A method for the concurrent design and analysis of networked manufacturing systems

Multistage manufacturing processes (MMPs) require multiple stations and operations. Traditionally, analysis of MMPs focused on material planning and control strategies. For a given MMP, the effect of the strategy on the volume and rate of production, ability to handle product type variability, and the effects of process variability on production rate, on-process inventory, etc., have been studied individually. Such approaches, while necessary, do not address the combined effects of MMP design choices on the final product quality. In this article, a method based on the compromise decision support problem and stream of variation model is proposed to provide a way to evaluate suitable designs for the implementation of MMPs. Using the dimensional quality of the product as a measure of quality, the proposed method is illustrated using a three-stage MMP in an automobile panel stamping process while considering the conflicting requirements of diagnosability and controllability.     

Characterization of B4C-SiC ceramic composites prepared by ultra-high pressure sintering

Additive-free boron carbide (B₄C) – silicon carbide (SiC) ceramic composites with different B₄C and β-SiC powders ratio were densified using the high-pressure “anvil-type with hollows” apparatus at 1500 °C under a pressure of 4 GPa for 60 s in air. The effect of starting powders ratio on the composites sintering behavior, relative density, microstructural development, and thermomechanical properties was studied. The sintered samples hardness was found to be in the range from 24 to 31 GPa. The thermal conductivity measurements, conducted in the temperature range from room temperature to 1000 °C, showed that the thermal diffusivity of sintered samples was between 6 and 9.5 mm²/s whereas the thermal conductivity was in the range from 16 to 28 W/(m K). The results of this study show that the high-pressure sintering can be a very effective low-temperature densification method for the obtainment of additive-free B₄C - β-SiC ceramic composites.     

An Evaluation of Steel Embrittlement Caused by Welding

The fracture toughness of the HAZ in welds on a HSLA structural steel was assessed by using two types of precracked small-scale fracture-mechanics specimens. The microstructure of the single- and double-pass HAZs was simulated on a Gleeble machine at two different cooling rates. A direct measurement of K_Ic was not possible due to the limited size of both kinds of specimens. A suitable adaptation of the loading diagrams was performed in order to produce relevant data about the fracture properties of the investigated sub-zones of the HAZ.     

Liquid–liquid equilibrium for the systems hydrocarbon–thiophene or pyridine–1-hexyl-3,5-dimethylpyridinium bis(trifluoromethylsulfonyl)imide

Liquid–liquid equilibrium for eight ternary systems involving one hydrocarbon (n-hexane, n-heptane, i-octane or toluene), thiophene or pyridine and an ionic liquid (1-hexyl-3,5-dimethylpyridinium bis(trifluoromethylsulfonyl)imide) was experimentally determined at atmospheric pressure and 25°C. Equilibrium data are presented with binodal curves as well as with tie lines. The suitability of ionic liquid (IL) for extractive desulfurization and denitrification was evaluated in terms of solute distribution ratio and selectivity. Extraction experiments with three-component and seven-component (n-hexane, n-heptane, i-octane, toluene, thiophene, pyridine and IL) systems have been performed. The equilibrium data in three-component systems were well described with Non-Random Two-Liquid (NRTL) and Universal Quasi-Chemical (UNIQUAC) models.     

DMSO Chemically Alters Cell Membranes to Slow Exocytosis and Increase the Fraction of Partial Transmitter Released

Dimethyl sulfoxide (DMSO) is frequently used as a solvent in biological studies and as a vehicle for drug therapy; but the side effects of DMSO, especially on the cell environment, are not well understood, and controls with DMSO are not neutral at higher concentrations. Herein, electrochemical measurement techniques are applied to show that DMSO increases exocytotic neurotransmitter release, while leaving vesicular contents unchanged. In addition, the kinetics of release from DMSO‐treated cells are faster than that of untreated ones. The results suggest that DMSO has a significant influence on the chemistry of the cell membrane, leading to alteration of exocytosis. A speculative chemical mechanism of the effect on the fusion pore during exocytosis is presented.     

