Longitudinal Air Research Articles

Composition Studies with the Pierre Auger Observatory

We report on studies of the composition of ultra high energy cosmic rays with the Pierre Auger Observatory. The detection of longitudinal air shower profiles with the fluorescence detector is described and the measurement of the average shower maximum as a function of energy is presented. Furthermore, mass sensitive parameters that can be obtained from the observatory's surface detector data are discussed.

Experimental study on burning rates of square/rectangular gasoline and methanol pool fires under longitudinal air flow in a wind tunnel

Square pool fires with length of 5, 7.5, 10, 15, 20, 25 and 30 cm and rectangular pool fires with dimensions of 10 cm × 20 cm and 10 cm × 40 cm were burned in a wind tunnel, under a longitudinal air flow ranged from 0 to 3 m/s with incremental change of about 0.5 m/s. Methanol and gasoline were burned and compared, with results indicated that their burning rates showed different response to the longitudinal air flow. With the increase of the longitudinal air flow speed, the burning rates of methanol pool fires, except the 5 cm square one, first decreased and then increased, but those of the 5 cm methanol square one and the gasoline pool fires increased monotonously. The burning rate of smaller square pool fires increased more significantly than that of the larger ones, as well as the enlargement of their flame attachment length along the ground. The burning rate of a rectangular pool fire with longer rim parallel to the longitudinal flow increased faster, but the flame attachment length seemed to increase more gradually, with the increase of the longitudinal air flow speed than that perpendicular to.

An Analysis of Air Flow at Various Spacing of Fans on a Physical Model of a Road Tunnel

In this article, the influence of a jet fan spacing in a longitudinal air conditioning system in a road tunnel on a physical model of the tunnel is analyzed. The analysis of air transport on a physical model with a length of 30 metres was accomplished for various combinations of the connection of 8 jet fans (parallel connection of 8 fans, combined connection of 2 X 4 parallel fans, combined connection (of) 4 X 2 parallel fans and serial connection of 8 fans). From the analysis of measurement on the physical model follows what a big influence the fan spacing has on the speed profile, which to a great extent influences air transport in the tunnel. Our contribution deals with the interpretation of vibration data from the point of view of vibration sources identification. These sources are searched and evaluated from the measured data using a frequency and phase spectrum.

Anatomia foliar de bromélias ocorrentes em áreas de cerrado do Estado de São Paulo, Brasil

Visando apontar características inerentes à família Bromeliaceae e indicar possíveis adaptações anatômicas encontradas nas espécies de cerrado, foram estudadas as folhas de cinco Bromelioideae, sete Tillandsioideae e uma Pitcairnioideae. Em geral, nas Bromelioideae, os estômatos estão aprofundados na epiderme e verifica-se um tecido mecânico epidérmico e subepidérmico; observa-se um tecido parenquimático armazenador de água, células esclerificadas não relacionadas aos tecidos vasculares, além de canais de aeração percorrendo longitudinalmente o mesofilo. Nas Tillandsioideae, as folhas são densamente recobertas por escamas, os estômatos ocorrem nas duas superfícies e o mesofilo é bastante compacto. Em Pitcairnioideae, a estrutura foliar é bastante semelhante à das Bromelioideae, embora os estômatos sejam ligeiramente elevados em relação à epiderme e não ocorram grupos de células esclerificadas extravasculares. Os resultados foram avaliados dentro de um contexto adaptativo e taxonômico.

Estimation of the PCR mass composition in the energy range 1017–1019 eV on the basis of multicomponent analysis of the characteristics of EASs detected at the Yakutsk array

The characteristics of longitudinal and radial extensive air shower development derived from the results of detection of the charged particle flux and Cherenkov light in extensive air showers at the Yakutsk array. To estimate the primary cosmic ray composition, a combination of the parameters Xmax and ρ600 and the database simulated using the CORSIKA code (QGSJET model) for showers generated by five types of nuclei (p, He, C, Si, Fe) in the energy range 1017–1019 eV were used. Application of the multicomponent method made it possible to divide the showers into three groups (p + He), C, and (Si + Fe) and estimate their percentage. The error in identifying nuclei in the energy range 1017–1018 eV does not exceed 30%.

