scholarly journals On the cooling and evaporative powers of the atmosphere, as determined by the kata-thermometer

1919 ◽  
Vol 90 (632) ◽  
pp. 438-447 ◽  
Keyword(s):  
Body Temperature ◽  
Skin Temperature ◽  
Cross Section ◽  
Cooling Power ◽  
Mean Velocity ◽  
Cross Section Area ◽  
Section Area ◽  
Order Of Magnitude ◽  
The Mean ◽  
A Current

In a paper published in ‘Phil. Trans.’ (B, vol. 207, 1916, pp. 183-220) by L. Hill, O. W. Griffiths, and M. Flack, there was detailed the theory and use of an instrument, the kata-thermometer, a large-bulbed alcohol thermometer, for determining the cooling power of the atmosphere on a surface at body temperature. A formula H/ θ = 0⋅27 + 0⋅36 √V, where H = heat lost in mille-calories per square centimetre per second, θ = (36⋅5— t )°C., where t = temperature of enclosure, and V = velocity of air current in metres per second, was obtained for the loss of heat of the dry kata-thermometer in a current of air; 36⋅5° C. was chosen as the skin temperature. This is a variable, and only reaches that figure in warm atmospheres. The constant 0⋅36 in the above formula was determined from experiments which were carried out with the apparatus then available in a tube of which the cross-section area was of the same order of magnitude as that of the kata. Therefore, in calculating the velocity of the air current i.e ., the mean velocity of the air striking the kata, the area of cross-section of the kata was subtracted from that of the tube.

Modeling and Projecting the Onset and Subsequent Failure Rate of Corroding Bridge Post-Tension Tendons Arising from Deficient Grout

CORROSION ◽  
10.5006/2465 ◽  
2017 ◽  
Vol 74 (2) ◽  
pp. 241-248 ◽  
Author(s):  
William H. Hartt ◽  
Seung-Kyoung Lee
Keyword(s):  
Cross Section ◽  
Free Water ◽  
Elevated Concentration ◽  
Cross Section Area ◽  
Section Area ◽  
Important Approach ◽  
First Occurrence ◽  
The Mean ◽  
Post Tension ◽  
Integrity Assurance

Post-tensioning (PT) has become an important approach to affecting integrity of large reinforced concrete structures, including bridges. While there are a number of advantages to PT construction compared to conventional reinforcement, corrosion caused bridge tendon failures have recently been reported, in some cases within but a few years of construction, as a consequence of either chemically or physically deficient grout (or a combination of the two), where the former involves elevated concentration of chlorides or free sulfates (or both) and the latter voids with free water, and soft, chalky, segregated, separated grout. The present paper reviews a predictive model that was developed to project the onset and subsequent rate of wire and strand fractures and tendon failures as a function of time, given information regarding the present extent of corrosion. Inputs to the model are the mean and standard deviation of, first, remaining cross-section area at the most corroded location on individual wires and, second, an experimentally determined relationship between residual fracture stress and remaining cross-section area of corroded wires, both of which are represented as distributions. Particular emphasis is placed upon fracture and failure rates subsequent to first occurrence, because these can provide useful information for assuring timely intervention and integrity assurance of PT structures with corrosion issues. The results indicate that tendon failures, once initiated, can occur at an unmanageable rate even for relatively modest rates of corrosion.

scholarly journals Long-term evaluation of rootstock effects on cropping and tree parameters of selected sweet cherry cultivars

2020 ◽  
Vol 47 (No. 1) ◽  
pp. 13-20
Author(s):  
Jitka Blažková ◽  
František Paprštein ◽  
Lubor Zelený ◽  
Adéla Skřivanová ◽  
Pavol Suran
Keyword(s):  
Sweet Cherry ◽  
Cross Section Area ◽  
Section Area ◽  
Natural Tendency ◽  
Term Evaluation ◽  
The Mean ◽  
Sweet Cherry Cultivars ◽  
Tree Characteristics ◽  
Gisela 5

The cropping of six sweet cherry cultivars that originated in the Research and Breeding Institute of Pomology at Holovousy, and a standard one, ‘Burlat’, were evaluated on three rootstocks in the period of 2007–2017. Trees planted in a spacing of 1.5 m × 5.0 m were trained as tall spindle axes utilising their natural tendency to develop a central leader. On the standard rootstock, P-TU-2, ‘Tim’ was the most productive with a mean total harvest of 47.6 kg per tree. ‘Sandra’ yielded the most on the PHLC rootstock with 56.2 kg per tree and ‘Helga’ yielded the most on Gisela 5 with a mean total harvest of 55.9 kg per tree. The mean impact of the rootstock on the tree vigour, measured upon the trunk cross section area, ranged from 148.4 cm2 on the standard rootstock P-TU-2 to 114.1 cm2 on the PHLC and 125.2 cm2 on Gisela 5 . On the standard rootstock P-TU-2, the most vigorous one according to this criterion was ‘Jacinta’ (178.0 cm2) whereas ‘Justyna’ (109.7 cm2) was the least vigorous. On the PHLC, the most vigorous was ‘Sandra’ (147.2 cm2) and the least was ‘Amid’ (94.0 cm2). The other tree characteristics were mainly dependant on the cultivar and minimally, or not at all, influenced by the rootstock vigour.

