scattering

摘要： Recent investigations have derived the relation between the near-field plane amplitude and the surface deformation of reflector antenna,namely deformation-amplitude equation(DAE),which could be used as a mathematical foundation of antenna surface measurement if an effective numerical algorithm is employed.Traditional algorithms are hard to work directly due to the complex mathematical model.This paper presents a local approximation algorithm based on artificial neural network to solve DAE.The length factor method is used to construct a trial solution for the deformation,which ensures the final solution always satisfies the boundary conditions.To improve the algorithm efficiency,Adam optimizer is employed to train the network parameters.Combining the application of the data normalization method proposed in this paper and a step-based learning rate,a further optimized loss function could be converged quickly.The algorithm proposed in this paper could effectively solve partial differential equations without boundary conditions such as DAE,which at the same time contains the first-order and the second-order partial derivatives,and constant terms.Simulation results show that compared with the original algorithm by Fast Fourier transform,this algorithm is more stable and accurate,which is significant for the antenna measurement method based on DAE.

摘要： Perovskite solar cells(PSCs)are becoming a promising candidate for next-generation photovoltaic cells due to their attractive power conversion efficiency(PCE).Plasmonic enhancement is regarded as an optical tuning approach for further improving the PCE of single-junction PSCs toward Shockley-Queisser limit.Herein,we introduce molecularly isolated gold nanorods(Au NRs),bearing relatively stronger scattering ability and localized surface plasmonic resonance(LSPR)effect,in the rear side of perovskites in PSCs,for promoting light harvesting and for electrical enhancement.Owing to the larger refractive index and better matched energy level alignment,the 4-mercaptobenzoic acid molecules coated on Au NRs prove to play important dual roles:isolating the metallic Au NRs from contacting with perovskite,and facilitating more efficient charge separation and transport across the interface under the synergetic LSPR effect of Au NRs.Our work highlights the capability of the plasmonic approach by nanorods and by molecular isolation,extending nanoparticle-based plasmonic approaches,toward highly efficient plasmon-enhanced PSCs.

摘要： Energetic X-ray radiations emitted from various accretion systems are widely considered to be produced by Comptonization in the hot corona.The corona and its interaction with the disk play an essential role in the evolution of the system and are potentially responsible for many observed features.However,many intrinsic properties of the corona are still poorly understood,especially for the geometrical configurations.The traditional spectral fitting method is not powerful enough to distinguish various configurations.In this paper,we intend to investigate the possible configurations by modeling the polarization properties of X-ray radiations.The geometries of the corona include the slab,sphere and cylinder.The simulations are implemented through the publicly available code,Lemon,which can deal with the polarized radiative transfer and different electron distributions readily.The results demonstrate clearly that the observed polarizations are dependent heavily on the geometry of the corona.The slab-like corona produces the highest polarization degrees(PDs),followed by the cylinder and sphere.One of the interesting things is that the PDs first increase gradually and then decrease with the increase of photon energy.For slab geometry,there exists a zero-point where the polarization vanishes and the polarization angle(PA)rotates by 90°.These results may potentially be verified by the upcoming missions for polarized X-ray observations,such as IXPE and e XTP.

摘要： A method is proposed for compressing laser pulses by fast-extending plasma gratings(FEPGs),which are created by ionizing a hypersonic wave generated by stimulated Brillouin scattering in a background gas.Ionized by a short laser pulse,the phonon forms a light-velocity FEPG to fully reflect a resonant pump laser.As the reflecting surface moves with the velocity of light,the reflected pulse is temporally overlapped and compressed.One-and two-dimensional fully kinetic particle-in-cell simulations with a laser wavelength of 1μm show that in this regime,a pump pulse is compressed from 10–40 ps to 7–10 fs(i.e.,a few optical cycles),with a two-dimensional transfer efficiency up to 60%.This method is a promising way to produce critical laser powers while avoiding several significant problems that arise in plasma-based compressors,including an unwanted linear stage,major plasma instabilities,and the need for seed preparation.

摘要： A miniaturized neutron spin flipper based on a high-TC superconductor film,developed at the China Spallation Neutron Source(CSNS),is presented.A neutron spin flipper is an essential component for performing polarized neutron experiments and,as such,constitutes a high priority for developing CSNS’s polarized neutron capability.To provide the beamlines with a universal neutron spin flipper operating over a wide wavelength band,the neutron spin flipper utilizes non-adiabatic spin flipping during transit through opposite magnetic fields that are mutually shielded by the superconductor Meissner effect.A compact vacuum heat shield and a low-power consumption sterling refrigerator maintained the superconducting condition while reducing the size and power input of the flipper.The prototype device was tested at the CSNS BL-20,which demonstrated a flipping efficiency of 99%at 4 A°.

摘要： In this paper,we study the Cauchy problem for the nonlinear Schrodinger equations with Coulomb potential i■tu+△u+k/|x|u=λ/|u|^(p-l)u with 10,and the scattering theory when the Coulomb potential is repulsive,i.e.,when K≤O.The argument is based on the newlyestablished interaction Morawetz-type inequalities and the equivalence of Sobolev norms for the Laplacian operator with the Coulomb potential.

