An Investigation of Error Sources in Computational Fluid Dynamics Modelling of a Co-current Spray Dryer

The paper is focused on identifying error sources in computational fluid dynamics(CFD) predictions of a spray drying process. Seven groups of drying and atomisation parameters were selected for analysis and 13simulation trials were performed. The theoretical results were compared with experimental data and sensitivity of the simulation results to the analysed factors was determined. The following parameters affecting the accuracy of CFD spray modelling were found: gas turbulence model, particle dispersion, atomising air, initial parameters of atomisation and heat losses to the environment. A major difference in the errors committed during modelling of spray drying process for fine and coarse sprays was observed.

Properties of Electrical Discharges Developing in Transformer Oil Under Lightning Impulse in the Setup of Insulated Electrodes

Looking at the problem of electrical discharge development in mineral oil, it is easy to see that most studies in this area focused on the setups of bare high voltage electrodes having a point-plane electrode arrangement. The setups with insulated electrodes are the mar- gin of these studies but it seems to be important to find the dependences between the paper insulation on high voltage electrode and parameters of the discharges initiated in the vicinity of this electrode. Hence, in this paper the results of researches intended to reveal the role of insulation wrapping on a HV electrode in the mechanism of electrical discharges in transformer oil under lightning impulse of both polar- ities are presented. This role is determined by analysis of the parameters characterizing the discharges (onset voltage, propagation velocity, time to initiation, rise-time of light impulses) and also by observation of their spatio-temporal development and oscillograms of the light emitted by their channels. The research was performed for two model electrode configurations: an electrode with paper insulation and a bare electrode which had the same outer dimensions as the insulated one. The most essential conclusion from performed experiment is related to times to initiation. These times, equal in the case of insulated electrodes and model bare electrode, indicate that the source of "weak points" of the paper-oil insulation system is the oil, not the surface of insulation wrapping or the metal.

Modelling of the Phenomenon Known as “the Miracle of the Sun” as the Reflection of Light from Ice Crystals Oscillating Synchronously

The work includes a mathematical model of the phenomenon seen by the witnesses on 13th October, 1917 in the Cova da Iria near Fatima, and similar phenomena recorded in recent years throughout the world, known as the “miracle of the Sun”, allowing for qualitative and quantitative analysis of the phenomenon. The work includes a mathematical model of a cloud of the vibrating charged ice crystals. The paper shows the dynamic optical effects associated with the passage of light through such a vibrating medium. It also presents the simplest solution to the model in the form of graphs, which have been compared with the graphs obtained from the analysis of the amateur observations of the phenomenon in question.

Hydrogen bonds of interfacial water in human breast cancer tissue compared to lipid and DNA interfaces

The paper presents the results for water confined in a human breast cancerous tissue, a single stranded DNA, a double stranded DNA and in phospholipids (DPPC - D-a-Phosphati dylcholine, dipalmitoyl). The interfacial water in DNA and lipids is represented by a double band in the region of the OH stretching mode of water corresponding to the symmetric and asymmetric vibrational modes, in contrast to water confined in the cancerous breast tissue where only one band at 3311 cm-1 has been recorded. The marked red-shift of the maximum peak position of the OH stretching mode confirms that the vibrational properties of the interfacial water observed in restricted biological environment differ drastically from those in bulk water. The change of vibrational pattern of behavior may be due to the decoupling of the vibrations of the OH bonds in water molecule or change of the vibrational selection rules at biological interfaces. According to our knowledge Raman vibrational properties of water confined in the normal and cancerous breast tissue of the same patient have not been reported in literature yet. Here we have also presented the first Raman ‘optical biopsy’ images of the non-cancerous and cancerous (infiltrating ductal cancer) human breast tissues.

Assessment of the Influence of Paper Insulation on the Discharge Initiation in Oil

The results of the assessment of the influence of paper insulation on the discharge initiation in oil were presented in this paper. This assessment based on the results of performed experimental works and on the analysis of electrical field distribution. Both types of the studies were connected with the model HV （high voltage） electrode setups covered by paper and immersed in oil. Experimental works indicated that the source of ＂weak points＂ of paper-oil model electrode setup is oil, not the surface of metal or insulation wrapping. Such hypothesis, resulting mainly from the measured times to initiations of discharges developing from bare and insulated HV electrodes, was verified by the analysis of electrical field distribution performed on the basis of finite element method applied in the COMSOL Multiphysics software. This analysis confirmed preliminary the made hypothesis. Correlation with the most stressed oil volume law was also observed.

