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Our ability to observe the network topology and nodes' behaviors of complex systems has significantly advanced in the past decade, giving rise to a new and fast-developing frontier—inferring the underlying dynamical mechanisms of complex systems from the observation data. Here we explain the rationale of data-driven dynamics inference and review the recent progress in this emerging field. Specifically, we classify the existing methods of dynamics inference into three categories, and describe their key ideas, representative applications and limitations. We also discuss the remaining challenges that are worth the future effort.

An ensemble pulsar timescale derived from the traditional Wiener filtration still contains some high level noise. To improve this situation we developed a Wiener filtration algorithm of the ensemble pulsar timescale based on a power-law model of power spectrum for pulsars. Our algorithm has three strengths: (1) mitigating spectral leakage between frequency bins for Fourier techniques; (2) using a power-law model for power spectrum; (3) signal realization in original residuals of data set by the power-law model. According to improved algorithm we constructed an ensemble pulsar timescale EPT−TAI using timing data with respect to International Atomic Time (TAI) about 16 yr time span of ten pulsars from International Pulsar Timing Array second data release (version A). The results show that EPT−TAI detected correctly the differences TT(BIPM2015)−TAI between terrestrial time TT(BIPM2015) and TAI. Fractional frequency stability σ z analysis shows that EPT−TAI does not indicate red noise for 16 yr time interval, and fractional frequency stability for 8 yr and longer time intervals is slightly better than that of TT(BIPM2015)−TAI. Stability for short time intervals of TT(BIPM2015)−TAI is better than that of EPT−TAI, but TT(BIPM2015)−TAI shows red noise for longer time intervals. Using the same algorithm we also derived an ensemble pulsar timescale EPT−TT(BIPM2015) with respect to TT(BIPM2015). The fractional frequency stability curve of EPT−TT(BIPM2015) shows similar characteristics as that of EPT−TAI but with slightly lower values.

We investigate the optimal convex approximation, optimally approximating a desired and unavailable qubit state by the convex mixing of a given set of available states. When the available states are the eigenvectors of three Pauli matrices, we present the complete exact solution for the optimal convex approximation of an arbitrary qubit state based on the fidelity distance. By the comparison of optimal states based on fidelity and trace norm, the advantages and disadvantages of the optimal convex approximation are identified. Several examples are provided to support this. We also analyze the geometrical properties of the target states which can be completely represented by a set of available states. Using the feature of convex combination, we derive the maximum range of completely represented states and clearly illustrate that any qubit state can be optimally prepared by at most three available states in known useable states.

When a laser is transmitted in fog, and the water droplets will scatter and absorb the laser, which affects the intensity of the laser transmission and the accuracy of radar detection. Therefore, it is of great significance to study the laser transmission in the fog. At present, the main method of calculating the scattering and attenuation characteristics of fog is based on the radiation transmission theory, which is realized by a large number of numerical calculations or physical simulation methods, which takes time and cannot meet the requirements for obtaining the fast and accurate results. Therefore, in this paper established are a new laser forward attenuation model and backward attenuation model in low visibility fog. It is found that in low visibility environments, the results calculated by the Monte Carlo method are more accurate than those from most of the existing forward attenuation models. For the cases of 0.86-μm, 1.06-μm, 1.315-μm, 10.6-μm typical lasers incident on different fogs with different visibilities, a backscatter model is established, the error between the fitting result and the calculation result is analyzed, the backward attenuation fitting parameters of the new model are tested, and a more accurate fitting result is obtained.

In the era of information explosion, "information overload" has become an unavoidable problem. Vital information acquisition is an unavoidable problem. In the era of big data, using big data technology is undoubtedly an important thinking direction to solve data problems. Based on big data analysis and recommendation, this paper takes DIKW as the model support and takes short video personalized recommendation as an example to provide different personalized short video recommendations for different scenes. Aimed at the current information explosion era, looking for a good recommendation information system.

As the satellite power supply and distribution functions and complexity are gradually strengthened, the reliability requirements of the aerospace secondary power supply are getting higher and higher. Based on the basic composition and working principle of aerospace secondary power supply, this paper analyzes the reliability of the fault tree analysis method (FTA), combs the weak link of the product, and proposes design improvement measures for the weak link.

We investigate optimization of dichotomic local phase measurement settings for multipartite quantum systems. We first describe a method of constructing a single multipartite Bell inequality by treating correlation function as an $n$-index tensor. Under a set of local phase measurement settings, we calculate quantum prediction of generalized Greenberger-Horne-Zeilinger state and show the exact relationship between quantum prediction and the phase factors. We show that there exists a set of optimal measurement settings relevant to maximal quantum prediction, which can contribute to testing multipartite Bell inequality in a straightforward manner. Also, we provide quantum simulation and numerical analysis with these optimal measurement settings.

