Solitons in systems of coupled scalar fields

We present a method to obtain soliton solutions to relativistic system of coupled scalar fields. This is done by examining the energy associated to static field configurations. In this case we derive a set of first-order differential equations that solve the equations of motion when the energy saturates its lower bound. To illustrate the general results, we investigate some systems described by polynomial interactions in the coupled fields.Comment: RevTex4, 5 page

Numerical Study on Impulse Ventilation for Smoke Control in an Underground Car Park

AbstractThis study examines smoke control capacity of impulse ventilation system (IVS) in an underground car park. An analysis is made in relation to important parameters including jet fan number, jet fan velocity, extract rate and system robustness on fire position. The comparison with ductwork system is also performed to determine the different effect of smoke control between two systems. Fire Dynamic Simulator version 5.30 is applied to simulate 10 scenarios in a 80 m long, 40 m wide and 3.2 m height domain witha fire source simulating a car fire with an peak heat release rate of 4 MW. Results show that impulse ventilation system not noly prohibit fire smoke spreading but also maintain a good visibility providing clear access for fighters. However it may cause temperature rise on the downwind zone of fire source with a maximum value between 80-100 and fire plume e tilt. Smoke control capacity of impulse ventilation system is sensitive to jet fan numbers. Too high jet fan velocity may cause severe smoke recirculation. Increment in extract rate is conductive to relay jet flows. An impulse ventilation system can effectively control smoke movement and induce smoke to extract points under two typical different fire locations, which is of great practical importance. Impulse ventilation system seems superior to ductwork system in maintaining high visibility

Pt decorated amorphous RuIr alloys as high efficiency electrocatalyst for methanol oxidation

This study focuses primarily on improving the utilization and activity of anodic catalysts for methanol electro-oxidation. The Direct Methanol Fuel Cell (DMFC) anodic catalyst, a carbon supported Pt decorated amorphous RuIr nanoparticles catalyst (Pt@RuIr/C) was prepared by a two-step reduction method. The structure of Pt@RuIr/C nanoparticles was confirmed by Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). The Pt@RuIr electrocatalysts exhibited good uniformity in distribution. Cyclic Voltammetry experiments showed that under the same quality of noble-metal, the Pt@RuIr/C catalyst had higher activity than the PtRuIr/C catalyst for methanol oxidation. It was also shown that the as-prepared structure of the Pt decorated amorphous RuIr alloys could obviously decrease the usage of noble-metal and enhance its catalytic activity at the same time.Web of Scienc

Properties of a beam splitter entangler with Gaussian input states

An explicit formula is given for the quantity of entanglement in the output state of a beam splitter, given the squeezed vacuum states input in each mode.Comment: To appear in Phys. Rev.

Long-Term Variations in the Growth and Decay Rates of Sunspot Groups

Using the combined Greenwich (1874-1976) and Solar Optical Observatories Network (1977-2009) data on sunspot groups, we study the long-term variations in the mean daily rates of growth and decay of sunspot groups. We find that the minimum and the maximum values of the annually averaged daily mean growth rates are ~52% per day and ~183% per day, respectively, whereas the corresponding values of the annually averaged daily mean decay rates are ~21% per day and ~44% per day, respectively. The average value (over the period 1874-2009) of the growth rate is about 70% more than that of the decay rate. The growth and the decay rates vary by about 35% and 13%, respectively, on a 60-year time-scale. From the beginning of Cycle 23 the growth rate is substantially decreased and near the end (2007-2008) the growth rate is lowest in the past about 100 years.Comment: 1 table, 13 figures, accepted by Solar Physic

Tur\'an Graphs, Stability Number, and Fibonacci Index

The Fibonacci index of a graph is the number of its stable sets. This parameter is widely studied and has applications in chemical graph theory. In this paper, we establish tight upper bounds for the Fibonacci index in terms of the stability number and the order of general graphs and connected graphs. Tur\'an graphs frequently appear in extremal graph theory. We show that Tur\'an graphs and a connected variant of them are also extremal for these particular problems.Comment: 11 pages, 3 figure

Impactos del riego con aguas cloacales en las propiedades del suelo de una granja en China: Una revisión

