Resumen: The author shows there is a non-Archimedean ordering of the field R(x, y), where x and y are algebraically independent over K, for which the identity is the only order-preserving automorphism.
The author proves the partly known result that the following statements about an ordered field K are equivalent: (1) each polynomial in K[x] satisfies the intermediate value theorem; (2) if f 2 K[x] and a
Palabras
clave
: real closed fields; automorphism of rational function field; non- archimedean ordered field; EP fields
Resumen: We present the results of an optical polarization survey toward the galactic anticenter, in the area 5(h) greater than or equal to alpha greater than or equal to 2(h) and 6 degrees less than or equal to delta less than or equal to 12 degrees. This region is characterized by the presence of a stream of high-velocity H I as well as high galactic latitude molecular clouds. We
used our polarization data together with 100 mu m IRAS maps of the region to study the relation between the dust distribution and the geometry of the magnetic field. We find that there is a correlation between the percent polarization and the 100 mu m flux such that P(%) less than or equal to (0.16 +/- 0.05)F-100. When the IRAS flux is converted into H I column densities this becomes P(%) less than or equal to (0.13 +/- 0.03)N-20 - 0.22, which is consistent with previous interstellar medium studies on the relation between reddening and polarization. This correlation indicates that our survey is as deep as IRAS and that the magnetic field geometry does not change strongly with the optical depth in the lines of sight that we have studied. The implied lower limit to the distance of our survey is 500-700 pc at galactic latitudes b = -20 degrees and 100 pc at b = -50 degrees. Our main finding is that the magnetic field is perpendicular to the H I high-velocity stream as well as the molecular cloud MBM 16 in the high-latitude region. The field is also perpendicular to the velocity gradient in the stream. Closer to the plane, the magnetic field is parallel to the dust filaments that extend like a plume toward the halo. Our observations indicate that the galactic magnetic field toward the high-latitude clouds is toroidal. We propose a model in which flux tubes that rise out of the galactic plane become force-free and predominantly toroidal at high latitudes. The high-latitude clouds may be gas streams that are falling back toward the galactic plane within such buoyant braided ropes of magnetic flux.
Resumen: It is well-known that if C is an algebraic curve over the real closed field R and is a total ordering of the function field R(C) of C then there is a semi-algebraic embedding w : (0, 1) ! C such that f 2 R(C) is positive with respect to if and only if there is some t 2 R, 0
Palabras clave: total orderings of the function field of an algebraic
Resumen: Tradicionalmente, las prácticas de cultivo se han orientado hacia una gestión uniforme del campo, ignorando la variabilidad espacial y temporal, debido al alto coste
que supone un tratamiento desigual. Es decir, todo el campo se trata del mismo modo todos los años, a pesar de que puede presentar necesidades distintas según la zona o de
un año a otro. En los últimos años, se ha producido un importante
avance con la aplicación de sistemas de control y automatización en agricultura, apareciendo el concepto de Agricultura de Precisión (AP). Uno de los aspectos más importantes de la AP son las técnicas orientadas a la aplicación selectiva de tratamientos, que proponen ajustar las dosis de herbicidas a las necesidades de cada unidad de terreno, traduciéndose en una reducción de los costes de producción y una gestión agrícola más respetuosa con el
medioambiente.
Para ser capaces de ajustar las dosis de herbicidas a las necesidades de cada unidad de terreno, primero se deben localizar las distintas especies de malas hierbas (etapa de
Percepción), y a continuación se debe realizar la aplicación de tratamientos de modo que se eliminen todas las malas hierbas encontradas, minimizando el uso de productos fitosanitarios (etapa de Actuación). En esta tesis se presentan nuevos métodos tanto de Percepción como de Actuación para una aplicación selectiva de tratamientos automática, precisa y barata.
