Effects of operator learning on production output: a Markov chain approach

We develop a Markov chain approach to forecast the production output of a human-machine system, while encompassing the effects of operator learning. This approach captures two possible effects of learning: increased production rate and reduced downtime due to human error. In the proposed Markov chain, three scenarios are possible for the machine at each time interval: survival, failure, and repair. To calculate the state transition probabilities, we use a proportional hazards model to calculate the hazard rate, in terms of operator-related factors and machine working age. Given the operator learning curves and their effect on reducing human error over time, the proposed approach is considered to be a non-homogeneous Markov chain. Its result is the expected machine uptime. This quantity, along with production forecasting at various operator skill levels, provides us with the expected production output.     

Choosing the optimal intervention method to reduce human-related machine failures

This paper presents a novel method to quantify the effects of human-related factors on the risk of failure in manufacturing industries. When failures can be caused by operators, the decision maker must intervene to mitigate operator-related risk. There are numerous intervention methods possible; we develop a revenue model that provides the decision-maker with a systematic tool to perform a cost-benefit analysis, balancing the advantage of risk reduction, against the direct cost of the intervention method.     

Electrochemical and catalytic investigations of epinephrine,acetaminophen and folic acid at the surface of titanium dioxide nanoparticle-modified carbon paste electrode

In the present paper, the use of a carbon paste electrode modified with 1-(4-(1, 3-dithiolan-2-yl)-6, 7-dihydroxy-2-methyl-6, 7-dihydrobenzofuran-3-yl)ethanone (DDE) and TiO₂ nanoparticles prepared by a simple and rapid method was described. The modified electrode showed excellent properties for electrocatalytic oxidization of epinephrine (EP), acetaminophen (AC) and folic acid (FA). The apparent charge transfer rate constant, k _s?=?1.14 s^?1, and transfer coefficient, α?=?0.54, for electron transfer between the modifier and carbon paste electrode were calculated. It has been found that under optimum condition (pH?=?7.0) in cyclic voltammetry, the oxidation of EP occurs at a potential about 280 mV less positive than that of an unmodified carbon paste electrode. The values of transfer coefficients (α?=?0.46), catalytic rate constant (k?=?1.2?×?10⁴ M^?1 s^?1) and diffusion coefficient (D?=?2.70?×?10^?5 cm² s^?1) were calculated for EP. Differential pulse voltammetry (DPV) exhibited two linear dynamic ranges of 0.5 to 50.0 μM and 50.0 to 1,000 μM for EP. This modified electrode is quite effective not only for the detection of EP, AC and FA but also for the simultaneous determination of these species in a mixture. The limit of detection for EP, AC and FA is 0.10, 1.80 and 2.36 μM, respectively.     

Cohesive energy and physical properties of nanocrystals

Recently, a lattice-type-sensitive model, free of any adjustable parameter, for the size dependence of the cohesive energy of nanocrystals (nanodisks, -films, -wires and -particles) has been developed, taking into account the effects of the averaged structural and energetic properties of their surface and volume. These effects are related to the first- and second-nearest-neighbor atomic interactions. Now, considering the intimate relation between cohesive energy and other physical properties of materials, the recently obtained formula for the cohesive energy of nanocrystals has been applied to the cases of melting point (In, Bi, Si and Ag), evaporation temperature (Ag and Au), vacancy formation energy (Au), diffusion activation energy (Au), surface energy (Au, Al and Na), liquid–vapor interfacial energy (Al and Na), Curie temperature (Pb), Debye temperature (Au and Fe) and band gap energy (Si) of nanocrystals. In general, good agreement between the present model and the data has been obtained. Moreover, the surface-area-difference (SAD) model has been derived as a first-order approximation of the present model.     

Simultaneous Determination of Epinephrine and Folic Acid Using the Fe3O4@SiO2/GR Nanocomposite Modified Graphite

Russian Journal of Electrochemistry - A sensitive and convenient electrochemical sensor was developed for determination of epinephrine by using the Fe3O4@SiO2/GR nanocomposite modified graphite...     