El agua limpia es un recurso valioso y juega un rol importante en mantener los desarrollos económico y social. La limitación de recursos hídricos ciertamente no permitirá un desarrollo sostenible de las industrias básicas en China en un futuro cercano, considerando su gran población y potencial de consumo. La aplicación de aguas cloacales, hasta cierto punto, se observó como un camino alternativo para resolver el problema de la escasez de agua en agricultura en algunas áreas (tales como en el Norte de China). Sin embargo, acompañado con una implementación extensiva de riego con aguas cloacales, algunos problemas se hicieron obvios, especialmente aquellos relacionados con la contaminación y destrucción de granjas. En este manuscrito se revisaron los efectos del riego con aguas cloacales en granjas en China sobre algunas características físicas (densidad aparente del suelo, resistencia del suelo a la penetración y capacidad de campo), químicas (pH, materia orgánica del suelo, nitrógeno, fósforo, potasio, metales pesados y contaminantes orgánicos) y biológicas de suelo (microorganismos del suelo, y actividad enzimática). Esto se basó en el grado actual de utilización del riego con aguas cloacales de las granjas de China. Se propusieron algunas sugerencias posibles con respecto a las perspectivas de desarrollo en el futuro. Esta revisión será benéfica para promover un desarrollo saludable del riego con aguas cloacales y proveer un apoyo teórico para el reclamo y un gran uso eficiente de los efluentes en China.Fresh water is a valuable nonrenewable resource and plays an important role in maintaining economic and social development. Considering its large population and consumption potential, water resource deficits will certainly not allow a sustainable development of basic industries in China in the near future. Application of sewage irrigation, to some extent, was regarded as an alternative way to solve the problem of agricultural water shortage in some areas (such as North China). However, accompanied with an extensive implementation of sewage irrigation, some problems with sewage irrigation became gradually obvious in agriculture, especially those related with pollution and destruction of farmlands. In this paper, the effects of sewage irrigation on soil physical (soil bulk density, soil resistance to penetration and field capacity), chemical (pH, soil organic matter, nitrogen, phosphorus, potassium, heavy metal and organic pollutants) and biological characteristics (soil microorganisms and enzyme activities) were systematically reviewed on farmlands in China, based on the current utilization status of China’s farmland sewage irrigation. Some feasible suggestions were put forward to the development prospects in the future. This review will be beneficial for promoting a healthy development of sewage irrigation and providing a theoretical support for reclamation and a high efficiency use of effluents in China.Fil: Li, Q.K.. Yellow River Conservancy Commission. Yellow River Institute of Hydraulic Research; ChinaFil: Tang, J.. Henan Institute of Science and Technology. School of Resource and Environment ; ChinaFil: Wang, T.. Henan Bureau of Geo-Exploration & Mineral Development. Third Institute of Geo-exploration Institute; ChinaFil: Wu, D.. Henan Institute of Science and Technology. School of Resource and Environment ; ChinaFil: Busso, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Jiao, R.F.. Henan Institute of Science and Technology. School of Resource and Environment ; ChinaFil: Ren, J.X.. Henan Institute of Science and Technology. School of Resource and Environment ; Chin

Evolution of active and polar photospheric magnetic fields during the rise of Cycle 24 compared to previous cycles

The evolution of the photospheric magnetic field during the declining phase and minimum of Cycle 23 and the recent rise of Cycle 24 are compared with the behavior during previous cycles. We used longitudinal full-disk magnetograms from the NSO's three magnetographs at Kitt Peak, the Synoptic Optical Long-term Investigations of the Sun (SOLIS) Vector Spectro-Magnetograph (VSM), the Spectromagnetograph and the 512-Channel Magnetograph instruments, and longitudinal full-disk magnetograms from the Mt. Wilson 150-foot tower. We analyzed 37 years of observations from these two observatories that have been observing daily, weather permitting, since 1974, offering an opportunity to study the evolving relationship between the active region and polar fields in some detail over several solar cycles. It is found that the annual averages of a proxy for the active region poloidal magnetic field strength, the magnetic field strength of the high-latitude poleward streams, and the time derivative of the polar field strength are all well correlated in each hemisphere. These results are based on statistically significant cyclical patterns in the active region fields and are consistent with the Babcock-Leighton phenomenological model for the solar activity cycle. There was more hemispheric asymmetry in the activity level, as measured by total and maximum active region flux, during late Cycle 23 (after around 2004), when the southern hemisphere was more active, and Cycle 24 up to the present, when the northern hemisphere has been more active, than at any other time since 1974. The active region net proxy poloidal fields effectively disappeared in both hemispheres around 2004, and the polar fields did not become significantly stronger after this time. We see evidence that the process of Cycle 24 field reversal has begun at both poles.Comment: Accepted for publication in Solar Physic

Effects of Temperature and Moisture on Sheet Molding Compounds

A summary is given on the effects of moisture and temperature on the properties of chopped fiber reinforced sheet molding compounds. The properties surveyed include tensile strength and modulus, compression strength and modulus, shear strength and modulus, flexural strength and modulus, fatigue, creep, vibration damping, moisture absorption characteristics, and thermal expansion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68648/2/10.1177_073168448300200201.pd