PM6 and DFT study of free radical scavenging activity of morin

Flavonoids have long been recognised for their general health-promoting properties, of which their antioxidant activity may play an important role. In this work, we have studied the properties of flavonoid morin using semiempirical and density functional theory (DFT) methods in order to validate the application of the recently developed parametric method 6 (PM6). Reaction enthalpies related to mechanisms of free radical scavenging by flavonoid morin were calculated by DFT and PM6 methods in gas-phase, water, DMSO and benzene. It has been shown that fast semiempirical PM6 method can mimic results obtained by means of more accurate time consuming DFT calculations. Thermodynamically favoured mechanism depends on reaction medium: SPLET (sequential proton loss electron transfer) is preferred in water and DMSO, and HAT (hydrogen atom transfer) is predominant in gas-phase. In benzene these two mechanisms are competitive.     

Analysis of Slovenian research community through bibliographic networks

Science is a societal process, designed on widely accepted general rules which facilitate its development. Productive researchers are viewed from the perspective of a social network of their interpersonal relations. In this paper we address performance of Slovenian research community using bibliographic networks between the years 1970 and 2015 from various aspects which determine prolific science. We focus on basic determinants of research performance including productivity, collaboration, internationality, and interdisciplinarity. For each of the determinants, we select a set of statistics and network measures to investigate the state of each in every year of the analyzed period. The analysis is based on high quality data from manually curated information systems. We interpret the results by relating them to important historical events impacting Slovenia and to domestic expenditure for research and development. Our results clearly demonstrate causal relations between the performance of research community and changes in wider society. Political and financial stability together with concise measuring of scientific productivity established soon after Slovenia won independence from Yugoslavia in 1991 had positive influence on all determinants. They were further leveraged by foundation of Slovenian research agency and joining EU and NATO. Publish and perish phenomenon, negative impacts of financial crisis in 2008–2014 and reshaping the domestic expenditure for research and development after 2008 have also clear response in scientific community. In the paper, we also study the researcher’s career productivity cycles and present the analysis of the career productivity for all registered researchers in Slovenia.     

Reliability of force–time curve characteristics during maximal isometric leg press in differently trained high-level athletes

The aim of this research was to establish the metrologic values of the isometric force–time characteristics of leg extensors in differently trained, healthy male athletes and non-athletes. 99 subjects performed a standardized “isometric leg press” test. Even though the results showed a high statistical significance in terms of representativeness, generalizability and reliability for all contractile characteristics of observed measured variables, different methodological approaches were required in order to obtain the most valid results for differently trained and untrained subjects. Based on the results obtained, and from the aspect of the methodology of testing different isometric force characteristics, it was possible to conclude that the standardization of the isometric leg press requires two trials in football, where the most reliable data was from the first trial (the communality rates (H²) from 0.866 to 0.969). Water polo and basketball require three trials. The most reliable data was from the third and second trial in water polo (H² from 0.909 to 0.986). In basketball the most reliable data was from the second trial (H² from 0.824 to 0.987). The untrained healthy adult population requires four trials, and the most reliable data was from the third trial (H² from 0.961 to 0.995).     

Effects of access phases lengths on performance of IEEE 802.15.6 CSMA/CA

In this paper, we study interplay of prioritizing mechanisms in recently released IEEE 802.15.6 standard for Wireless Body Area Networks (WBANs). Among eight User Priorities (UPs) we study the impact of access phases lengths and CSMA/CA mechanism on the network performance. We consider a star-topology single-hop WBAN in which the hub operates in beacon mode with superframe boundaries. Our study is conducted in saturation regime and an error prone channel in order to indicate performance bounds for all UPs. We have developed an analytical model for the CSMA/CA-based Medium Access Control (MAC) layer of IEEE 802.15.6 which includes Markov chain and probabilistic models for all UPs. In order to validate the analytical model we have developed a simulation model in OPNET. We investigate the effectiveness of deploying exclusive access phases and second random access phase on the network performance. We also examine the medium utilization and normalized throughputs of all UPs. Obtained performance bounds indicate potential tradeoff between the prioritizing parameters which affect the saturation throughputs.