The Experts below are selected from a list of 462651 Experts worldwide ranked by ideXlab platform
Masahisa Wada - One of the best experts on this subject based on the ideXlab platform.
-
thermal expansion behavior of a and b type amylose crystals in the low Temperature Region
Carbohydrate Polymers, 2015Co-Authors: Kayoko Kobayashi, Satoshi Kimura, Eiji Togawa, Masahisa Wada, Philipkunio NaitoAbstract:The thermal expansion behaviors of A-type and B-type amylose crystals, which were prepared by recrystallization of short amylose chains synthesized by phosphorylase, were investigated using synchrotron X-ray powder diffraction between 100 and 300K. For both types of crystals, the room-Temperature phase (RT phase), which is the usually observed phase, transitioned to a low-Temperature phase (LT phase), on cooling. The phase transitions took place reversibly with rapid changes in the unit-cell parameters around 200-270K. The differences between the RT and LT phase were investigated using solid-state (13)C NMR spectroscopy, which revealed there were changes in molecular chain conformations. These results suggest that the phase transition of water molecules on the crystalline surfaces affects the thermal behavior and structure of polysaccharide crystals.
-
thermal expansion behavior of hydrate paramylon in the low Temperature Region
Carbohydrate Polymers, 2013Co-Authors: Kayoko Kobayashi, Satoshi Kimura, Eiji Togawa, Masahisa WadaAbstract:Abstract The thermal expansion behavior of hydrate paramylon between 100 and 300 K has been investigated using synchrotron X-ray powder diffraction. The X-ray diffraction profile at 300 K showed a typical pattern of the hydrate triple helical (1→3)-β- d -glucan with a hexagonal unit cell ( a = 15.782 A and c = 18.580 A). On cooling, the hydrate paramylon had converted to a “low-Temperature phase” around 270 K. On passing through the phase transition, the a -axis and c -axis values decreased and increased, respectively, and the low-Temperature phase at 100 K exhibited a hexagonal unit cell ( a = 15.586 A and c = 18.619 A). The phase transition took place reversibly. Below the transition point, both the a -axis and c -axis values decreased linearly. The thermal expansion coefficients are: α a = 1.50 × 10 −5 K −1 , α c = 0.33 × 10 −5 K −1 , and β = 3.08 × 10 −5 K −1 .
Yong Jiang - One of the best experts on this subject based on the ideXlab platform.
-
negative spin hall magnetoresistance in antiferromagnetic cr2o3 ta bilayer at low Temperature Region
Applied Physics Letters, 2018Co-Authors: J Miao, Yuanmin Zhu, K K Meng, J K Chen, Yong JiangAbstract:We demonstrate the negative spin Hall magnetoresistance (SMR) observed in antiferromagnetic Cr2O3/Ta bilayers at low Temperature. The SMR signals are changed from the positive to negative magnitude when monotonously reducing the Temperature from 300 K to 50 K. The positive and negative SMR signals are expected to be associated with the two different ways for injection of the spin current, into the boundary ferromagnetic Region and the bulk antiferromagnetic Region of α-Cr2O3 (0001), respectively. The slopes of the abnormal Hall curves exhibit the same sign with the SMR signal. From the SMR ratio under 3 T, the spin mixing conductance at the Cr2O3/Ta interface is estimated to be 1.12 × 1014 Ω−1·m−2, which is comparable to the one observed in the Y3Fe5O12(YIG)/Pt structure and our early results of the Cr2O3/W structure.
-
negative spin hall magnetoresistance in antiferromagnetic cr2o3 ta bilayer at low Temperature Region
arXiv: Materials Science, 2018Co-Authors: J Miao, Yuanmin Zhu, K K Meng, J K Chen, Yong JiangAbstract:We investigate the observation of negative spin Hall magnetoresistance (SMR) in antiferromagnetic Cr2O3/Ta bilayers at low Temperature. The sign of the SMR signals is changed from positive to negative monotonously from 300 K to 50 K. The change of the signs for SMR is related with the competitions between the surface ferromagnetism and bulky antiferromagnetic of Cr2O3. The surface magnetizations of Cr2O3 (0001) is considered to be dominated at higher Temperature, while the bulky antiferromagnetics gets to be robust with decreasing of Temperature. The slopes of the abnormal Hall curves coincide with the signs of SMR, confirming variational interface magnetism of Cr2O3 at different Temperature. From the observed SMR ratio under 3 T, the spin mixing conductance at Cr2O3/Ta interface is estimated to be 1.12*10^14 (ohm^-1*m^-2), which is comparable to that of YIG/Pt structures and our early results of Cr2O3/W. (Appl. Phys. Lett. 110, 262401 (2017))
Toshiyuki Meshii - One of the best experts on this subject based on the ideXlab platform.
