Search results for "PERT"

Políticas sanitarias locales puestas a prueba: consultores, expertos, misiones internacionales y poliomielitis en España, 1950-1975 = Local health po…

2015

Aquest treball analitza les missions d'experts d'organismes sanitaris internacionals a Espanya destinades a informar sobre la situació, les activitats realitzades i les intervencions necessàries en la lluita contra la discapacitat física dels xiquets. El Pla Espanya-23 va ser l'instrument utilitzat per l'OMS i altres agències per a posar en marxa el procés de canvi en un país en transformació durant la llarga etapa de vigència de la dictadura franquista. El treball utilitza com a fonts informes inèdits d'experts de l'OMS, que van ser resultat de visites realitzades al país entre 1950 i 1975. L'abordatge metodològic va consistir en una anàlisi del discurs que es troba en les fonts i la seua …

On the effectiveness of different additives and concentrations on the re-building of the molecular structure of degraded polyethylene

2006

Mechanical recycling is an easy and economic way to re-use plastic waste as secondary materials, but, in general, their properties are worse with respect to the reclaimed materials and the virgin polymer. The aim of this work was to study the effect of concentration and reaction kinetics of two additives, an ethylene-co-glycidyl methacrylate (Lotader) and a hydroxylamine derivative (CGX), in the re-building of a degraded polyethylene. CGX is a nitroxyl radical generator able to form branching in polyolefins while the epoxy groups of Lotader can react with the functional groups present in the recycled polyethylene. The results indicate that the CGX has a higher reaction rate than Lotader, pr…

An investigation of the compatibilization of blends of polyethylene and a semirigid liquid crystalline polymer

1996

The mechanical properties of blends with liquid crystalline polymers are in general poor and lower than those expected on the basis of additivity rule because of the strong incompatibility between the flexible and rigid components. Compatibilization is then necessary to enhance the adhesion between the two phases and then to improve the final properties of these blends. The addition of maleic anhydride functionalized polymers could give rise to some compatibilization because of possible reactions between the maleic anhydride group and the end groups of the liquid crystalline polymers. These reactions do not seem to occur in blends of polyethylene and a semirigid liquid crystalline polymer. …

On the Preparation and the Characterization of Polyethylene/Polyamide Blends by Melt Processing in the Presence of an Ethylene(co)acrylic Acid Copoly…

2006

Samples of HDPE and PA6 have been meltprocessed in the presence of two new phosphazene compounds, CP-2EPOX and CP-2OXA together with an ethylene/ acrylic acid copolymer. The blends have been prepared in an industrial twin-screw extruder by using PA6 and PE in weight ratios of 25/75 and 75/25. When used, 5 phr of EAA and 0.2 phr of CP have been added. The materials have been completely characterized from a rheological, morphological, and mechanical point of view. The results indicate that the additives used caused an increase in the rupture tensile properties, of the impact strength and viscosity especially in the PE-rich blend in the presence of CP-2EPOX. This result can be attributed both …

Rheological Properties of Different Film Blowing Polyethylene Samples Under Shear and Elongational Flow

2005

Summary: The rheological behavior of polyethylenes ismainly dominated by the molecular weight, the molecularweight distribution and by the type, the amount and thedistribution of the chain branches. In this work a linearmetallocenecatalyzedpolyethylene(m-PE),abranchedme-tallocene catalyzed polyethylene (m-bPE), a conventionallinear low density polyethylene (LLDPE) and a low densitypolyethylene (LDPE) have been investigated in order tocompare their rheological behavior in shear and in elonga-tional flow. The four samples have similar melt flow indexand in particular a value typical of film blowing grade.The melt viscosity has been studied both in shear and inisothermal and non-isothermal elonga…

Functional Bionanocomposite Fibers of Chitosan Filled with Cellulose Nanofibers Obtained by Gel Spinning

2021

Extremely high mechanical performance spun bionanocomposite fibers of chitosan (CHI), and cellulose nanofibers (CNFs) were successfully achieved by gel spinning of CHI aqueous viscous formulations filled with CNFs. The microstructural characterization of the fibers by X-ray diffraction revealed the crystallization of the CHI polymer chains into anhydrous chitosan allomorph. The spinning process combining acidic–basic–neutralization–stretching–drying steps allowed obtaining CHI/CNF composite fibers of high crystallinity, with enhanced effect at incorporating the CNFs. Chitosan crystallization seems to be promoted by the presence of cellulose nanofibers, serving as nucleation sites for the gr…

Soybean Diseases Caused by Genus Pseudomonas Phytopathenes Bacteria

2019

The rationale and experimental confirmation of the role of the bacteria of the Pseudomonas genus in the pathogenesis of soybean, and the investigation of the biological properties of the main causative agent Pseudomonas savastanoi pv. glycines. Methods. Theoretical generalization, laboratory-model research, phytopathological, microbiological, physiological, biochemical and genetic methods. Results. The largest group of pathogens in different soil-climatic zones of Ukraine consists of bacteria of the genus Pseudomonas was established. Their biological properties have been investigated and the methods for identification of the dominant type of phytopathogenic bacteria causing bacterial blight…

FRESH AND DEHYDRATED SULLA FORAGE IN DAIRY EWES FEEDING: EFFECTS ON FEED UTILIZATION, OXIDATIVE STATUS AND PROPERTIES OF MILK AND CHEESE

2022

Invasive alien species – potential cheap resources of plant substances for medicinal use

2018

Some alien species demonstrate rather invasive behaviour. They have high tolerance of various habitat conditions and potent propagation ability. They not only over-compete the local vegetation but suppress the seed development of the native plants. In the newly invaded habitats they might not have suitable herbivores to control their populations. The only effective enemy might be Homo sapiens. Humans are known with their destructive power once an object has become significant for industrial utilization. The aim of this study is to review research data and reveal the potential of Ambrosia artemisiifolia L., Erigeron canadensis L., Xanthium strumarium L. and Dittrichia graveolens (L.) W. Greu…

COMPUTATIONAL HOMOGENIZATION OF POLYCRYSTALLINE MATERIALS WITH PORES: A THREE-DIMENSIONAL GRAIN BOUNDARY FORMULATION

2012

In this study, the influence of porosity on the elastic effective properties of polycrystalline materials is investigated using a 3D grain boundary micro mechanical model. The volume fraction of pores, their size and distribution can be varied to better simulate the response of real porous materials. The formulation is built on a boundary integral representation of the elastic problem for the grains, which are modeled as 3D linearly elastic orthotropic domains with arbitrary spatial orientation. The artificial polycrystalline morphology is represented using 3D Voronoi Tessellations. The formulation is expressed in terms of intergranular fields, namely displacements and tractions that play …