908 resultados para ASHRAE Standard 55
Resumo:
The effect of structure height on the lightning striking distance is estimated using a lightning strike model that takes into account the effect of connecting leaders. According to the results, the lightning striking distance may differ significantly from the values assumed in the IEC standard for structure heights beyond 30m. However, for structure heights smaller than about 30m, the results show that the values assumed by IEC do not differ significantly from the predictions based on a lightning attachment model taking into account the effect of connecting leaders. However, since IEC assumes a smaller striking distance than the ones predicted by the adopted model one can conclude that the safety is not compromised in adhering to the IEC standard. Results obtained from the model are also compared with Collection Volume Method (CVM) and other commonly used lightning attachment models available in the literature. The results show that in the case of CVM the calculated attractive distances are much larger than the ones obtained using the physically based lightning attachment models. This indicates the possibility of compromising the lightning protection procedures when using CVM. (C) 2014 Elsevier B.V. All rights reserved.
Resumo:
Seismic site characterization is the basic requirement for seismic microzonation and site response studies of an area. Site characterization helps to gauge the average dynamic properties of soil deposits and thus helps to evaluate the surface level response. This paper presents a seismic site characterization of Agartala city, the capital of Tripura state, in the northeast of India. Seismically, Agartala city is situated in the Bengal Basin zone which is classified as a highly active seismic zone, assigned by Indian seismic code BIS-1893, Indian Standard Criteria for Earthquake Resistant Design of Structures, Part-1 General Provisions and Buildings. According to the Bureau of Indian Standards, New Delhi (2002), it is the highest seismic level (zone-V) in the country. The city is very close to the Sylhet fault (Bangladesh) where two major earthquakes (M (w) > 7) have occurred in the past and affected severely this city and the whole of northeast India. In order to perform site response evaluation, a series of geophysical tests at 27 locations were conducted using the multichannel analysis of surface waves (MASW) technique, which is an advanced method for obtaining shear wave velocity (V (s)) profiles from in situ measurements. Similarly, standard penetration test (SPT-N) bore log data sets have been obtained from the Urban Development Department, Govt. of Tripura. In the collected data sets, out of 50 bore logs, 27 were selected which are close to the MASW test locations and used for further study. Both the data sets (V (s) profiles with depth and SPT-N bore log profiles) have been used to calculate the average shear wave velocity (V (s)30) and average SPT-N values for the upper 30 m depth of the subsurface soil profiles. These were used for site classification of the study area recommended by the National Earthquake Hazard Reduction Program (NEHRP) manual. The average V (s)30 and SPT-N classified the study area as seismic site class D and E categories, indicating that the city is susceptible to site effects and liquefaction. Further, the different data set combinations between V (s) and SPT-N (corrected and uncorrected) values have been used to develop site-specific correlation equations by statistical regression, as `V (s)' is a function of SPT-N value (corrected and uncorrected), considered with or without depth. However, after considering the data set pairs, a probabilistic approach has also been presented to develop a correlation using a quantile-quantile (Q-Q) plot. A comparison has also been made with the well known published correlations (for all soils) available in the literature. The present correlations closely agree with the other equations, but, comparatively, the correlation of shear wave velocity with the variation of depth and uncorrected SPT-N values provides a more suitable predicting model. Also the Q-Q plot agrees with all the other equations. In the absence of in situ measurements, the present correlations could be used to measure V (s) profiles of the study area for site response studies.
Resumo:
With the renewed interest in vector-like fermion extensions of the Standard Model, we present here a study of multiple vector-like theories and their phenomenological implications. Our focus is mostly on minimal flavor conserving theories that couple the vector-like fermions to the SM gauge fields and mix only weakly with SM fermions so as to avoid flavor problems. We present calculations for precision electroweak and vector-like state decays, which are needed to investigate compatibility with currently known data. We investigate the impact of vector-like fermions on Higgs boson production and decay, including loop contributions, in a wide variety of vector-like extensions and their parameter spaces.
Resumo:
We consider the possibility that the heavier CP-even Higgs boson (H-0) in the minimal supersymmetric standard model (MSSM) decays invisibly into neutralinos in the light of the recent discovery of the 126 GeV resonance at the CERN Large Hadron Collider (LHC). For this purpose we consider the minimal supersymmetric standard model with universal, nonuniversal and arbitrary boundary conditions on the supersymmetry breaking gaugino mass parameters at the grand unified scale. Typically, scenarios with universal and nonuniversal gaugino masses do not allow invisible decays of the lightest Higgs boson (h(0)), which is identified with the 126 GeV resonance, into the lightest neutralinos in the MSSM. With arbitrary gaugino masses at the grand unified scale, such an invisible decay is possible. The second lightest Higgs boson can decay into various invisible final states for a considerable region of the MSSM parameter space with arbitrary gaugino masses as well as with the gaugino masses restricted by universal and nonuniversal boundary conditions at the grand unified scale. The possibility of the second lightest Higgs boson of the MSSM decaying into invisible channels is more likely for arbitrary gaugino masses at the grand unified scale. The heavier Higgs boson decay into lighter particles leads to the intriguing possibility that the entire Higgs boson spectrum of the MSSM may be visible at the LHC even if it decays invisibly, during the searches for an extended Higgs boson sector at the LHC. In such a scenario the nonobservation of the extended Higgs sector of the MSSM may carefully be used to rule out regions of the MSSM parameter space at the LHC.
