scholarly journals Hemispherical–directional reflectance measurements of natural snow in the 0.9–1.45 μm spectral range: comparison with adding–doubling modelling

1998 ◽  
Vol 26 ◽  
pp. 59-63 ◽  
Author(s):  
Claude Sergent ◽  
Catherine Leroux ◽  
Evelyne Pougatch ◽  
Florence Guirado
Keyword(s):  
Temperature Gradient ◽  
Spectral Range ◽  
Experimental Results ◽  
Natural Snow ◽  
Reflectance Measurements ◽  
Directional Reflectance ◽  
Made In

The authors present the results of snow hemispherical–directional reflectance measurements on natural snow in the 0.9–1.45 μm spectral range. The measurements were made in a cold laboratory on snow collected in the field. Some of the samples have been subjected to controlled metamorphism in the laboratory before measurements were made. In the first part, the adding–doubling model, experimental assumptions and methodology are described. In the second part, experimental results are discussed and compared with theoretical values for different typical snow types and for different stages of snow evolution when subjected to temperature-gradient and wetness metamorphisms.

scholarly journals Hemispherical–directional reflectance measurements of natural snow in the 0.9–1.45 μm spectral range: comparison with adding–doubling modelling

1998 ◽  
Vol 26 ◽  
pp. 59-63 ◽  
Author(s):  
Claude Sergent ◽  
Catherine Leroux ◽  
Evelyne Pougatch ◽  
Florence Guirado
Keyword(s):  
Temperature Gradient ◽  
Spectral Range ◽  
Experimental Results ◽  
Natural Snow ◽  
Reflectance Measurements ◽  
Directional Reflectance ◽  
Made In

The authors present the results of snow hemispherical–directional reflectance measurements on natural snow in the 0.9–1.45 μm spectral range. The measurements were made in a cold laboratory on snow collected in the field. Some of the samples have been subjected to controlled metamorphism in the laboratory before measurements were made. In the first part, the adding–doubling model, experimental assumptions and methodology are described. In the second part, experimental results are discussed and compared with theoretical values for different typical snow types and for different stages of snow evolution when subjected to temperature-gradient and wetness metamorphisms.

scholarly journals Helical growth during the phototropic response, avoidance response, and in stiff mutants of Phycomyces blakesleeanus

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Joseph K. E. Ortega ◽  
Revathi P. Mohan ◽  
Cindy M. Munoz ◽  
Shankar Lalitha Sridhar ◽  
Franck J. Vernerey
Keyword(s):  
Avoidance Response ◽  
Experimental Results ◽  
Sensory Transduction ◽  
Growth Responses ◽  
Phycomyces Blakesleeanus ◽  
Sensory Stimuli ◽  
Phototropic Response ◽  
Biophysical Models ◽  
Helical Growth ◽  
Made In

AbstractThe sporangiophores of Phycomyces blakesleeanus have been used as a model system to study sensory transduction, helical growth, and to establish global biophysical equations for expansive growth of walled cells. More recently, local statistical biophysical models of the cell wall are being constructed to better understand the molecular underpinnings of helical growth and its behavior during the many growth responses of the sporangiophores to sensory stimuli. Previous experimental and theoretical findings guide the development of these local models. Future development requires an investigation of explicit and implicit assumptions made in the prior research. Here, experiments are conducted to test three assumptions made in prior research, that (a) elongation rate, (b) rotation rate, and (c) helical growth steepness, R, of the sporangiophore remain constant during the phototropic response (bending toward unilateral light) and the avoidance response (bending away from solid barriers). The experimental results reveal that all three assumptions are incorrect for the phototropic response and probably incorrect for the avoidance response but the results are less conclusive. Generally, the experimental results indicate that the elongation and rotation rates increase during these responses, as does R, indicating that the helical growth steepness become flatter. The implications of these findings on prior research, the “fibril reorientation and slippage” hypothesis, global biophysical equations, and local statistical biophysical models are discussed.

scholarly journals Tests of a Gust-Alleviating Flap in the Gust Tunnel

1940 ◽  
Vol 44 (351) ◽  
pp. 283-294 ◽  
Author(s):  
Philip Donely ◽  
C. C. Shufflebarger
Keyword(s):  
Experimental Results ◽  
Sharp Edge ◽  
Wing Loading ◽  
Longitudinal Stability ◽  
Maximum Acceleration ◽  
Long Period ◽  
Good Agreement ◽  
Made In

