• Title/Summary/Keyword: Mexico

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Entropy-based optimal sensor networks for structural health monitoring of a cable-stayed bridge

  • Azarbayejani, M.;El-Osery, A.I.;Taha, M.M. Reda
    • Smart Structures and Systems
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    • v.5 no.4
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    • pp.369-379
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    • 2009
  • The sudden collapse of Interstate 35 Bridge in Minneapolis gave a wake-up call to US municipalities to re-evaluate aging bridges. In this situation, structural health monitoring (SHM) technology can provide the essential help needed for monitoring and maintaining the nation's infrastructure. Monitoring long span bridges such as cable-stayed bridges effectively requires the use of a large number of sensors. In this article, we introduce a probabilistic approach to identify optimal locations of sensors to enhance damage detection. Probability distribution functions are established using an artificial neural network trained using a priori knowledge of damage locations. The optimal number of sensors is identified using multi-objective optimization that simultaneously considers information entropy and sensor cost-objective functions. Luling Bridge, a cable-stayed bridge over the Mississippi River, is selected as a case study to demonstrate the efficiency of the proposed approach.

Highly Economic and High Quality Zinc-flake Manufacturing by High Kinetic Processing

  • Ren, H.;Benz, H.U.;Chimal V., O.;Corral G., M.S.;Zhang, Y.;Jaramillo V., D.;Zoz, H.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.975-976
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    • 2006
  • The present paper is a parameter study of zinc flake production using a Simoloyer CM01 horizontal high energy rotary ball mill. The manufactured flakes have a dimension in thickness (t) < $1{\mu}m$ and diameters (d) 5-100 ${\mu}m$, consequently a ratio d/t up to 200. The flake geometry is mainly controlled by the variation of process parameters such as rotary speed of the rotor, ratio of powder/ball charge, load ratio of the system, process temperature, operating model and the quantity of process control agent (PCA). The Zn flakes were characterized by SEM, tap densitometry, laser diffraction and water coverage measurement.

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On Output Feedback Tracking Control of Robot Manipulators with Bounded Torque Input

  • Moreno-Valenzuela, Javier;Santibanez, Victor;Campa, Ricardo
    • International Journal of Control, Automation, and Systems
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    • v.6 no.1
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    • pp.76-85
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    • 2008
  • Motivated by the fact that in many industrial robots the joint velocity is estimated from position measurements, the trajectory tracking of robot manipulators with output feedback is addressed in this paper. The fact that robot actuators have limited power is also taken into account. Let us notice that few solutions for the torque-bounded output feedback tracking control problem have been proposed. In this paper we contribute to this subject by presenting a theoretical reexamination of a known controller, by using the theory of singularly perturbed systems. Motivated by this analysis, a redesign of that controller is introduced. As another contribution, we present an experimental evaluation in a two degrees-of-freedom revolute-joint direct-drive robot, confirming the practical feasibility of the proposed approach.

Dry Coated Particle for Plasma Spraying

  • Briones-Rodriguez, C.;Mayagoitia-Barragan, V.;Cuenca-Alvarez, R
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.156-157
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    • 2006
  • The preparation of composite powders for plasma spraying by an in-house designed mechanofusion process is investigated. Results show that dry particle coating depends on the chemical and mechanical properties of powders. In metal/oxide and metal/oxide/carbide powder mixtures, fine ceramic particles coat the surface of the metallic coarser particles. A nearly rounded shape of the final composite particles is induced by the mechanical energy input with no formation of new phases. However with the carbide/metal powdered system, only an intimate mixture of components is achieved. It is suggested that the coating mechanism is governed by agglomeration and rolling phenomena.

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A homogenization approach for uncertainty quantification of deflection in reinforced concrete beams considering microstructural variability

  • Kim, Jung J.;Fan, Tai;Reda Taha, Mahmoud M.
    • Structural Engineering and Mechanics
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    • v.38 no.4
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    • pp.503-516
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    • 2011
  • Uncertainty in concrete properties, including concrete modulus of elasticity and modulus of rupture, are predicted by developing a microstructural homogenization model. The homogenization model is developed by analyzing a concrete representative volume element (RVE) using the finite element (FE) method. The concrete RVE considers concrete as a three phase composite material including: cement paste, aggregate and interfacial transition zone (ITZ). The homogenization model allows for considering two sources of variability in concrete, randomly dispersed aggregates in the concrete matrix and uncertain mechanical properties of composite phases of concrete. Using the proposed homogenization technique, the uncertainty in concrete modulus of elasticity and modulus of rupture (described by numerical cumulative probability density function) are determined. Deflection uncertainty of reinforced concrete (RC) beams, propagated from uncertainties in concrete properties, is quantified using Monte Carlo (MC) simulation. Cracked plane frame analysis is used to account for tension stiffening in concrete. Concrete homogenization enables a unique opportunity to bridge the gap between concrete materials and structural modeling, which is necessary for realistic serviceability prediction.

