Double casing warhead with sandwiched charge:The axial distribution of fragments velocities

The double casing warhead with sandwiched charge is a novel fragmentation warhead that can produce two groups of fragments with different velocity,and the previous work has presented a calculation formula to determine the maximum fragment velocity.The current work builds on the published formula to further develop a formula for calculating the axial distribution characteristics of the fragment velocity.For this type of warhead,the simulation of the dispersion characteristics of the detonation products at different positions shows that the detonation products at the ends have a much larger axial velocity than those in the middle,and the detonation products have a greater axial dispersion velocity when they are closer to the central axis.The loading process and the fragment velocity vary with the axial position for both casing layers,and the total velocity of the fragments is the vector sum of the radial velocity and the axial velocity.At the same axial position,the acceleration time of the inner casing is greater than that of the outer casing.For the same casing,the fragments generated at the ends have a longer acceleration time than the fragments from the middle.The proposed formula is validated with the X-ray radiography results of the four warheads previously tested experimentally and the 3D smoothedparticle hydrodynamics numerical simulation results of several series of new warheads with different configurations.The formula can accurately and reliably calculate the fragment velocity when the lengthto-diameter ratio of the charge is greater than 1.5 and the thickness of the casing is less than 20%its inner radius.This work thus provides a key reference for the theoretical analysis and the design of warheads with multiple casings.

Taxonomy and regeneration of a newly recorded Polychaete Capitella teleta(Annelida,Capitellidae)in the coastal water of Shandong,China

The polychaete species of Capitella are widely distributed in the China seas,however little is known about Capitella taxonomy,and specimens collected from China have been identifi ed as Capitella capitata(Fabricius,1780)for more than 50 years.C.capitata was considered to be Arctic and subarctic in distribution,therefore the records of C.capitata in the China seas probably represent other species.A taxonomic study based on the samples collected from the northeast coastal water of Shandong Province reveals a diff erent species,Capitella teleta Blake et al.,2009,which is recorded in the China seas for the fi rst time.Morphologically,C.teleta can be easily distinguished from C.capitata by the absence of neuropodial capillaries on chaetigers 8 and 9.The identity of C.teleta is further supported by genetic distance and phylogenetic analyses assessed from mitochondrial cytochrome c oxidase subunit I(COI)gene.In addition,the regeneration feature of C.teleta was studied through whole mount immunohistochemistry and chemical staining.After amputation,the wound of C.teleta was healed within 24 h,forming a signifi cant regeneration blastema by 3 days post amputation(dpa).By 5 dpa,muscle tissues regenerated,nerve fi bers also extended.By 7 dpa,neurites and muscle tissues are both signifi cantly regenerated.Notably,there are more than ten segments regenerated until 16 dpa.As a highly opportunistic species,Capitella teleta is distributed in China,Japan,Korea,North America,and the Mediterranean.It is expected to be an excellent model for studying developmental genetics and evolution of regeneration.

Generation and Tunable Focal Shift of the Hybridly Polarized Vector Optical Fields with Parabolic Symmetry

Based on a parabolic coordinate system,we theoretically design and experimentally generate hybridly polarized vector optical fields with parabolic symmetry of the first and second kinds,which can further enrich the family of vector optical fields.The wavefront of this new-kind vector optical field contains circular,elliptic and linear polarizations,and the polarizations can keep the same or change along the parabolic curves.Then we present the realization of tunable focal shift with the hybridly polarized vector optical field,and show a specific law of the focal shift of the focused hybridly polarized vector optical field with the parabolic symmetry.We hope these results can provide a new way to flexibly modulate focal fields,which can be applied in realms such as optical machining,optical trapping and information transmission.

Asymptotical Locking Tomography of High-Dimensional Entanglement

High-dimensional(HD)entanglement provides a very promising way of transcending the limitations of the twodimensional entanglement between qubits for increasing channel capacity in many quantum protocols.In the pursuit of capitalizing on the HD entangled states,one of the central issues is to unambiguously and comprehensively quantilfy and reconstruct them.The full quantum state tomography is a unique solution,but it is undesirable and even impractical because the measurements increase rapidly in d^4 for a bipartite d-dimensional quantum state.Here we present a very efficient and practical tomography method—asymptotical locking tomography(ALT),which can harvest full information of bipartite d-dimensional entangled states by very few measurements less than 2 d^2 only.To showcase the validity and reasonableness of our ALT,we carry out the test with the two-photon spin-orbital angular momentum hyperentangled states in a four-dimensional subspace.Besides high-efficiency and practicality,our ALT is also universal and can be generalized into multipartite HD entanglement and other quantum systems.

