Maintenance of Millimeter-level Geodetic Reference Framework

The high-precision terrestrial reference frame,as the spatial benchmark for geodesy,is an important national infrastructure.However,due to the influence of nonlinear factors related to geophysical phenomena,the overall maintenance accuracy of the ITRF framework is still at the centimeter level.Therefore,accurately characterizing the true trajectories of linear motion,nonlinear motion,and geocentric motion of the reference station is the key to achieve the construction and maintenance technology of a millimeter level terrestrial reference framework.Based on long-term global and regional GNSS observation data,more Chinese geodesy scientists devoted much efforts to the maintenance of millimeter-level geodetic reference framework.The main contributions of this work included the followings:①Dynamic maintenance of millimeter-level terrestrial reference frame;②Research progress on the method of maintenance of regional reference frame based on GNSS;③The progress of CGCS2000 frame maintenance in millimeter level accuracy;④Reprocessing and reanalysis of two-decade GNSS observation in continental China;⑤Research on current GNSS velocity field model and deformation in Chinese mainland;⑥The preliminary realization and evaluation of CTRF2020.

FKF1b controls reproductive transition associated with adaptation to geographical distribution in maize

Maize(Zea mays subspecies mays)is an important commercial crop across the world,and its flowering time is closely related to grain yield,plant cycle and latitude adaptation.FKF1 is an essential clock-regulated blue-light receptor with distinct functions on flowering time in plants,and its function in maize remains unclear.In this study,we identified two FKF1 homologs in the maize genome,named ZmFKF1a and ZmFKF1b,and indicated that ZmFKF1a and ZmFKF1b independently regulate reproductive transition through interacting with ZmCONZ1 and ZmGI1 to increase the transcription levels of ZmCONZ1 and ZCN8.We demonstrated that ZmFKF1b underwent artificial selection during modern breeding in China probably due to its role in geographical adaptation.Furthermore,our data suggested that ZmFKF1bHap_C7 may be an elite allele,which increases the abundance of ZmCONZ1 mRNA more efficiently and adapt to a wider range of temperature zone than that of ZmFKF1bHap_Z58 to promote maize floral transition.It extends our understanding of the genetic diversity of maize flowering.This allele is expected to be introduced into tropical maize germplasm to enrich breeding resources and may improve the adaptability of maize at different climate zones,especially at temperate region.

Repairing damaged reputations through targeted poverty alleviation:Evidence from private companies’strategies to deal with negative media coverage

When negative media coverage causes reputational crises,companies must find suitable tools to repair their reputation and reverse their negative image.As a CSR activity with political-and livelihood-related implications,targeted poverty alleviation may be an effective tool.Using data on negative media coverage of Chinese A-share private listed companies,we examine whether companies engage in targeted poverty alleviation in response to reputational crises caused by negative media coverage.We find that negative media coverage leads private companies to engage more actively and intensively in targeted poverty alleviation because of the significant increase in public attention to the bad news.These companies must urgently rebuild their positive image using targeted poverty alleviation to resolve their public opinion crisis.Further analyses suggest that original and in-depth negative media coverage is more likely to cause companies’active participation in targeted poverty alleviation.In addition,negative media coverage is more likely to lead companies to engage in targeted poverty alleviation when they are in heavily polluting industries or face greater pressure from external investors.Finally,we find that active involvement in targeted poverty alleviation helps companies improve their market reputation and thus effectively manage public relations crises caused by negative media coverage.

Efficient high harmonic generation in nonlinear photonic moiré superlattice

Photonic moirésuperlattice as an emerging platform of flatbands can tightly confine the light inside the cavity and has important applications not only in linear optics but also in nonlinear optics.In this paper,we numerically investigate the third-and fifth-order harmonic generation(THG and FHG)in photonic moirésuperlattices fabricated by the nonlinear material silicon.The high conversion efficiency of THG and FHG is obtained at a relatively low intensity of fundamental light,e.g.,the maximum conversion efficiency of THG and FHG arrives even up to be 10^(−2) and 10^(−9) at the fundamental intensity of 30 kW/m^(2),respectively,in the moirésuperlattice of near flat band formed by the twist angle 6.01°.The results indicate the photonic moirésuperlattice of a high-quality factor and flatbands is a promising platform for efficient nonlinear processes and advanced photonic devices.

Design and Experimentation of a Novel Separable Vibration-Assisted Stage

In this paper,a novel,separable two-degrees-of-freedom stage with high-precision motion and resolution is proposed for the application of vibration-assisted micromilling.A separable design was realized on the basis of the detachable structure of the platform.Flexible stages with different dimensions and types can be utilized in the devices.A circular-fillet hinge is selected as the flexible unit with a parallel structure to realize output decoupling and reduce the coupling error between the two vibration directions.Analytical modeling is conducted to explore the static and dynamic characteristics of the stage.Results reveal a good agreement with the finite element simulation result.A series of experiments were conducted to assess the static and dynamic performances of the flexible stage,encompassing tests such as amplitude response,motion trajectory,and coupling trajectory.The results of these tests revealed that the designed vibration-assisted system exhibits precise movement capabilities.

