Studies on polymer blends with special reference to NBR/PVC and CR/PVC blends

The study is undertaken on PVC blends because of their all-round importance-One of the most prominent needs of PVC in application end-use is permanent plasticizationlo. Butadiene-acrylonitrile rubber (NBR) has been utilized as permanent plasticizer for PVC since the 1940s for wire and cable insulation, food contact, and pondliners used for oil containment23'24. Also plasticized PVC has been added to vulcanizable nitrile rubber, to yield improved ozone, thermal ageing, and chemical resistance resulting in applications including fuel hose covers, gaskets, conveyor belt covers, and printing roll covers. This blend is miscible in the range of 23 to 45 per cent acrylonitrile content in the butadiene-acrylqnitrile copolymerzs. The first phase of the study was directed towards modification blends. These blends, in addition to the polymers, require a host of additives like curatives for the NBR phase and stabilizers for the PVC phase26of the existing PVC blends, especially NBR/PVC. The second phase of the study was directed towards the development of novel PVC based blends. Chloroprene rubber (polychloroprene) (CR) is structurally similar to PVC and hence is likely to form successful blends with PVC32.

On the Tailoring of Magnetic Properties of Fe-Based Alloy Thin Films by Swift Heavy Ion Irradiation and Thermal Annealing

The development of new materials has been the hall mark of human civilization. The quest for making new devices and new materials has prompted humanity to pursue new methods and techniques that eventually has given birth to modern science and technology. With the advent of nanoscience and nanotechnology, scientists are trying hard to tailor materials by varying their size and shape rather than playing with the composition of the material. This, along with the discovery of new and sophisticated imaging tools, has led to the discovery of several new classes of materials like (3D) Graphite, (2D) graphene, (1D) carbon nanotubes, (0D) fullerenes etc. Magnetic materials are in the forefront of applications and have beencontributing their share to remove obsolescence and bring in new devices based on magnetism and magnetic materials. They find applications in various devices such as electromagnets, read heads, sensors, antennas, lubricants etc. Ferromagnetic as well as ferrimagnetic materials have been in use in the form of various devices. Among the ferromagnetic materials iron, cobalt and nickel occupy an important position while various ferrites finds applications in devices ranging from magnetic cores to sensors.

Studies On Preparation And Characterization Of Hts Current Leads Using Multifilamentary Ag And Ag-Alloy Sheathed (Bi,Pb)-2223 Superconducting Tapes

The application vistas of superconductors have widened very much since the discovery of high TC superconductors (HTS) as many of the applications can be realised at 77 K rather than going down to 4.2 K, the liquid He temperature. One such application is the HTS current lead which is used to connect a superconducting system with a room temperature power source. Minimising heat leak to the cryogenic environment is the main advantage of introducing current leads into superconducting systems. The properties of HTSS likes zero resistance (avoiding joule heating) and very low thermal conductivity (minimized conductive heat transfer) make them ideal candidates to be used as current leads. There are two forms of HTS current leads. (i) bulk form (tube or rod) prepared either from YBCO or BSCCO and (ii) tape form prepared from Bi-2223 multifilamentary tapes. The tape form of current leads has many advantages with respect to the mechanical and thermal stability related criteria. Crucial information on various aspects of HTS current lead development are not available in the literature as those are kept proprietary by various companies around the world. The present work has been undertaken to tailor the properties of multifilamentary tapes for the current lead application and to optimise the processing parameters of the same for enhanced critical current density and field tolerance. Also it is the aim of the present investigation is to prepare prototype current leads engineered for operation in conduction cooled mode and test them for operational stability

Structural, topographical and magnetic evolution of RF-sputtered Fe-Ni alloy based thin films with thermal annealing

Metglas 2826 MB having a nominal composition of Fe40Ni38Mo4B18 is an excellent soft magnetic material and finds application in sensors and memory heads. However, the thin-film forms of Fe40Ni38Mo4B18 are seldom studied, although they are important in micro-electro-mechanical systems/nano-electromechanical systems devices. The stoichiometry of the film plays a vital role in determining the structural and magnetic properties of Fe40Ni38Mo4B18 thin films: retaining the composition in thin films is a challenge. Thin films of 52 nm thickness were fabricated by RF sputtering technique on silicon substrate from a target of nominal composition of Fe40Ni38Mo4B18. The films were annealed at temperatures of 400 °C and 600 °C. The micro-structural studies of films using glancing x-ray diffractometer (GXRD) and transmission electron microscope (TEM) revealed that pristine films are crystalline with (FeNiMo)23B6 phase. Atomic force microscope (AFM) images were subjected to power spectral density analysis to understand the probable surface evolution mechanism during sputtering and annealing. X-ray photoelectron spectroscopy (XPS) was employed to determine the film composition. The sluggish growth of crystallites with annealing is attributed to the presence of molybdenum in the thin film. The observed changes in magnetic properties were correlated with annealing induced structural, compositional and morphological changes