Determination of l-histidine by modified carbon paste electrode using tetra-3,4-pyridinoporphirazinatocopper(II)

This paper describes a potentiometric method for determination of l-histidine (l-his) in aqueous media, using a carbon paste electrode modified with tetra-3,4-pyridinoporphirazinatocopper(II) (Cu (3,4tppa)). The electrode exhibits linear response to the logarithm of the concentration of l-histidine from 2.4 × 10⁻⁵ to 1.0 × 10⁻² M, with a response slope of −49.5 ± 1 mV and response time of about 1.5 min. The detection limit according to IUPAC recommendation was 2.0 × 10⁻⁵ M. The proposed electrode shows a good selectivity for l-his over a wide variety of anions. This chemically modified carbon paste electrode was successfully used for the determination of l-his in a synthetic serum and RANDOX control serum solutions.     

Simultaneous Spectrophotometric Determination of Aluminum and Iron in Micellar Media by Using the H‐Point Standard Addition Method

A very simple spectrophotometric method for simultaneous determination of aluminum(III) and iron(III) based on formation of their complexes with pyrocatechol violet (PCV) in micellar media, using the H‐point standard addition method (HPSAM), is described. In micellar media, the metal complexes of Al‐PCV and Fe‐PCV are formed very fast. Formation of both of the complexes was complete within 5 min at pH 8.5. The linear ranges for aluminum and iron were 0.05‐2.50 and 0.10‐4.00 μg mL^?1, respectively. The relative standard deviation (R.S.D.) for the simultaneous determination 0.40 μg mL^?1 of Al(III) and 0.20 μg mL^?1 of Fe(III) were 3.24% and 4.22%, respectively. Interference effects of common anions and cations were studied. The method was applied to simultaneous determination of Al(III) and Fe(III) in standard reference material and alloy samples.     

Thermal and mechanical design of tangential hybrid microchannel and high-conductivity inserts for cooling of disk-shaped electronic components

The efficiency of electronic equipment is the cornerstone of technology development. Thermal conditions significantly affect the performance of electronic components. Moreover, mechanical strength, size, and mass are the parameters that impose some limitations. Thus, they should be considered in the high tech industry. Therefore, it is needed to examine both mechanical and thermal behaviors simultaneously. Microchannel and inserted high-conductivity materials are two usual cooling approaches. To improve cooling efficiency and mechanical strength, a new method named Hybrid is introduced here. This method is a combination of microchannel and high-conductivity methods. In this study, the consumed energy, the conductivity ratio of the material with high conductivity, peak temperature, and maximum Von Mises stress have been investigated and analyzed. For the hybrid method, the peak temperature and stress were minimized regarding the volume of high-conductivity change in the tangential direction of the duct. The results showed that the tangential hybrid method could decrease the peak temperature and peak Von Mises stress, up to 40% and 34% in comparison to the microchannel and high-conductivity inserts method.

     

Screen‐printed Electrode Modified with ZnFe2O4 Nanoparticles for Detection of Acetylcholine

In this paper a sensor to detect acetylcholine on the basis of ZnFe₂O₄ nanoparticles modified screen printed electrode (SPE) is reported. In the range 0.08–500.0 μM, with the detection limit of 0.024±0.001 μM, acquired anodic peak currents where shown to be linearly dependent on acetylcholine concentrations by differential pulse voltammetry (DPV). It was proven that acetylcholine oxidation at adjusted electrode surface takes place at 100 mV potential less positive compared to an unadjusted screen printed electrode. The electron transfer coefficient (α=0.51) and diffusion coefficient (D=9.3×10^?6 cm²/s) of acetylcholine oxidation were determined too. In addition, this original sensor possesses numerous benefits such as reproducibility, high stability and rapid response (20 s).     

The effect of relative phase on the stability of temporal dark soliton in $${{\mathcal {}}}$$-symmetric nonlinear directional fiber coupler

In this paper, we numerically investigate the effect of relative phase on the stability of dark solitons in \({\mathcal {PT}}\)-Symmetric nonlinear directional coupler (NLDC), by considering gain in the bar and loss in the cross in the range of \(\theta =0^\circ\) to \(180^\circ\). The \({\mathcal {PT}}\)-Symmetric perturbed eigenfunctions are used to study the soliton stability. The results of simulations are shown that in the first half region of the relative phase the soliton is unstable while in the second one, is stable. In the stable region gain and loss cancel each other and also the perturbed eigenfunctions have no effect on solitons while in the unstable region solitons are amplified in the bar and attenuated in the cross except for some small intervals which the roles are changed. The behavior of such perturbation can be interpreted as self all-optical phase soliton switching and optical logic gates.