LiNbO_(3) channel and ridge waveguides based on helium ion implantation combined with lithography and precise diamond dicing

Lithium niobate(LiNbO_(3),LN)channel and ridge waveguides have been successfully fabricated by He ion implantation,which has energy of 500 keV and fluence of 1.5×10^(16)ions/cm^(2) and is combined with lithography and the precise diamond dicing technique.The refractive index profile of the annealed LN planar waveguide was reconstructed.The propagation loss of the channel waveguide with a width of 10μm and that of the ridge waveguides with widths of 25μm and 15μm were investigated by the end-face coupling method.In our work,the factors that affect the waveguide properties of channel and ridge waveguides were revealed.

Near-infrared lasing and tunable upconversion from femtosecond laser inscribed Nd,Gd:CaF_(2)waveguides

Optical channel waveguides with depressed cladding configurations have been produced in Nd,Gd∶CaF_(2)laser crystals by using ultrafast laser inscription.Waveguide properties are investigated in terms of guiding behaviors and localized laserinduced lattice damages.Under an optical pump of 808 nm light,continuous-wave waveguide lasing at 1.06μm is achieved,with a single-mode operation and a minimum lasing threshold of 98.8 m W.Furthermore,the visible emissions of Nd^(3+)with short wavelengths ranging from 415 nm to 550 nm and long wavelengths from 550 nm to 625 nm are observed upon 808 nm laser excitation via the up-converted process.The intensity ratios of two wavelength ranges are proved to be tunable through changing the pumping polarizations.

Laser emission from low-loss cladding waveguides in Pr:YLF by femtosecond laser helical inscription

Depressed cladding waveguides are fabricated in Pr:LiYF_(4)(YLF)crystal by femtosecond laser inscription following a helical scheme.With the optimized parameters,the propagation loss of the waveguide is around 0.12 dB/cm for multimode guiding.Under optical pumping with InGaN laser diodes at 444 nm,efficient waveguide lasers in the orange around604 nm(π-polarized)are achieved with minimum lasing threshold of 119.8 mW,maximum slope efficiency of 16.6%,and maximum output power of 120.6 mW.Benefiting from their optimized performances,the waveguides produced in this work are promising for applications as compact orange laser sources.

Surface lattice resonances in dielectric metasurfaces for enhanced light-matter interaction [Invited]

Lithium niobate(LiNbO_(3)) is a versatile crystalline material for various photonic applications. With the recent advances in LiNbO_(3)-on-insulator(LNOI) thin film technology, LiNbO_(3) has been regarded as one of the most promising platforms for multifunctional integrated photonics. In this work, we present the field enhancement due to collective resonances in arrayed LiNbO_(3) nanoantennas. These resonances arise from the enhanced radiative coupling of localized Mie resonances in the individual nanoparticles and Rayleigh anomalies due to in-plane diffraction orders of the lattice. We describe the pronounced differences in field enhancement and field distributions for electric and magnetic dipoles, offering valuable information for the design and optimization of high-quality-factor optical metasurfaces based on LiNbO_(3).

Lithium niobate planar and ridge waveguides fabricated by 3 MeV oxygen ion implantation and precise diamond dicing

We report on the fabrication and optimization of lithium niobate planar and ridge waveguides at the wavelength of 633 nm.To obtain a planar waveguide, oxygen ions with an energy of 3.0 Me V and a fluence of 1.5 × 10^(15) ions=cm^(2) are implanted in the polished face of Li Nb O_(3) crystals. For planar waveguides, a loss of 0.5 d B/cm is obtained after annealing at 300°C for30 min. The ridge waveguide is fabricated by the diamond blade dicing method on optimized planar waveguides. The guiding properties are investigated by prism coupling and end-face coupling methods.

Dynamic relaxation process of a 3D super crystal structure in a Cu:KTN crystal

In this Letter,we report the existence and relaxation properties of a critical phenomenon on called a 3D super crystal that emerges at T=TC?3.5℃,that is,in the proximity of the Curie temperature of a Cu:KTN sample.The dynamics processes of a 3D super crystal manifest in its formation containing polarized nanometric regions and/or polarized clusters.However,with strong coupling and interaction of microcomponents,the characteristic relaxation time measured by dynamic light scattering demonstrates a fully new relaxation mechanism with a much longer relaxation time.As the relaxation mechanism of a relaxator is so-far undetermined,this research provides a novel perspective.These results can help structure a fundamental theory of ferroelectric relaxation.

Field-induced transformation of ferroelectric domain states in KTN crystal

We report an interesting study of electric-field-induced transformation from a single domain ferroelectric state to the multiple domain ferroelectric state in a KTa_(1-x)Nb_(x)O_(3)(KTN) crystal. Experimental results obtained using the confocalμ-Raman spectroscopy confirm the dynamic change of lattice structures induced by an external electric field.Furthermore, the dependence of relative permittivity on the applied voltage also indicates the transformation of ferroelectric states involving the processes of splintering, inversion, and re-formation of ferroelectric domains.