Non-Carbohydrate Components on the Surface of Starch Granules According to the Hardness of Wheat

An attempt was made to demonstrate the usefulness of pre-knowledge of the quality and quantity analysis of non-carbohydrate components of starch surface, such as proteins and lipids, in starch isolated from wheat with varying degrees of hardness, for receiving glucose hydrolysates. The chemical composition of starches isolated from wheat grains of different hardness was examined. The amount of protein fraction (surface proteins, puroindolins and internal proteins), total and surface lipids, apparent amylose, phosphorous and pentosans contents were evaluated. It was found that starches, depending on the hardness of wheat grain, have a different chemical composition. A clear influence of wheat hardness on lipid and proteins content on the surface of starch grains and on apparent amylose was proved. It was showed that the presence of polar lipids (glyco and phospholipids) on the surface of starch was connected with their role in binding of surface proteins fraction (friabilins) to starch grains. There was a clear positive correlation between the amount of lipid fraction on starch surface and the amount of protein fraction, depending on wheat hardness. Starches from soft wheat varieties were characterized by higher amounts of proteins and lipids on their surface. In addition, it was determined that basing on the knowledge of mechanical properties of wheat grains, namely its hardness and initial starch chemical content analysis, one may predict its further directions of processing, including evaluation, whether the starch from a given wheat variety would be appropriate for obtaining hydrolysates with good physicochemical properties.

Nonlinearity of muscle stiffness

In this letter, a comparison between three types （two linear and one nonlinear） of models of skeletal muscle stiffness is shown. Results are compared with experimental data for biceps brachii in the case of muscle stretching and with the Hill equation for a biological muscle. It is shown that results for nonlinear stiffness model in case of length-force relationship fits to the experimental data.

ECT Image Analysis Methods for Shear Zone Measurements during Silo Discharging Process

The paper covers the electrical capacitance tomography(ECT) data analysis on shear zones formed during silo discharging process.This is due to the ECT aptitude for detection of slight changes of material concentration.On the basis of ECT visualisations,wall-adjacent shear zone profiles are analysed for different wall roughness parameters.The analysis on changes of material concentration,based on ECT images,enables the calculation for the characteristic parameters of shear zones-size and material concentration inside the shear zone in a dynamic process of silo discharging.In order to verify the methodology a series of experiments on gravitational flow of bulk solids under various conditions were conducted with different initial granular material packing densities and silo wall roughness.The investigation shows that the increase in container wall roughness is an effective method for reducing the dynamic effects during the material discharging,since these effects are resulted from the resonance between hopper construction and trembling material.Such effects will damage industrial equipment in practical applications and need further investigation.

Effect of Turbulence on Flame Propagation in Comstarch Dust-Air Mixtures

Following the quantitative determination of dust cloud parameters, this study investigated the flame propagation through cornstarch dust clouds in a vertical duct of 780 mm height and 160×160 mm square cross section, and gave particular attention to the effect of turbulence on flame characteristics. The turbulence induced by dust dispersion process was measured using a particle image velocimetry （PIV） system. Upward propagating dust flames were visualized with direct fight and shadow photography. The results show that a critical value of the turbulence intensity can be specified below which laminar flame propagation would be established. This transition condition is about 10 cm/s. The measured propagation speed of laminar flames appears to be in the range of 0.45-0.56 m/s, consistent with the measurements reported in the literature. For the present experimental conditions, the flame speed is little sensitive to the variations in dust concentration. Some information on the flame structure was revealed from the shadow records, showing the typical heterogeneous feature of dust combustion process.