-
application of stress to predict the lower bound fracture toughness for increasing the test specimen thickness in the transition Temperature Region
Advances in Materials Science and Engineering, 2014Co-Authors: Kai Lu, Toshiyuki MeshiiAbstract:This work was motivated by the fact that although fracture toughness of a material in the ductile-to-brittle transition Temperature Region exhibits the test specimen thickness (TST) effect on , frequently described as , experiences a contradiction that is deduced from this empirical formulation; that is, = 0 for large TST. On the other hand, our previous works have showed that the TST effect on could be explained as a difference in the out-of-plane constraint and correlated with the out-of-plane -stress. Thus, in this work, the TST effect on for the decommissioned Shoreham reactor vessel steel A533B was demonstrated from the standpoint of out-of-plane constraint. The results validated that was effective for describing the decreasing tendency. Because the Shoreham data included a lower bound for increasing TST, a new finding was made that successfully predicted the lower bound of with increasing TST. This lower bound prediction with conquered the contradiction that the empirical predicts = 0 for large TST.
-
extended investigation of test specimen thickness tst effect on the fracture toughness jc of a material in the transition Temperature Region as a difference in the crack tip constraint what is a loss in constraint in the tst effect on jc
Procedia Materials Science, 2014Co-Authors: Toshiyuki Meshii, Kai Lu, Yuki FujiwaraAbstract:Abstract This paper is an extension of our recent work (Meshii et al., 2013), which demonstrated through experiments and elastic-plastic (EP) finite element analysis (FEA) that the test specimen thickness (TST) effect on the fracture toughness of a material Jc in the ductile-to-brittle transition Temperature Region, together with the bounded nature of Jc for large TST, had a correlation with the out-of-plane constraint parameter T33-stress. Because a definite measure of the crack tip constraint magnitude, especially for EP issues, does not exist, several well-known constraint parameters were tested from the standpoint of whether they have correlations to the decreasing and then the bounded nature of Jc for increasing TST. The results clearly indicated that Tz = σ33/(σ11+ σ22) at the specimen mid-plane could not be directly correlated with the TST effect on Jc, based on the observation that the highest Tz did not coincide with the fracture location predicted by the (4δt, σ22c) criterion, in which σ22c denotes the critical crack opening stress value at a distance ahead of the crack tip that is equal to four times the crack tip opening displacement δt. On the other hand, the results indicated that the well-known constraint parameter Θ = (hydrostatic stress)/(von Mises stress), measured at 4δt, has an ability to monitor the loss in constraint in the TST effect on Jc. Θ at 4δt had a linear relationship with the σ22 up to the fracture load Pc for thick specimens of thickness-to-width ratio of B/W = 1.0 and 1.5, while Θ at 4δt for thin specimens of B/W = 0.25 and 0.5 began to decrease before reaching Pc. In addition, Θ at 4δt for Pc exhibited a good correlation with the TST effect and bounded nature of Jc for increasing TST.
-
a failure criterion to explain the test specimen thickness effect on fracture toughness in the transition Temperature Region
Engineering Fracture Mechanics, 2013Co-Authors: Toshiyuki Meshii, Kai Lu, Ryota TakamuraAbstract:Abstract This paper considered the test specimen thickness (TST) effect on the fracture toughness of a material Jc in the transition Temperature Region for 3 point bending (3 PB) specimens. Fracture toughness tests and elastic–plastic finite element analyses (FEA) with non-standard test specimens, which are non-standard because the specimen thickness-to-width ratio B/W was varied in the range of 0.25–1.5, were conducted. Based on these tests and the FEA results, it was demonstrated that the “planar” (4δt, σ22c) failure criterion—which states that cleavage fracture after significant plastic deformation occurs when the crack opening stress σ22 at a distance from the crack-tip that is equal to four times the crack-tip opening displacement δt exceeds a critical value σ22c—was verified to effectively explain the TST effect. This (4δt, σ22c) criterion also successfully predicted the tendency of Jc to saturate to some bounding value for B/W = 1.0. This tendency was similar to that of the T33-stress, which is the out-of-plane elastic crack-tip constraint parameter. Because the (4δt, σ22c) criterion could predict the TST effect on Jc and because the criterion could predict the bounded behavior of Jc for large B/W, the TST effect was concluded to be mainly mechanical in nature, which the weakest link model fails to predict. The mechanical cause of the TST effect on Jc was considered to be an out-of-plane crack-tip constraint, and one of its measures of magnitude is the T33-stress.
