scholarly journals Determination of the polarity of carrier traps in .GAMMA.-irradiated polyethylene by temperature gradient thermally stimulated current.

1986 ◽  
Vol 106 (8) ◽  
pp. 384-390
Author(s):  
Keizo Kato ◽  
Mitsumasa Iwamoto ◽  
Taro Hino
Keyword(s):  
Temperature Gradient ◽  
Thermally Stimulated Current ◽  
Carrier Traps ◽  
Gamma Irradiated

3D Freeze Printing: Development of an Experimental Setup and Determination of 3D Printing Parameters

2020 ◽  
Author(s):  
Halil Tetik ◽  
Dong Lin
Keyword(s):  
3D Printing ◽  
Low Temperature ◽  
Temperature Gradient ◽  
Freeze Casting ◽  
Printing Process ◽  
Print Head ◽  
Freezing Temperatures ◽  
Fabrication Parameters ◽  
Printing Parameters

Abstract 3D freeze printing is a hybrid manufacturing method composed of freeze casting and inkjet-based printing. It is a facile method to fabricate lightweight, porous, and functional structures. Freeze casting is a well-known method for fabricating porous bodies and is capable of manipulating the micro-structure of the resulting product. Freeze casting simply involves solidification of a liquid suspension using low temperature and sublimation of the solvent using low temperature and pressure. After the sublimation of the solvent crystals, we obtain a porous structure where the pores are a replica of solvent crystal. Making use of the temperature gradient, as seen in unidirectional and bidirectional freeze casting, during the solidification with low temperature values, the solvent crystals grow along the temperature gradient. Furthermore, by manipulating the freezing kinetics during solidification, we can have a control on the average pore size distribution. For instance, when lower freezing temperatures result in finer pores with higher amount, higher freezing temperatures result in coarser pores with less amount. Also, the use of some additives inside the suspension leads to changes in the morphology of the solvent crystals as well as the resulting pores. However, the macro-structure of the fabricated body is highly dependent on the mold used during the process. In order to eliminate the dependency on the mold during the freeze casting process, our group recently combined this technique with inkjet-based 3D printing. With inkjet-based 3D printing, we fabricated uniform lines from single droplets, and complex 3D shapes from the lines. This provided us the ability of tailoring the macro structure of the final product without any dependency on a mold as seen in freeze casting. As a result of the 3D freeze printing process, we achieved fabricating lightweight, porous, and functional bodies with engineered micro and macro-structures. However, achieving fine droplets, and uniform lines by merging the droplets requires a good combination of fabrication parameters such as pressure adjustment inside the print head, print head speed, jetting frequency. Also, fabricating complex shapes from uniform lines requires well-adjusted parameters such as line thickness and layer height. In this study, we briefly explained the mechanics of the 3D freeze printing process. Following that we presented the development process of an open-source inkjet-based 3D printer. Finally, we explained the determination of inkjet dispensing and 3D printing parameters required for a high-quality 3D printing. During our experiments for the determination of fabrication parameters, we used a nanocellulose crystals-based ink due to its low cost and ease of preparation.

Direct Determination of the Velocity of Vortices in High-Tc Superconductors by a Non-Equilibrium Method

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3288-3291
Author(s):  
I. Kirschner ◽  
R. Laiho ◽  
A. C. Bódi ◽  
E. Lähderanta ◽  
I. Vajda
Keyword(s):  
Magnetic Field ◽  
Temperature Gradient ◽  
Vortex Motion ◽  
Direct Determination ◽  
Field Investigation ◽  
High Tc Superconductors ◽  
High Tc ◽  
Pinning Centers ◽  
Non Equilibrium

As is shown, thermally assisted vortex motion can come into being in high-T c superconductors due to the applied temperature gradient. Its behavior strongly depends on the local and global microstructure of the samples, moreover on the temperature and magnetic field. Investigation of the density, size and intensity of the pinning centers of specimens leads to the conclusion that the higher homogeneity immediately weakens and the lower one strenghtens the pinning, thus the former promotes and the latter impedes the vortex motion. The non-equilibrium experimental technique together with a.c. susceptibility measurements render possible the direct determination of the velocity of vortices. Depending on the actual microstructural state of samples it has the values between 6 × 10-2 mm/s and 18 × 10-2 mm/s in the case of Y-Ba-Cu-O specimens investigated.

