Short-Range Order of the Rotational Degree of Freedom of the Glycine Molecule in Triglycine Sulfate Glass State

The unit cell of triglycine sulfate (TGS) contains the following glycine ions: dimers (GIISHBGIII)⁺ with a short hydrogen bond (SHB) and a monomer (SO₄LHBGI)⁺ with a long hydrogen bond (LHB) to the SO₄ ²⁻ anion. The spontaneous polarization results from a statistical charge distribution and the Coulomb interaction between SO₄ ²⁻ and fast rotating –NH₃ ⁺ groups. In the lamellar model, chains of –SO₄–(GIISHBGIII)–SO₄–(GIISHBGIII)–SO₄ lying along the polar b-axis are linked perpendicularly to this axis by SO₄LHBGI⁺ units. Tilting the LHBGI⁺ ion around the axis in the mirror plane decides on the direction of the charge displacement from this symmetry plane. The reversal of the spontaneous polarization, i.e., −P _S↔ +P _S, is related to the rotation of the NH₃ group. If this rotation becomes slowed down at low temperature and/or under high pressure, the coercive field increases dramatically. Application of an external electric field E _⊥ perpendicular to the b-axis leads to a hysteresis loop of the polarity P(E), and finally to its disappearance. This phenomenon comes from an ordering of protons in hydrogen bonds perpendicular to the polar axis. This is the first study of the E _⊥ effect by nuclear magnetic resonance. Authors' address: Jan Stankowski, Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, Poznań 60-179, Poland     

Structure of Graphene Oxide in a Polymer Matrix and Its Effect on the Degree of Reinforcement of a Nanocomposite

Doklady Physics - A method for the structural characterization of 2D-nanofiller tactoids in the polymer matrix of a nanocomposite has been proposed to demonstrate that the mentioned tactoids are...     

Effect of Quenching on the Grain Boundary Relaxation in PM2000 ODS Alloy

Grain boundary relaxation in a Fe-based ODS alloy is studied by internal friction measurements. It is found that a grain-boundary peak appears at a lower temperature in the quenched specimens than that in the annealed specimens. The activation energy of the peak is H=2.82±0.11 eV for the former while H = 2.53±0.08 eV for the latter. In addition, a new relaxation peak is observed at the high temperature side of the grain boundary peak in the quenched specimens with an activation energy of 4.41±0.25 eV. The height of the peak increases with increasing quenching temperature. The results suggest that both the shift of the grain-boundary peak and the appearance of the new peak are due to increasing vacancies by quenching that are favourable for the motion of the grain boundaries.     

Effect of Structural Relaxation on Deformation Behaviour of Zr-Based Metallic Glass

Structural relaxation through isothermal annealing at temperature below glass transition is conducted on Zr46.75 Ti8.25 CU7.5Ni11Be27.5 （Vitreloy-4） bulk metallic glass. Defect concentration is correlated with the annealing time t according to differential scanning calorimetry thermalgrams. The effects of structural relaxation on mechanical properties and deformation behaviour are investigated by using instrumented nanoindentation. It is found that the as-cast alloy exhibits pronounced serration flow during the loading process of nanoindentation, and the size and number of the serrations decrease with the annealing time. The change of the deformation behaviour with structural relaxation is explained using a free volume model.     

基于灰关联和灵敏度的BP网络隐含层结构优化

在优化BP神经网络隐含层结构时,采用灰关联剪枝法是每次删除灰关联度小于灰关联阈值的隐节点,该方法学习时间短,但由于灰关联阈值的选取具有一定的主观性,可能会导致误删节点或不能完全删除冗余节点;而采用灵敏度剪枝法是每次只删除灵敏度最小的一个隐节点,故学习时间较长;因此,提出一种基于灰关联-灵敏度的BP神经网络隐含层结构调整算法;首先在网络前期学习过程中,采用灰关联法对隐含层节点进行“粗删”,直到剩余隐节点的灰关联度都大于动态灰关联阈值,然后在网络后期学习过程中,采用灵敏度剪枝法对隐含层节点进行“细删”,直到删除后的学习误差增大,则保留该节点,并结束学习;文章将结构优化后的神经网络应用于风电功率预测,仿真结果表明,该方法在满足学习误差要求的同时,不仅精简了神经网络结构,而且避免了灰关联剪枝法中灰关联阈值精确选取困难所带来的问题。     

光纤陀螺消偏结构与偏振度关系的研究

利用在光源出端加单段保偏光纤和在消偏器后端加Loyt消偏器,可以使进入光纤线圈的光的偏振度降到10－3数量级,降低了因外界因素对线圈中光偏振态的影响而产生的光纤陀螺偏振误差.并用琼斯矩阵计算的方法,分析了光路中四个胶合角与偏振度的关系及每个角度的取值范围.最后探讨了工艺上胶合角度测量与实现.     

Protein Backbone N Relaxation Rates as a Tool for the Diagnosis of Structure Quality

In the work reported herein we define a structure validation factor that depends on protein backbone ¹⁵N relaxation rates. This is an alternative method to the previously defined quality factors derived from anisotropic chemical shifts or residual dipolar couplings. We have used the structure dependence of ¹⁵N relaxation rates of anisotropically tumbling proteins to calculate this structure diagnosis factor and have used it to demonstrate the improvement of protein structures refined with residual dipolar couplings.     