Shape Optimization of the Turbomachine Channel by a Gradient Method - Accuracy Improvement

An algorithm of the gradient method of the channel shape optimization has been built on the basis of 3D equations of mass, momentum and energy conservation in the fluid flow. The gradient of the functional that is posed for minimization has been calculated by two methods, via sensitivities and - for comparison - by the finite difference approximation. The equations for sensitivities have been generated through a differentiate-then-discretize approach. The exemplary optimization of the blade shape of the centrifugal compressor wheel has been carried out for the inviscid gas flow governed by Euler equations with a non-uniform mass flow distribution as the inlet boundary condition. Mixing losses have been minimized downstream the outlet of the centrifugal wheel in this exemplary optimization. The results of the optimization problem accomplished by the two above-mentioned methods have been presented. In the case sparse grids have been used, the method with the gradient approximated by finite differences has been found to be more consistent. The discretization accuracy has turned out to be crucial for the consistency of the gradient method via sensitivities.

Chlorophyll extraction from leaves,needles and microalgae:A kinetic approach

Currently,there is a strong focus on industrial production of chlorophyll as a natural pigment.Two factors are required in the economically feasible process to make chlorophyll production:material with high pigment content and efficient extraction mechanism.In this work,extraction of chlorophyll from harvested black locust(Robinia pseudoacacia)leaves,Scots pine(Pinus sylvestris)needles,field sow thistle(Sonchus arvensis)leaves,and green microalga(Chlorella sp.)was discussed.The highest pigment content was detected in Chlorella cells(4.46%)followed by black locust leaves(1.63%),sow thistle leaves(1.48%)and pine needles(0.38%).The chlorophyll extraction rate was the highest for black locust leaves(k=3.59 h^(-1)),sow thistle leaves(k=2.90 h^(-1))and Chlorella cells(k=2.80 h^(-1))with the use of methanol as a solvent.In investigated materials,needles showed higher resistance for chlorophyll extraction(k=0.93 h^(-1))when compared to leaves and microalgae.Values of extraction kinetic constant were much lower for all materials(0.22-1.12 h^(-1))in the case of using ethanol as a solvent.Black locust leaves and Chlorella cells were proved to be the most attractive materials for chlorophyll production.

Poriferan chitin as a template for hydrothermal zirconia deposition

Chitin is a thermostable biopolymer found in various inorganic-organic skeletal structures of numerous invertebrates including sponges （Porifera）. The occurrence of chitin within calcium- and silica-based biominerals in organisms living in extreme natural conditions has inspired development of new （extreme biomimetic） synthesis route of chitin-based hybrid materials in vitro. Here, we show for the first time that 3D-a-chitin scaffolds isolated from skeletons of the marine sponge Aplysina aerophoba can be effectively mineralized under hydrothermal conditions （150℃） using ammonium zirconium（IV） carbonate as a precursor of zirconia. Obtained chitin-ZrO2 hybrid materials were characterized by FT-IR, SEM, HRTEM, as well as light and confocal laser microscopy. We suggest that formation of chitin-ZrO2 hybrids occurs due to hydrogen bonds between chitin and ZrO2.

电磁学中的计算机工程

2003年9月在斯洛文尼亚举行了“第十一届电子工程中的电磁场国际会议（ISEF’03）”，本书有选择性地收集了此次会议上的部分论文。ISEF的传统是包括广泛的计算和应用电磁学的范围，并促进理论与实际的结合，因此，大部分论文来自工程问题。

Extreme biomimetic approach for developing novel chitin-GeO2 nanocomposites with photoluminescent properties

This work presents an extreme biomimetics route for the creation of nano- structured biocomposites utilizing a chitinous template of poriferan origin. The specific thermal stability of the nanostructured chitinous template allowed for the formation under hydrothermal conditions of a novel germanium oxide- chitin composite with a defined nanoscale structure. Using a variety of analytical techniques （FTIR, Raman, energy dispersive X-ray （EDX）, near-edge X-ray absorption fine structure （NEXAFS）, and photoluminescence （PL） spectroscopy, EDS-mapping, selected area for the electron diffraction pattern （SAEDP）, and transmission electron microscopy （TEM））, we showed that this bioorganic scaffold induces the growth of GeO2 nanocrystals with a narrow （150-300 nm） size distri- bution and predominantly hexagonal phase, demonstrating the chitin template＇s control over the crystal morphology. The formed GeO2-chitin composite showed several specific physical properties, such as a striking enhancement in photo- luminescence exceeding values previously reported in GeOR-based biomaterials. These data demonstrate the potential of extreme biomimetics for developing new-generation nanostructured materials.