scholarly journals Dynamic Behaviour of Dislocations in HF-Doped Ice Ih

1980 ◽  
Vol 25 (91) ◽  
pp. 133-150 ◽  
Author(s):  
J. Perez ◽  
C. Maï ◽  
J. Tatibouët ◽  
R. Vassoille
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
High Temperature ◽  
Internal Friction ◽  
Dynamic Behaviour ◽  
Dislocation Glide ◽  
Linear Defects ◽  
Doping Effects ◽  
Crystalline Core ◽  
Accumulation Effect

AbstractA model of dislocation glide in ice Ih was recently proposed. This model was developed on certain assumptions, namely that transitions occur through cooperative movements of H2O molecules in the non-crystalline core of dislocations. A relation between the velocityvdof linear defects and shear stressτor temperatureTis obtained. This relation shows thatvdvaries linearly withτat low values ofτand (or)Tbut varies more rapidly at higher stresses; this non-linearity is more pronounced the higher the temperature. Such an analysis is extended in order to take into account doping effects. The case of HF-doped ice is considered: it is shown that there is a strong accumulation effect of HF molecules in the dislocation cores, which induces an increase of the rate of transitions. The results are in agreement with experimental data concerning both the velocity of dislocations and high-temperature internal friction in HF-doped ice.

scholarly journals Dynamic Behaviour of Dislocations in HF-Doped Ice Ih

1980 ◽  
Vol 25 (91) ◽  
pp. 133-150
Author(s):  
J. Perez ◽  
C. Maï ◽  
J. Tatibouët ◽  
R. Vassoille
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
High Temperature ◽  
Internal Friction ◽  
Dynamic Behaviour ◽  
Dislocation Glide ◽  
Linear Defects ◽  
Doping Effects ◽  
Crystalline Core ◽  
Accumulation Effect

AbstractA model of dislocation glide in ice Ih was recently proposed. This model was developed on certain assumptions, namely that transitions occur through cooperative movements of H2O molecules in the non-crystalline core of dislocations. A relation between the velocity vd of linear defects and shear stress τ or temperature T is obtained. This relation shows that vd varies linearly with τ at low values of τ and (or) T but varies more rapidly at higher stresses; this non-linearity is more pronounced the higher the temperature. Such an analysis is extended in order to take into account doping effects. The case of HF-doped ice is considered: it is shown that there is a strong accumulation effect of HF molecules in the dislocation cores, which induces an increase of the rate of transitions. The results are in agreement with experimental data concerning both the velocity of dislocations and high-temperature internal friction in HF-doped ice.

scholarly journals Cooperative Movement of H2O Molecules and Dynamic Behaviour of Dislocations in Ice Ih

1978 ◽  
Vol 21 (85) ◽  
pp. 361-374 ◽  
Author(s):  
J. Perez ◽  
C. MaÏ ◽  
R. Vassoille
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Dynamic Behaviour ◽  
New Model ◽  
Cooperative Movement ◽  
The Core ◽  
Linear Defects

Abstract A new model of dislocations glide in ire Ih is proposed. In developing this model certain assumptions are made: (i) dislocations have a non-crystalline extended core, and (ii) transitions occur through cooperative movements of ?2? molecules in the core of dislocations. A relation between the velocity ν d of linear defects and shear stress τ or temperature T is obtained. This relation shows that ν d varies linearly with τ at low values of τ and (or) T but varies more rapidly at higher stresses; this non-linearity is more pronounced the higher the temperature. Such results are in agreement with experimental data.

scholarly journals Cooperative Movement of H2O Molecules and Dynamic Behaviour of Dislocations in Ice Ih

1978 ◽  
Vol 21 (85) ◽  
pp. 361-374
Author(s):  
J. Perez ◽  
C. MaÏ ◽  
R. Vassoille
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Dynamic Behaviour ◽  
New Model ◽  
Cooperative Movement ◽  
The Core ◽  
Linear Defects

AbstractA new model of dislocations glide in ire Ih is proposed. In developing this model certain assumptions are made: (i) dislocations have a non-crystalline extended core, and (ii) transitions occur through cooperative movements of ?2? molecules in the core of dislocations. A relation between the velocity νd of linear defects and shear stress τ or temperature T is obtained. This relation shows that νd varies linearly with τ at low values of τ and (or) T but varies more rapidly at higher stresses; this non-linearity is more pronounced the higher the temperature. Such results are in agreement with experimental data.