Thermoacoustic Shape Optimization of a Subsonic Nozzle

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Alexis Giauque ◽  
Maxime Huet ◽  
Franck Clero ◽  
Sébastien Ducruix ◽  
Franck Richecoeur
Keyword(s):  
Acoustic Emission ◽  
Cross Section ◽  
Source Term ◽  
Combustion Noise ◽  
Noise Emission ◽  
Cross Section Area ◽  
Section Area ◽  
The Cross ◽  
Nozzle Flows ◽  
Subsonic Nozzle

Indirect combustion noise originates from the acceleration of nonuniform temperature or high vorticity regions when convected through a nozzle or a turbine. In a recent contribution (Giauque et al., 2012, “Analytical Analysis of Indirect Combustion Noise in Subcritical Nozzles,” ASME J. Eng. Gas Turbies Power, 134(11), p. 111202) the authors have presented an analytical thermoacoustic model providing the indirect combustion noise generated by a subcritical nozzle when forced with entropy waves. This model explicitly takes into account the effect of the local changes in the cross-section area along the configuration of interest. In this article, the authors introduce this model into an optimization procedure in order to minimize or maximize the thermoacoustic noise emitted by arbitrarily shaped nozzles operating under subsonic conditions. Each component of the complete algorithm is described in detail. The evolution of the cross-section changes are introduced using Bezier's splines, which provide the necessary freedom to actually achieve arbitrary shapes. Bezier's polar coordinates constitute the parameters defining the geometry of a given individual nozzle. Starting from a population of nozzles of random shapes, it is shown that a specifically designed genetic optimization algorithm coupled with the analytical model converges at will toward a quieter or noisier population. As already described by Bloy (Bloy, 1979, “The Pressure Waves Produced by the Convection of Temperature Disturbances in High Subsonic Nozzle Flows,” J. Fluid Mech., 94(3), pp. 465–475), the results therefore confirm the significant dependence of the indirect combustion noise with respect to the shape of the nozzle, even when the operating regime is kept constant. It appears that the quietest nozzle profile evolves almost linearly along its converging and diverging sections, leading to a square evolution of the cross-section area. Providing insight into the underlying physical reason leading to the difference in the noise emission between two extreme individuals, the integral value of the source term of the equation describing the behavior of the acoustic pressure of the nozzle is considered. It is shown that its evolution with the frequency can be related to the global acoustic emission. Strong evidence suggest that the noise emission increases as the source term in the converging and diverging parts less compensate each other. The main result of this article is the definition and proposition of an acoustic emission factor, which can be used as a surrogate to the complex determination of the exact acoustic levels in the nozzle for the thermoacoustic shape optimization of nozzle flows. This acoustic emission factor, which is much faster to compute, only involves the knowledge of the evolution of the cross-section area and the inlet thermodynamic and velocity characteristics to be computed.

scholarly journals Using the SWEPT Methodology for a Preliminary Wind Potential Estimation

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Jean-Luc Menet
Keyword(s):  
Wind Turbine ◽  
Characteristic Curve ◽  
Rayleigh Distribution ◽  
Mean Velocity ◽  
Technical Data ◽  
Wind Potential ◽  
Order Of Magnitude ◽  
General Data ◽  
The Mean ◽  
A Site

The implantation of wind turbines generally follows a wind potential study which is made using specific numerical tools; the generated expenses are only acceptable for great projects. The purpose of the present paper is to propose a simplified methodology for the evaluation of the wind potential, following three successive steps for the determination of (i) the mean velocity, either directly or by the use of the most occurrence velocity (MOV); (ii) the velocity distribution coming from the single knowledge of the mean velocity by the use of a Rayleigh distribution and a Davenport-Harris law; (iii) an appropriate approximation of the characteristic curve of the turbine, coming from only two technical data. These last two steps allow calculating directly the electric delivered energy for the considered wind turbine. This methodology, called the SWEPT approach, can be easily implemented in a single worksheet. The results returned by the SWEPT tool are of the same order of magnitude than those given by the classical commercial tools. Moreover, everybody, even a “neophyte,” can use this methodology to obtain a first estimation of the wind potential of a site considering a given wind turbine, on the basis of very few general data.

An Analytical Method of Analyzing the Heat Conduction for the Unequal Cross-Section Straight Fin

2013 ◽  
Vol 365-366 ◽  
pp. 1211-1216
Author(s):  
Fan Zhang ◽  
Peng Yun Song
Keyword(s):  
Heat Conduction ◽  
Cross Section ◽  
Analytical Method ◽  
Thermal Analyses ◽  
Cross Sectional ◽  
Cross Section Area ◽  
Section Area ◽  
Calculation Results ◽  
The Cross ◽  
Analytical Expressions

The cross-section area of straight fin is often considered to be equal in the thermal analyses of straight fin, but sometimes it is unequalin actual situation. Taking a straight fin with two unequal cross-sectional areas as an example,an analytical method of heat conduction for unequal section straight fin is presented. The analytical expressions of temperature field and heat dissipating capacity about the fin,which has a smaller cross-section area near the fin base and a larger one, is obtained respectively. The calculation results of the unequal cross-section are fully consistent with the equal area one, so the method is proved right. The results show that the larger the cross section areanear the base,the better is the heat transfer, and the temperature at the base with larger cross-section area is lower than that with smaller cross-section area when the amount of heat is fixed.

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