Photon pair generation in lithium niobate waveguide periodically poled by femtosecond laser

Reliable generation of single photons is of key importance for fundamental physical experiments and quantum protocols.The periodically poled lithium niobate[LN]waveguide has shown promise for an integrated quantum source due to its large spectral tunability and high efficiency,benefiting from the quasi-phase-matching.Here we demonstrate photon-pair sources based on an LN waveguide periodically poled by a tightly focused femtosecond laser beam.The pair coincidence rate reaches~8000 counts per second for average pump power of 3.2 m W[peak power is 2.9 k W).Our results prove the possibility of application of the nonlinear photonics structure fabricated by femtosecond laser to the integrated quantum source.This method can be extended to three-dimensional domain structures,which provide a potential platform for steering the spatial degree of freedom of the entangled two-photon states.

Multi-Path Ghost Imaging by Means of an Additional Time Correlation

Ghost imaging functions achieved by means of the spatial correlations between two photons is a new modality in imaging systems. With a small number of photons, ghost imaging is usually realized based on the position correlation of photon pairs produced from the spontaneous parametric down-conversion process. Here we demonstrate a way to realize multi-path ghost imaging by introducing an additional time correlation. Different delays of paths will induce the shift of the coincidence peak, which carries the information about objects. By choosing the suitable coincidence window, we obtain images of three objects simultaneously, with a visibility of 87.2%.This method provides insights and techniques into multi-parameter ghost imaging. It can be applied to other correlated imaging systems, for example, quantum spiral imaging.

Identifying the Symmetry of an Object Based on Orbital Angular Momentum through a Few-Mode Fiber

In recent years,orbital angular momentum(OAM),as a new usable degree of freedom of photons,has been widely applied in both classical optics and quantum optics.For example,digital spiral imaging uses the OAM spectrum of the output beam from the object to restore the symmetry information of the object.However,the related experiments have been carried out in free space so far.Due to the poor anti-noise performance,limited transmission distance and other reasons,the practicability is seriously restricted.Here,we have carried out a digital spiral imaging experiment through a few-mode fiber,to achieve the identification of the symmetry of object by measuring the OAM spectrum of the output beam.In experiment,we have demonstrated the identification of the symmetry of amplitude-only and phase-only objects with the two-,three-and four-fold rotational symmetries.We also give the understanding of the physics.We believe that our work has greatly improved the practical application of digital spiral imaging in remote sensing.

Study on the Layout of Forestry Industry in Yanbian

Yanbian is a key state-owned forest area and timber production base in Jilin Province and Yanbian's five pillar industries rely heavily on the survival and development of forestry. Reasonable industrial layout can not only help to play the regional resource advantages,but also help to promote the sustainable economic development of Yanbian. Using location quotient method,this paper analyzes the layout of forestry industry in Yanbian,and brings forward the several recommendations for optimizing the layout of forestry industry in Yanbian.

Observation of polarization topological singular lines

We have theoretically designed and experimentally observed free-space propagation of topological singular lines of cylindrical vector optical fields with non-integer topological charges. The polarization singular lines are due to the orientation uncertainty of the polarization states, caused by non-integer topological charges. The results reveal that during propagation, evolution of the polarization singular lines results in the special intensity pattern,distribution of polarization states, and chains of polarization singularities. We have also proposed a method to generate triple straight and spiral singular lines, which may contribute to the research of complex optical fields.

Unveiling stability of multiple filamentation caused by axial symmetry breaking of polarization

Femtosecond laser filamentation is generally initialized from unpredictable symmetry breaking caused by random noise, causing it to be barely controlled. However, it is always anticipated for stable and controllable filamentation.We present and demonstrate the idea that hybridly polarized vector fields with axial symmetry broken polarization, associated with a pair of orthogonally linearly polarized vortices carrying the opposite-handed orbital angular momenta, could achieve controllable and robust multiple filamentation. Here, our motivation is to unveil the underlying physics behind such controllable and robust multiple filamentation. The symmetry breaking should first be actively controllable and then be able to effectively inhibit random noise. Robust multiple filamentation is inseparable from the fact that the phases between the multiple filaments are always locked. In contrast, uncontrollable multiple filamentation is always accompanied with loss of phase, i.e., the multiple filaments become incoherent to each other. Our results may offer a suggestion for achieving controllable and robust multiple filamentation in other systems.

Real-time transition dynamics and stability of chipscale dispersion-managed frequency microcombs

Femtosecond mode-locked laser frequency combs have served as the cornerstone in precision spectroscopy,alloptical atomic clocks,and measurements of ultrafast dynamics.Recently frequency microcombs based on nonlinear microresonators have been examined,exhibiting remarkable precision approaching that of laser frequency combs,on a solid-state chip-scale platform and from a fundamentally different physical origin.Despite recent successes,to date,the real-time dynamical origins and high-power stabilities of such frequency microcombs have not been fully addressed.Here,we unravel the transitional dynamics of frequency microcombs from chaotic background routes to femtosecond mode-locking in real time,enabled by our ultrafast temporal magnifier metrology and improved stability of dispersion-managed dissipative solitons.Through our dispersion-managed oscillator,we further report a stability zone that is more than an order-of-magnitude larger than its prior static homogeneous counterparts,providing a novel platform for understanding ultrafast dissipative dynamics and offering a new path towards high-power frequency microcombs.