A Comparative Study Of Tensile And Microstructural Characteristics Of Friction Welded Joints And Conventionally Welded Joints Of Aluminium Alloy 6061

Welding of high strength and low weight materials like Aluminium Alloys without any defects by conventional welding techniques is a major challenge in industries. Hence research on solid state welding techniques like Friction stir welding and Friction welding techniques have got much importance in joining of Aluminium alloys. However most of the industries are not changing conventional techniques as skilled workers are available on that area. Most common conventional welding techniques used for joining of Aluminium alloys are Gas welding and Arc welding. Friction welding is a solid-state welding process that generates heat through mechanical friction between a moving and a stationary component with the addition of a lateral force called “upset” to plast ically displace and fuse the materials. In this work, experimental study on tensile and micro structural characteristics of welded joints formed from conventional welding techniques and Rotary friction welding(suitable for weld specimens with circular cross section) has been carried out and the same were compared. The process parameters for arc welding used was 50-70 Amp reverse polarity DC and electrodes of 2.3mm diameter. In Gas welding, the parameters were oxy acetylene neural flame at 3200°C and 3mm electrodes . In the case of friction welding an axial pressure loading of 3Mpa with 5 MPa as upsetting pressure and 500 rpm were used to obtain good welded joints. Tensile characteristic studies of Arc welded joints and Gas welded joints showed 48% and 60 % variations respectively from the maximum load bearing characteristics of parent metal. In the case of friction welded joint, the variation was found to 46%. Micro structural evaluation of conventionally welded joints exhibited clear distinct zones of various weld regions. In the case of friction welded joint micro structural photographs showed comparable features both in parent metal and welded region. Thus the tensile characteristic study and microstructure evaluations proved that friction welded joints are good in both aspects compared to conventionally welded joints.

The electronic structure of the group 6 oxyanions [MO_4]^2-, where M = Cr, Mo, W, and element 106

The electronic structure of the group 6 oxyanions [MO_4]^2-, where M = Cr, Mo, W, and element 106 have been calculated using the Dirac-Slater Discrete Variational method. Results of the calculations show a relative decrease in the metal-oxygen bond strengths for the [E106O_4]^2- ion in the solid state compared to that for the [WO_4]^2- anion. Calculated energies of the electronic charge-transfer transitions are indicative of a strong possible luminescence of [El06O_4]^2- in the blue-violet area. In solutions [El06O_4]^2- will be the most stable ion out of the entire series. Estimated reduction potential E^0 (El06O^2-_4/E106O^3-_4) equal to -1.60V shows only a slightly increased stability of the +6 oxidation state for element 106 in comparison with W.

Theoretical study of magnetism, structure and chemical order in transition-metal alloy clusters

Research on transition-metal nanoalloy clusters composed of a few atoms is fascinating by their unusual properties due to the interplay among the structure, chemical order and magnetism. Such nanoalloy clusters, can be used to construct nanometer devices for technological applications by manipulating their remarkable magnetic, chemical and optical properties. Determining the nanoscopic features exhibited by the magnetic alloy clusters signifies the need for a systematic global and local exploration of their potential-energy surface in order to identify all the relevant energetically low-lying magnetic isomers. In this thesis the sampling of the potential-energy surface has been performed by employing the state-of-the-art spin-polarized density-functional theory in combination with graph theory and the basin-hopping global optimization techniques. This combination is vital for a quantitative analysis of the quantum mechanical energetics. The first approach, i.e., spin-polarized density-functional theory together with the graph theory method, is applied to study the Fe$_m$Rh$_n$ and Co$_m$Pd$_n$ clusters having $N = m+n \leq 8$ atoms. We carried out a thorough and systematic sampling of the potential-energy surface by taking into account all possible initial cluster topologies, all different distributions of the two kinds of atoms within the cluster, the entire concentration range between the pure limits, and different initial magnetic configurations such as ferro- and anti-ferromagnetic coupling. The remarkable magnetic properties shown by FeRh and CoPd nanoclusters are attributed to the extremely reduced coordination number together with the charge transfer from 3$d$ to 4$d$ elements. The second approach, i.e., spin-polarized density-functional theory together with the basin-hopping method is applied to study the small Fe$_6$, Fe$_3$Rh$_3$ and Rh$_6$ and the larger Fe$_{13}$, Fe$_6$Rh$_7$ and Rh$_{13}$ clusters as illustrative benchmark systems. This method is able to identify the true ground-state structures of Fe$_6$ and Fe$_3$Rh$_3$ which were not obtained by using the first approach. However, both approaches predict a similar cluster for the ground-state of Rh$_6$. Moreover, the computational time taken by this approach is found to be significantly lower than the first approach. The ground-state structure of Fe$_{13}$ cluster is found to be an icosahedral structure, whereas Rh$_{13}$ and Fe$_6$Rh$_7$ isomers relax into cage-like and layered-like structures, respectively. All the clusters display a remarkable variety of structural and magnetic behaviors. It is observed that the isomers having similar shape with small distortion with respect to each other can exhibit quite different magnetic moments. This has been interpreted as a probable artifact of spin-rotational symmetry breaking introduced by the spin-polarized GGA. The possibility of combining the spin-polarized density-functional theory with some other global optimization techniques such as minima-hopping method could be the next step in this direction. This combination is expected to be an ideal sampling approach having the advantage of avoiding efficiently the search over irrelevant regions of the potential energy surface.