Los métodos de Percepción desarrollados son capaces, mediante técnicas de Visión Artificial, de estimar las densidades de cultivo, malas hierbas y suelo tanto en fotos
del campo (sin restricciones en tiempo de c´omputo) como en vídeos adquiridos por una cámara instalada directamente sobre el tractor y procesados en tiempo real. Dichos
métodos hacen frente a las dificultades producidas por la inmensa variabilidad encontrada en el campo (distintos estados de crecimiento de la vegetación, errores de
sembrado, densidad variable de la infestación, etc.) y por el hecho de trabajar en exteriores (iluminación cambiante y dificil de controlar). Los métodos han sido probados
sobre un conjunto grande de imágenes y vídeos tomados a lo largo de los últimos cuatro años en varios campos, demostrando ser capaces de extraer los elementos naturales con gran precisión y de forma robusta.
La información recogida en la etapa de Percepción se pasa a un controlador borroso, que, haciendo uso de conocimiento experto, permite calcular la dosis óptima de herbicida a aplicar en cada unidad del terreno en función de las densidades presentes de infestación y cultivo. La aplicación de dicha dosis se realiza de forma automática,
actuando sobre el equipo de tratamiento, automatizado para su control desde un ordenador a través de una tarjeta de adquisición de datos y el circuito electrónico diseñado
a medida.
Una vez integradas todas las partes, se ha simulado la aplicación selectiva de tratamientos sobre campos reales. Partiendo de muestreos fotográficos discretos llevados
a cabo en los últimos tres años en distintos campos, se han alcanzado ahorros medios de herbicida del 76% con picos del 93 %, poniendo de manifiesto el claro beneficio de la aplicación de las técnicas propuestas.
Traditionally, management of agricultural fields has not taken into account existing
spatial and temporal variability, and herbicides have been applied to a crop in a uniform
manner, regardless of site conditions. All the field is treated the same way every year,
even though each area shows different conditions each year.
In the last years, important advances have been made thanks to the appearance of
Precision Agriculture (PA), a concept that addresses the in-field variability of factors
that influence crop growth, through the application of control sistems and automation
in agriculture. One of the most important goals of PA is site-specific management
practices, which seek to adjust the herbicide dosage to the amount of weed present at
each field unit. The benefits of site-specific management include a cost reduction to
produce the crop and a reduction in environmental pollution.
In order to adjust the herbicide dosage to the needs of each field unit, it is essential
to know the degree of weed coverage in each area of the field (Data collection stage) and
to plan the herbicide spraying accordingly (Interpretation/Application stage). In this
thesis, novel Data collection and Interpretation/Application methods are presented,
leading to an automatic, precise and cheap site-specific management of weeds.
The developed Computer Vision-based data collection methods are able to estimate
weed, crop and soil percentages both from still images of the field (processed without
time restrictions) and from videos taken by a camera placed directly on the tractor and
processed in real-time. In this context, the main challenge in terms of image analysis
is to achieve an appropriate discrimination among weed, crop and soil in outdoor field
images under varying conditions of illumination, soil background texture, crop damage and weed patchiness. The proposed methods have been tested on a wide variety of
images and videos taken in different crop fields during the last four years, performing
a robust and precise discrimination.
The information gathered in the data collection stage is then passed to a fuzzy
controller that determines the optimal dosage of herbicide for each field unit, based on
the computed weed and crop coverages, using expert knowledge. The desired dosage is
applied controlling the spraying bar from a computer, through a data acquisition card
and the custom-made electronic circuit.
Once all the parts finished, the site-specific spraying system’s use was simulated
on real crop fields, starting from photographic samplings carried out during the last
three years in different fields. The results show mean herbicide savings of 76% and up
to 93% in the best cases, clearly showing the benefits of the site-specific management
techniques proposed.