Characterization of Shear Strength and Interface Friction of Organic Soil

2020 ◽  
Vol 857 ◽  
pp. 203-211
Author(s):  
Majid Hamed ◽  
Waleed S. Sidik ◽  
Hanifi Canakci ◽  
Fatih Celik ◽  
Romel N. Georgees
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Internal Friction ◽  
Moisture Content ◽  
Water Content ◽  
Friction Angle ◽  
Structural Materials ◽  
Organic Soil ◽  
Internal Friction Angle ◽  
Interface Friction

This study was undertaken to investigate some specific problems that limit a safe design and construction of structures on problematic soils. An experimental study was carried out to examine the influence of loading rate and moisture content on shear strength of organic soil. Influece of moisture content on interface friction between organic soil and structural materials was also attempted. A commonly used soil in Iraq was prepared at varying moisture contents of 39%, 57% and 75%. The experimental results showed that the increase in water content will decrease the shear stress and the internal friction angle. An increase of the shearing rate was found to decrease the shear stress and internal friction angle for all percetanges of water contents. Further, direct shear tests were carried out to detect the interface shear stress behavior between organic soil and structural materials. The results revealed that the increase in water content was shown to have significant negetavie effects on the interface internal friction and angle shear strength.

scholarly journals High temperatures during microsporogenesis fatally shorten pollen lifespan

2021 ◽  
Author(s):  
Maurizio Iovane ◽  
Giovanna Aronne
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Heat Stress ◽  
High Temperature ◽  
Male Gametophyte ◽  
Crop Productivity ◽  
Anther Dehiscence ◽  
Optimal Temperature ◽  
Drastic Reduction ◽  
Crop Species

AbstractMany crop species are cultivated to produce seeds and/or fruits and therefore need reproductive success to occur. Previous studies proved that high temperature on mature pollen at anther dehiscence reduce viability and germinability therefore decreasing crop productivity. We hypothesized that high temperature might affect pollen functionality even if the heat treatment is exerted only during the microsporogenesis. Experimental data on Solanum lycopersicum ‘Micro-Tom’ confirmed our hypothesis. Microsporogenesis successfully occurred at both high (30 °C) and optimal (22 °C) temperature. After the anthesis, viability and germinability of the pollen developed at optimal temperature gradually decreased and the reduction was slightly higher when pollen was incubated at 30 °C. Conversely, temperature effect was eagerly enhanced in pollen developed at high temperature. In this case, a drastic reduction of viability and a drop-off to zero of germinability occurred not only when pollen was incubated at 30 °C but also at 22 °C. Further ontogenetic analyses disclosed that high temperature significantly speeded-up the microsporogenesis and the early microgametogenesis (from vacuolated stage to bi-cellular pollen); therefore, gametophytes result already senescent at flower anthesis. Our work contributes to unravel the effects of heat stress on pollen revealing that high temperature conditions during microsporogenesis prime a fatal shortening of the male gametophyte lifespan.

Estimation of Back Stress Produced by Dislocation Interaction in Icosahedral Al-Pd-Mn

2000 ◽  
Vol 643 ◽  
Author(s):  
Hisatoshi Hirai ◽  
Akira Kitahara ◽  
Fuyuki Yoshida ◽  
Hideharu Nakashima
Keyword(s):  
Shear Stress ◽  
High Temperature ◽  
Main Part ◽  
Unit Length ◽  
Back Stress ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Dislocation Interaction ◽  
Burgers Vector ◽  
Phonon Component

AbstractWe attempted to calculate the breakaway stress σb of dislocation from attractive junction made by reaction of dislocations. Assuming that the force f acting on the unit length of dislocation with the Burgers vector B under a shear stress τa is f τ∣b˝∣ where b˝ is the phonon component of B, and that the elastic energy per unit length of dislocation W is approximated by W = G(∣b˝∣2 + c2 ∣b˔∣2) where G is the shear modulus, b˔ the phason component of B and c2 a coefficient of about 3.1 × 10−3. Using the values G = 48.4 GPa at 1070 K, the Taylor factor M = 3 and the measured dislocation density of 1.8 × 1013 m−2, we calculated σb for 21 possible dislocation reactions. Picking up the most possible dislocation reactions, σb distributed between 50 and 80 MPa, and the average of them was 64 MPa. This result strongly suggested the possibility that the main part of the internal stress of the high-temperature deformation of icosahedral Al-Pd-Mn is explained by σb.

