Preparation of TiB2-20 Wt Pct MoSi2 Composite Material by Mechanochemical Synthesis and Spark Plasma Sintering

Metallurgical and Materials Transactions A - The mechanosynthesis process of composite powders for the preparation of a TiB2-20 wt pct MoSi2 composite material from...     

Modification of surface layers of quick-speed powdered metal steels using welding heat sources

Powdered metal steel S390 and its equivalents are manufactured in a traditional way, that is, steel 10-4-3-10 (SK10V) which is subjected to modification of its surface layer. An analysis was made of the changes to the structure and mechanical properties of the above-mentioned steels at each individual stage of a heat treatment process carried out after soft annealing, quenching, tempering, and joint penetration surface treatment. The scope of this analysis included optimization of the joint penetration parameters, macro-, and micro-testing with utilization of scanning and light microscopy, preliminary tests of phase composition as well as comparative hardness measurement. The major practical purpose of the experiment was to assess the feasibility of using welding heat sources for joint penetration surface treatment of quick-speed steels.     

Assessing Acute Toxicity of Selected Packages Internal Layers Extracts using Microtox®

In the scientific literature related to the widely understood issue of packaging materials designed to have contact with food (food contact materials), there is much information on raw materials used for their production, as well as their physiochemical properties, types and parameters. Unfortunately, not much attention is given to the issues concerning migration of toxic substances from packaging and its actual influence on the health of the final consumer, even though health protection and food safety are the priority tasks. The goal of this study was to estimate the impact of particular foodstuff packaging type, food production and storage conditions on the degree of leaching of potentially toxic compounds to foodstuffs with the use of the acute toxicity test Microtox^®. From all simulants studied, the 3% acetic acid in water proved to cause significant migration of toxic compounds with increase of time and temperature of extraction and justified the hypothesis that food products with low pH values (stored in cans) cause significant damage to cans internal resin filing and is a reason of increased migration rate of package material to foodstuff. Copyright © 2017 John Wiley & Sons, Ltd.     

Hot-forged wear-resistant powder meterials based on stainless steels of the austenitic class

The microstructure, tribological and physicomechanical properties of hot-forged composites based on stainless steel of the austenitic class with additions of carbon, Cr₃C₂ and MoS₂ are studied. The possibility is established of using these composites for powder structural articles resistant to wear and corrosion. __________ Translated from Poroshkovaya Metallurgiya, Nos. 1–2(447), pp. 26–35, January–February, 2006.     

Interactions between toxic chemicals and natural environmental factors — A meta-analysis and case studies

The paper addresses problems arising from effects of natural environmental factors on toxicity of pollutants to organisms. Most studies on interactions between toxicants and natural factors, including those completed in the EU project NoMiracle (Novel Methods for Integrated Risk Assessment of Cumulative Stressors in Europe) described herein, showed that effects of toxic chemicals on organisms can differ vastly depending purely on external conditions. We compiled data from 61 studies on effects of temperature, moisture and dissolved oxygen on toxicity of a range of chemicals representing pesticides, polycyclic aromatic hydrocarbons, plant protection products of bacterial origin and trace metals. In 62.3% cases significant interactions (p ≤ 0.05 or less) between natural factors and chemicals were found, reaching 100% for the effect of dissolved oxygen on toxicity of waterborne chemicals. The meta-analysis of the 61 studies showed that the null hypothesis assuming no interactions between toxic chemicals and natural environmental factors should be rejected at p = 2.7 × 10^− 82 (truncated product method probability). In a few cases of more complex experimental designs, also second-order interactions were found, indicating that natural factors can modify interactions among chemicals. Such data emphasize the necessity of including information on natural factors and their variation in time and across geographic regions in ecological risk assessment. This can be done only if appropriate ecotoxicological test designs are used, in which test organisms are exposed to toxicants at a range of environmental conditions. We advocate designing such tests for the second-tier ecological risk assessment procedures.     

Effective synchronizing algorithms

The notion of a synchronizing sequence plays an important role in the model-based testing of reactive systems, such as sequential circuits or communication protocols. The main problem in this approach is to find the shortest possible sequence which synchronizes the automaton being a model of the system under test. This can be done with a synchronizing algorithm. In this paper we analyze the synchronizing algorithms described in the literature, both exact (with exponential runtime) and greedy (polynomial). We investigate the implementation of the exact algorithm and show how this implementation can be optimized by use of some efficient data structures. We also propose a new greedy algorithm, which relies on some new heuristics. We compare our algorithms with the existing ones, with respect to both runtime and quality aspect.