SummaryTests were made in the N.A.C.A. gust tunnel to determine the effectiveness of a long-period dynamically overbalanced flap in reducing aeroplane accelerations due to atmospheric gusts. For two gust shapes, one gust velocity, one forward velocity, and one wing loading, a series of flights was made with the flap locked and was then repeated with the flap free to operate. The records obtained were evaluated by routine methods.The results indicate that the flap reduced the maximum acceleration increment 39 per cent, for a severe gust with a representative gust gradient distance of 8 chord lengths and that, for an extreme gust shape (a sharp-edge gust), the reduction was only 3 per cent. The results also indicate that the flap tended to reduce the longitudinal stability of the aeroplane. Computations made of the effectiveness and the action of the flap were in good agreement with the experimental results.

THERMAL CHARACTERISTICS OF FOAMS AND DISCHARGE FROM FIRE-EXTINGUISHMENT FOAM SPRAY NOZZLE

2009 ◽  
Vol 23 (03) ◽  
pp. 381-384
Author(s):  
YOUN-JEA KIM ◽  
JIN-SOO PYO
Keyword(s):  
Heat Flux ◽  
Temperature Gradient ◽  
Thermal Characteristics ◽  
Expansion Ratio ◽  
Experimental Results ◽  
Orifice Diameter ◽  
Spray Nozzle ◽  
Foam Expansion ◽  
Fire Extinguishment ◽  
Air Hole

To evaluate the performance of discharged foam agents used to protect structures from heat and fire damages, the thermal characteristics of fire-extinguishment foams were experimentally investigated. Especially, two different parameters of a spray nozzle, that is, the number of air holes and the orifice diameter, were considered. A simple repeatable test for fire-extinguishment foams subjected to fire radiation was performed. Experimental results showed that the expansion ratio of the discharged foam with the small orifice throat ( d 0= 9.5 mm ) and opened air hole ( N h =9) was large. Results also showed that although the temperature gradient in the foam increased as the foam expansion ratio is increased, it remained constant as the intensity of heat flux increased.

A Study of Wickability of Gauze Products for Infant

2019 ◽  
Vol 814 ◽  
pp. 291-296
Author(s):  
Wen Yi Wang ◽  
Yi Lam Stephanie Yau ◽  
Chi Wai Kan ◽  
Kasem Manarungwit ◽  
Nattadon Rungruangkitkrai ◽  
...  
Keyword(s):  
Fiber Content ◽  
Experimental Results ◽  
Hydrophilic Property ◽  
Fabric Structure ◽  
Cotton Material ◽  
Significant Difference ◽  
Made In

Gauze is an excellent material for infant apparel which can made in various forms and by a variety of methods, and thus have attracted great attention in baby care market. This study aims to identify the wicking property of the gauze fabric in baby care products, and to analyse the relationships between the wicking ability and fabric structure of baby soft gauze products. The experimental results revealed that a significant difference occurred for the gauze in the wicking ability. The cotton gauzes were found to show higher wicking rate than bamboo counterparts because of the higher hydrophilic property of cotton material. The fiber content and structure of fabric were the major parameters that affects the wicking ability.

Low-frequency modulation of thermal instability

1970 ◽  
Vol 43 (2) ◽  
pp. 385-398 ◽  
Author(s):  
S. Rosenblat ◽  
D. M. Herbert
Keyword(s):  
Temperature Gradient ◽  
Asymptotic Solution ◽  
Frequency Modulation ◽  
Thermal Instability ◽  
Low Frequency ◽  
Experimental Results ◽  
Stability Criteria ◽  
The Stability ◽  
Boussinesq Fluid

A Boussinesq fluid is heated from below. The applied temperature gradient is the sum of a steady component and a low-frequency sinusoidal component. An asymptotic solution is obtained which describes the behaviour of infinitesimal disturbances to this configuration. The solution is discussed from the viewpoint of the stability or otherwise of the basic state, and possible stability criteria are analyzed. Some comparison is made with known experimental results.

scholarly journals A theory of meteors, and the density and temperature of the outer atmosphere to which it leads

1923 ◽  
Vol 102 (717) ◽  
pp. 411-437 ◽  
Keyword(s):  
Temperature Gradient ◽  
Consistent Theory ◽  
Amount Of Information ◽  
Outer Atmosphere ◽  
Considerable Detail ◽  
Made In

