conditions. Theoretical analysis of its performance shows that the communication costs (when normalized by computational costs) decline linearly with the number and size of the diagonalized matrices. This is also confirmed by experimental results: the measured speedup ratio yields 42.2 when jointly diagonalizing 800 matrices of size 400 × 400 on a cluster of 50 personal computers.     

An approach to surface EMG decomposition based on higher-order cumulants

We are addressing a possible approach to the decomposition of surface electromyograms (SEMGs). It is based on higher-order cumulants implemented in a two-step procedure. Firstly, a multivariate version of the w-slice method is applied in order to extract coarse approximations of motor-unit action potentials (MUAPs) out of the measured SEMGs. Secondly, these coarse estimates are refined by modified Newton-Gauss iteration to achieve an optimum fit of the model-based and the observation-based cumulant estimates. All the necessary conditions are derived theoretically and, afterwards, implemented in simulation runs in order to prove the decomposition power of the proposed approach on synthetic SEMGs. The first-norm difference between the original and the decomposed MUAPs, obtained at the signal length of 102400 samples and expressed in percentage of the MUAP amplitude span, yields 5.4% in the noise-free case, 6.0% with a signal-to-noise ratio (SNR) of 10dB, and 6.5% with a SNR of 0 dB.     

Cost function analysis in the structural optimization of steel frames

An objective function used in structural optimization should be formulated in such a way that the most economic solution can be found. However, the objective function is usually simplified to represent the weight, disregarding the fabrication and erection costs of the structure. The paper presents a very detailed objective function that considers the self-manufacturing costs of the whole structure. The cost function includes all essential fabrication and erection activities. It considers both manufacturing costs as well as material costs. It is formulated in an open manner, offering users the possibility to define their own parameters on the basis of a certain production line. The cost function is implemented into the optimization system for planar steel frames.