XXV.—The Determination of Temperature Gradients over the Greenland Ice Sheet by Optical Methods

1957 ◽  
Vol 64 (4) ◽  
pp. 381-397
Author(s):  
R. A. Hamilton
Keyword(s):  
Temperature Gradient ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Temperature Gradients ◽  
Lower Atmosphere ◽  
Optical Methods ◽  
Snow Surface ◽  
Vertical Angle ◽  
Gradient Measurements

SynopsisThe temperature gradient in the lower atmosphere can be directly determined by measuring the optical refractive index of the air. This method is suitable for use on the Greenland ice sheet where errors introduced by water vapour are small, and where the strong solar radiation reflected by the snow surface makes it difficult to measure temperature differences over height differences of about I metre.The refraction was measured by observing the apparent vertical angle of each of a set of targets at distances up to 4 km. from a theodolite. The refraction was found to vary linearly with the distance of the target. The true vertical angle to the targets was determined when a second theodolite was available and reciprocal sights could be taken with it from the site of target to the fixed theodolite. The true vertical angle varied with time due to slow descent of the theodolite as the firn slumped; a correction for this was made. The standard error of the temperature gradient measurements was about 1.5 × 10−2 C.° per metre. It is considered that the method could be developed and improved so that over a range of only 100 metres temperature gradients could be measured to an accuracy of about 0·1° C. per metre.

Memoirs: The Effect of a Temperature Gradient on the Early Development of the Chick

1928 ◽  
Vol s2-72 (287) ◽  
pp. 419-445
Author(s):  
MARIA A. TAZELAAR
Keyword(s):  
Temperature Gradient ◽  
Incubation Temperature ◽  
Primitive Streak ◽  
Blood System ◽  
Area Vasculosa ◽  
Exact Position ◽  
The Mean ◽  
Late Stages ◽  
Lateral Temperature

1. Owing to the difficulty of ascertaining the exact position of the embryo in the egg there was much waste of material. Hens' eggs are not ideal for temperature gradient experiments, for the mean between the temperatures which can be used is below normal incubation temperature. The egg of a cold-blooded animal would be far simpler to deal with. 2. The part most easily affected by a temperature gradient was the area vasculosa and its blood-vessels. This was to be expected, since the size of this extra-embryonic part is not strictly limited; the arrangement of the blood system of the area vasculosa was also modified in some cases. 3. Slight disproportion of parts was effected in some cases. The head was sometimes slightly more developed than the posterior end, and in some cases the posterior limbs were precociously developed. Differences in size between the limb buds on each side also occurred. The ratio of embryo to primitive streak was decreased considerably in the case of two embryos, treated with antagonistic gradients. 4. In some embryos treated with a lateral temperature gradient the somites had become shifted up on the heated side. The greatest effect was obtained in an embryo whose somites of one side alternated with those of the opposite side. It is possible that this condition may be regulated after normal incubation; results, however, were too few for certainty. 5. The numbers used were not sufficient for the conclusive determination of the degree of regulation which experimentally treated embryos underwent. However, all late stages when examined were normal; whether these cases were correctly treated or not it is impossible to say.

Stresses Induced in Fiber-Reinforced Tubes Due to Changes in Temperature and Moisture

1995 ◽  
Vol 117 (2) ◽  
pp. 228-234 ◽  
Author(s):  
Byung S. Kim ◽  
Terry F. Lehnhoff
Keyword(s):  
Temperature Gradient ◽  
Moisture Content ◽  
Boundary Conditions ◽  
Arbitrary Orientation ◽  
Fiber Reinforced ◽  
Stress Solution ◽  
Hygrothermal Stress

An orthotropic hygrothermal stress solution has been formulated for an infinitely long fiber-reinforced tube of any number of plies of any material, with arbitrary orientation of each of the plies. The solution allows the determination of stresses when the tube is subjected to changes in temperature and moisture content. In the formulation, a temperature gradient through the thickness has been taken into account such that the formulation can be applied when the temperature inside the tube is not the same as that outside. This set of equations, together with the prescribed boundary conditions, has been solved numerically. It is shown that the stresses induced due to moisture absorbed from the environment are significant.

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