The effect of sliding speed and amount of loading on friction and wear behavior of Cu–0.65 wt.%Cr alloy

Friction and wear behavior of a peak aged Cu–0.65 wt.%Cr alloy was investigated. The friction and wear experiments were run under ambient conditions with a pin-on-disk tribometer. Experiments were performed using various applied normal loads and sliding velocities. The tribological behavior of the studied alloy was discussed in terms of friction coefficient, wear loss and wear mechanism.Friction coefficient and wear loss have shown large sensitivity to the applied normal load and the sliding velocity. At the sliding velocity of 0.3 m/s weight loss increased from 6.9 to 51 mg by increasing the normal load from 20 to 40 N. At higher sliding velocity minimum weight loss is achieved at 60 N normal load. So it can be seen that with increasing normal load wear rate decreases due to the formation of a continuous tribofilm which consists of Fe–Cu intermetallic. Varying of friction coefficients in different conditions of normal load and sliding velocity is correlated to the wear behavior.The analysis of worn surfaces by XRD and SEM showed that an increase in normal load and sliding velocity creates an intermetallic wear-induced layer, which modifies the wear behavior of the alloy. The XRD result indicates that new phase of Cu_9.9Fe_0.1 is generated on worn surfaces of the pin specimens during the wear tests. There is a significant correlation between the micrograph of worn surfaces and the wear rate of specimens.     

Dry-or-buy decision support for dry kiln scheduling in furniture production

In this paper, a dry-or-buy cost model for a dry kiln scheduling problem in the furniture manufacturing industry is considered. Factory-specified due-dates for jobs, kiln availability, kiln capacity, and drying and buying costs are incorporated into an Integer-Programming (IP) model. As it may be difficult (i.e., because of due-dates, kiln availability, processing times, etc.) to meet all the due-dates, certain jobs may have to be out-sourced. The objective of the model is to minimize the total drying and buying costs while satisfying all due-dates. Because of the computational complexity of the problem, a heuristic approach is developed. Computational experience indicates that the heuristic gives high quality solutions with significant savings in time over standard IP algorithms.     

Incorporating microgrids coupling with utilization of flexible switching to enhance self-healing ability of electric distribution systems

Electric distribution networks have to deal with issues caused by natural disasters. These problems possess unique characteristics, and their severity can make load restoration methods impotent. One solution that can help in alleviating the aftermath is the use of microgrids (MGs). Employing the cumulative capacity of the generation resources through MG coupling facilitates the self-healing capability and leads to better-coordinated energy management during the restoration period, while the switching capability of the system should also be considered. In this paper, to form and schedule dynamic MGs in distribution systems, a novel model based on mixed-integer linear programming (MILP) is proposed. This approach employs graph-related theories to formulate the optimal formation of the networked MGs and management of their proper participation in the load recovery process. In addition, the Benders decomposition technique is applied to alleviate computability issues of the optimization problem. The validity and applicability of the proposed model are evaluated by several simulation studies.     

Event‐triggered optimal tracking control of nonlinear systems

We propose a novel event‐triggered optimal tracking control algorithm for nonlinear systems with an infinite horizon discounted cost. The problem is formulated by appropriately augmenting the system and the reference dynamics and then using ideas from reinforcement learning to provide a solution. Namely, a critic network is used to estimate the optimal cost while an actor network is used to approximate the optimal event‐triggered controller. Because the actor network updates only when an event occurs, we shall use a zero‐order hold along with appropriate tuning laws to encounter for this behavior. Because we have dynamics that evolve in continuous and discrete time, we write the closed‐loop system as an impulsive model and prove asymptotic stability of the equilibrium point and Zeno behavior exclusion. Simulation results of a helicopter, a one‐link rigid robot under gravitation field, and a controlled Van‐der‐Pol oscillator are presented to show the efficacy of the proposed approach. Copyright © 2016 John Wiley & Sons, Ltd.     

An unusual cause of subacute airway obstruction in a hemodialysis patient with brachio‐cephalic arteriovenous fistula: A rare presentation of central venous occlusion

A young lady with an arteriovenous (AV) fistula on hemodialysis was referred for surgical management following a failed endovascular approach to relieve central venous occlusion. She had an obstructed left brachiocephalic vein with a history of numerous central vein catheter placements. Alternative routes for new arteriovenous fistula creation had been exhausted due to previous contralateral upper limb fistula rupture and ligation. To the best of our knowledge, no similar cases of airway obstruction in central venous occlusion occurring in hemodialysis patients with AV fistula have been reported. The importance of identifying the possible emergency red flags in hemodialysis patients with central venous occlusion is important to prevent unwanted consequences.     

Correction to: Dependence of Tribological Performance and Tribopolymerization on the Surface Binding Strength of Selected Cycloalkane-Carboxylic Acid Additives

Tribology Letters - In an elastohydrodynamic lubricated (EHL) contact under Zero Entrainment Velocity (ZEV) condition, surfaces cannot be separated by hydrodynamic lift. In this work, two other...     

