Influence of Cr, Mn and Mo Addition on Structure and Properties of V Microalloyed Medium Carbon Steels

The effect of austenitizing temperature and Cr, Mo and Mn addition on microstructure and mechanical properties of V microalloyed medium carbon steel has been studied by means of metallography and mechanical testing. The addition of Cr, Mn and Mo leads to a decrease in yield strength (YS) by approximate 100 MPa in comparison to the base steel. It is assumed that Mn and Mo increase hardenability by promoting the formation of bainitic sheaves (BS), i.e. by suppressing the formation of ferrite-pearlite and acicular ferrite (FP-AF). Cr at the level used in this work is not that effective. Presence and packet size of bainitic sheaves decrease the Charpy V-notch impact energy at 20℃ (CVN20) in comparison to ferrite-pearlite and acicular ferrite microstructures.     

Pyrolysis and Pt(IV)- and Ru(III)-ion catalyzed pyrolysis of asphaltenes in organic geochemical investigation of a biodegraded crude oil (Gaj, Serbia)

This paper is aimed at investigating the origin and geological history of the biodegraded Gaj (Serbia) crude oil, based on comparison of biomarkers, particularly alkylaromatics, in crude oil maltene fraction, with those in the liquid raw asphaltene pyrolysis products. The content of asphaltenes in crude oils being generally very low, expecting a higher yield of pyrolysate, pyrolysis of raw asphaltenes was also carried out in the presence of Pt(IV)- and Ru(III)-ions. The used metal ions demonstrated positive effects on the yields of total liquid pyrolysate and corresponding hydrocarbons. Occluded maltene and asphaltene pyrolysis products showed that metal ions had considerably stronger effect on maturation changes in naphthalene and phenanthrene rings than in polycyclic alkanes. The values of maturity parameters observed in maltenes and pyrolysates suggested this crude oil to have been expelled from the source before the “oil window” maximum. The investigated sample of the Gaj crude oil was shown to be in the 4th stage of biodegradation scale and to have originated from source rocks poor in clays, most probably carbonates, with significant contribution of algae to oil precursor biomass, deposited under a stratified saline water column.     

Activation studies with an iron fischer-tropsch catalyst in fixed bed and stirred tank slurry reactors

A precipitated iron catalyst (100 Fe/5 Cu/4.2 K/25 SiO₂ on a mass basis) was tested in a fixed bed reactor and a stirred tank slurry reactor under the same process conditions (250°C, 1.48 MPa, 2 L (STP)/gcat · h, H₂ : CO = 2:3). Two different pretreatment procedures were employed (hydrogen reduction at 220°C and carbon monoxide activation at 280°C) in each of the two reactor types. In the stirred tank slurry reactor tests the activity (based on an apparent first order reaction rate constant) of the carbon monoxide pretreated catalyst was about 25% higher than that of hydrogen reduced catalyst, due to incomplete reduction of the latter. In all tests the catalyst selectivity changed slowly with time on stream. Hydrocarbon distribution shifted toward lower molar mass products, and secondary reactions (l-olefin hydrogenation, isomerization and readsorption) increased with time. The secondary reactions were the most pronounced on the hydrogen reduced catalyst in the fixed bed reactor.     

Training in coordinate measurement using 3D virtual instruments

Coordinate metrology is a subject that has evolved driven by two important vectors: hardware and software development. At present, most 3D measuring software offer features for offline programming of the Coordinate Measuring Machines (CMM). A few software solutions enable the simulation of both the CMM and other elements involved in the measuring process, such as the human operator or an automated system for loading and unloading the measured parts. The paper presents the features and advantages offered by Delmia V5 for simulating a complete measuring environment encompassing: the CMM, the human operator, a robot or automated system for manipulating the parts. The simulations developed represent a powerful learning tool that can complement existing models for CMM training.     