Palabras clave: Inteligencia Artificial, Software, Visión artificial, Procesamiento de imágenes, Agricultura de precisión, Detección de malas hierbas, Tiempo real, Algoritmos evolutivos, Razonamiento basado en casos,
Automatización, Control borroso, Sistemas expertos, Sistemas de aplicación selectiva de tratamientos, Computer vision, Image processing, Precision agriculture, Weed detection, Realtime,
Evolutionary algorithms, Case based reasoning, Automation, Fuzzy control, Expert systems, Site specific management systems
Editorial: Universidad Complutense de Madrid, Servicio de Publicaciones
Departamento: Fac. de Informática - Depto. de Ingeniería de Software e I. A. - Lenguajes y Sistemas Informáticos
ISBN: 978-84-693-3464-5
CDU: 004.8(043.2)
Notas: Tesis de la Universidad Complutense de Madrid, Facultad de Informática, Departamento de Ingeniería del Software e Inteligencia Artificial, leída el 20-11-2009
Resumen: This paper gives a very good systematic presentation of the equivalence between the algebraic function fields in one variable over the field $\bbfR$ of real numbers and the Klein surfaces. In section 1 Klein surfaces and morphisms between them are defined, and example as well as the basic facts about them are given.
The double covering of a Klein surface and the quotient of a Riemann surface under an antianalytic involution is described, and it is noted that these two constructions are mutually inverse. Section 2 is devoted to the notion of a meromorphic function of a compact Klein surface. It is shown that the field of meromorphic functions of a compact Klein surface is an algebraic function field in one variable over $\bbfR$. Also there exists a functor of the category $\cal K$ of compact Klein surfaces to the category ${\cal F}\sb \bbfR$ of the algebraic function fields in one variable over $\bbfR$. An intensive study of the set $S(E\mid\bbfR)$ of proper valuation rings $V$ of $E\in{\cal F}\sb \bbfR$ with $V\supset\bbfR$ is the object of section 3. The main results of this section are:\par (a) The residue field of $V\in S(E\mid\bbfR)$ is $\bbfR$ iff $E$ admits some ordering with respect to which $V$ is convex.\par (b) The Riemann theorem about the dimension $\ell(L)$ of the space $L(D)$ associated to the divisor $D$ of $E\mid \bbfR$.\par With these notations it is proved in section 4 that $S(E\mid\bbfR)$ admits a unique structure of a Klein surface for which $p:S(E(\sqrt{- 1})(\bbfC)\to S(E\mid\bbfR)$ is a morphism of Klein surfaces and $M(S(E\mid\bbfR))=E$. Further it is shown that every compact Klein surface $S$ is isomorphic to $S(M(S)\mid\bbfR)$. Also: $S\mapsto M(S)$ and $E\mapsto S(E\mid\bbfR)$ give an equivalence between $\cal K$ and ${\cal F}\sb \bbfR$. Here the Klein surfaces with non empty boundary correspond to the formally real fields. Among a series of interesting comments and remarks we mention merely two:\par (i) There are several non homeomorphic curves with the same field of rational functions, but there is a unique one among them which is irreducible, compact, non-singular and affine.\par (ii) The Klein surface $S$ with empty boundary is orientable iff $M(S)$ contains $\bbfC$.\par This carefully written paper is very interesting and recommended even for specialists.
Palabras clave: Real algebraic sets; Compact Riemann surfaces and uniformization
Resumen: The Department of Crystallography and Mineralogy (Complutense University, Madrid) carries
out every year a field geology course in San José - Rodalquilar (Almería, SE Spain. The region of
Almería offers a unique opportunity for the teaching of field geology because of the variety of contrasted
geologic scenarios:
1) Alpine metamorphic complexes; 2) Miocene sedimentary basins; 3) Miocene
volcanic rocks including world-class pyroclastic deposits of almost every possible type; 4) epithermal
gold and industrial minerals deposits; and 5) a second to none large fault zone (Carboneras Fault Zone,
Serrata de Níjar). However, what makes different our field geology course is the fact that the students, in
teams of 3 to 4 members, simulate a professional survey. Given that most students will end up working
for companies, it is important that they receive some practical training before they leave the university.
