The influence of organobentonite clay on CO2 laser grooving of nylon 6 composites

The popular polycaprolactam (polyamide PA6), commonly referred to as nylon 6, widely used as a construction plastic, is not a typical material for micromachining by CO₂ laser vaporization. In this paper, we describe investigations of the pulsed CO₂ laser grooving of both the chemically pure and the organobentonite clay modified nylon 6. Our results indicate that doping of nylon 6 with nanoparticles of organophilized bentonite significantly improves the grooving ability, predictability of the process, and its quality. In order to determine the nature of the changes in the depth and width of the grooves as a function of the laser process parameters, theoretical modeling of the laser grooving of nylon was carried out. The basic parameters of the laser grooving process versus laser beam intensity, pulse repetition rate, scanning speed of the material and various compositions of the organophilized bentonite dopant are presented. Additionally, an example of a three-dimensional engraving/milling of tested materials as well as the impact of doping on the channel profile are examined. The modification of nylon 6 by appropriate doping with bentonite clay radically improves the quality of micromachining with a CO₂ laser.     

Anisotropic and tension–compression asymmetric model for composites consolidation

A constitutive model for anisotropic and tension–compression asymmetric response of a fibrous preform is developed and solved using a FE software. Applicability of the method to complex geometries is demonstrated by analysis the consolidation of an axisymmetric filament wound pressure vessel made from commingled yarns. Three different winding patterns are considered. In conclusions, the consolidation of the whole vessel, except at the opening, is prevented by the loading mode, where the pressure is applied on the interior. To succeed in manufacturing of this type of pressure vessel, use of an oversized preform that allows extension in the fibre direction is suggested.     

Metal magnetic memory testing of welded joints of ferritic and austenitic steels

The method of the metal magnetic memory testing is a passive method of non-destructive testing based on the residual magnetic field (RMF) of a component. It allows the localization of stress concentration zones in the objects under examination. The defects in welded joints are places of stress concentration. Also, due to the geometric notch effect and thermal deformations after welding, the welded joint is a stress concentrator. Therefore, not all indications obtained in the method of the MMM testing are defects in the common, standard meaning. Additionally, in the weld seams of austenitic steels, the non-uniformity of delta ferrite in the joint results in changes in the RMF distribution and gives rise to indications. The paper presents the ways of examination and assessment of welded joints by means of the method of the MMM testing. The presented research methodology is the outcome of a synthesis of own experience and the provisions of standards ISO 24497-1, 2, 3: 2007. The results obtained in the MMM testing were compared to the results of the radiographic testing (RT). It was found that the MMM testing allowed the detection of imperfections, including defects, in welded joints at the production stage. Knowing the potential of the method of the MMM testing it seems well justified that it should be used in the examination of welded joints at the operation stage. These joints, after non-destructive testing at the production stage, are not free from defects. The defects, together with imperfections at the micro-level, concentrate stresses from working loads. Wear processes and the development of micro- and macro-cracks proceed in them the fastest. By finding the stress concentration zones, the areas of potential cracks can be found. The development of reliable procedures of examination and assessment of welded joints with the use of the method of the metal magnetic memory testing still needs a lot of research.     

Gadolinium-modified titanium oxide materials for photoenergy applications：a review

Gadolinium doped titania materials were explored for application in photoenergy production. Incorporation of gadolinium into titania permitted improvement of photocatalytic or photovoltaic performance of the latter. This review provided a deep analysis of gadolinium applications in photoenergy processes and devices with the main focus on explanation of gadolinium doping effect on physicochemical properties of titania.     

On improving accuracy of computationally efficient nonlinear predictive control based on neural models

For nonlinear processes the classical model predictive control (MPC) algorithm, in which a linear model is used, usually does not give satisfactory closed-loop performance. In such nonlinear cases a suboptimal MPC strategy is typically used in which the nonlinear model is successively linearised on-line for the current operating point and, thanks to linearisation, the control policy is calculated from a quadratic programming problem. Although the suboptimal MPC algorithm frequently gives good results, for some nonlinear processes it would be beneficial to further improve control accuracy. This paper details a computationally efficient nonlinear MPC algorithm in which a neural model is linearised on-line along the predicted trajectory in an iterative way. The algorithm needs solving on-line only a series of quadratic programming problems. Advantages of the discussed algorithm are demonstrated in the control system of a high-purity ethylene–ethane distillation column for which the classical linear MPC algorithm does not work and the classical suboptimal MPC algorithm is slow. It is shown that the discussed algorithm can give practically the same control accuracy as the algorithm with on-line nonlinear optimisation and, at the same time, the algorithm is significantly less computationally demanding.     