Miniaturized calorimeter for thermal screening of energetic materials

The use of chip-scale calorimeters for research and development has increased during the last two decades. The high sensitivity of these devices allows their use for characterization of very small amounts of sample. However, the potential for using them for screening of highly energetic materials (i.e., explosives) has not been fully explored. In this paper, we present the design aspects of two chip-scale calorimeter prototypes based on thick silicon membranes for liquid and solid thermal characterizations. The ultimate goal of the proposed work is to produce a portable calorimeter that can be incorporated as a new approach for detection of highly energetic materials such as explosives based on the information obtained from the calorimeter. The concept of this application is that indirect detection via the determination of thermal energy released in exothermic reactions can be detected by chip-scale calorimetric sensors. Details about the calorimeter design using finite element analysis are presented along with the fabrication procedure of the proposed sensor. Finally, preliminary results that provide experimental validation of the device design are presented.     

Improving the multicaloric properties of Pb(Fe0.5Nb0.5)O3 by controlling the sintering conditions and doping with manganese

Designing multicaloric single-phase materials with combined electro- and magnetocaloric effects is still at its initial stage and presents a number of challenges. One of the main challenges encountered so far is to reduce the excessive electrical conductivity, which leads to the appearance of Joule heating that might completely degrade the electrocaloric response. In this work, multicaloric Pb(Fe_0.5Nb_0.5)O₃ material was successfully prepared exhibiting pronounced electrocaloric effect above room temperature and maximum magnetocaloric effect at cryogenic temperature. The conductivity was suppressed by controlling the sintering temperature. The ceramic sintered at 1000 °C exhibits maximum electrocaloric effective cooling of 0.88 °C at 28 °C and maximum magnetocaloric effect of 0.14 °C at ?271 °C. The caloric properties can be further improved by doping Pb(Fe_0.5Nb_0.5)O₃ with manganese. In comparison to the undoped sample, Pb(Fe_0.5Nb_0.5)O₃ doped with 0.5 mol% of manganese exhibits three times higher maxima of electrocaloric effective cooling (2.47 °C at 80 °C) and magnetocaloric temperature change (0.44 °C at ?271 °C).     

Multidepot pickup and delivery problems in multiple regions: a typology and integrated model

The rapid development experienced by the transportation industry in the past decades has led to many configurations of networks and therefore to an explosion of variants in transportation problems, motivating researchers to look at broader logistic problems, beyond the basic vehicle routing problems. This work introduces a new type of problem scenario combining various attributes: a pickup and delivery problem with multiple regions, multiple depots, and multiple transportation modes. We provide definitions, a literature review, and a step‐by‐step construction of the mathematical models from a simple and well‐known scenario to the multiregion multidepot pickup and delivery problem (MR‐MDPDP). For each step the relevant literature is examined. Furthermore, we suggest possible extensions for prospective research.     

Hippocampal gamma oscillations in rats

Previous studies suggested that γ oscillations in the brain are associated with higher order cognitive functions, including selective visual attention, motor task planning, sensory perception, working memory, and dreaming rapid eye movement (REM) sleep [1]--[7]. These oscillations are mainly observed in the cortical regions and also occur in neocortical and subcortical areas and hippocampus. These oscillations may occur under certain pathological conditions, such as epilepsy, and are mainly observed in the cortical regions and hippocampus. The previous studies have suggested that epilepsy may be associated with disturbances of autonomic nervous system(ANS) andwith changes in autonomic cardioregulatory function [8]--[13]. In this article, we investigate the influence of acute exposure to 2-aminoethoxy-diphenylborate (2-APB), a membrane-permeable inositol 1,4,5-trisphosphate (IP₃) receptor, and store-operated Ca²⁺ channel (SOC) blocker on the complexity of hippocampal γ oscillations. Our central hypothesis is that acute exposure to 2-APB significantly reduces the hippocampal γ oscillations. To test this hypothesis, we use brain-slice recordings and the advanced nonlinear dynamical analysis method based on the Lempel-Ziv (LZ) estimator. Our nonlinear dynamical analysis results estimated from brain-slice recordings suggested that 2-APB exposure significantly reduces the hippocampal γ oscillations.     

The Ostrowski's integral inequality for Lipschitzian mappings and applications

A generalization of Ostrowski's inequality for Lipschitzian mappings and applications in numerical analysis and for Euler's Beta function are given.