Resumo:
In this paper, we propose a new state transition based embedding (STBE) technique for audio watermarking with high fidelity. Furthermore, we propose a new correlation based encoding (CBE) scheme for binary logo image in order to enhance the payload capacity. The result of CBE is also compared with standard run-length encoding (RLE) compression and Huffman schemes. Most of the watermarking algorithms are based on modulating selected transform domain feature of an audio segment in order to embed given watermark bit. In the proposed STBE method instead of modulating feature of each and every segment to embed data, our aim is to retain the default value of this feature for most of the segments. Thus, a high quality of watermarked audio is maintained. Here, the difference between the mean values (Mdiff) of insignificant complex cepstrum transform (CCT) coefficients of down-sampled subsets is selected as a robust feature for embedding. Mdiff values of the frames are changed only when certain conditions are met. Hence, almost 50% of the times, segments are not changed and still STBE can convey watermark information at receiver side. STBE also exhibits a partial restoration feature by which the watermarked audio can be restored partially after extraction of the watermark at detector side. The psychoacoustic model analysis showed that the noise-masking ratio (NMR) of our system is less than -10dB. As amplitude scaling in time domain does not affect selected insignificant CCT coefficients, strong invariance towards amplitude scaling attacks is also proved theoretically. Experimental results reveal that the proposed watermarking scheme maintains high audio quality and are simultaneously robust to general attacks like MP3 compression, amplitude scaling, additive noise, re-quantization, etc.
Resumo:
The effectiveness of Oliver & Pharr's (O&P's) method, Cheng & Cheng's (C&C's) method, and a new method developed by our group for estimating Young's modulus and hardness based on instrumented indentation was evaluated for the case of yield stress to reduced Young's modulus ratio (sigma(y)/E-r) >= 4.55 x 10(-4) and hardening coefficient (n) <= 0.45. Dimensional theorem and finite element simulations were applied to produce reference results for this purpose. Both O&P's and C&C's methods overestimated the Young's modulus under some conditions, whereas the error can be controlled within +/- 16% if the formulation was modified with appropriate correction functions. Similar modification was not introduced to our method for determining Young's modulus, while the maximum error of results was around +/- 13%. The errors of hardness values obtained from all the three methods could be even larger and were irreducible with any correction scheme. It is therefore suggested that when hardness values of different materials are concerned, relative comparison of the data obtained from a single standard measurement technique would be more practically useful. It is noted that the ranges of error derived from the analysis could be different if different ranges of material parameters sigma(y)/E-r and n are considered.
Resumo:
En la Estación Experimental de Las Mercedes municipio de Managua, se inició en la época de postrera en 1991, un experimento de rotación de cultivos bajo diferentes niveles de control de malezas. El presente trabajo evaluó el efecto de los cultivos antecesores sorgo, maíz y pepino con tres niveles de control de malezas : químico, período crítico y limpias periódicas a la dinámica de la cenosis de malezas, crecimiento y rendimiento del cultivo sucesor sorgo. Cuando antecedió el pepino la abundancia de maleza fue mayor con 504 Ind/m2 reduciéndose considerablemente a la cosecha obteniendo una biomasa promedio de 133.9 gr/m2. Sucedió lo contrario con maíz como cultivo antecesor ya que al principio la abundancia fue de 201 Ind/m2 y se obtuvo la mayor biomasa con 259.8 gr/m2 y para sorgo-sorgo tuvo valores de 232 Ind/m2 y a la cosecha en menor valor en biomasa de sorgo 130.0 gr/m2. En el rendimiento se enmarcó una tendencia a favor de maíz como cultivo antecesor con 1878 Kg/ha de sorgo, mientras sorgo-sorgo obtuvo un rendimiento de 1839 Kg/ha comparándose con pepino como antecesor con 1832 Kg/ha de sorgo. Comparando los controles aquí hubo diferencias significativas y en mayor valor le correspondió al control químico con 2048.0 Kg/ha, control período crítico con 1786 Kg/ha y el menor valor le correspondió a limpia periódica con sólo 1715 Kg/ha. En el control período crítico presentó mayor abundancia la maleza al inicio con 444 Ind/m2, teniendo una reducción hasta 62 Ind/m2 en la cosecha. El control químico tuvo un comportamiento similar que el control período crítico con 295 Ind/m2, reduciendo al final del ciclo con 135 Ind/m2. El control limpias periódicas tuvo al inicio la menor abundancia con 200 Ind/m2, reduciendo a la cosecha a 3 Ind/m2.