RESEARCH ON SHAPE MEMORY ALLOYS IN MEXICO

  • Jara, David Rios
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.1-1
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    • 1992
  • Shape Memory Alloys have attracted the interest of a great number of researchers in the world, and Mexico is not the exception. Research in this field started ten years ago, and is actually an active line covering the classical Cu-based and Ti-Ni alloys, but also the new Fe-based alloys. Although more basic studies have been performed at the present time, interest for applied research and technological goals is increasing. In this work we present a series of studies carried on these Shape Memory Alloys by the groups in Mexico, and explain what the interest of our groups are in the next future in this are of the Materials Science. Interdisciplinary work has been necessary in the characterization of the different alloys, and multiple techniques have been used, like Mossbauer spectroscopy, thermoelectric power, electron microscopy, ultrasound techniques, neutron and x-ray diffraction, calorimetry, among others. Collaboration With other groups in Europe and in the United States have become highly useful and productive, and some examples of such activities are also reported.

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Observations Made in Exploring a Pyridinium Salt Photochemical Approach to the Synthesis of (+)-Lactacystin

  • Zhou, Jiwen;Gong, Maozhen;Mariano, Patrick S.;Yoon, Ung-Chan
    • Bulletin of the Korean Chemical Society
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    • v.29 no.1
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    • pp.89-93
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    • 2008
  • The key step in a strategy for the synthesis of (+)-lactacystin involving photocyclization reaction of a cyclopenta-fused pyridinium salt has been probed by using a model substrate. Observations made in this effort led to the discovery of a highly unusual cascade process that leads to stereoselective formation of an interesting tricyclic carbamate. The results of this study are presented and discussed in the context of a (+)-lactacystin synthetic approach.

First Record of Scytosiphon gracilis Kogame (Scytosiphonaceae,Phaeophyceae) for the Pacific coast of Mexico

  • Raul , Aguilar-Rosas;Luis E. , Aguilar-Rosas;Cho, Ga-Youn;Boo, Sung-Min
    • ALGAE
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    • v.21 no.1
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    • pp.11-13
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    • 2006
  • In this work we report the occurrence of Scytosiphon gracilis Kogame (Scytosiphonaceae, Phaeophyceae) on the Pacific coast of Mexico. This is the first report of S. gracilis outside its previously known distribution in the western North Pacific (Korea and Japan). The identification was based on a morphological revision and a comparison of the plastid-encoded RuBisCO spacer sequences determined for Korean and Mexican algal material. Thalli were collected from the intertidal zone of Saldamando Beach, Baja California, in January 2003. The vegetative structure, as well as habitat and geographic distribution of the species are described. Reproductive structures were not found in our specimens. The poor presence/absence of S. gracilis in previous floristic studies of the area could be due to its small size and low frequency.

Morphometrics of Scinaia latifrons (Nemaliales, Rhodophyta) in the Southwestern Gulf of California, Mexico

  • Leon-Cisneros, Karla;Riosmena-Rodriguez, Rafael
    • ALGAE
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    • v.20 no.1
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    • pp.31-36
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    • 2005
  • Scinaia latifrons Howe occurs in rhodolith beds between 9 to 27 m depths at San Lorenzo channel, Gulf of California, Mexico. As very little was known about the morphometrics of this normally temperate species in a subtropical area, we investigated the phenological changes from December 1998 to December 1999. The gametophytic phase of the species was present from late February to late May, which represented a shorter time period to other known species in the genus. Our results suggested that two gametophytic cohorts develop over winter and early spring based on the size class structure of the frond height. Thalli became reproductively mature at a small size (1-2 cm in height) and all the plants were monoecious. Scinaia latifrons at the study location underwent allometric growth, indicated by the lack of correlation between size, width of the plants, or branching patterns.

New Records of Marine Rhodophyta from the Pacific Coast of Mexico

  • Aguilar-Rosas, Raul;Aguilar-Rosas , Luis E.;Mateo-Cid, Luz Elena;Mendoza-Gonzalez, Catalina
    • ALGAE
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    • v.22 no.3
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    • pp.153-157
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    • 2007
  • Two species of marine red algae, Jania ungulata (Yendo) Yendo f. brevior (Yendo) Yendo and Peyssonnelia japonica (Segawa) Yoneshigue (Rhodophyta) were collected for the first time from Mexican Pacific coast. Their vegetative and reproductive structures are described, as well as the habitat where they were found and their geographical distribution along the Pacific coasts of Mexico. Jania ungulata f. brevior is a commonly growing epiphytic and Peyssonnelia japonica is epiphyte. The fact that we found this new records in Mexican coast is noteworthy, due that this species are originally described in Japanese coast. The absence of records of this species in the Mexican coast is likely related in part to the lack of specific collections and the fact that the specimens are small and delicate, and may commonly be unnoticed during samplings.