Studies on the synthesis of fiber-forming block copolymers of polyacrylonitrile and poly(ethylene oxide)

Modified PEO (MW 6000) containing xanthate groups was used for the synthesis of block copolymers of PAN and PEO. Principal parameters affecting the synthesis were examined. To confirm the segmental structure of the obtained products, precipitation fractionation, gel permeation chromatography, infrared, and ¹H nuclear magnetic resonance methods were used. The fiber-forming properties were investigated by means of rheological examination of concentrated solutions of PAN–PEO and confirmed by spinning the fibers under laboratory conditions. The physical and mechanical properties of the fibers were also determined.     

Empathy and Modern Technology: A Neuroergonomics Perspective

The primary purpose of this paper is to discuss the role of empathy in the design of advanced systems in manufacturing and service industries in order to ensure suitable working conditions for employees from the social and technological point of view. The origins and components of empathy are briefly reviewed. The neural underpinnings of three components of empathy, including cognitive, emotional, and behavioral aspects, are considered in the context of human–human and human–machine interactions, as well as design of working environments. Finally, the potential advantages of applying empathy‐related knowledge to the design and development of human‐centered technology are discussed.     

Implementation of a strain energy-based nonlinear finite element in the object-oriented environment

The objective of the paper is to describe a novel finite element computational method based on a strain energy density function and to implement it in the object-oriented environment. The original energy-based finite element was put into the known standard framework of classes and handled in a different manner. The nonlinear properties of material are defined with a modified strain energy density function. The local relaxation procedure proposed as a method used to resolve a nonlinear problem is implemented in C++ language. The hexahedral element with eight nodes as well as the adaptation of the nonlinear finite element is introduced. The chosen numerical model is made of nearly incompressible hyperelastic material. The application of the proposed element is shown on the example of a rectangular parallelepiped with a hollow port.     

Selection of a dynamic supply portfolio in make-to-order environment withrisks

The problem of a multi-period supplier selection and order allocation in make-to-order environment in the presence of supply chain disruption and delay risks is considered. Given a set of customer orders for finished products, the decision maker needs to decide from which supplier and when to purchase product-specific parts required for each customer order to meet customer requested due date at a low cost and to mitigate the impact of supply chain risks. The selection of suppliers and the allocation of orders over time is based on price and quality of purchased parts and reliability of supplies. For selection of dynamic supply portfolio a mixed integer programming approach is proposed to incorporate risk that uses conditional value-at-risk via scenario analysis. In the scenario analysis, the low-probability and high-impact supply disruptions are combined with the high probability and low impact supply delays. The proposed approach is capable of optimizing the dynamic supply portfolio by calculating value-at-risk of cost per part and minimizing expected worst-case cost per part simultaneously. Numerical examples are presented and some computational results are reported.     

Sliding wear resistance of Fe-, Ni- and Co-based alloys for plasma deposition

Performance of Fe-, Ni- and Co-based alloys was evaluated in sliding wear and in the impact wear tests to simulate wear of valves and valve inserts in internal combustion engines. From the SEM investigations adhesive wear was confirmed by metal transfer between rubbing surfaces while surface deformation testify to abrasive wear. It was found that oxides formed on the surface prevented direct metal-to-metal contact and reduced the coefficient of friction thereby reducing wear. A comparison of wear resistances of Fe, Ni- and Co-based alloys used as hardfacings were given. It is also shown that Ni–Co alloys with Ni-alloy content between 40.4 and 64.3 have a considerable potential, they reveal above 2 times higher wear resistance than plasma-deposited cobalt alloy.     