Resumo:
El presente Vallejo experimental se realizó a partir del 18 de Agosto de 1989, día en que se realizó la siembra de postrera en la hacienda "Las Mercedes”, evaluándose la rotación de cultivos y diferentes métodos de control de malezas en el cultivo de sorgo. Dicho experimento culminó el 2 de Diciembre del mismo año. Se utilizó el diseño de Bloques Completos al Azar en parcelas divididas, siendo el factor A: el cultivo antecesor; sorgo, maiz y pepinillo; y el factor los métodos de control de malezas; Atrazina (en pre-emergencia a dosis de 1.5 kg/ha), Limpia mecánica en periodo crítico (5ta y 6ta hoja) y limpia periódica cada 15 días con azadon. Los resultados demuestran que tanto en los cultivos antecesores al sorgo como en los diferentes métodos de control se presentó el Cypenis rotundus como presdominante, seguido por las Poáceas, en donde sobresale la Rottboellia cochichinensis , observándose más individuos cuando antecedía el sorgo y en la aplicación de Atrazina. Esto permitió una mayor acumulación de biomasa de malezas al momento de la cosecha en ambos casos (monocultivo sorgo y método de control con atrazina). En las variables de crecimiento, desarrolla y rendimiento del sorgo los cultivos antecesores presentaron diferencias significativas en: El diámetro del tallo, longitud de panoja y peso de mil semillas. Referente al efecto de los diferentes métodos de control de malezas sobre dichos caracteres en el cultivo de sorgo hubo diferencias significativas en la longitud de panoja, peso seco de paje y en el rendimiento. Siendo la rotación maíz - sorgo la que presentó los mejores resultados en las diferentes variables evaluadas. El método de control de malezas que mejor comportamiento tuvo fue la limpia en periodo crítico principalmente en las variables como el rendimiento que obtuvo 2,822.19 kg/he y peso de mil semillas de 14.53 gramos. Es importante señalar el alto rendimiento que se obtuvo con la rotación antes mencionada, lo cual es de 3,190.49 kg/ha, sin embargo no presentaron diferencias significativas.
Resumo:
Contenido: Contemplación y acción / Octavio N. Derisi – El humanismo de Heidegger / José Ignacio Alcorta – Cultura o humanismo cristiano / Octavio N. Derisi – Notas y comentarios -- Bibliografía
Resumo:
Contenido: Editorial – Sobre la guerra: El uso de la fuerza frente a las agresiones de baja intensidad / Hernando V. Cañardo – Derecho de la alta tecnología: El orden público tecnológico / Horacio R. Granero – El gobierno electrónico como un nuevo paradigma de administración / Pablo Castoldi – Reforma del Estado: Crisis y reforma estructural del Estado / Vicente Gonzalo Massot – La reforma del Estado en sus aspectos estructurales y de gestión / Hugo Luis Dalbosco – Crisis y reforma del estado / Roberto Antonio Punte – Cómo recorrer virtualmente al estado argentino / Federico Ricciardi – La región como alternativa política / Carlos A. de Jorge – Algunos problemas actuales del federalismo y la regionalización como respuesta / Eugenio Luis Palazzo – La reforma administrativa del estado / Alfredo G. Barros – La reforma impostergable y largamente esperada del Poder Judicial / Silvana M. Stanga – Recensiones
Resumo:
Contenido: La naissance du roman moderne / Pierre Brunel – Tras las huellas de María Teresa Maiorana y Rubén Darío / Martha V. de Burbridge – Ver en la oscuridad. Poéticas de la ceguera según Rimbaud y Borges / Magdalena Cámpora – Giovanni Papini, un escritor olvidado / Daniel Capano – Recreación del laberinto kafkiano en “El Proceso”, de Orson Welles / Adriana Cid – Amistades paralelas: Miguel Cané-Martín García Mérou/Jorge Luis Borges-Adolfo Bioy Casares / Jorge Cruz – Crítica literaria y literatura comparada. Entre selectores y comediantes / Biagio D’Angelo – Lucía Miranda: un mito de origen protonacional en varias lenguas: castellano, latín, francés e inglés / María Rosa Lojo – Don Juan diabólico y periodización literaria / José Manuel Losada – Reseñas bibliográficas