Optimal priorities in GI|Gn|1 queue

A polynomial-time algorithm based on reduction to a polyhedron minimization problem is proposed for minimizing a given function F(W₁,...,W_n) that depends on the mean waiting times in the Gl|G_n|l queue.Translated from Kibernetika, No. 2, pp. 80–85, March–April, 1991.     

Thermodynamic assessments of the Ni–Pt and Al–Ni–Pt systems

The Ni–Pt system is assessed using the CALPHAD method. The four fcc-based phases, i.e. disordered solid solution phase, Ni₃Pt–L1₂, NiPt–L1₀ and NiPt₃–L1₂, are described by a four-sublattice model. The calculated thermodynamic properties and order/disorder phase transformations are in good agreement with the experimental data. In order to facilitate the assessment, first-principles pseudopotential calculations are also performed to calculate the enthalpy of formation at 0 K, and comparison with the assessed values is discussed. By combining the assessments of Al–Ni and Al–Pt, the Al–Ni–Pt ternary system is assessed within a narrow temperature range, focusing on the fcc-based phases and their phase equilibria with B2 phase.     

Thermodynamic modeling of the C–Pu–U system

The ternary C–Pu–U system is thermodynamically assessed to pursue the development of a thermodynamic database for future nuclear fuels. The substitution model was used for the liquid phase, and a two-sublattice model for the PuC–UC monocarbide, PuC₂–UC₂ dicarbide and Pu₂C₃–U₂C₃ sesquicarbide phases. Ternary interaction parameters were adjusted on the experimental information for the phase relationships. Isoplethal and isothermal ternary sections, as well as some liquidus temperatures are calculated and compared with the experimental data. The overall agreement is discussed, and shows that experimental uncertainties still remain.     

First-principles calculations assisted thermodynamic assessment of the Pt–Ga–Ge ternary system

The Pt–Ga–Ge ternary system was thermodynamically assessed by the CALPHAD (CALculaton of PHAse Diagram) approach with help of first-principles calculations. Firstly, the formation enthalpies of the Pt–Ge and Pt–Ga compounds were calculated by the first-principles method. Subsequently, the Pt–Ge system was modeled and the Pt–Ga system was re-assessed. The solution phases, Liquid, Diamond_A4 (Ge) and Fcc_A1 (Pt), were modeled as substitutional solutions, of which the excess Gibbs energy was formulated with the Redlich–Kister polynomial. The binary intermetallics, Ga₇Pt₃, Ga₂Pt, Ga₃Pt₂, GaPt, Ga₃Pt₅, GaPt₂, Ge₂Pt, Ge₃Pt₂, GePt, Ge₂Pt₃ and GePt₂, were treated as stoichiometric compounds while GePt₃ was described with a two-sublattice model. Finally, based on the currently optimized Pt–Ga and Pt–Ge binary systems along with the already assessed Ga–Ge system, phase equilibria in the Pt–Ga–Ge ternary system were extrapolated. The isothermal sections at 473 K, 973 K and 1073 K of the ternary system were calculated, showing good agreement with the experimental data. In addition, the liquidus projection of the Pt–Ga–Ge ternary system was predicted using the obtained model parameters.     

Ab initio calculation of the BCC Fe–Al–Mo (Iron–Aluminum–Molybdenum) phase diagram: Implications for the nature of the phase

The metastable phase diagram of the BCC-based ordering equilibria in the Fe–Al–Mo system has been calculated via a truncated cluster expansion, through the combination of Full-Potential-Linear augmented Plane Wave (FP-LAPW) electronic structure calculations and of Cluster Variation Method (CVM) thermodynamic calculations in the irregular tetrahedron approximation. Four isothermal sections at 1750 K, 2000 K, 2250 K and 2500 K are calculated and correlated with recently published experimental data on the system. The results confirm that the critical temperature for the order–disorder equilibrium between Fe₃Al–D0₃ and FeAl–B2 is increased by Mo additions, while the critical temperature for the FeAl–B2/A2 equilibrium is kept approximately invariant with increasing Mo contents. The stabilization of the Al-rich A2 phase in equilibrium with overstoichiometric B2–(Fe,Mo)Al is also consistent with the attribution of the A2 structure to the τ₂ phase, stable at high temperatures in overstoichiometric B2–FeAl.     