Monte Carlo simulations of geosynchrotron radio emission from CORSIKA-simulated air showers

We present simulations performed with REAS2, a new Monte Carlo code for the calculation of geosynchrotron radio emission from extensive air showers. The code uses thoroughly tested time-domain radio emission routines in conjunction with a realistic air shower model based on per-shower multi-dimensional CORSIKA-generated histograms. We assess in detail how the transition from simpler, parametrised, to realistic, CORSIKA-based particle distributions affects the predicted radio emission from a typical 10 17 eV air shower. The effects of eliminating a previously needed free parameter and adopting realistic electron to positron ratios are also discussed. Compared with earlier calculations based on parametrised showers, REAS2 simulations predict slightly weaker and in some cases narrower pulses. In addition, a pronounced east–west versus north–south asymmetry arises in the emission pattern, and the radio pulses become generally unipolar. Finally, we demonstrate how REAS2 can be used to study radio pulse shapes and their relation to shower characteristics such as the longitudinal air shower development.

Longitudinal air permeability of pinewood with beetle transmitted blue-stain

The mountain pine beetle epidemic is destroying an extensive volume of the lodgepole pine forests being one of the most commercially harvested trees in British Columbia. The purpose of this study was to test the permeability of wood of four different classes regarding the time of the beetle attack. The experiments used the ‘‘falling water’’ unsteady-steady method of measuring superficial air permeability. The results showed that the specific permeability is not significantly different between the infested classes tested. The same conclusion could be reached for comparisons of uninfected and infested wood.

Bubbly flow structure in hydraulic jump

In an open channel, a hydraulic jump is the rapid transition from super- to sub-critical flow associated with strong turbulence and air bubble entrainment in the mixing layer. New experiments were performed at relatively large Reynolds numbers using phase-detection probes. Some new signal analysis provided characteristic air–water time and length scales of the vortical structures advecting the air bubbles in the developing shear flow. An analysis of the longitudinal air–water flow structure suggested little bubble clustering in the mixing layer, although an interparticle arrival time analysis showed some preferential bubble clustering for small bubbles with chord times below 3 ms. Correlation analyses yielded longitudinal air–water time scales T x x V 1 / d 1 of about 0.8 in average. The transverse integral length scale Z / d 1 of the eddies advecting entrained bubbles was typically between 0.25 and 0.4, irrespective of the inflow conditions within the range of the investigations. Overall the findings highlighted the complicated nature of the air–water flow.

Influence of Stationary Vehicles on Backlayering Characteristics of Fire Plume in a Large Cross Section Tunnel

This study is a part of an investigation project to examine emergencies in a large cross sectional tunnel, to be constructed on the New Toumei Expressway in Japan. Backlayering characteristics, the most important behavior in tunnel fires, are investigated through large-eddy simulation for various longitudinal air flows and fire sizes. The accuracy of this simulator has been previously confirmed by comparing with experimental results. In this study, specifically, stationary vehicles in a tunnel are considered in the simulation for the first time. Their presence induces turbulence in the longitudinal air flow and greatly affects the backlayering characteristics. However, earlier studies have not yet considered these effects. The results show that the presence of stationary vehicles reduces the backlayering length. Furthermore, the ratio of large-sized vehicles to total traffic is found to have little effect on fire behavior.

Anatomia foliar de Tillandsia L. (Bromeliaceae) dos Campos Gerais, Paraná, Brasil

The leaf anatomy of Tillandsia crocata (E. Morren) Baker, T. gardneri Lindl., T. geminiflora Brongn., T. linearis Vell., T. lorentziana Griseb., T. mallemontii Glaziou ex Mez, T. recurvata L., T. streptocarpa Baker, T. stricta Soland ex Sims, T. tenuifolia L., T. usneoides L., and Tillandsia sp. were studied. They occur in the Campos Gerais, State of Parana, southern Brazil. In surface view epidermis presents cells with linear to sinuous anticlinal walls, silica bodies and scales covering anomocytic stomata. Epidermis and first hypodermal layer are lignified. Transversal view reveals below surface stomata, aquiferous parenchyma, longitudinal air canals and collateral vascular bundles with double sheath. These anatomical features are xeromorphic and usually considered as an adaptation to the epiphytic habit of the atmospheric Tillandsia. Moreover, they could be also used for diagnostic purposes. Leaf shape in cross section, cuticle ornamentation, epidermal scale structures, thickening of the epidermal wall cells, stomata distribution, structure and distribution of the aquiferous parenchyma cells, presence of air canals, and size of vascular bundle could help the taxonomic delimitation of the species within the genus.