Double-slit interference of single twisted photons

Optical orbital angular momentum(OAM) is a special property of photons and has evoked research onto the light–matter interaction in both classical and quantum regimes. In classical optics, OAM is related to an optical vortex with a helical phase structure. In quantum optics, photons with a twisted or helical phase structure will carry a quantized OAM. To our knowledge, however, so far, no experiment has demonstrated the fundamental property of the OAM at the single-photon level. In this Letter, we have demonstrated the average photon trajectories of twisted photons in a double-slit interference. We have experimentally captured the double-slit interference process of twisted photons by a time-gated intensified charge-coupled device camera, which is trigged by a heralded detection. Our work provides new perspectives for understanding the micro-behaviors of twisted particles and enables new applications in imaging and sensing.

Stronger Hardy-like proof of quantum contextuality

A Hardy-like proof of quantum contextuality is a compelling way to see the conflict between quantum theory and noncontextual hidden variables(NCHVs),as the latter predict that a particular probability must be zero,while quantum theory predicts a nonzero value.For the existing Hardy-like proofs,the success probability tends to 1/2when the number of measurement settings n goes to infinity.It means the conflict between the existing Hardy-like proof and NCHV theory is weak,which is not conducive to experimental observation.Here we advance the study of a stronger Hardy-like proof of quantum contextuality,whose success probability is always higher than the previous ones generated from a certain n-cycle graph.Furthermore,the success probability tends to 1 when n goes to infinity.We perform the experimental test of the Hardy-like proof in the simplest case of n=7 by using a four-dimensional quantum system encoded in the polarization and orbital angular momentum of single photons.The experimental result agrees with the theoretical prediction within experimental errors.In addition,by starting from our Hardy-like proof,one can establish the stronger noncontextuality inequality,for which the quantumclassical ratio is higher with the same n,which provides a new method to construct some optimal noncontextuality inequalities.Our results offer a way for optimizing and enriching exclusivity graphs,helping to explore more abundant quantum properties.

Extending optical filaments with phase-nested laser beams

Extending the length of femtosecond laser filamentation has always been desired for practical applications. Here,we demonstrate that significant extending of a single filament in BK7 glass can be achieved by constructing phasenested beams. The filamentation and the following energy replenishment are assembled in a single phase-nested beam. The central part of the phase-nested beam is an apertured Gaussian beam, which is focused into one focal spot to produce a short filament. In contrast, the rest of the annular part converges gradually towards the central axis to continuously replenish the energy for supporting the regeneration of filaments. The common-path generating system ensures the stability of generated filaments and easily optimizes the beam parameters to obtain the longest high-quality filament due to its flexibility. In addition, we discuss the significance of continuous replenishment for extending filaments and the potential for generating more extended filaments based on this method.

Tunable azimuthally non-uniform orbital angular momentum carried by vector optical fields

Orbital angular momentum(OAM), as a fundamental parameter of a photon, has attracted great attention in recent years. Although various properties and applications have been developed by modulating the OAM of photons, there is rare research about the non-uniform OAM. We propose and generate a new kind of continuously tunable azimuthally non-uniform OAM for the first time, to the best of our knowledge, which is carried by a hybridly polarized vector optical field with a cylindrically symmetric intensity profile and a complex polarization singularity. We also present the perfect vector optical field carrying non-uniform OAM with a fixed radius independent of topological charges, which can propagate steadily without radial separation, solving the problem of the unsteady propagation due to the broadened OAM spectrum of the non-uniform OAM. This new kind of tunable non-uniform OAM with a cylindrical symmetric intensity profile, complex polarization singularity, and propagation stability enriches the family of OAMs and can be widely used in many regions such as optical manipulation, quantum optics, and optical communications.

Propagation characteristics of orbital angular momentum modes at 810 nm in step-index few-mode fibers

In free-space or in optical fibers,orbital angular momentum(OAM)multiplexing for information transmission has been greatly developed.The light sources used were well coherent communication bands,and the fibers used were customized.Here,we use an 810 nm femtosecond laser to generate optical vortices carrying OAM and then feed them into two kinds of commercial step-index few-mode fibers to explore the transmission characteristics of OAM modes.We also propose a method without multiple-input multiple-output digital signal processing to identify the input OAMs.It is of great guiding significance for high-dimensional quantum information experiments via the OAMs as a degree of freedom,using the light generated by the spontaneous parametric down-conversion as the source and the commercial fibers for information transmission.