A new equation of state and Fortran 77 program to calculate vapor–liquid phase equilibria of CH4–H2O system at low temperatures

A new equation of state (EOS) and the corresponding computer program package VLEWM are developed to calculate vapor–liquid phase equilibria and volumetric properties of CH₄–H₂O system at low temperatures. The EOS can predict vapor–liquid equilibria and volumetric properties of CH₄–H₂O system accurately at temperatures 273–383 K, and at pressures 0–1000 bar. The program package VLEWM is written in FORTRAN 77. It provides two main functions: (1) to calculate the composition in vapor phase and liquid phase of CH₄–H₂O system at equilibrium and (2) to judge the phase and to calculate molar volume of CH₄–H₂O mixture.     

Sensing properties of organised films based on a bithiophene derivative

Highly reproducible optic and electrochemical sensors have been developed using organised films from a polar bithiophene derivative, the 5-(dimethylamino)-5′-nitro-2,2′-bithiophene (Me₂N–T₂–NO₂). The strength of the molecular dipole moment of this push–pull end-capped bithiophene has permitted to obtain highly ordered, homogeneous and reproducible films by using both the Langmuir–Blodgett and the casting techniques. The organisation of the molecules in LB films and cast films has been established by means of UV–vis, infrared and Raman spectroscopy and by AFM.Me₂N–T₂–NO₂ thin films possess appealing optical and electrochemical sensing capabilities. UV–vis spectra can be modified in the presence of a variety of volatile organic compounds and the sensitivity is related to the polarity of the gas analysed. Films can also be used as electrochemical sensors because the characteristics of the current/potential curves are sensitive to the nature of the electrolytic solution. The spectral changes accompanying the applied voltage could be used to produce ionochromic sensor electrodes.The structure of the films has an important impact in the sensing properties of the films and in their stability. The optical and electrochemical sensing properties of Langmuir–Blodgett films are more reproducible than those observed in cast films. This makes films prepared using the LB technique to be preferred as sensing devices. However the casting technique provides a fast method to obtain cheap and highly ordered sensors.     

Micro-hotplates for high-throughput thin film processing and in situ phase transformation characterization

This paper presents the use of micro-hotplates (MHPs) as thermal processing and in situ characterization platforms for phase transformations in thin films. MHPs are fabricated by microsystem technology processes and consist of a SiO₂/Si₃N₄ membrane (app. 1 μm) supported by a bulk Si frame. Several embedded Pt thin films serve as heater and electrical measurement electrodes. It is shown that the MHPs have unique properties for the controlled annealing of thin film materials (up to 1270 K), as the annealing temperature and heating/cooling rates can be precisely controlled by in situ measurements. These rates can be extremely high (up to 10⁴ K/s), due to the low thermal mass of MHPs. The high cooling rates are especially useful for the fabrication of metastable phases (e.g. Fe₇₀Pd₃₀) by quenching. By measuring the resistivity of a thin film under test in situ as a function of the MHP temperature, microstructural changes (e.g. phase transformations) can be detected during heating and cooling cycles. In this paper, examples are presented for the determination of phase transitions in thin films using MHPs: the solid–liquid–gas phase transition (Al), the ferromagnetic–paramagnetic phase transition (Fe–Pt) and martensitic transformations (Ni–Ti–Cu, Fe–Pd). Furthermore, it is demonstrated that crystallization processes from amorphous to crystalline (Ni–Ti–Cu) can be detected with this method. Finally the application of MHPs in thin film combinatorial materials science and high-throughput experimentation is described.     

Speed–accuracy tradeoff in Fitts’ law tasks—on the equivalency of actual and nominal pointing precision

Pointing tasks in human–computer interaction obey certain speed–accuracy tradeoff rules. In general, the more accurate the task to be accomplished, the longer it takes and vice versa. Fitts’ law models the speed–accuracy tradeoff effect in pointing as imposed by the task parameters, through Fitts’ index of difficulty (I_d) based on the ratio of the nominal movement distance and the size of the target. Operating with different speed or accuracy biases, performers may utilize more or less area than the target specifies, introducing another subjective layer of speed–accuracy tradeoff relative to the task specification. A conventional approach to overcome the impact of the subjective layer of speed–accuracy tradeoff is to use the a posteriori “effective” pointing precision W_e in lieu of the nominal target width W. Such an approach has lacked a theoretical or empirical foundation. This study investigates the nature and the relationship of the two layers of speed–accuracy tradeoff by systematically controlling both I_d and the index of target utilization I_u in a set of four experiments. Their results show that the impacts of the two layers of speed–accuracy tradeoff are not fundamentally equivalent. The use of W_e could indeed compensate for the difference in target utilization, but not completely. More logical Fitts’ law parameter estimates can be obtained by the W_e adjustment, although its use also lowers the correlation between pointing time and the index of difficulty. The study also shows the complex interaction effect between I_d and I_u, suggesting that a simple and complete model accommodating both layers of speed–accuracy tradeoff may not exist.     

