Isothermal Section of the Al-Pd-Co Phase Diagram at 850 °C Delimited by Homogeneity Ranges of Phases Epsilon,U, and F

Eight alloys with metal compositions (at.%) ranging between (68-76)Al, (9-25)Pd and (5-20)Co were investigated after annealing at 850 °C for 500 h. In the investigation, the scanning electron microscopy including energy dispersive x-ray spectroscopy and the x-ray diffraction were used. In the investigated alloys, various combinations of phases β, U, F, ε₆, ε₁₆, ε₂₈, δ, Al₅Co₂, and Al₉Co₂ were identified. Partial isothermal section at 850 °C of the Al-Pd-Co phase diagram was proposed, containing homogeneity ranges of six phases (ε_n, U, F, β, δ, and Al₅Co₂).     

Recognition of business risks when purchasing goods on the Internet using GIS: experience from Slovakia

For operators of Internet shops and their investors on the one hand, and suppliers on the other hand, knowledge of the consumer market is becoming critical in terms of the risk of non-payment for purchased goods, as most small e-shops maintain their stocks according to current demand. The aim of this paper is to identify customers who come from different districts of Slovakia and display a certain type of consumer behavior regarding the risk connected with willingness to pay for goods purchased via the Internet. To solve this problem we used data from a specialized e-retailer and Geographic Information Systems (GIS) as a Decision Support System generator for constructing maps of consumers to investigate the operation of an e-shop. In the article, we used data from the years 2012–2015 concerning 489 buyers, including their addresses and other geographical data about the consumers and their purchases, and integrated them into the GIS environment. Subsequently, the data were analyzed and documented by means of GIS and maps of consumers were generated. The result of this study is to show that GIS can play a significant role in the decision-making process of e-shops in support of a manager’s experience. The geographical results were evaluated statistically in order to offer a better information capability.     

Relationship between Microstructure, Toughening Mechanisms, and Fracture Toughness of Reinforced Silicon Nitride Ceramics

Different microstructures in Si₃N₄ ceramics containing Y₂O₃and Al₂O₃ as sintering additives were prepared by two-step sintering. Pull-out and elastic bridging were most frequently observed as the toughening mechanisms in samples with fine-grained microstructures having needlelike β-Si₃N₄grains with diameters of <1 μm. Crack deflection was the main toughening mechanism observed in samples with coarse-grained microstructures having grains with diameters of >1 μm. The values of fracture toughness were varied from 6.1 to 8.2 MPa·m^1/2 with respect to the microstructural characteristics, characterized by the volume fraction of needlelike grains and their diameter.     

A minimum-area circuit forl-selection

We prove tight upper and lower bounds on the area of semelective, when-oblivious VLSI circuits for the problem ofl-selection. The area required to select thelth smallest ofn k-bit integers is found to be heavily dependent on the relative sizes ofl,k, andn. Whenl<2 ^k , the minimal area isA = (minn,l(k-logl)). Whenl2 ^k ,A = (2 ^k (logl-k + 1)).This work was supported in part by National Science Foundation Grant DMC 84-06408 and by the Slovak Academy of Sciences.     

Two-Stage Sintering of Alumina with Submicrometer Grain Size

This work verifies the applicability of two-stage sintering as a means of suppressing the final stage grain growth of submicrometer alumina. The first heating step should be short at a relatively high-temperature (1400°–1450°C) in order to close porosity without significant grain growth. The second step at temperatures around 1150°C facilitates further densification with limited grain growth. Fine-grained alumina with a relative density of 98.8% and a grain size of 0.9 μm was prepared by two-stage sintering. A standard sintering process resulted in ceramics with identical relative density and a grain size of 1.6 μm.     

Monitoring of swelling of interpenetrating polymer network of polyethylene/poly(styrene-co-butylmethacrylate) (PE/P(S-co-BMA)) in toluene and cyclohexane using fluorescence spectroscopy

A real-time monitoring of excimer emission fluorescence probe di(1-pyrenemethyl)ether (DiPyM) was used for study swelling interpenetrating polymer network (IPN) consisting of polyethylene/poly(styrene-co-butylmethacrylate) (PE/P(S-co-BMA)) and containing different network density. DiPyM was introduced into IPN during polymerisation or was penetrated into blocks from toluene solution. The effect of solvent quality for swelling of IPN and density of IPN network was also studied. From steady-state measurements of monomer and excimer emission ratio (I_e/I_m), no difference was found between rate of swelling IPN with 0.5, 1 and 3 mol% of cross-linker. The rate of IPN swelling seems to be rather high. Some differences was found at real-time monitoring of excimer emission (λ_em=495 nm) of DiPyM measured during desorption of DiPyM from swelled IPN blocks. At higher content of cross-linker, a slower rate of DiPyM desorption from IPN matrix was observed.     