Some thirty years ago Teisserenc de Bort announced the discovery that the temperature gradient in the atmosphere, which amounts to some 6.5 . 10 -5 degree/cm. for the first 10 km., becomes negligibly small at greater heights. Since this time it has become usual to treat the temperature as constant for all heights above this limit, and various detailed numerical estimates, extending to heights of hundreds of kilometres, have been published, which are based on this assumption. So far, however, no evidence for it has been adduced beyond the “ballon sonde” observations, which scarcely extend above 25 km. The purpose of this note is to examine how much information about conditions at greater heights may be gained from a study of meteors. For this purpose it is necessary to study in considerable detail the theory of what happens when a meteor appears. It will be seen that a consistent theory can be developed, which accounts for all the observed phenomena, and that this theory enables one to derive a considerable amount of information about conditions in the upper air. It will be shown that existing observations enable us to say with considerable certainty that the density at heights above 65 kilom. is very much higher than is commonly supposed, and that the temperature must increase from its value of something like 220° abs. at heights between 12 and 50 km., to something like 300° abs. at these heights. It is evident that accurate results can only be obtained when the required quantities, viz., heights of appearance and disappearance, length of path, velocity and luminosity have been determined for a number of meteors. It is hoped that experiments, now in progress to determine these quantities photographically, will enable more accurate calculations to be made. In the meantime, the broad results obtained from the data due to W. F. Denning and his co-workers may be outlined.

Effects of Growth Rates on Directionally Solidified Microstructure of Al-Ni-Y Ternary Alloy

2012 ◽  
Vol 562-564 ◽  
pp. 477-481
Author(s):  
Rui Xu
Keyword(s):  
Temperature Gradient ◽  
Directional Solidification ◽  
Ternary Alloy ◽  
Growth Rates ◽  
Optical Microscope ◽  
Experimental Results ◽  
Al Alloy ◽  
Directionally Solidified ◽  
X Ray Diffraction ◽  
X Ray

The directional solidification of the ternary Al alloy with composition of 2.6 at%Ni, 0.9 at%Y and 96.5 at% Al was carried out under the temperature gradient of 5 K/mm and the droping velocities of 0.5 mm/min, 1 mm/min, 5 mm/min, 10 mm/min, and 25 mm/min. The microstructure of the Al-Ni-Y ternary alloy was also analyzed by X-ray diffraction and optical microscope. The experimental results show that the microstructures of the Al-Ni-Y ternary alloy are consisted of ª-Al2, Al3Ni and Y4Ni6Al23phase when the alloy was directionally solidified in all directionally solidified rates in the experiments. No primary -Al can be found in the sample with directionally solidified rate of 0.5 mm/min. When the rates higher than 1 mm/min, the primary ª-Al can be observed. The microstructure of the directionally solidified alloy becomes finer and the primary ª-Al is smaller gradually with the increasing of growth velocities when the dropping rate of directional solidification is higher than 5 min/min. Two eutectic structures, Y4Ni6Al23andª-Al eutectic and Al3Ni and ª-Al eutectic, can be found when the dropping rate is higher than 10 mm/min.

scholarly journals X-ray microtomography analysis of isothermal densification of new snow under external mechanical stress

2013 ◽  
Vol 59 (214) ◽  
pp. 233-243 ◽  
Author(s):  
Stefan Schleef ◽  
Henning Löwe
Keyword(s):  
Mechanical Stress ◽  
High Specific Surface Area ◽  
Transient Creep ◽  
Ice Crystals ◽  
X Ray ◽  
Single Temperature ◽  
Polycrystalline Ice ◽  
Natural Snow ◽  
Made In ◽  
Snow Samples

AbstractWe have investigated the isothermal densification of new snow under an external mechanical stress. New snow samples that mimic natural snow were made in the laboratory by sieving ice crystals grown in a snowmaker. This allowed us to assemble homogeneous initial samples with reproducible values of low density and high specific surface area (SSA). Laboratory creep experiments were conducted in an X-ray microtomograph at −20°C for 2 days. We focused on the evolution of density and SSA as a function of constant stress at a single temperature. External mechanical stresses resembled natural overburden stresses of a snow sample at depths of ∼0–30 cm of new snow. We demonstrate that densification increases with higher external stress and lower initial densities. We find that the evolution of the SSA is independent of the density and follows a unique decay for all measurements of the present type of new snow. The results suggest that details of the SSA decrease can be investigated using carefully designed experiments of short duration which are convenient to conduct. Additionally, we calculated the strain evolution and identify transient creep behavior that does not follow the Andrade creep law of denser snow or polycrystalline ice.

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