温度和场冷间隙对高温超导磁悬浮系统弛豫的影响

悬浮力是高温超导磁悬浮列车运行中的一个至关重要的参数.悬浮力的弛豫特性是高温超导磁悬浮列车安全运行的一大阻碍.适度降低工作温度是有效改善悬浮力弛豫特性的有效手段之一.本文从数值计算和实验两个层面研究了不同冷却温度和不同场冷间隙下的悬浮力的弛豫现象.发现悬浮力的弛豫现象随着超导块冷却温度的降低而减弱，随着场冷间隙的增大而略微增大，但是随着冷却温度的降低，增大程度会有所减弱.该研究有助于通过合理设计高温超导材料工作温度，以提高磁悬浮系统性能表现.     

Spin Parity Effect on Magnetic Relaxation by Quantum Tunneling in Nanomagnets

Spin parity effect on magnetic relaxation by quantum tunneling in the biaxial spin model is studied by taking into account the transverse local stray field. It is shown that the square root time dependence in the even resonance occurs in the presence of a distribution of transverse anisotropic parameters, while the odd resonance always shows exponential relaxation. Magnetic relaxation under a sweeping field is also studied. The variation of the relaxation curve with the increasing distribution width of the local stray field for even resonance is qualitatively different from that of the odd resonance. The theoretical result on even resonance is in agreement with experimental results on Fe₈ system, while the prediction for odd resonance awaits the experimental verification.     

Spin Parity Effect on Magnetic Relaxation by Quantum Tunneling in Nanomagnets

Spin parity effect on magnetic relaxation by quantum tunneling in the biaxial spin model is studied by taking into account the transverse local stray field. It is shown that the square root time dependence in the even resonance occurs in the presence of a distribution of transverse anisotropic parameters, while the odd resonance always shows exponential relaxation. Magnetic relaxation under a sweeping field is also studied. The variation of the relaxation curve with the increasing distribution width of the local stray field for even resonance is qualitatively different from that of the odd resonance. The theoretical result on even resonance is in agreement with experimental results on Fe8 system, while the prediction for odd resonance awaits the experimental verification.     

Domain Structure of Hexaferrite BaFe12O19 Near the Curie Temperature

Physics of the Solid State - The features of the structure of domain walls in hexaferrite BaFe12O19 have been studied near the Curie temperature TC = 724 K. The studies have been performed on the...     

Effect of Quasi-Fermi Level on the Degree of Electron Spin Polarization in GaAs

With spin-polarized-dependent band gap renormahzation effect taken into account,the energy-dependent evolution of electron spin polarization in GaAs is calculated at room temperature and at a low temperature of 10 K.We consider the exciting light with right-handed circular polarization,and the calculation results show that the degree of electron spin polarization is dependent strongly on the quasi-Fermi levels of |1/2 and |-1/2 spin conduction bands.At room temperature,the degree of electron spin polarization decreases sharply from 1 near the bottom of the conduction band,and then increases to a stable value above the quasi-Fermi level of the |—1/2 band.The greater the quasi-Fermi level is,the higher the degree of electron spin polarization with excessive energy above the quasi-Fermi level of the |-1/2 band can be achieved.At low temperature,the degree of electron spin polarization decreases from 1 sharply near the bottom of the conduction band,and then increases with the excessive energy,and in particular,up to a maximum of 1 above the quasi-Fermi level of the |1/2 band.     

The Effect of Selenium Supplementation on the NMR Proton Relaxation Time T1 in Plasma

Selenium has been identified as an essential dietary trace e1ementQ)which is a component of glutathione peroxidase (GSH-Px)(₂)and a cytochrome C-like protein(₃), The enzyme,the four subunits of which each contain one atom of selenium in the form of selenocysteine, the selenium containing active centre being amenable to chemical modification, catalyses the reduction of H,O,and organic hydroperoxides to water.In this way GSH-Px plays an important role in the protection of the cell from oxidative stresses such as the superoxide anion,organic hydroperoxides and H₂O₂     

弛豫对光磁共振实验的影响

研究了弛豫对光磁共振实验的影响,弛豫过程影响粒子的分布,进而影响光抽运信号以及光磁共振信号的观测,但是对g因子的测量几乎没有影响。本文的研究结果将会加深对光磁共振实验及仪器工作原理的认识。     

Influence of the Piezoelectric Effect on the Maxwellian Relaxation Time of Holographic Gratings in Cubic Photorefractive Crystals

The influence of the inverse piezoelectric effect on the effective permittivity, the Maxwellian relaxation time, and the space-charge field amplitude in cubic photorefractive crystals is examined. Analytical orientational dependences of the effective permittivity are derived for crystals of , , and cuts. It is demonstrated that in an external field of 10 kV/cm, the space-charge field may change by 4.9% due to the piezoelectric effect.     

Effect of Pulse Width and Fluence of Femtosecond Laser on Electron--Phonon Relaxation Time

The electron phonon relaxation time as functions of pulse width and fluence of femtosecond laser is studied based on the two-temperature model. The two-temperature model is solved using a finite difference method for copper target. The temperature distribution of the electron and the lattice along with space and time for a certain laser fluence is presented. The time-dependence of lattice and electron temperature of the surface for different pulse width and different laser fluence are also performed, respectively. Moreover, the variation of heat-affected zone per pulse with laser Auence is obtained. The satisfactory agreement between our numerical results and experimental data indicates that the electron-phonon relaxation time is reasonably accurate with the influences of pulse width and Auence of femtosecond laser.