Flower-like Bi_2WO_6/ZnO composite with excellent photocatalytic capability under visible light irradiation

The photocatalytic ability of ZnO is improved through the addition of flower‐like Bi2WO6 to prepare a Bi2WO6/ZnO composite with visible light activity.The composite is characterized by X‐ray diffraction,transmission electron microscopy,scanning electron microscopy with UV–vis diffuse reflectance spectroscopy,X‐ray photoelectron spectroscopy and N2 adsorption‐desorption isotherms.After modification,the band gap energy of Bi2WO6/ZnO is reduced from 3.2 eV for ZnO to 2.6 eV.Under visible light irradiation,the Bi2WO6/ZnO composite shows an excellent photocatalytic activity for degrading methylene blue(MB)and tetracycline.The photo‐degradation efficiencies of(0.3:1)Bi2WO6/ZnO for MB and tetracycline are approximately 246 and 4500 times higher than those of bare ZnO,respectively,and correspondingly,the photo‐degradation rates for the two pollutants are approximately 120 and 200 times higher than those with bare ZnO,respectively.Moreover,the photocatalyst of(0.3:1)Bi2WO6/ZnO exhibits a higher transient photocurrent density of approximately 4.5μA compared with those of bare Bi2WO6 and ZnO nanoparticles.The successful recombination of Bi2WO6 and ZnO enhances the photocatalytic activity and reduces the band gap energy of ZnO,which can be attributed to the effective separation of electron–hole pairs.Active species trapping experiments display that[O2]-is the major species involved during photocatalysis rather than·OH and h+.This study provides insight into designing a meaningful visible‐light‐driven photocatalyst for environmental remediation.

Improve the performance of interferometer with ultra-cold atoms

Ultra-cold atoms provide ideal platforms for interferometry.The macroscopic matter-wave property of ultra-cold atoms leads to large coherent length and long coherent time,which enable high accuracy and sensitivity to measurement.Here,we review our efforts to improve the performance of the interferometer.We demonstrate a shortcut method for manipulating ultra-cold atoms in an optical lattice.Compared with traditional ones,this shortcut method can reduce the manipulation time by up to three orders of magnitude.We construct a matter-wave Ramsey interferometer for trapped motional quantum states and significantly increase its coherence time by one order of magnitude with an echo technique based on this method.Efforts have also been made to enhance the resolution by multimode scheme.Application of a noise-resilient multi-component interferometer shows that increasing the number of paths could sharpen the peaks in the time-domain interference fringes,which leads to a resolution nearly twice compared with that of a conventional double-path two-mode interferometer.With the shortcut method mentioned above,improvement of the momentum resolution could also be fulfilled,which leads to atomic momentum patterns less than 0.6hkL. To identify and remove systematic noises,we introduce the methods based on the principal component analysis (PCA) that reduce the noise in detection close to the 1/√2 of the photon-shot noise and separate and identify or even eliminate noises.Furthermore,we give a proposal to measure precisely the local gravity acceleration within a few centimeters based on our study of ultracold atoms in precision measurements.

AN EMPIRICAL FEASIBILITY STUDY OF SOCIETAL RISK CLASSIFICATION TOWARD BBS POSTS

Societal risk classification is the fundamental issue for online societal risk monitoring. To show the challenge and feasibility of societal risk classification toward BBS posts, an empirical analysis is implemented in this paper. Through effectiveness analysis, Support Vector Machine based on Bag-Of-Words （BOW-SVM） is adopted for challenge validation, and the distributed document embeddings of BBS posts generated by Paragraph Vector are applied to feasibility study. Based on BOW-SVM, cross-validations of BBS posts labeled by different groups and annotators are conducted. The big fluctuation of cross-validation results indicates the differences of individual risk perceptions, which brings more challenges to societal risk classification. Furthermore, based on the distributed document embeddings of BBS posts, the pairwise similarities of more than 300 thousands BBS posts from different societal risk categories are compared. The higher similarities of BBS posts in the same societal risk category reveal that BBS posts in the same societal risk category share more features than BBS posts in different categories, which manifests the feasibility of societal risk classification of BBS posts, and also reflects the possibility to improve the performance of societal risk monitoring.

Momentum filtering scheme of cooling atomic clouds for the Chinese Space Station

To obtain cold atom samples with temperatures lower than 100 pK in the cold atom physics rack experiment of the Chinese Space Station,we propose to use the momentum filtering method for deep cooling of atoms.This paper introduces the experimental results of the momentum filtering method verified by our ground testing system.In the experiment,we designed a specific experimental sequence of standing-wave light pulses to control the temperature,atomic number,and size of the atomic cloud.The results show that the momentum filter can effectively and conveniently reduce the temperature of the atomic cloud and the energy of Bose–Einstein condensation,and can be flexibly combined with other cooling methods to enhance the cooling effect.This work provides a method for the atomic cooling scheme of the ultra-cold atomic system on the ground and on the space station,and shows a way of deep cooling atoms.