La escuela como comunidad cr??tica para el desarrollo de una sociedad democr??tica

Ponencia presentada en las Terceras Jornadas de Educaci??n y Democracia organizadas por Caja Murcia en 1993. El autor realiza una reflexi??n en torno a los siguientes ejes principales: en primer lugar, plantea una concepci??n de los centros escolares como espacios de mediaci??n y construcci??n cultural que pueden ser pensados como contextos socioeducativos para la resistencia y reconstrucci??n cr??tica de la educaci??n; en segundo lugar, destaca algunas esferas concretas de la vida de los centros que han de ser reconstruidas y en tercer lugar, se centra en las implicaciones que comporta la expresi??n de la escuela como comunidad cr??tica que contempla entre sus proyectos asumir valores democr??ticos.

Diagn??stico de la situaci??n familiar en la enfermedad mental cr??nica en Asturias

a) Conocer el estado y situaci??n actual de las familias con un miembro afectado de una enfermedad mental cr??nica en el Principado de Asturias; b) Establecer una comparativa entre los distintos territorios del Principado de Asturias (Oviedo, Gij??n, Avil??s, Cuenca del Nal??n, Cuenca del Caudal, Oriente y Occidente) en base a los objetivos espec??ficos del estudio; c) Se??alar pautas para la mejora de su situaci??n y orientar sobre las diferentes l??neas o proyectos de investigaci??n a desarrollar a partir de las conclusiones de este estudio. La hip??tesis global de este estudio es que la familia sufre un cambio total ante la enfermedad mental de uno de sus integrantes. La composici??n de la muestra se hizo en base a criterios estrat??gicos y estad??sticos de tal manera que resultara representativa de las familias que tienen una persona con enfermedad mental severa o grave en el Principado de Asturias. Para ello, se cont?? con la colaboraci??n de la Asociaci??n de Familiares de Enfermos Mentales de Asturias (AFESA). La muestra final la componen 213 personas. Desarrollo de un marco te??rico donde se hace un recorrido hist??rico sobre la 'locura' en Espa??a hasta llegar a la situaci??n actual y se analiza cu??l es la situaci??n de las familias que tienen a su cargo a personas afectadas por una enfermedad mental severa o grave. Al mismo tiempo, se realiza un estudio de car??cter descriptivo cuyo proceso de investigaci??n se divide en varias etapas: la elaboraci??n y planificaci??n del estudio, la recogida y an??lisis de los datos a trav??s del correo postal y, por ??ltimo, la comunicaci??n de los resultados y conclusiones. Utilizaci??n de la encuesta postal como procedimiento de recogida de informaci??n. Elaboraci??n de un cuestionario con 58 ??tems estructurados en 11 grandes bloques: datos de identificaci??n; actividades de la vida diaria; contenci??n de comportamientos alterados; gasto econ??mico extra; cambios en la rutina diaria; repercusi??n en la salud, sentimiento y sobrecarga; satisfacci??n del servicio de Salud Mental; repercusi??n global sobre el n??cleo familiar; preocupaciones, demandas y actuaciones; ayuda recibida y satisfacci??n. El tratamiento de los datos se lleva a cabo a trav??s del programa inform??tico SPSS versi??n 12.0. Dado el car??cter descriptivo, exploratorio y explicativo del mismo, se utilizan t??cnicas descriptivas e inferenciales de car??cter tanto param??trico como no param??trico. A) La madre es la cuidadora del enfermo esquizofr??nico por antonomasia mientras que el padre es quien trabaja fuera del hogar y reporta el sustento econ??mico a la familia. B) Sin atender a su parentesco, el cuidador principal del enfermo es una mujer. C) Los hombres cuidadores son, mayoritariamente, los padres que se encuentran jubilados o viudos. D) Las mujeres cuidadoras presentan una configuraci??n distinta entre ellas, especialmente las esposas de las personas enfermas. E) Las esposas que persisten al lado de la persona esquizofr??nica o afectada de otra enfermedad mental cr??nica representan un grupo de cuidadores distintivos al del resto de las mujeres. La esposa presenta una mayor intensidad de la carga subjetiva, manifiesta carecer de vida propia y ven c??mo su proyecto de vida, su proyecto de familia se derrumba y desaparece. F) Gran parte de las personas cuya enfermedad se inicia ya dentro del matrimonio est??n separados o divorciados. G) La forma de afrontar la enfermad es diferente en la madre y en la esposa del paciente. La madre ejerce el rol de cuidador como una obligaci??n, la esposa ve truncado su futuro al lado de la persona con la que se caso. H) Las hermanas cuidadoras se encuentran en una situaci??n similar al de las esposas del enfermo, por cuanto intentan mantener una vida propia al margen del cuidado de su familiar. I) El principal cuidador debe estar pendiente con gran frecuencia de que el enfermo tome correctamente la medicaci??n. J) Hay un alto porcentaje de hombres afectados de una enfermedad mental cr??nica, fundamentalmente la esquizofrenia. K) Las necesidades asistenciales y existenciales de la familia del enfermo mental est??n directamente relacionadas con la posibilidad y demanda de mejora de la asistencia de los Servicios Sociales y de Salud Mental.

