Solution validation technique for optimal shakedown design problems

Modern computer technology allows conjoining shakedown theory, optimization and ever stricter standardized design requirements in a single mathematical problem formulation. However it raises a question of reliability: easily achieved solution should not be taken for granted but should be adequately assessed. This paper focuses on the physical validation technique for optimal shakedown design problem solution in the aspect of Melan theorem (statics) and residual deformation compatibility (kinematics). For that purpose Rosen gradient projection method is used. Optimization problem of bending circular, symmetric plate at shakedown, which is subjected by a variable repeated load, is considered for illustration of the validation technique.     

The effect of viscosity of polyethylene on the evolution of phase structure during the mixing of polypropylene/EPDM elastomer/polyethylene blends

The dependences of phase structure and notch impact strength on conditions of mixing have been compared for the binary blend PP/EPDM and for two ternary blends PP/EPDM/PE possessing different viscosities of polyethylene. At low rates and short times of mixing a phase structure with pronounced inhomogeneities (particles of the dispersed phase having diameters of tens μm) is formed in all blends. Conditions of mixing needed for the formation of a homogeneous phase structure (with particles having diameters of several μm) depend on the average viscosity of the components forming the inclusions (EPDM elastomer or EPDM elastomer/polyethylene). Depending on the conditions of mixing and on the rheological properties of components, substitution of one part of the EPDM elastomer with PE may lead to an increase or decrease in the impact strength of the final blend.     

Effects of Regioselectivity and Lipid Class Specificity of Lipases on Transesterification,Exemplified by Biodiesel Production

Lipase-catalyzed ethanolysis of triolein was studied as a model for biodiesel production. Four lipases were immobilized on porous polypropylene, and ethanolysis reactions were carried out in methyl t-butyl ether. The reaction products were analyzed using gas chromatography. Three of the four lipases studied were efficient in the conversion of triolein to 2-monoolein, but slow in the final step of producing glycerol. However, Candida antarctica lipase B was slow in the conversion of triolein, but more efficient in the subsequent two steps than the other lipases. The 1,3-selectivity of the lipases was less pronounced for the monooleins than for triolein. Silica gel was investigated as a catalyst for acyl migration, showing an increase in biodiesel yield with three of the lipases, but a reduction in yield when C. antarctica lipase B was used. The highest biodiesel yield (96 %) was obtained with a combination of Rhizopus arrhizus lipase and C. antarctica lipase B.     

Luminescent properties of rare earth (Er,Yb) doped yttrium aluminium garnet thin films and bulk samples synthesised by an aqueous sol–gel technique

Yttrium aluminium garnet (YAG) powders and thin films deposited on silicon substrates were prepared by an aqueous sol–gel route using metal nitrates. The sol–gel process resulted in an amorphous gel, and the thermal decomposition and successive crystallization were characterized by thermal analysis and X-ray diffraction. Powders were prepared by heat treatment of the amorphous gel, while crack-free thin films of densely packed nano-crystalline particles were obtained on silicon substrates by dip-coating technique. Photoluminescence (PL) properties as well as up-conversion (anti-stoke emission) of Er, Yb co-doped YAG phosphors were investigated. Green (555 nm) and red (650 nm) photoluminescence up-conversion emissions arising due to ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions, respectively for Er³⁺ ion were observed. Photoluminescence and radiative life-times of the exited states of Er³⁺ in the visible and near IR ranges are also reported.     

Risk assessment of Fusarium mycotoxins in Lithuanian small cereal grains

A total of 125 small grain samples, including 60 of winter crop and 65 of spring crop collected during 2006–2007 at harvesting in Lithuanian fields, were involved in the current study on co-occurrence of three Fusarium mycotoxins. All grain samples tested were found to be contaminated with mycotoxins. In 2006, winter cereal grain samples contaminated with one mycotoxin accounted for 16%, and those contaminated with three mycotoxins for 25%. No spring cereal grain samples containing only one toxin were found, while those contaminated with three toxins accounted for 91% of the total samples tested. In the year 2007 winter cereal grain samples contaminated with one toxin accounted for as little as 4%, and all spring cereal grain samples tested were found to be 100% contaminated with deoxynivalenol, zearalenone, and T-2 toxin. Mycotoxin concentrations in grain samples, in most cases, were within the permissible range. A trend was revealed that spring barley grain samples tested contained higher T-2 concentrations irrespective of the test year.     

A new high-molecular-weight glutenin subunit from the slovak wheat (Triticum aestivum L.) cultivar ‘Trebišovská 76’

Historical and local varieties are an important source of genetic diversity in connection with the wheat baking quality. By analysis of DNA from the coding part of the genome of the Slovak regional wheat (Triticum aestivum L.) variety ‘Trebišovská 76’, differences in the Dy subunit composition coded by locus Glu-1D were found. Comparing the newly found sequence with a generally used 1Dy12 (GenBank accession no. X03041) sequence, existence of a new high-molecular-weight glutenin subunit, which was marked as 1Dy12* (GenBank accession no. EU266533) was confirmed. The molecular weight of probable protein coded by 1Dy12* subunit reaches 72.35 kDa comparing to the 1Dy12, which reaches 68.71 kDa. This difference is not likely to distinguish by SDS-PAGE. The easiest way for cereal genotyping according to baking quality is proteomic analysis. More exact and suitable method for genotype identification appears to be marker assisted selection using PCR.

     

Trends and sustainability criteria of the production and use of liquid biofuels

Environmental impacts associated with the use of fossil fuels, rising prices, potential limitations in supply and concerns about regional and national security are driving the development and use of biomass for bioenergy, biofuels and bioproducts. However, the use of biomass does not automatically imply that its production, conversion and use are sustainable. Conflicts between various ecosystem services (economic production of food, fodder and fuels, biodiversity, social and cultural values, etc.) that are provided by fertile land are increasing as well. Hence, a developed thinking on how to balance between these services is desirable.There is a significant amount of information available on biofuels and their sustainability. In this paper, different initiatives and sustainability criteria for biofuels are presented and assessed.35 criteria were found in emerging sustainability assessment frameworks. The majority of 12 criteria were focused on environmental issues, 4 were social and only 1 was economic. Energy balance and greenhouse gas balance were perceived as especially critical, social criteria ranked generally low. Although being perceived as important, food security ranked very low.     

The effect of conditions of mixing of polypropylene/ethylene-propylene elastomer blends on their morphological structure and impact strength

The dependence of morphological structure and notch impact strength of polypropylene/ethylene-propylene elastomer blends on conditions of mixing was investigated. Two types of polypropylene and two types of ethylene-propylene elastomer having different viscosities were used. At low rates and short times of mixing the samples contain both regions showing fine dispersion and regions showing large elastomeric inclusions surrounded with pure polypropylene. With increasing rate and time of mixing the large inclusions gradually disappear. The conditions of mixing which are necessary for reaching a homogeneous structure of the blends depend on viscosities of the components. The independence of particle size of the rate of mixing in homogeneous samples is discussed on the basis of a dynamic equilibrium between the break up and coalescence of droplets. The notch impact strength of the individual samples of the same blend is determined by the size and number of inhomogeneities (large inclusions) in the given sample.