Apatite ceramics Ca10(PO4)6 X 2 (X = F, OH) were prepared by the standard solid state sintering method and irradiated with He ions under a fluence of 5 × 1016 ions/cm2 at 450 °C. Irradiation induced formation and growth of the He bubbles were observed by a transmission electron microscope. Hydroxyapatite Ca10(PO4)6(OH)2 and fluoroapatite Ca10(PO4)6F2 with different He bubble morphologies indicate the influence of OH –/F – substitution on the He-ion annealing efficiency, as well as the structure itself, which affects the process of He bubble evolution and formation. The grain boundaries also act as sinks to accumulate He bubbles. No obvious irradiation damage but slight intensity reduction and left shift of diffraction peaks were observed according to the grazing incidence x-ray diffraction and Raman spectra characterizations, indicating that defects of interstitials and vacancies were generated.

Development of advanced materials with high energy density for thermochemical energy storage may contribute to the efficient utilization of solar energy and waste heat. In this work, Ce(NO3)3/Mg(OH)2 as a new heat storage material for TCEs was investigated. The effect of Ce(NO3)3 on dehydration of Mg(OH)2 was investigated by differential scanning calorimetry and thermogravimetry techniques. The addition of Ce(NO3)3 can significantly reduce the dehydration temperature and accelerate the dehydration of Mg(OH)2. The temperature reduction depends on the Ce(NO3)3 content W and reaches 29 ?C at W = 10 wt%, while the dehydration heat was reduced only slightly (1086 J/g). The new material exhibits an adjustable decomposition temperature, fast dehydration rate and large heat storage density, and may be considered as a promising candidate for thermochemical storage of concentrated solar energy.

We report the realization of acoustic energy harvesting for low-frequency sound in a subwavelength system consisting of eight multiple-cavity units. This exotic energy harvesting phenomenon arises from a compound monopole Mie resonance (MMR) induced by mutual coupling between the system structure and the MMR of each unit. More importantly, the center intensity can reach about 9000 Pa2 with the parameter r/r 0 of 0.73, providing the feasibility for realizing energy harvesting in a low-energy environment. The proposed system has rich compound Mie resonances, high energy harvesting, and strong robustness, which provides diverse routes to design novel acoustic devices with versatile applications.

An approximation of the orography gravity wave, which is induced by mountainous topography, is considered in this study. By assuming that the horizontal wind is a linear function with respect to the height, the approximating equation for the orography gravity waves is obtained. Four topography functions are considered in this study and the orography gravity wave are obtained. The dynamics of the orography gravity wave is then discussed by considering the effect of the surface topography and background horizontal wind.

The remnants of two gamma-ray bursts, GRB 030329 and GRB 041227, have been resolved by Very Long Baseline Interferometry observations. The radio counterparts were observed to expand with time. These observations provide an important way to test the dynamics of the standard fireball model. We show that the observed size evolution of these two events cannot be explained by a simple jet model, rather, it can be satisfactorily explained by the two-component jet model. It strongly hints that gamma-ray burst ejecta may have complicated structures.

We propose a simultaneous quantum secure direct communication scheme between one party and other three parties via four-particle GHZ states and swapping quantum entanglement. In the scheme, three spatially separated senders, Alice, Bob and Charlie, transmit their secret messages to a remote receiver Diana by performing a series local operations on their respective particles according to the quadripartite stipulation. From Alice, Bob, Charlie and Diana's Bell measurement results, Diana can infer the secret messages. If a perfect quantum channel is used, the secret messages are faithfully transmitted from Alice, Bob and Charlie to Diana via initially shared pairs of four-particle GHZ states without revealing any information to a potential eavesdropper. As there is no transmission of the qubits carrying the secret message in the public channel, it is completely secure for the direct secret communication. This scheme can be considered as a network of communication parties where each party wants to communicate secretly with a central party or server., Comment: 4 pages, no figure

We present a controlled quantum teleportation protocol. In the protocol, quantum information of an unknown state of a 2-level particle is faithfully transmitted from a sender (Alice) to a remote receiver (Bob) via an initially shared triplet of entangled particles under the control of the supervisor Charlie. The distributed entangled particles shared by Alice, Bob and Charlie function as a quantum information channel for faithful transmission. We also propose a controlled and secure direct communication scheme by means of this teleportation. After insuring the security of the quantum channel, Alice encodes the secret message directly on a sequence of particle states and transmits them to Bob supervised by Charlie using this controlled quantum teleportation. Bob can read out the encoded message directly by the measurement on his qubit. In this scheme, the controlled quantum teleportation transmits Alice's message without revealing any information to a potential eavesdropper. Because there is not a transmission of the qubit carrying the secret message between Alice and Bob in the public channel, it is completely secure for controlled and direct secret communication if perfect quantum channel is used. The feature of this scheme is that the communication between two sides depends on the agreement of the third side., Comment: 4 pages

