ISSN 0253-2778

CN 34-1054/N

2019 Vol. 49, No. 11

Display Method:
Single spin quantum metrology: Microscopic magnetic resonance based on quantum diamond sensor
CHENG Chunyang, ZHANG Qi, SHI Fazhan
2019, 49(11): 861-872. doi: 10.3969/j.issn.0253-2778.2019.11.001
As a precision measurement technology based on the principle of quantum mechanics, quantum metrology is becoming an important driving force for the development of various disciplines. The so-called single-spin quantum metrology here has two connotations. One is to use nitrogen-vacancy (NV) center, a kind of point defect in diamond, as single spin quantum information carrier, which could be accessed by optically detected magnetic resonance (MR). The other aspect refers to utilizing NV center as a single-spin quantum sensor through the manipulation of microwave/radio frequency, achieving microscopic MR with high sensitivity and high spatial resolution, and even reaching the level of single electron/nuclear spin detection. This technology replaces the traditional coil detection with quantum sensing, pushing MR study from macroscale to nanoscale, and the sample requirement from billions to single molecule level. Quantum metrology based on NV center is still in the stage of rapid growth. It has been applied in the research of two-dimensional material magnetism, superconductivity, single molecular structure and single cell magnetic detection. It is expected to provide significant support for the development of physics, chemistry, life science and even medicine. In this review, the basic concept and principle of single spin quantum metrology were introduced, and then the recent experimental progress of our group was elaborated on
The effects of light exposure on the nervous system: Advances in researches of effects of light exposure on learning, memory,and emotion
WANG Ziyi, YI lin, CHEN Qi, XIONG Wei
2019, 49(11): 873-877. doi: 10.3969/j.issn.0253-2778.2019.11.002
Light is the most common environmental exposure to all organisms with long lasting effects. Advanced brain functions including learning, memory and emotion and their related behaviors are modulated by light exposure through various mechanisms. Most studies on the effects of light on learning, memory and emotion have mainly focused on psychological and behavioral changes of volunteers and patients.In addition, studies based on animal models have mostly concentrated
Research progress in developing functional polymers for flexible electronics
WANG Zhiyong, WANG Tao, ZHUANG Mengdi, XU Hangxun
2019, 49(11): 878-891. doi: 10.3969/j.issn.0253-2778.2019.11.003
As an emerging technology, flexible electronics is fabricated by integrating flexible organic/inorganic functional materials and flexible substrates using unconventional manufacturing techniques.Compared to conventional electronics,flexible electronics are more compatible for advanced applications such as wearable electronics,human-machine interfaces and soft robotics due to their exceptional mechanical performance.Soft polymers play a crucial role in fabricating flexible electronics. They can be widely used as flexible substrates,functional components, and interfacial modification materials.In certain cases, the intrinsic properties of functional polymers determine the ultimate performance or specific applications of flexible electronics were summarized
Linear inviscid damping for monotonic shear flows under the two dimensional β-plane equation
LUO Xiang
2019, 49(11): 892-896. doi: 10.3969/j.issn.0253-2778.2019.11.004
The linear asymptotic stability of a class of strictly monotonic shear flows was established under the two dimensional β-plane equation in an infinite periodic channel of period 2π, T×R.
Principal eigenvectors of nonnegative tensors and hypergraphs
HAO Huanhuan
2019, 49(11): 897-901. doi: 10.3969/j.issn.0253-2778.2019.11.005
Let T be a nonnegative weakly irreducible tensor, and Q (G) be the signless Laplacian tensor of a connected uniform hypergraph G. Some lower bounds of the principal ratio and some bounds on the entries for the principal eigenvector of T and Q (G) were given, respectively.
The asymptotic behavior of a logistic SIR epidemic model with stochastic perturbation
ZHU Ling
2019, 49(11): 902-911. doi: 10.3969/j.issn.0253-2778.2019.11.006
A asymptotic behavior of a stochastic logistic SIR epidemic model was studied, whose natural death rates are subject to the environmental white noise. First, it was demonstrated that the model possesses non-negative solutions with probability one. Then, the stochastically asymptotical constancy of the equilibrium was obtained by means of the stochastic Lyapunov functional technique, when R0≤1. Additionally, when R0>1, some asymptotic outcomes regarding large time behavior were given. When the noise is small and the diseased death rate is limited, the solution will oscillate around the endemic equilibrium of the deterministic model for a long time, and the fluctuation decreases with the decrease of white noise, which reflects the prevalence of the disease.