Mejorar la autoestima, el respeto y el esp??ritu cr??tico del alumnado

a. Los de naturaleza cognitiva referidos al juicio, razonamiento y conciencia moral;es decir, los referentes a hechos, conceptos y sistemas conceptuales. b. Los de naturaleza estrictamente comportamental o pr??ctica ( procedimientos). c. Los de actitudes, valores y normas, que constan de elementos cognitivos,emotivos y de orientaci??n a la pr??ctica y sirven de enlace entre los dos contenidos anteriores.. Durante el primer a??o los profesores se dedican a recabar informaci??n sobre el tema de educaci??n en valores; definir y concretar los valores objeto de la investigaci??n; plantear al claustro de profesores y consejo escolar las medidas necesarias para la organizaci??n del alumnado de 3?? de ESO. en el siguiente curso escolar. Durante el segundo a??o se realiza la intervenci??n propiamente dicha. Los instrumentos utilizados en la investigaci??n son cuestionarios diversos.. Como conclusi??n se??alar que la intervenci??n educativa llevada a cabo ha provocado los siguientes cambios en el curso escolar: a)mejora significativa en la actitud y disciplina del alumnado de tercero de ESO, b)significativo descenso de las medidas disciplinarias; c)descenso del n??mero de faltas injustificadas a clase; d) mejora en las relaciones entre el alumnado y con el profesorado. Para justificar este punto el centro cuenta con los partes de faltas durante todo los ??ltimos cursos,memoria del n??mero de incidencias disciplinarias de los ??ltimos cursos, as?? como de las memorias finales de las tutor??as donde se especifica concretamente la relaci??n entre alumnado y con el profesorado.Una nueva conclusi??n que puede establecerse a ra??z de este estudio es lo motivador de las din??micas de grupo para el alumnado participante de las mismas. Mejor que cualquier charla te??rica, las din??micas de grupo son recibidas con muy buen talante y deseos de participaci??n. Adem??s el alumnado de 3?? de ESO en el centro, se siente especialmente tratado y observado por el grupo de profesoras/es y creen que ese sentimiento de sentirse objeto de la investigaci??n y recibir un trato especial al resto de sus compa??eros de otros cursos les hace ser m??s receptivos en los temas tratados.Una conclusi??n muy importante a destacar de esta investigaci??n es la elaboraci??n por parte del grupo de un cuestionario sobre respeto. Como queda expuesto en el informe, el grupo de investigadores de la Facultad de Psicolog??a de la Universidad de Granada no pudo encontrar un cuestionario estandarizado sobre el tema. Por lo tanto,fue necesaria su elaboraci??n. Las pruebas pasadas al test sobre fiabilidad son consideradas m??s que suficientes, lo cual indica que el cuestionario elaborado mide realmente lo que pretend??an medir. Respecto al cuestionario sobre esp??ritu cr??tico,el grupo de investigaci??n pretende continuar con su mejora ya que considera interesante poder igualmente proporcionar a la comunidad investigadora de una escala fiable en dicho tema. A pesar de los problemas sobre fiabilidad encontrados en dicho cuestionario resulta importante la informaci??n que de ??l se desprende de cada item por separado..

Participaci??n en la escuela : visi??n cr??tica y propuestas para su mejora

Resumen tomado de la publicaci??n

La Teor??a de la Identidad Social : una s??ntesis cr??tica de sus fundamentos, evidencias y controversias

Resumen tomado de la publicaci??n

Pensamiento cr??tico y alta habilidad

Resumen tomado de la publicaci??n

El control de l'entrenament de la resist??ncia : import??ncia de la freq????ncia cr??tica de fusi?? ocular

Resumen tomado del autor. Contiene fotograf??as y tablas de las diferentes situaciones experimentales