Structure and Dielectric Properties of Pb(Sc2/3W1/3)O3–Pb(Zr/Ti)O3 Relaxors

The structure and dielectric properties of (1− x )Pb(Sc_2/3W_1/3)O₃–( x )Pb(Zr/Ti)O₃ ceramics have been investigated over a full substitution range. All compositions with x < 0.5 adopt a cubic perovskite structure; however, for x ≤ 0.25 a doubled cell results from a 1:1 ordered distribution of the B-site cations. The structural order in Pb(Sc_2/3W_1/3)O₃ (PSW) can be described by a random-site model with one cation site occupied by Sc³⁺ and the other by a random distribution of (Sc_1/3³⁺W_2/3⁶⁺). The ordering is destabilized in solid solutions of PSW with PbZrO₃ (PSW–PZ), but stabilized by PbTiO₃ in the (1− x )PSW–( x )PT system. The changes in order are accompanied by alterations in the dielectric response of the two systems. For PSW–PZ the temperature of the permittivity maximum ( T _ɛ,max) increases linearly with x ; however, for PSW–PT T _ɛ,max decreases in the ordered region (up to x = 0.25) and then increases rapidly as the order is lost. Similar effects were produced by modifying the degree of order of (0.75)PSW–(0.25)PT; when the order parameter was reduced from ∼1.0 to ∼0.65, T _ɛ,max increased by more than 60°C.     

Methyl acetate–methanol mixture separation by extractive distillation: Economic aspects

Methyl acetate is considered low toxicity volatile solvent produced either as a by-product during methanol carbonylation or via acetic acid esterification with methanol. In both cases, pure methyl acetate has to be isolated from the reaction mixture. Simulation of methyl acetate separation from its mixture with methanol by extraction distillation was carried out in ASPEN + software. In total three case studies were assumed using two different extraction solvents and two solvent regeneration strategies. In case A, novel extraction solvent 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, was considered. Raw material separation was achieved in an extraction distillation column while the solvent regeneration was accomplished in a second distillation column in this case. In case study B, the same extraction solvent was used; however, its regeneration was carried out in a single-effect evaporator. Dimethyl sulfoxide was the second extraction solvent selected. Its use in methyl acetate-methanol separation is presented in case study C. As high purity of dimethyl sulfoxide was required for the methyl acetate-methanol azeotrope breaking, its regeneration was carried out in the second distillation column only. To simulate the ternary methyl acetate–methanol–extraction solvent mixtures separation, vapor–liquid equilibrium was predicted based on the NRTL equation. Further, unknown properties of the considered ionic liquid and variation of these properties with temperature were predicted and introduced into the ASPEN + components properties database. Based on these data, optimum operation parameters of the respective separation equipment were established. In all case studies, the same condition had to be fulfilled, namely minimum methyl acetate content in the distillate from the extraction distillation column of 99.5mol-%. Results of simulations using the respective optimum operation parameters were employed in the economic evaluation of the three separation unit designs studied. It was found that the least energy-demanding design corresponds to the case study B in terms of both capital as well as operation expenses.

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Surface integrity of Mg-based nanocomposite produced by Abrasive Water Jet Machining (AWJM)

This paper investigates the influence of jet traverse speed on the surface integrity of 0.66?wt% Al₂O₃ nanoparticle reinforced metal matrix composite (MMC) generated by Abrasive Water Jet Machining (AWJM). Surface morphology, surface topography, and surface roughness (SR) of the AWJ surface were analyzed. The machined surfaces of the nanocomposites were examined by laser confocal microscope and field emission scanning electron microscope (FESEM). Microhardness and elasticity modulus measurement by nanoindentation testing were also performed across thickness of the samples to see depth of the zone, affected by AWJ cutting. The result reveals that extent of grooving by abrasive particle and irregularity in AWJ machined surface increases as the traverse speed increased. Similarly, the rise in value of surface roughness parameters with traverse speed was also seen. In addition, nanoindentation testing represents the lower hardness and elastic modulus due to softening occurs in AWJ surface.