摘要： The necessity for safety in oil-gas storage and transportation has led to increasing technical requirements for on-line monitoring of damaged pores and oil leakage from tanks. In this study, the severity of damage of the oil tank at the micron level was detected by terahertz time-domain spectroscopy(THz-TDS), which is of great significance for the early detection and prevention of oil leakage. The THz amplitude(EP) was related to the severity of damaged according to the THz-TDS measurement of oil tanks with various degrees of damage, including intact, partially damaged, completely damaged, and seriously damaged points.Absorption and scattering effects co-occurred when the THz wave penetrated the tanks, with the collective tendencies being used to expressly monitor oil leakage from tanks. When the oil tank was damaged to form micron-level pores and the crude oil had not overflowed, the pore size was close to THz wavelength and the Mie scattering effect was obvious. After further destruction of the pores, the crude oil gradually spilled over and the scattering effect was gradually transformed from Mie scattering to Rayleigh scattering. In addition, the polar molecules in crude oil have strong resonance under the irradiation of THz wave, and the THz wave has strong attenuation. Eventually, surface tension of the oil flattens the surface of the tank, the scattering effect is gradually suppressed and replaced by the absorption effect. Absorption and scattering caused by THz waves passing through tanks coexist and have competing relationships. The change rule of EPcan successfully prove the phenomenon and can be considered as an important alternative for application to predict the degree of tank damage. Therefore, in this study, the detection of pores as small as micrometers on the oil tank was expected to greatly prevent oil leakage accidents and improve the safety of oil and gas storage and transportation.

摘要： Anharmonic lattice vibrations play pivotal roles in the thermal dynamics in condense matters and affect how the atoms interact and conduct heat.An in-depth understanding of the microscopic mechanism of phonon anharmonicity in condensed systems is critical for developing better functional and energy materials.In recent years,various novel behaviors in condense matters driven by phonon anharmonic effects were discovered,such as soft mode phase transition,negative thermal expansion(NTE),multiferroicity,ultralow thermal conductivity(κ),high thermal resistance,and high-temperature superconductivity.These properties have endowed anharmonicity with many promising applications and provided remarkable opportunities for developing“Anharmonicity Engineering”-regulating heat transport towards excellent performance in materials.In this work,we review the recent development of studies on phonon anharmonic effect and summarize its origin,mechanism,research methods,and applications.Besides,the remaining challenges,future trends,and prospects of phonon anharmonicity are also discussed.

摘要： Dear editor,According to the electromagnetic theory,each scattering center(SC)is equivalent to a mathematical discontinuity in Stratton-Chu integrals[1].From the view of geometrical structure,the positions of SCs correspond to the discontinuities of surface and specular points.Therefore,the signatures of SCs in radar images can represent the actual geometric characteristics.Three-dimension SC model has been successfully applied for the radar target reconstruction and automatic target recognition(ATR)[2].

摘要： We present particle-in-cell(PIC)simulations of laser plasma instabilities(LPIs)with a laser pulse duration of a few picoseconds.The simulation parameters are appropriate to the planar-target LPI experimental conditions on SG-II.In this regime,the plasmas are characterized by a long electron density scale length and a large electron density range.It is found that when the incident laser intensity is well above its backward stimulated Raman scattering(backward SRS,BSRS)threshold,the backscattered light via the primary BSRS is intense enough to excite secondary SRS(Re-SRS)in the region below one-ninth of the critical density of the incident laser.The daughter light wave via the secondary BSRS(Re-BSRS)is amplified as it propagates toward the higher-density region in the bath of broadband light generated through the primary BSRS process.A higher intensity of the incident laser not only increases the amplitude of the BSRS light but also increases the convective amplification lengths of the Re-BSRS modes by broadening the spectrum of the BSRS light.Convective amplification of Re-BSRS causes pump depletion of the primary BSRS light and may lead to an underestimate of the primary BSRS level in SP-LPI experiments.Asignificant fraction of the generation of energetic electrons is strongly correlated with the Re-BSRS modes and should be considered as a significant energy loss.

摘要： 本发明公开一种Scatter‑Gather DMA的数据传输缓冲区设计方法，涉及数据传输技术领域；使用scatter‑gather DMA进行数据传输时，创建两个scatter‑gather DMA链表，并将两个scatter‑gather DMA链表分别指向两组内核空间缓冲区，每组内核空间缓冲区的数量对应相应的scatter‑gather DMA链表节点数，用户空间数据拷贝到一组内核空间缓冲区并进行DMA传输的同时，利用CPU将下次需传输的用户空间数据拷贝入另一组内核空间缓冲区，当上一次DMA传输完成，利用中断处理程序启动下一次DMA传输，直至将用户空间数据完全写入设备。

摘要： 本发明公开了一种SG DMA的数据传输方法，包括：以数组形式创建SG DMA数据传输链表一和链表二并且创建第一组缓冲区和第二组缓冲区；通过CPU将用户空间数据拷贝入第一组缓冲区、将链表一的地址写入IO设备；在启动SG DMA数据传输的同时通过CPU将用户空间数据拷贝入第二组缓冲区；创建中断处理程序，待SG DMA传输完成后，CPU接收SG DMA发送的传输完成中断指令将链表二的地址写入IO设备；依次循环直到用户空间数据完全写入IO设备内存位置。本发明还公开了一种SG DMA的数据传输装置。该方法和装置解决了CPU同DMA无法同时参与数据传输的问题，提高数据在DMA传输时的效率。