Prescribed performance adaptive neural output control for a class of switched nonstrict‐feedback nonlinear time‐delay systems: State‐dependent switching law approach

This paper investigates the tracking problem for a class of uncertain switched nonlinear delayed systems with nonstrict‐feedback form. To address this problem, by introducing a new common Lyapunov function (CLF), an adaptive neural network dynamic surface control is proposed. The state‐dependent switching rule is designed to orchestrate which subsystem is active at each time instance. In order to compensate unknown delay terms, an appropriate Lyapunov‐Krasovskii functional is considered in the constructing of the CLF. In addition, a novel switched neural network–based observer is constructed to estimate system states through the output signal. To maintain the tracking error performance within a predefined bound, a prescribed performance bound approach is employed. It is proved that by the proposed output‐feedback control, all the signals of the closed‐loop system are bounded under the switching law. Moreover, the transient and steady‐state tracking performance is guaranteed by the prescribed performance bound. Finally, the effectiveness of the proposed method is illustrated by two numerical and practical examples.     

EBG design and analysis for wideband isolation improvement between aircraft blade monopoles

A new lightweight multilayer mushroom EBG is proposed to significantly improve the isolation between collocated aircraft L‐band blade monopole antennas. Isolation improvement between two L‐bands (960‐1220 MHz) blade monopoles of nearly 20 dB is obtained with a three‐layer EBG design without requiring any redesigning or tuning of the antennas. Since the proposed EBG structure only contains very thin dielectric sheets and foam substrates it would be a lightweight structure. Moreover, the EBG being a stand‐alone structure from the antenna it can be designed, built, and placed between the antennas as an add‐on device to significantly improve antenna isolation over a relatively wide bandwidth (25%). An experimental EBG structure was built and tested demonstrating wideband isolation improvement performance.     

Ploidy and liquid-holding recovery in yeasts sensitive to radiation and nitrous acid

The effects of genome ploidy and posttreatment incubation on inactivation by nitrous acid (NA) were studied in normal, radio- and nitrous acid-sensitive strains of yeast. In normal yeast cells the increase of ploidy (haploid to triploid) resulted in "the protective effect", i.e. haploid cells were the most sensitive, triploid -- the most resistant. This "protective effect" is absent in polyploid yeast homozygous for the xrs1-5 (rad 54) mutation; in this case the NA-sensitivity rises with the increase of ploidy, i.e. haploid cells are the most resistant ones. The effect of liquid holding (LH) after the NA treatment depends on the genetic background and ploidy of treated cells. Posttreatment incubation in buffer has practically no effect on the survival of wild-type Berkeley's yeast strains (1n, 2n, 3n). The highly homozygous haploid strains from Zakharov' collection, both wild type and xrs1-5 mutant, exhibit no LH-recovery too. However the death of wild-type cells drastically rises in LH-condition as the ploidy increases. 24 hours incubation in buffer results in at least a ten-fold decrease in survival of wild type 2n, 3n, 4n cells. The loss of viability is proportional to the time of incubation, but the cell titer being constant. The strains (2n, 3n, 4n) homozygous for the xrs1-5 mutation (rad 54) show considerable LH-recovery. It is supposed that the xrs1-5 mutation results in the derepression of the prereplicative pathway of LH-recovery which eliminates the NA-INDUCED DAMAGE OF DNA.     

Male Aggregation Pheromone of Date Palm Fruit Stalk Borer Oryctes elegans

Laboratory and field investigations were carried out to characterize the chemical communication system of the date palm fruit stalk borer, Oryctes elegans, and to develop pheromone-based trapping in Eastern Iran. Adults of both sexes feeding on date palm pieces attracted conspecifics, whereas date palm alone was minimally attractive. Males were twice as attractive as females. More beetles were captured at the palm crown than at ground level. Odors from adults feeding on sugarcane were sampled and analyzed by gas chromatography and mass spectrometry. Whereas females did not emit sex specific volatiles, males emitted a blend of 4-methyloctanoic acid (1: major component) and ethyl 4-methyloctanoate (2), occasionally mixed with minor components: 4-methyloctanyl acetate (3), methyl 4-methyloctanoate (4), 4-methyloctanol (5), and nonanyl acetate (6). Electroantennography and field trapping experiments demonstrated that compound 1 is an essential component of the male aggregation pheromone of O. elegans. It was barely attractive by itself but synergistic with fresh date palm odor. It attracted many more beetles than any of compounds 2-6. The addition of one or several of compounds 2-6 to 1 did not improve trap captures. During the course of 2 years, we captured 4000 beetles, with a weekly average of 6.3 beetles/trap, and were able to monitor the seasonal flight of O. elegans. Our results provide the basis for developing mass trapping for control of this pest.