Thermodynamic modeling of the Mg–Ge–Pb system

All available thermodynamic and phase diagram data of the Mg–Ge and Mg–Pb binary systems, and the Mg–Ge–Pb ternary system have been critically evaluated and all reliable data have been simultaneously optimized to obtain one set of model parameters for the Gibbs energies of the liquid and all solid phases as functions of composition and temperature. The liquid phase was modeled using the Modified Quasichemical Model in order to describe the strong ordering in Mg–Ge and Mg–Pb liquid. Mg₂Ge–Mg₂Pb solid solution phase was modeled with consideration of a solid miscibility gap. All calculations were performed using the FactSage thermochemical software.     

Electrical and photoelectrical characterizations of isotype GaAs15P85/GaP heterojunctions prepared by liquid phase epitaxy

The present work deals with the electrical and optoelectronic characterizations of the isotype GaAs₁₅P₈₅/GaP devices prepared by liquid phase epitaxy. The electrical properties of the fabricated junction were studied by analyzing its current–voltage (I–V) characteristics, capacitance–voltage (C–V) characteristics in the dark at different temperatures in the range of 300–450 K. The analysis of dark current–voltage (I–V) characteristics at different temperatures were presented in order to elucidate the conduction mechanism and to evaluate the important device parameters. The predominant charge transport mechanism in these devices was found to be thermionic emission in the depletion layer and over the barrier of GaAs₁₅P₈₅/GaP heterojunction at forward bias voltage. From the capacitance–voltage, measurements at high frequency (1 MHz) information can be obtained about the carrier concentration, the diffusion potential, the barrier height of GaAs₁₅P₈₅/GaP heterojunction. The current–voltage characteristics of the GaAs₁₅P₈₅/GaP heterojunction under different illumination intensities were studied. The power low dependence of the reverse current voltage is characterized by space charge limited conduction, SCLC dominated by exponential trap distribution at the higher reverse voltage region.     

A large-displacement 65Pb(Mg1/3Nb2/3)O3–35PbTiO3/Pt bimorph actuator prepared by screen printing

In this paper we present a novel approach to preparing large-displacement 65Pb(Mg_1/3Nb_2/3)O₃–35PbTiO₃/Pt (65/35 PMN–PT/Pt) bimorph actuators. These “substrate-free”, bending-type actuators were prepared by screen-printing the 65/35 PMN–PT and Pt thick-film pastes as the electrodes on alumina substrates. After this screen printing and the subsequent firing the 65/35 PMN–PT/Pt composites were peeled off from the substrates. Displacements of nearly 100 μm at 18 V were achieved for actuators with dimensions of 1.8 cm × 2.5 mm × 50 μm for the 65/35 PMN–PT layer. The normalized displacement (the displacement per unit length) was 40 μm/cm at 18 V. The experimental results together with a computation procedure were used to obtain the material parameters for a finite-element analysis of the 65/35 PMN–PT/Pt bimorph actuators.     

Thermodynamic assessments of binary phase diagrams in organic and polymeric systems

The Sanchez–Lacombe (SL) model and the Flory–Huggins model were used for the calculation of binary phase diagrams in organic and polymer systems, respectively. The thermodynamic parameters of the liquid and gas phases in acetone–carbon disulfide (CS₂), butane–heptane, cyclohexane–aniline systems, and liquid phases in polystyrene–polybutadiene and polystyrene–bisphenol A poly-carbonate systems were optimized, based on the experimental data. The calculated results with various pressures are in good agreement with the experimental data. It is hoped that this method will be widely applied in the prediction of binary phase diagrams in organic and polymer systems.     

Fast algorithms for estimating the correlation functions of large signals

A fast algorithm is proposed for estimating the auto- and cross-correlation functions of a large signal. The algorithm is based on the sectioning method by the fast Fourier transform. We determine the optimal length of the portion of data read from external memory into RAM which achieves T_min—a minimum processing time. An estimate of T_min is obtained.Translated from Kibernetika, No. 3, pp. 78–81, May–June, 1991.     