[RESUMEN]
El Departamento de Cristalografía y Mineralogía de la Universidad Complutense de Madrid
realiza anualmente un curso de geología de campo en San José – Rodalquilar (Almería, Sureste de
España). La región de Almería ofrece una oportunidad única para la enseñanza de la geología de campo
ya que en ella encontramos una gran variedad de escenarios geológicos: 1) complejos alpinos; 2)
cuencas sedimentarias del Mioceno; 3) rocas volcánicas del Mioceno con extraordinarios ejemplos de
diferentes tipos de depósitos piroclásticos; 4) yacimientos epitermales de oro, yacimientos de bentonitas,
alunita, y zeolitas; y 5) una gran zona de falla (Zona de Falla de Carboneras, Serrata de Níjar). Sin
embargo, lo que hace diferente nuestro curso de campo es el hecho de que los alumnos, en equipos de 3 o
4 miembros, simulan estar realizando un trabajo profesional. Dado que la mayor parte de los alumnos
acabará trabajando para alguna empresa, nos parece importante que reciban alguna formación
práctica antes de que acaben la carrera.
Palabras clave: Field geology, Almería, Volcanic rocks, Training in geology, Geología de campo, Almería, Rocas volcánicas, Educación de la geología
Resumen: Let K be a formally real field with space of orderings X(K). Then Aut(K) operates on X(K). K is said to have the ”dense orbits property” if for any x 2 X(K) the orbit of
x is dense in X(K). Fields with the dense orbits property were introduced by D. W.
Dubois and T. Recio in Contemp. Math. 8, 265-288 (1982; Zbl 0484.12003) under the name of Q1-fields. They were further studied
by the author and T. Recio [J. Pure Appl.
Algebra 30, 237-246 (1983; Zbl 0533.12018)]. In the present paper the dense orbits property is studied for function fields of real algebraic varieties. So, let V be a real
algebraic variety over the field R of real numbers, R(V ) the function field of V. It is proved that Aut(R(V )) is infinite if R(V ) has the dense orbits property. If V is a curve then R(V ) has the dense orbits property if and only if V is a rational or elliptic curve.
Palabras clave: rational curve; formally real field; space of orderings; dense orbits property;
Q1-fields; function fields of real algebraic varieties; elliptic curve
Resumen: The Baer-Krull theorems deal with the relationship between orderings of a valued field compatible with the valuation, and orderings of the residue class field. For these theorems it is necessary that the valuation ring should be convex with respect to the ordering.
For a real field R, and an extension K _ R, the author defines SpecC(K/R) in terms of equivalence classes of embeddings of K
over R into an algebraic closure C of K. This is done in such a way that when K is also real, the points of SpecC(K/R) correspond to the orderings of K
over R. Given a point of SpecC(K/R), the author extends the definition of convexity to subsets of K (again this is the usual definition when K is real).
Now let R be real, K be an extension of R, and B be a valuation ring in K. Let R be the residue class field of R\B. Suppose that R is a real subfield of K. The author studies relations between SpecC(K/R) and SpecC(K/R). In particular, it is shown that there is a lifting of each element of SpecC(K/R) to an element of SpecC(K/R), compatible with the valuation, and such that the lifting has the generalised convexity property.
While a more elementary treatment of this result is possible if R = Q, for general R the proof involves model theory in a nontrivial way.
Palabras clave: Real spectrum; Complex spectrum; Involution; Residually real; Valuation ring; Canonical place
Resumen: For a formally real field K let X(K) be the space of orderings.
The automorphism group Aut(K) of K operates on X(K).
K is said to have the ’dense orbits property’ (DOP) if for all 2 X(K) the orbit of is dense in X(K). The study of such fields, which was begun in D. W. Dubois and the second author [Contemp. Math. 8, 265-288 (1982; Zbl 0484.12003)], is continued
here.
The main question considered is the behavior of the DOP under purely transcendental and under algebraic field extensions.
Palabras clave: ordered fields; dense orbits property; automorphisms acting on spaces of orderings; behavior under field extensions; formally real field
Colección: Archivo institucional e-prints complutense
Colección: Portal de revistas científicas complutenses