-
prediction of lower bound fracture toughness in the transition Temperature Region by t33 stress
Volume 9: Rudy Scavuzzo Student Paper Symposium and Competition, 2012Co-Authors: Kai Lu, Toshiyuki MeshiiAbstract:It is well known that the fracture toughness Jc in the ductile-to-brittle transition Temperature Region depends highly on the specimen thickness (hereafter, TST). The TST effect on Jc, which Wallin [1] described as Jc (∝ KJc2) ∝ B(-1/2) (Jc was calculated from the equations outlined in ASTM E1820 [2], KJc was derived from Jc as KJc = (Jc·E′)1/2; E′ = E/(1−ν2), B: TST), has been reproduced by Anderson et al. [3] based on the weakest link model. However, as Anderson et al. [3] themselves admit, Jc does not decrease indefinitely with B. On the other hand, Meshii et al. [4–6] tried to explain this TST effect on Jc as a mechanical issue. They obtained the same relationship, Jc ∝ B(-1/2) from the fracture toughness test for a non-standard CT and 3PB specimen (non-standard on the point that planar configuration was identical and thickness to width ratio B/W was varied from 0.25 to 0.5) and the stress intensity factor (SIF) corresponding to fracture load Pc denoted as Kc (Kc was calculated from the equations outlined in ASTM E399 [7]), was almost constant for TST. They also reproduced the experimental tendency by large strain FEA under the assumption based on their experimental observation that Kc was independent of TST. In addition, they expressed the TST effect on Jc by correlating Jc with the out-of-plane elastic T-stress T33.We thought that if TST effect on Jc is a mechanical issue, the lower bound Jc for TST could be predicted by FEA under some assumption such as Kc = constant for TST, and the TST corresponding to the lower bound Jc could be predicted by T33. However, before proceeding to this prediction, we thought we have to understand the candidate assumption for prediction more deeply, i.e, understand why Kc was constant for TST.Thus in this work, we attempted to explain the reason why Kc was constant for TST. Our idea was to apply the well-known “planar” failure criterion to our out-of-plane TST issue. After demonstrating our idea was valid, the lower bound Jc of carbon S55C for non-standard 3PB specimen was predicted based on this planar failure criterion and the large strain elastic-plastic FEA. The results showed that Jc showed a lower bound for specimen of B/W ≥ 1.5. In addition, it was shown that this threshold B/W could be estimated by the elastic out-of-plane T33.Copyright © 2012 by ASME
-
experimental t33 stress formulation of test specimen thickness effect on fracture toughness in the transition Temperature Region
Engineering Fracture Mechanics, 2010Co-Authors: Toshiyuki Meshii, Tomohiro TanakaAbstract:Abstract This paper describes a study of the test specimen thickness effect on fracture toughness of a material, in the transition Temperature Region, for CT specimens. In addition we studied the specimen thickness effect on the T33-stress (the out-of-plane non-singular term in the series of elastic crack-tip stress fields), expecting that T33-stress affected the crack-tip triaxiality and thus constraint in the out-of-plane direction. Finally, an experimental expression for the thickness effect on the fracture toughness using T33-stress is proposed for 0.55% carbon steel S55C. In addition to the fact that T33 (which was negative) seemed to show an upper bound for large B/W, these results indicate the possibility of improving the existing methods for correlating fracture toughness obtained by test specimen with the toughness of actual cracks found in the structure, using T33-stress.
Satoshi Kimura - One of the best experts on this subject based on the ideXlab platform.