Definition and experimental evaluation of the smoke “confinement velocity” in tunnel fires

An experimental study is carried out on a reduced scale tunnel model (scale reduction is 1:20). The main objective is to evaluate the longitudinal velocity induced into a tunnel when a fire plume continuously released is confined and extracted between two exhaust vents located on both sides of the fire source. For the experimental simulations, fire-induced smoke is simulated by an air and helium mix release. Smoke flow is symmetrical as regards the fire location and experiments are realized for an half tunnel with only one vent activated downstream the source. The vent extraction flow rate is step by step increased and the length of the stratified smoke layer downstream the vent as well as the longitudinal fresh air flow induced, are measured. A confinement velocity is then associated to the minimum value of the longitudinal air flow needed to prevent the smoke layer propagation downstream the vent. This velocity is evaluated for several values of the fire heat release rate and finally compared with the corresponding critical velocity obtained for a longitudinal ventilation system.

On The Permeability of Main Wood Species in China

Summary This research dealt with the longitudinal air permeability of 40 important Chinese woods. The air permeabilities measured at about 10% moisture content for softwoods ranged between 0.00759 and 1.87130 darcy, while for hardwoods ranged between 0.00182 and 13.49867 darcy. The sapwood permeability of both softwoods and hardwoods was generally much higher than that of heartwood with 3 to 144 and 1 to 1302 times, respectively. The permeability values of wood were not affected by density between and within species. In all species studied, the permeability of heartwood of all softwoods, about 70% ring-porous and about 30% diffuse-porous or semi-diffuse porous hardwoods were below 0.1 darcy. The number of low permeability softwoods was higher than that of hardwoods. The number of low permeability ring-porous hardwoods was higher than that of diffuse-porous or semi-diffuse porous hardwoods. Finally, all the studied species were classified into five categories by their longitudinal permeabilities.

Equivalent thermophysical properties and surface heat transfer coefficient of fruit layers in trays during cooling

Experimental engineering data and predictive equations are established for the equivalent thermophysical properties (thermal conductivity, thermal diffusivity, specific heat capacity and density) and surface heat transfer coefficient of bulk layers of fruits (strawberries, raspberries, apricots, peaches, grapes and apples) in trays. Both packed layers and uncovered trays are considered as a system of fruits and air. In the first case the influence of air inclusions and free convection in closed space is taken into account, while in the second – special attention is devoted to the effect of air infiltration between the fruits placed in trays and pallets. The regression equations derived give the relationship between the considered equivalent values and the velocity of longitudinal air flow between the trays. The results are appropriate to be used for mathematical modelling and engineering calculations in real industrial heat transfer scenarios.

Similarity of plasmatron characteristics for longitudinal vortex flow around the arc with variations in the gas flow rate

The volt-ampere charateristics (VAC) of an elecric arc are correlated with longitudinal vortex air and nitrogen flows in plasmatrons with a rod-like cathode and two tubular electrodes. Two types of exponent approximations are used: a simple empirical formula and a relationship between generalized variables. It is shown by methods of regression analysis that the use of generalized variables provides similarity of the VAC upon variations in the gas-flow rate.

The mechanical behavior of a mammalian lung alveolar duct model.

A model for the mechanical properties of an alveolar duct is analyzed using the finite element method. Its geometry comprises an assemblage of truncated octahedral alveoli surrounding a longitudinal air duct. The amounts and distributions of elastin and collagen fiber bundles, modeled by separate stress-strain laws, are based upon published data for dogs. The surface tension of the air-liquid interface is modeled using an area-dependent relationship. Pressure-volume curves are computed that compare well with experimental data for both saline-filled and air-filled lungs. Pressure-volume curves of the separate elastin and collagen fiber contributions are similar in form to the behavior of saline-filled lungs treated with either elastase or collagenase. A comparison with our earlier model, based upon a single alveolus, shows the duct to have a behavior closer to reported experimental data.

