Dynamic dislocation–defect analysis

The dynamic internal variables which control plastic flow can only be assessed by dynamic materials testing at any given instance. The testing method championned by our studies has been precision strain rate sensitivity (PSRS) whereby the change in flow stress due to a set change in strain rate is taken to be an operational measure of the activation volume and its product with the flow stress gives rise to the operational activation work. Also, from the work hardening slope, a modelled parameter proportional to the mean slip distance (λ) is simultaneously determined. The deviation from the linear Cottrell–Stokes relation as determined with the Haasen plot indicates the evolution of secondary defects other than monopole dislocations. Hence PSRS can assess the theoretical predictions of the activation distance (d) and work as a function of temperature, resulting in quantitative values that are in accord with dislocation theory at temperatures below that where point defects become mobile. A method to calibrate λ using Stage II slope θ_II shows that λ/?, where ? is the mean forest dislocation spacing, is inversely proportional to θ, the work hardening coefficient. This analysis has led to a new plot of θ_II/θ versus b ²λ/ν where b is the Burgers vector and its slope is directly proportional to d. An example using an alumina-dispersed high conductivity copper shows that geometrically necessary punched out loops are continuously generated. The role of point defect mobility is dramatically illustrated by load drops in [001] aluminium crystals with the formation of slip clusters.     

Coupling of two defect modes in photonic crystal fibers

The coupling characteristics of two defect modes in photonic crystal fibers are investigated theoretically by the finite-difference time-domain (FDTD) method. The transmission spectrum and eigenmodes of optical wave are found to be very sensitive to the geometrical and physical parameters of the structure, as well as to the relative position of the two defects.     

To cooperate or to defect? Altruism and reputation

The basic difficulty in cooperation theory is to justify the cooperation. Here we propose a new approach, where players are driven by their altruism to cooperate or not. The probability of cooperation depends also on the co-player’s reputation. We find that players with positive altruism cooperate and meet cooperation. In this approach, payoffs are not relevant.     

Quantization of the space－time with topological defect

We present the classical solution of Lagrange equations for the black hole with a global monopole or with a cosmic string. Then we obtain the wavefunction of the space－time by solving the Wheeler－De Witt equation. De Broglie－Bohm interpretation applied to the wavefunction gives the quantum solution of the space－time. In the end, the quantum effect on Hawking radiation is studied.     

Rapid calibration method for rank defect marine geodetic station network

A rapid calibration method for marine geodetic control networks based on the combination of beacon mutual ranging information and absolute coordinate information is proposed.Compared with existing methods, the rapid calibration method reduces the initial condition restriction of free net adjustment, the number of absolute calibration points is reduced by more than 50%, and the calibration efficiency and absolute coordinate precision are significantly improved. In addition, several typical format...     

The 220°K defect in electron irradiated p-Type Germanium

Lattice defects introduced in p-type nondegenerate germanium by 1.5 MeV electron irradiation at liquid nitrogen temperature was investigated by means of electrical resistivity and Hall coefficient measurements. The annealing behavior of two kinds of defects, which anneal at about 220 °K, was investigated in detail. Each of them has an electron trap. Making use of trap-filling and emptying processes, the 220 °K defects are separated from other defects.     

Characterization for defect modes of one-dimensional photonic crystals containing metamaterials

Transmission studies for one-dimensional photonic crystals(1DPCs)containing single-negative(SNG) materials inserted with multiple defects are presented.The numbers and positions of the defect modes inside zero-phase(zero-φeff)gap are found to be well characterized by effective medium theory.     

Size determination of subsurface defect by active thermography – Simulation research

This paper presents the results of 3D numerical simulations of thermal phenomena in uniform material with subsurface defect located at some depth. The material is aimed to be tested by means of IR active thermography. The temperature field of the front surface of material tested is observed and analysed. The results of modelling are suitable for step heating as an external thermal stimulation – heat flux. The heating duration needed for accurately defect sizing is discussed. Also, an effect of two defects with different thermal properties and simultaneously occurring in the material tested is analysed.     

Optically-induced defect states in photonic lattices: formation of?defect channels, directional couplers, and disordered lattices leading to Anderson-like light localization

Formation of defect states by optical induction in one-dimensional photonic lattices fabricated in photorefractive lithium niobate is investigated experimentally. First, by using a moving narrow laser beam for defect recording, we investigate light propagation in samples containing single line defects and adjacent channel defects forming directional couplers. Then, these results are used to create lattices with randomly distributed defects, resembling a disordered optical potential. In such lattices, wave propagation is found to change from ballistic transport to transverse Anderson-like light localization as a function of induced disorder.     