Analysis of polymer foil heaters as infrared radiation sources

Infrared radiation as a heat source is used in many fields. In particular, the positive effect of far-infrared radiation on living organisms has been observed. This paper presents two technological solutions for infrared heater production using polymer-silver and polymer-carbon pastes screenprinted on foil substrates. The purpose of this work was the identification of polymer layers as a specific frequency range IR radiation sources. The characterization of the heaters was determined mainly by measurement of the surface temperature distribution using a thermovision camera and the spectral characteristics were determined using a special measuring system. Basic parameters obtained for both, polymer silver and polymer carbon heaters were similar and were as follows: power rating of 10–12 W/dm², continuous working surface temperature of 80–90 °C, temperature coefficient of resistance (TCR) about +900 ppm/K for polymer-carbon heater and about +2000 ppm/K for polymer-silver, maximum radiation intensity in the wavelength range of 6–14 μm with top intensity at 8.5 μm and heating time about 20 min. For comparison purposes, commercial panel heater was tested. The results show that the characteristics of infrared polymer heaters are similar to the characteristics of the commercial heater, so they can be taken into consideration as the alternative infrared radiation sources.     

Influence of hydrodynamic instability on the heat transfer coefficient during condensation of R134a and R404A refrigerants in pipe mini-channels

This paper presents the results of an investigation of the influence of hydrodynamic instabilities on heat transfer intensity during the condensation of R134a and R404A refrigerants in pipe mini-channels. The heat transfer coefficient h is a measure of the effectiveness of the condensation process. It is particularly important to determine the value of the coefficient in the two-phase condensation area in a compact condenser. In other condenser areas (i.e., precooling of superheated vapor and subcooling of condensate), the heat efficiency is substantially smaller. Hydrodynamic instabilities of a periodic nature have an influence on size changes in these areas. A decrease in the heat transfer coefficient h in the two-phase area results in decreased intensity of the heat removal process in the whole condenser.The experimental investigations were based on the condensation of R134a and R404A refrigerants in horizontal pipe mini-channels with internal diameters of d = 0.64; 0.90; 1.40; 1.44; 1.92; 2.30 and 3.30 mm. Disturbances of the condensation process were induced with a periodic stop and a repetition of the flow of the refrigerant.In the range of frequencies, f = 0.25–5 Hz, of the periodically generated disturbances, an unfavorable influence on the intensity of the heat transfer during the condensation process in pipe mini-channels was identified. The reduction in the intensity of the heat transfer during the condensation process, which was induced with hydrodynamic instabilities, was presented in the form of the dependence of the heat transfer coefficient h on the vapor quality x and the frequencies f of the disturbances.The influence of the refrigerant, the diameter of the mini-channels and the frequency f on the damping phenomenon of the periodical disturbances in the pipe mini-channels was identified.     

Effect of Tempering on the Structure and Coercive Force in the AISI D3 (217H12WF) Ledeburite Chromium Steel

The main purpose of the studies was to establish the effect of the tempering temperature on the changes of carbide and retained austenite contents. It has been found that the course of changes of the coercive force of hardened steel after austenitizing is qualitatively similar to the hardness changes. That means in practice it is possible to determine the 217H12WF steel hardness based on the measurement of the coercive force.     

Fatty acid composition of egg yolk phospholipid fractions following feed supplementation of Lohmann Brown hens with humic-fat preparations

The effect of feed supplementation with humic-fat preparations on the fatty acid composition of egg yolk phospholipid fractions was studied. The Lohmann Brown was the experimental hen strain and two feeding mixtures were applied – the standard feed and the mixture supplemented with humic-fat preparations. The fatty acid profile of yolk lipids was significantly affected (P = .05) by the supplementation of feed and total increase of n-3 polyunsaturated fatty acids (PUFA) was established. A different distribution of n-3 PUFA in egg yolk lipid fractions was observed: α-linolenic acid (18:3) was found in the triacylglycerol fraction, whereas docosahexaenoic acid (22:6) was detected in the phospholipid fractions. Supplementation of the hen’s diet with humic-fat preparations resulted in the production of n-3 enriched eggs with decreased n-6/n-3 ratio in all phospholipid fractions in comparison to the eggs from the control group.