Steadying the instability of a glowing discharge in a longitudinal air stream

We have studied experimentally the temperature of a gas and the strength of the electric field for a glowing discharge in a longitudinal stream of air. We have derived a two-dimensional distribution of the reduced field strength E/N in the gas discharge tube. Numerical studies have been conducted into the kinetics of a dry-air plasma. We have calculated the ionization factors, and the factors for adhesion and separation of electrons. Through comparison of experimental and theoretical data we propose a model for the contraction of the glowing discharge with an adhesive instability mechanism.

The roots and mycorrhizas of herbaceous woodland plants: I. Quantitative aspects of morphology.

The time-course of development of the roots and endomycorrhizas of five common herbaceous plants in a southern Ontario hardwood forest (Arisaema atrorubens, Erythronium americanum, Asarum canadense, Smilacina racemosa, and Trillium grandiflorum) was examined. Root growth of these species was very slow. Formation of vesicular-arbuscular (VA) mycorrhizas was quantified by measuring the average distance from growing root tips at which (i) hyphal contact, (ii) root penetration, and (iii) arbuscule formation by hyphae of VA mycorrhizal fungi first occurred. The rate at which mycorrhizal colonies within roots expanded was also quantified. These measurements allowed the rate of mycorrhizal colonization of roots of species to be compared. All events were slower in woodland plant roots than in other previously investigated species. The rate of VA mycorrhizal colony-expansion was found to be significantly faster in roots containing longitudinal air channels, which apparently facilitated the spread of hyphae. Environmental factors may also have been important since events were even slower in those roots produced by Erythronium in the autumn. Reasons why slow, steady, root and mycorrhiza formation could be advantageous to woodland plants are considered.

Oscillating synchronous linear motor in electromechanical resonance

The symmetric double acting oscillating synchronous linear motor with longitudinal functional air gaps is very well suited to the system synthesis of the electronically controlled drive for working resonant machines used in industrial vibrational technique. It can be designed for a stroke of up to some centimetres and a working frequency ranging from about 6 to 70 Hz. What is important in practice is the motor operation in electromechanical resonance with a compensated synchronising (AC) motor circuit and a compensated mechanical load. Then, the operational motor characteristics, derived under the assumption of harmonic oscillations, are functions of real variables. An analysis of these characteristics yields the features of a steady-state motor with harmonic oscillations. Attention is paid above all to the motor self regulation and the control of the velocity or path amplitude of its oscillations. The theoretical outcome, applicable also for the case of a not fully harmonic motor power supply from a static convertor, is in good agreement with the experimental results obtained from researching motor prototypes of 1 and 5.7 kW.

On the significance of investigations of transformer core models

Many investigations of transformer core models have been reported in literature. However, low value has been set on the significance of the results for full size cores. It is the intention of this paper to collect experiences concerning model core experiments either from literature or from own investigations. The occurrence of stray fields and leakage fluxes during open-circuit operation prove to be the most serious effect influencing the significance of model core measurements. Stray fields are mainly caused by low numbers of lamination and narrow sheet widths respectively, especially in cases of cores including yokes without magnetization coils. In addition, investigations can be considerably impaired by longitudinal air gaps resulting from bad preparation or arrangement of the sheet samples.

Thermal radiation hazards from hydrocarbon pool fires

A rectangular pool fire may be formed which is essentially affected by ambient wind in open space. In this work, the experimental investigations of flame radiation of heptane fire in longitudinal wind are conducted using five rectangular containers with a constant surface area, and variable length-width ratios of 1, 2, 4, 8, 16. The longitudinal air speeds are 0, 0.71, 0.96, 1.22, 1.47, 1.73, 1.98, 2.24 and 2.49 m/s respectively. Results show that as air speed increases, the incident heat flux increases initially and then decreases afterwards, and the threshold value of air flow is approximately at v = 0.96 m/s. The heat flux is primarily determined by burning rate at v ≤ 0.96 m/s whereas it is determined by the combination of flame morphology and burning rate at v > 0.96 m/s. The theoretical formula of radiation emissivity of rectangular pan is deduced using mass burning rate and aspect ratio. The multi-inclined-cylinder model incorporating aspect ratio, flame height, tilt angle and mass burning rate is proposed to evaluate the rectangular flame radiation in air flows. The theoretical values of heat fluxes are acceptably consistent with measurements in longitudinal wind-blown condition.