-
thermal expansion behavior of a and b type amylose crystals in the low Temperature Region
Carbohydrate Polymers, 2015Co-Authors: Kayoko Kobayashi, Satoshi Kimura, Eiji Togawa, Masahisa Wada, Philipkunio NaitoAbstract:The thermal expansion behaviors of A-type and B-type amylose crystals, which were prepared by recrystallization of short amylose chains synthesized by phosphorylase, were investigated using synchrotron X-ray powder diffraction between 100 and 300K. For both types of crystals, the room-Temperature phase (RT phase), which is the usually observed phase, transitioned to a low-Temperature phase (LT phase), on cooling. The phase transitions took place reversibly with rapid changes in the unit-cell parameters around 200-270K. The differences between the RT and LT phase were investigated using solid-state (13)C NMR spectroscopy, which revealed there were changes in molecular chain conformations. These results suggest that the phase transition of water molecules on the crystalline surfaces affects the thermal behavior and structure of polysaccharide crystals.
-
thermal expansion behavior of hydrate paramylon in the low Temperature Region
Carbohydrate Polymers, 2013Co-Authors: Kayoko Kobayashi, Satoshi Kimura, Eiji Togawa, Masahisa WadaAbstract:Abstract The thermal expansion behavior of hydrate paramylon between 100 and 300 K has been investigated using synchrotron X-ray powder diffraction. The X-ray diffraction profile at 300 K showed a typical pattern of the hydrate triple helical (1→3)-β- d -glucan with a hexagonal unit cell ( a = 15.782 A and c = 18.580 A). On cooling, the hydrate paramylon had converted to a “low-Temperature phase” around 270 K. On passing through the phase transition, the a -axis and c -axis values decreased and increased, respectively, and the low-Temperature phase at 100 K exhibited a hexagonal unit cell ( a = 15.586 A and c = 18.619 A). The phase transition took place reversibly. Below the transition point, both the a -axis and c -axis values decreased linearly. The thermal expansion coefficients are: α a = 1.50 × 10 −5 K −1 , α c = 0.33 × 10 −5 K −1 , and β = 3.08 × 10 −5 K −1 .
J Miao - One of the best experts on this subject based on the ideXlab platform.
-
negative spin hall magnetoresistance in antiferromagnetic cr2o3 ta bilayer at low Temperature Region
Applied Physics Letters, 2018Co-Authors: J Miao, Yuanmin Zhu, K K Meng, J K Chen, Yong JiangAbstract:We demonstrate the negative spin Hall magnetoresistance (SMR) observed in antiferromagnetic Cr2O3/Ta bilayers at low Temperature. The SMR signals are changed from the positive to negative magnitude when monotonously reducing the Temperature from 300 K to 50 K. The positive and negative SMR signals are expected to be associated with the two different ways for injection of the spin current, into the boundary ferromagnetic Region and the bulk antiferromagnetic Region of α-Cr2O3 (0001), respectively. The slopes of the abnormal Hall curves exhibit the same sign with the SMR signal. From the SMR ratio under 3 T, the spin mixing conductance at the Cr2O3/Ta interface is estimated to be 1.12 × 1014 Ω−1·m−2, which is comparable to the one observed in the Y3Fe5O12(YIG)/Pt structure and our early results of the Cr2O3/W structure.
-
negative spin hall magnetoresistance in antiferromagnetic cr2o3 ta bilayer at low Temperature Region
arXiv: Materials Science, 2018Co-Authors: J Miao, Yuanmin Zhu, K K Meng, J K Chen, Yong JiangAbstract:We investigate the observation of negative spin Hall magnetoresistance (SMR) in antiferromagnetic Cr2O3/Ta bilayers at low Temperature. The sign of the SMR signals is changed from positive to negative monotonously from 300 K to 50 K. The change of the signs for SMR is related with the competitions between the surface ferromagnetism and bulky antiferromagnetic of Cr2O3. The surface magnetizations of Cr2O3 (0001) is considered to be dominated at higher Temperature, while the bulky antiferromagnetics gets to be robust with decreasing of Temperature. The slopes of the abnormal Hall curves coincide with the signs of SMR, confirming variational interface magnetism of Cr2O3 at different Temperature. From the observed SMR ratio under 3 T, the spin mixing conductance at Cr2O3/Ta interface is estimated to be 1.12*10^14 (ohm^-1*m^-2), which is comparable to that of YIG/Pt structures and our early results of Cr2O3/W. (Appl. Phys. Lett. 110, 262401 (2017))