We present an example of quantum computational tasks whose performance is enhanced if we distribute quantum information using quantum cloning. Furthermore we give achievable efficiencies for probabilistic cloning the quantum states used in implemented tasks for which cloning provides some enhancement in performance., Comment: 9 pages, 8 figures

Quantum coherence is a fundamental manifestation of the quantum superposition principle. Recently, Baumgratz \emph{et al}. [Phys. Rev. Lett. \textbf{113}, 140401 (2014)] presented a rigorous framework to quantify coherence from the view of theory of physical resource. Here we propose a new valid quantum coherence measure which is a convex roof measure, for a quantum system of arbitrary dimension, essentially using the generalized Gell-Mann matrices. Rigorous proof shows that the proposed coherence measure fulfills all the requirements dictated by the resource theory of quantum coherence measures. Moreover, strong links between the resource frameworks of coherence concurrence and entanglement concurrence is derived, which shows that any degree of coherence with respect to some reference basis can be converted to entanglement via incoherent operations. Our work provides a clear quantitative and operational connection between coherence and entanglement based on two kinds of concurrence. This new coherence measure, coherence concurrence, may be beneficial to the study of quantum coherence., 8 pages

The Geo REC is the digital remote sensing survey system which based on domestic satellites, and by means of it, the thesis carriedy out a remote sensing anomaly verification field application test in Nachitai area of Qinghai. Field test checks the system installation, the stability of the system operation, the efficiency of reading and show the romoate image or vector data, the security of the data management system and the accuracy of BeiDou navigation; through the test data, the author indicated that the hardware and software system could satisfy the remote sensing anomaly verification work in field, which could also could make it convenient forconvenient the workflow of remote sense survey and, improve the work efficiency,. Aat the same time, in the course of the experiment, we also found some shortcomings of the system, and give some suggestions for improvement combineding with the practical work for the system.

A goal of data assimilation is to infer stochastic dynamical behaviors with available observations. We consider transition phenomena between metastable states for a stochastic system with (non-Gaussian) -stable Levy noise. With either discrete time or continuous time observations, we infer such transitions between metastable states by computing the corresponding non-local Zakai equation (and its discrete time counterpart) and examining the most probable orbits for the state system. Examples are presented to demonstrate this approach.

Based on Clauser-Horner-Shimony-Holt inequality, we show a fruitful method to exploit Bell inequalities for multipartite qubit systems. These Bell inequalities are designed with a simpler architecture tailored to experimental demonstration. Under the optimal setting we derive a set of compact Mermin-type inequalities and discuss quantum violations for generalized Greenberger-Horne-Zeilinger (GGHZ) states. Also, we reveal relationship between quantum nonlocality and four-partite entanglement for four-qubit GGHZ states., Comment: 4 pages, 1 figure

We present a Bell-type inequality for four-qubit systems. Using the inequality we investigate quantum nonlocality of a generic family of states $\left|G_{abcd}\right >$ [Phys. Rev. A 65, 052112 (2002)] and several canonical four-qubit entangled states. It has been demonstrated that the inequality is maximally violated by so called "four-qubit maximal entangled state $\left|G_{m}\right >$" and it is also violated by the four-qubit W state and a special family of states $\left|G_{ab00}\right >$. Moreover, a useful entanglement-nonlocality relationship for the family of states $\left|G_{ab00}\right >$ is obtained.

We present an efficient scheme for preparing and purifying of four-photon Greenberger-Horne-Zeilinger (GHZ) state based on linear optics and postselection. First, we describe how to create a four-photon GHZ state in both polarization and spatial degrees of freedom from two pairs. Moreover, in the presence of depolarization noise our scheme is capable of purifying the desired state. In the regime of weak nonlinearity we design an indirect photon number-resolving detection to distinguish two states of the two pairs. At last, a fourfold coincidence detector click indicates creating of a polarization-entangled four-photon GHZ state., 13pages, 2 figures

We investigate classification and detection of entanglement of multipartite quantum states in a very general setting, and obtain efficient $k$-separability criteria for mixed multipartite states in arbitrary dimensional quantum systems. These criteria can be used to distinguish $n-1$ different classes of multipartite inseparable states and can detect many important multipartite entangled states such as GHZ states, W states, anti W states, and mixtures thereof. They detect $k$-nonseparable $n$-partite quantum states which have previously not been identified. Here $k=2,3,\cdots,n$. No optimization or eigenvalue evaluation is needed, and our criteria can be evaluated by simple computations involving components of the density matrix. Most importantly, they can be implemented in today's experiments by using at most $\mathcal{O}(n^2)$ local measurements., Comment: 6 pages, 4 figures