Impact of sampling domain and number of samples on the accuracy of large‐signal multisine measurement‐based behavioral model

This article evaluates two alternative ways to execute the sampling of modulated data for large‐signal behavioral modeling. We show that the nonlinear metric domain uniform sampling outperforms the time‐domain uniform approach, and examine how the level of improvement depends on the number of samples used for model generation. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Computer-Aided Design of Manufacturing Chain Based on Closed Die Forging for Hardly Deformable Cu-Based Alloys

Two copper-based alloys were considered, Cu-1 pct Cr and Cu-0.7 pct Cr-1 pct Si-2 pct Ni. The thermal, electrical, and mechanical properties of these alloys are given in the paper and compared to pure copper and steel. The role of aging and precipitation kinetics in hardening of the alloys is discussed based upon the developed model. Results of plastometric tests performed at various temperatures and various strain rates are presented. The effect of the initial microstructure on the flow stress was investigated. Rheologic models for the alloys were developed. A finite element (FE) model based on the Norton–Hoff visco-plastic flow rule was applied to the simulation of forging of the alloys. Analysis of the die wear for various processes of hot and cold forging is presented as well. A microstructure evolution model was implemented into the FE code, and the microstructure and mechanical properties of final products were predicted. Various variants of the manufacturing cycles were considered. These include different preheating schedules, hot forging, cold forging, and aging. All variants were simulated using the FE method and loads, die filling, tool wear, and mechanical properties of products were predicted. Three variants giving the best combination of forging parameters were selected and industrial trials were performed. The best manufacturing technology for the copper-based alloys is proposed.     

Solid substrate bioassay to evaluate impact of Trichoderma on trichothecene mycotoxin production by Fusarium species

BACKGROUND: Fusarium head blight of wheat is a destructive disease in various wheat‐growing regions and leads to significant yield losses for farmers and to contamination of cereal grains with mycotoxins, mainly deoxynivalenol and its derivatives. Toxigenic Fusarium species sporulate on cereal crop residues and produce significant inoculum for epidemics. Reduction of mycotoxin production and pathogen sporulation may be influenced by saprophytic fungal antagonists. RESULTS: Trichoderma isolates were examined in dual culture bioassays on rice with two isolates of Fusarium graminearum Schwabe and two isolates of Fusarium culmorum (W.G. Smith) Saccardo, belonging to three different chemotypes. Production of five trichothecene mycotoxins, deoxynivalenol (DON), 3‐acetyl‐deoxynivalenol (3AcDON), 15‐acetyl‐deoxynivalenol (15AcDON), nivalenol (NIV) and fusarenone X (FUS), was reduced by over 95%. Two Trichoderma isolates partially reduced the amounts of four metabolites when inoculated on autoclaved cultures of the same four Fusarium isolates. However, in the case of the 15AcDON chemotype of F. culmorum culture the content of DON increased and that of 15AcDON decreased. Isolates of Trichoderma varied in their ability to inhibit production of the five trichothecene mycotoxins by Fusarium. Susceptibility of the four Fusarium isolates to antagonistic activity of the same Trichoderma isolate differed significantly. CONCLUSION: Selected non‐toxigenic Trichoderma isolates proved to be useful biocontrol agents against toxigenic Fusarium pathogens of wheat, significantly reducing production of the trichothecene mycotoxins DON, NIV and their acetylated derivatives. Copyright © 2007 Society of Chemical Industry     

Association of a terpyridine ligand with lanthanide and copper(II) nitrates

Reactions between the 1,3-bis(6-methylpyridin-2-yl)pyridine ligand L, C₁₇H₁₅N₃ and Ln^III (1a, 1b, 1c, 1d) or a mixture of Ln^III and Cu^II nitrates (2a, 2b, 2c, 2d) resulted in a series of respectively novel mono- and heterodinuclear complexes, where Ln^III=Sm (a), Eu (b), Tb (c), Dy (d). The compounds were characterized by elemental analysis, ESI-MS and IR spectra, furthermore we obtained crystals of [H₂L][Eu(NO₃)₅] (1b) and [CuL₂][Eu(NO₃)₅] (2b) suitable for XRD characterization. In the crystal structures the Eu ions are 10-coordinated with quite a narrow range of Eu-O distances which are between 0.2436 and 0.2556 nm. In 1b the ligand molecule is protonated in both terminal rings, and the N-H groups are involved in the N-H···O hydrogen bonds with the same oxygen atom of one of the nitro groups. These hydrogen bonds connect the ions in 1b into the complex which is the principal building block of the structure. In 2b the [CuL₂]²⁺ counterions are present; the Cu is octahedrally coordinated by all nitrogen iatoms of two L molecules which are therefore almost perpendicular to each other. The electrostatic interactions between the charged species are in both cases the main driving force of the crystal packing.     

Effect of ceramic nanoadditive content and type on the rheological properties of poly(vinyl alcohol) spinning solutions

Rheological properties of aqueous PVA solutions within a wide concentration range have been examined to select a concentration at which apparent dynamic viscosity is suitable for fiber spinning from solution by the wet process. The rheological properties of PVA solutions containing various quantities of nanosilica and nanohydroxyapatite were assessed. It has been found that an increase in the quantity of both types of nanoadditives from 1 to 5% brings about a decrease in the value of the rheological parameter n and enhances the polymeric character of the fluid. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009