An Approximate Relation of a Regenerative Heat Exchanger Effectiveness in Off-Design Conditions

A regenerative heat exchanger is an important component of a thermal system in power units. It is crucial to know the performance of the regenerative heat exchanger in off-design conditions during its design and operation. Advanced regenerative heat exchanger simulators have been developed for many years to describe the performance in off-design conditions. The simulators involve the use of equations for mass, momentum, and energy balances and criteria relations for heat transfer coefficients; the geometrical data of the heat exchanger are also required. Due to high complexity, the calculations are performed iteratively. For this paper, a different approach was taken: The heat exchanger was considered as a “black box.” Based on the data obtained from the simulator, the effect of input variables on the output ones was investigated, so as to propose a relation describing the regenerative heat exchanger performance. To assess this performance, heat transfer effectiveness was proposed, and its two variants were considered. Since two heat transfer effectiveness definitions were assumed, two approximate relations concerning the regenerative heat exchanger were determined. The relations were verified against data obtained from a simulator of a high-pressure regenerative heat exchanger in a medium-power steam condensing unit. A satisfactory accuracy of the proposed relations was obtained.     

Contactless palmprint and knuckle biometrics for mobile devices

In this paper, biometric methods for contactless and unrestricted access control for mobile devices are proposed. The major contribution of this paper are palmprint and knuckles feature extraction methods dedicated for the mobile contactless biometrics. We use texture mask-based features for the palmprint. For the knuckles, we use Probabilistic Hough Transform and Speeded Up Robust Features as well as the 3-step classification methodology. We prove the efficiency of the presented methods by reporting promising results.     

Examining users’ preferences towards vertical graphical toolbars in simple search and point tasks

The main purpose of this study was to investigate the nature of preferences and their relation to the objective measures in simple direct manipulation tasks involving both the cognitive process as well as the visually guided pointing activities. The conducted experiment was concerned with the graphical structures resembling toolbars widely used in graphical interfaces. The influence of the graphical panel location, panel configuration as well as the target size on the user task efficiency and subjects’ preferences were examined. The participants were requested to express their attitudes towards the tested panels before and after the efficiency examination. This subjective evaluation was carried out within the framework of Analytic Hierarchy Process (AHP; Saaty, 1977, 1980). The subjective results that were obtained showed significant differences in the subjects’ preferences towards examined panels before and after completing the tasks. It seems that the users are able to comparatively quickly change their minds after gaining some experience with the investigated stimuli. Additionally, the applied cluster analysis revealed that the subjects were not homogenous in their opinions, and they formed groups having similar preference structures.     

Influence of inulin on physical characteristics and staling rate of gluten-free bread

Inulin preparations with different degree of polymerization (HSI with a DP < 10, GR − DP ? 10 and HPX − DP > 23) were used for the production of gluten-free bread. It was found that an addition of investigated compounds resulted in an increase of loaf volume and reduction of crumb hardness. However, internal structure of the obtained loaves was less uniform and more open than in control bread. Generally, inulin preparations with lower degree of polymerization had stronger effect on all analyzed parameters than that with higher DP. A decrease in staling was observed (measured as the rate of crumb hardening), which was caused by the presence of inulin. The highest content of retrograded amylopectin was found for crumb with HSI, and the lowest for samples with HPX.     

Relationship between the maximum and the random reflectance of vitrinite for coal from the Upper Silesian Coal Basin (Poland)

The relationship between the maximum and random reflectance of vitrinite, R_max and R_r, for Upper Silesian coal is represented by the equation: R_max=1.090R_r−0.052. When the random reflectance is higher than 0.90%, the difference between R_max and R_r values becomes significant. R_max is a more precise rank indicator, the standard deviation is much smaller than the standard deviation of the random reflectance value, which is larger due to the optical anisotropy of vitrinite.     

Two-dimensional point spread matrix of layered metal-dielectric imaging elements

We describe the change of the spatial distribution of the state of polarization occurring during two-dimensional (2D) imaging through a multilayer and in particular through a layered metallic flat lens. Linear or circular polarization of incident light is not preserved due to the difference in the amplitude transfer functions for the TM and TE polarizations. In effect, the transfer function and the point spread function (PSF) that characterize 2D imaging through a multilayer both have a matrix form, and cross-polarization coupling is observed for spatially modulated beams with a linear or circular incident polarization. The PSF in a matrix form is used to characterize the resolution of the superlens for different polarization states. We demonstrate how the 2D PSF may be used to design a simple diffractive nanoelement consisting of two radial slits. The structure assures the separation of nondiffracting radial beams originating from two slits in the mask and exhibits an interesting property of a backward power flow in between the two rings.     

Experimental investigation of CO2 separation from lignite flue gases by 100 cm single Molten Carbonate Fuel Cell

The paper presents an experimental investigation of using a Molten Carbonate Fuel Cell (MCFC) to reduce CO₂ emission from the flue gas of a lignite fired boiler. The MCFC is placed in the flue gas stream and separates CO₂ from the cathode side to the anode side. As a result, a mixture of CO₂ and H₂O is obtained from which pure CO₂ can be obtained through condensation of water and carbon dioxide. The main advantages of this solution are: additional electricity generated, reduced CO₂ emissions and higher system efficiency. The results obtained show that the use of an MCFC could reduce CO₂ emissions by 90% with over 30% efficiency in additional power generation.     

Studies of a mixing process induced by a transverse rotating magnetic field

This study reports on research results in the field of a mixing process under the action of a transverse rotating magnetic field (TRMF). The main objective of this paper is to present the effect of this type of a magnetic field on the mixing time. The proposed dimensional analysis of Navier–Stokes equation including the Lorentz force allows describing the analyzed process by means of the relationships basing on the dimensionless numbers (the mixing time number, the magnetic Taylor number, and the rotational Reynolds number). The possibility of using the magnetic particles (Fe₃O₄) as active micro-stirrers under the influence of a TRMF for active enhancement of a mixing process was considered. Moreover, the effect of a particle content on homogenization efficiency by applying a TRMF was also investigated. The obtained experimental results suggest that the mixing time under the TRMF and MDF conditions may be worked out by using the relation between the mentioned mixing time number and the modified Reynolds number (particle Reynolds number). Important conclusions referring to the discussion of experimental studies of a mixing process are also specified.