The global assessment of MODIS missed liquid water path retrievals in oceanic clouds
LI Jiangmei, WANG Yu
2019, 49(11): 912-919. doi: 10.3969/j.issn.0253-2778.2019.11.007
Liquid water path (LWP) from Moderate Resolution Imaging Spectroradiometer (MODIS) measurement has been used as an important data source in cloud microphysics studies. However, due to the limitation of the visible-band retrieval methods under ice cloud conditions, the LWPs of mixed clouds are usually missed by MODIS. Another retrieval algorithm based on microwave signals can avoid the limitation. In this study, ten years (2002~2011) of
Intra-seasonal and diurnal variations of summer surface thermal environment in the Yangtze River Delta
ZHANG Manyu, WANG Hong, YANG Yuanjian, LI Yubin, SHI Tao, GAO Zhiqiu
2019, 49(11): 920-929. doi: 10.3969/j.issn.0253-2778.2019.11.008
Based on MODIS-based land surface temperature(LST) data, land use and land cover change (LUCC) data and normalized difference vegetation index (NDVI) data, the temporal and spatial characteristics and the associated driving factors of summer surface thermal environment in the Yangtze River Delta(YRD) megalopolis from 2013 to 2017 were investigated. The results show that: ①The summer surface-high-temperature risk zones (i.e.,high LST zone and sub-high LST zone) were mainly distributed in the day time on the farmland covering areas in the north of Anhui, urban architectural covering areas of the YRD and some urban buildings and some farmland in southern Zhejiang, while the surface-high-temperature risk zones transferred to the water-covered areas and urban densely populated areas along the Yangtze River at night. ②The intra-seasonal variations show that from June to August, the surface-high-temperature risk zones gradually shifted from the north of Anhui and the north of Jiangsu to the YRD megalopolis. The study area presents two opposite trends of intra-seasonal variations: the surface-high-temperature risk zones in the northern part of the YRD are gradually mitigating, while the surface-high-temperature risk zones in the YRD Delta megalopolis are gradually increasing. ③The spatial distribution of the surface thermal environment is highly related to the spatial distribution of the underlying surface coverage type, and the surface-high-temperature risk zones of urban construction land areas are significantly higher than other underlying surface coverage types. Summer crop rotations in the northern part of YRD have changed the vegetation coverage of the surface, resulting in the difference between
Large eddy simulation on the wake of a circular disk at a high Reynolds number
XIE Chen, ZHU Minming, CHEN Yiliang
2019, 49(11): 930-939. doi: 10.3969/j.issn.0253-2778.2019.11.009
Large eddy simulations (LES) were performed to study the turbulent characteristics in the wake of a circular disk normal to the free air stream (the diameter of the disk is 40 mm, thickness is 8 mm). The Reynolds numbers are 1×104, 1×105and 2.5×105 respectively. It was found that when Re>1×104 , the distributions of mean velocity and Reynolds stress as well as drag coefficient vary little with Re. Drag coefficient is mainly contributed by the pressure difference between the front and rear of the disk. By means of power spectral density analysis, three most influential instability mechanisms are disclosed in the large scale structure of a disk’s near wake: a very low frequency (St≈0.028) corresponding to the recirculation bubble pulsation along an axis of symmetry; a natural frequency (St≈0.138~0.146) related to antisymmetric helical vortex shedding; and a high frequency (St≈1.437) associated with Kelvin-Helmholtz instability of the separated shear layer.
Numerical simulation of non-reacting flow fields in combustors
ZHANG Hongda, WAN Bin, ZHANG Chengkai, LIN Hongjun, SHANG Shoutang, HAN Xingsi, YE Taohong
2019, 49(11): 940-946. doi: 10.3969/j.issn.0253-2778.2019.11.010
Very large eddy simulation (VLES) was performed to study non-reacting flow fields in a combustor. Large scale vortex structures were investigated in the flow fields. A benchmark case for turbulent swirling flow in circular tube was studied by numerical simulation. The accuracy of VLES method was verified by a comparison with experimental data. The simulation results show that the shape of the recirculation zone in the combustor is reasonable. The counter-rotating vortex pairs are generated by the interaction between a large hole jet and a crossflow in the combustor. The jet trajectory formula given by Rothstein can reasonably predict the jet penetration of the main combustion hole. The precessing vortex core (PVC) originates from the combustor head swirler. The power spectral density was employed to predict the characteristic frequency of flow oscillation induced by PVC.