Experimental Study on Critical Shear Stress of Cohesive Soils and Soil Mixtures

2021 ◽  
Vol 64 (2) ◽  
pp. 587-600
Author(s):  
Xiaojing Gao ◽  
Qiusheng Wang ◽  
Chongbang Xu ◽  
Ruilin Su
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Critical Shear Stress ◽  
Cohesive Soil ◽  
Future Research ◽  
Cohesive Soils ◽  
List Type ◽  
Soil Mixture ◽  
Linear Relationships ◽  
Soil Mixtures

HighlightsErosion tests were performed to study the critical shear stress of cohesive soils and soil mixtures.Linear relationships were observed between critical shear stress and cohesion of cohesive soils.Mixture critical shear stress relates to noncohesive particle size and cohesive soil erodibility.A formula for calculating the critical shear stress of soil mixtures is proposed and verified.Abstract. The incipient motion of soil is an important engineering property that impacts reservoir sedimentation, stable channel design, river bed degradation, and dam breach. Due to numerous factors influencing the erodibility parameters, the study of critical shear stress (tc) of cohesive soils and soil mixtures is still far from mature. In this study, erosion experiments were conducted to investigate the influence of soil properties on the tc of remolded cohesive soils and cohesive and noncohesive soil mixtures with mud contents varying from 0% to 100% using an erosion function apparatus (EFA). For cohesive soils, direct linear relationships were observed between tc and cohesion (c). The critical shear stress for soil mixture (tcm) erosion increased monotonically with an increase in mud content (pm). The median diameter of noncohesive soil (Ds), the void ratio (e), and the organic content of cohesive soil also influenced tcm. A formula for calculating tcm considering the effect of pm and the tc of noncohesive soil and pure mud was developed. The proposed formula was validated using experimental data from the present and previous research, and it can reproduce the variation of tcm for reconstituted soil mixtures. To use the proposed formula to predict the tcm for artificial engineering problems, experimental erosion tests should be performed. Future research should further test the proposed formula based on additional experimental data. Keywords: Cohesive and noncohesive soil mixture, Critical shear stress, Erodibility, Mud content, Soil property.

HPHT synthesis and enhanced TE performance of Te and Sn/Se elements binary-doped CoSb3

2019 ◽  
Vol 12 (01) ◽  
pp. 1850105 ◽  
Author(s):  
Hairui Sun ◽  
Pin Lv ◽  
Chao Wang ◽  
Yunxian Liu ◽  
Xiaopeng Jia ◽  
...  
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
High Pressure ◽  
High Temperature ◽  
Seebeck Coefficient ◽  
Grain Boundaries ◽  
Preparation Methods ◽  
Synthesis Time ◽  
Lattice Disorder ◽  
Positive Effect

A series of binary-doped CoSb3 with Te and Se/Sn bulk compounds Co4Sb[Formula: see text]TexSny/Sey ([Formula: see text] and 0.6, [Formula: see text] and 0.3), have been successfully prepared via a simple high pressure and high-temperature (HPHT) method. And, the influence of the doping elements on the microstructure of the samples synthesized under diverse pressures and the corresponding TE performance were studied in detail. Comparing with other preparation methods, the synthesis time of HPHT was acutely shortened. The obtained samples contain more grain boundaries, lattice disorder, dislocations and the possible “nanodot”, which have positive effect on reducing thermal conductivity. The experimental data indicate that the absolute values of Seebeck coefficient increases with pressure. What’s more, the thermal conductivities show a monotone decreasing trend as the synthesis pressure rises. The minimum value obtained is 1.93[Formula: see text]Wm[Formula: see text]K[Formula: see text] at normal temperature for Co4Sb[Formula: see text]Te[Formula: see text]Se[Formula: see text] prepared under 3[Formula: see text]GPa.

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