Irradiation-induced defect states in Pb1−xSnxTe under high pressure

Abstract

The galvanomagnetic properties of electron-irradiate n^? and P-Pb_1?x,Sn_xTe (x=O.2) under high hydrostatic Pressure have been investigated. In the irradiated samples the “soft” stabilisation of Fermi level under the irradiation has been revealed and the model of the energy spectrum of irradiated Pb_1?x,Sn_xTe (x=O.2) proposed. The obtained experimental results were used to aetermine the Parameters of radiation-induced resonant band situated slightly below the valence band top.     

Topological defect formation in rotating binary dipolar Bose–Einstein condensate

We investigate the topological defects and spin structures of a rotating binary Bose–Einstein condensate, which consists of both dipolar and scalar bosonic atoms confined in spin-dependent optical lattices, for an arbitrary orientation of the dipoles with respect to their plane of motion. Our results show that the tunable dipolar interaction, especially the orientation of the dipoles, can be used to control the direction of stripe phase and its related half-vortex sheets. In addition, it can also be used to obtain a regular arrangement of various topological spin textures, such as meron, circular and cross disgyration spin structures. We point out that such topological defects and regular arrangement of spin structures arise primarily from the long-range and anisotropic nature of dipolar interaction and its competition with the spin-dependent optical lattices and rotation.     

High temperature electrical properties and defect structure of Co1−xMgxO

The electrical conductivity and thermoelectric power of Co_1−xMg_xO solid solutions with x ⩽ 0.85 were investigated in the range 700–1100°C and for oxygen partial pressures in the range 1–10⁻¹⁶ atm. The experimental results show that an ideal point defect model of isolated cobalt vacancies cannot explain nonstoichiometry of Co_1−xMg_xO materials with x, at least, less than 0.3. Furthermore, the hole mobility in Co_1−xMg_xO with x < 0.6 was found to be nonactivated suggesting that holes in these materials are itinerant carriers. For x > 0.6, the mobility is thermally activated indicating a change to small polaron conduction. The experimental evidence for complex defect structure and bandlike conduction in CoO is in agreement with the conclusions of recent theoretical studies of 3-D transition metal monoxides.     

Recognition algorithm of internal defect images of thermal battery北大核心CSCD

针对目前热电池内部装配缺陷检测效率低、准确度不高的问题,研究了一种可精准分割内部电池堆图像并能够准确识别缺陷种类的方法。首先采用水平、垂直积分投影法对目标电池堆边缘特征进行提取,利用局部自适应对比度增强算法对局部不清晰部分进行细节纹理增强;然后研究了缺陷结构的灰度特性,计算提取出缺陷特征参数;最后使用BP（back propagation）神经网络和CART（classification and regression tree）决策树对特征参数分类识别,并根据分类准确度进行权重分配,将加权融合后的结果作为检测的最终判据。实验结果表明:该方法对2 000个样本的检测准确度达98.9%,为热电池的X射线缺陷检测提供了有效的途径。     

Metastable Frenkel pair defect in graphite: source of Wigner energy?

The atomic processes associated with energy storage and release in irradiated graphite have long been subject to untested speculation. We examine structures and recombination routes for interstitial-vacancy (I-V) pairs in graphite. Interaction results in the formation of a new metastable defect (an intimate I-V pair) or a Stone-Wales defect. The intimate I-V pair, although 2.9 eV more stable than its isolated constituents, still has a formation energy of 10.8 eV. The barrier to recombination to perfect graphite is calculated to be 1.3 eV, consistent with the experimental first Wigner energy release peak at 1.38 eV. We expect similar defects to form in carbon nanostructures such as nanotubes, nested fullerenes, and onions under irradiation.     

High temperature point defect equilibrium of undoped α-ZnP2 at zinc pressure

The dependences of electric conductivity and Hall density of holes vs pressure of Zn vapour have been measured in α-ZnP₂ in the temperature range between 780 and 960K. Conductivity decreases with zinc pressure increasing with slope γ, which varies from γ = 0.14−0.15 at T = 780−830K to γ = 0.22−0.24 at 890−960K. Such slopes correspond to the following defect types 2[V″_Zw] = [(V′_ZwV_p)] at T = 780−830 K and [V′_Zw] = [(V′_ZnV_p)] at T = 890−960K. The formation enthalpy tor two doubly charged phosphorus vacancies was found to be 6.12 eV.     

Roper resonance and πN phase shift in the Skyrme model with defect

The quantum fluctuations of the two-phase Skyrme soliton model of the nucleon is formulated. The p-wave πN phase shift and the Roper to πN decay width are calculated as a function of the equlibrium defect radius R₀. It is found that there is a preferred region of R₀ between 0.4 and 0.5 fm where the experimental width can be fitted. It is also found that the region of R₀ between 0.1 and 0.36 fm should be excluded in the model due to its instability against small oscillations.