MAN-MACHINE COLLABORATED KNOWLEDGE CREATION IN HWMSE

The target of Hall for Workshop of Meta-synthetic Engineering （HWMSE） is to organically combine the human expert systems, machine systems and knowledge systems so as to realize meta-syntheses. The availability of HWMSE embodies in capabilities of knowledge using and knowledge creation. In HWMSE the knowledge systems could be classed into two types： general knowledge system and object knowledge system. A highly strong and continually accumulated object knowledge system is essential for complex system problem solving. Systematic study of the object system is the foundation for knowledge system construction in HWMSE. It is important to design the knowledge system as a whole for systematic research while at the meanwhile open for accumulation through utilization. Case of object knowledge system construction and utilization in the project Research on the Man-machine Collaborated HWMSE Supporting Macroeconomic Policy Making is discussed.

Quantum precision measurement of two-dimensional forces with 10^(-28)-Newton stability

High-precision sensing of vectorial forces has broad impact on both fundamental research and technological applications such as the examination of vacuum fluctuations and the detection of surface roughness of nanostructures.Recent years have witnessed much progress on sensing alternating electromagnetic forces for the rapidly advancing quantum technology-orders of magnitude improvement has been accomplished on the detection sensitivity with atomic sensors,whereas such high-precision measurements for static electromagnetic forces have rarely been demonstrated.Here,based on quantum atomic matter waves confined by a two-dimensional optical lattice,we perform precision measurement of static electromagnetic forces by imaging coherent wave mechanics in the reciprocal space.The lattice confinement causes a decoupling between real-space and reciprocal dynamics,and provides a rigid coordinate frame for calibrating the wavevector accumulation of the matter wave.With that we achieve a stateof-the-art sensitivity of 2.30(8)×10^(-26) N/√Hz.Long-term stabilities on the order of 10^(-28) N are observed in the two spatial components of a force,which allows probing atomic Van der Waals forces at one millimeter distance.As a further illustrative application,we use our atomic sensor to calibrate the control precision of an alternating electromagnetic force applied in the experiment.Future developments of this method hold promise for delivering unprecedented atom-based quantum force sensing technologies.

Probing quantum many-body correlations by universal ramping dynamics

Ramping a physical parameter is one of the most common experimental protocols in studying a quantum system, and ramping dynamics has been widely used in preparing a quantum state and probing physical properties. Here, we present a novel method of probing quantum many-body correlation by ramping dynamics. We ramp a Hamiltonian parameter to the same target value from different initial values and with different velocities, and we show that the first-order correction on the finite ramping velocity is universal and path-independent, revealing a novel quantum many-body correlation function of the equilibrium phases at the target values. We term this method as the non-adiabatic linear response since this is the leading order correction beyond the adiabatic limit. We demonstrate this method experimentally by studying the Bose-Hubbard model with ultracold atoms in three-dimensional optical lattices.Unlike the conventional linear response that reveals whether the quasi-particle dispersion of a quantum phase is gapped or gapless, this probe is more sensitive to whether the quasi-particle lifetime is long enough such that the quantum phase possesses a well-defined quasi-particle description. In the BoseHubbard model, this non-adiabatic linear response is significant in the quantum critical regime where well-defined quasi-particles are absent. And in contrast, this response is vanishingly small in both superfluid and Mott insulators which possess well-defined quasi-particles. Because our proposal uses the most common experimental protocol, we envision that our method can find broad applications in probing various quantum systems.

Influence of thermal effects on atomic Bloch oscillation

Advancements in the experimental toolbox of cold atoms have enabled the meticulous control of atomic Bloch oscillation(BO)within optical lattices,thereby enhancing the capabilities of gravity interferometers.This work delves into the impact of thermal effects on Bloch oscillation in 1D accelerated optical lattices aligned with gravity by varying the system's initial temperature,Through the application of Raman cooling,we effec-tively reduce the longitudinal thermal effect,stabilizing the longitudinal coherence length over the timescale of its lifetime.The atomic losses over multiple Bloch periods are measured,which are primarily attributed to transverse excitation.Furthermore,we identify two distinct inverse scaling behaviors in the oscillation lifetime scaled by the corresponding density with respect to temperatures,implying diverse equilibrium processes within or outside the Bose-Einstein condensate(BEC)regime.The compe-tition between the system's coherence and atomic density leads to a rela-tively smooth variation in the actual lifetime versus temperature.Our find-ings provide valuable insights into the interaction between thermal effects and BO,offering avenues for the refinement of quantum measurement technologies.