Toward the three-dimensional structure and lysophosphatidic acid binding characteristics of the LPA4/p2y9/GPR23 receptor: A homology modeling study

Lysophosphatidic acid (LPA) is a naturally occurring phospholipid that initiates a broad array of biological processes, including those involved in cell proliferation, survival and migration via activation of specific G protein-coupled receptors located on the cell surface. To date, at least five receptor subtypes (LPA_1–5) have been identified. The LPA_1–3 receptors are members of the endothelial cell differentiation gene (Edg) family. LPA₄, a member of the purinergic receptor family, and the recently identified LPA₅ are structurally distant from the canonical Edg LPA_1–3 receptors. LPA₄ and LPA₅ are linked to G_q, G_12/13 and G_s but not G_i, while LPA_1–3 all couple to G_i in addition to G_q and G_12/13. There is also evidence that LPA₄ and LPA₅ are functionally different from the Edg LPA receptors. Computational modeling has provided useful information on the structure–activity relationship (SAR) of the Edg LPA receptors. In this work, we focus on the initial analysis of the structural and ligand-binding properties of LPA₄, a prototype non-Edg LPA receptor. Three homology models of the LPA₄ receptor were developed based on the X-ray crystal structures of the ground state and photoactivated bovine rhodopsin and the recently determined human β₂-adrenergic receptor. Docking studies of LPA in the homology models were then conducted, and plausible LPA binding loci were explored. Based on these analyses, LPA is predicted to bind to LPA₄ in an orientation similar to that reported for LPA_1–3, but through a different network of hydrogen bonds. In LPA_1–3, the ligand polar head group is reported to interact with residues at positions 3.28, 3.29 and 7.36, whereas three non-conserved amino acid residues, S114(3.28), T187(EL2) and Y265(6.51), are predicted to interact with the polar head group in the LPA₄ receptor models.     

Robust control of uncertain differential linear repetitive processes

For two-dimensional (2-D) systems, information propagates in two independent directions. 2-D systems are known to have both system-theoretical and applications interest, and the so-called linear repetitive processes (LRPs) are a distinct class of 2-D discrete linear systems. This paper is concerned with the problem of L₂–L_∞ (energy to peak) control for uncertain differential LRPs, where the parameter uncertainties are assumed to be norm-bounded. For an unstable LRP, our attention is focused on the design of an L₂–L_∞ static state feedback controller and an L₂–L_∞ dynamic output feedback controller, both of which guarantee the corresponding closed-loop LRPs to be stable along the pass and have a prescribed L₂–L_∞ performance. Sufficient conditions for the existence of such L₂–L_∞ controllers are proposed in terms of linear matrix inequalities (LMIs). The desired L₂–L_∞ dynamic output feedback controller can be found by solving a convex optimization problem. A numerical example is provided to demonstrate the effectiveness of the proposed controller design procedures.     

Stochastic Routh-Hurwitz problem

The stochastic Routh—Hurwitz problem is considered, i.e., the probability of stability is obtained for a polynomial xⁿ + a₁x^n–1 + + a_n with random coefficients.Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 61–70, July–August, 1991.     

A sensitive nonenzymatic hydrogen peroxide sensor based on DNA–Cu complex electrodeposition onto glassy carbon electrode

In this paper, DNA–Cu²⁺ complex was electrodeposited onto the surface of glassy carbon (GC) electrode, which fabricated a DNA–Cu²⁺/GC electrode sensor to detect H₂O₂ with nonenzyme. Cyclic voltammogram of DNA–Cu²⁺/GC electrode showed a pair of well-defined redox peaks for Cu²⁺/Cu⁺. Moreover, the electrodeposited DNA–Cu²⁺ complex exhibited excellent electrocatalytic behavior and good stability for the detection of H₂O₂. The effects of Cu²⁺ concentration, electrodeposition time and determination conditions such as pH value, applied potential on the current response of the DNA–Cu²⁺/GC electrode toward H₂O₂ were optimized to obtain the maximal sensitivity. The linear range for the detection of H₂O₂ is 8.0 × 10⁻⁷ M to 4.5 × 10⁻³ M with a high sensitivity of −40.25 μA mM⁻¹, a low detection limit of 2.5 × 10⁻⁷ M and a fast response time of within 4 s. In addition, the sensor has good reproducibility and long-term stability and is interference free.