Journal of University of Chinese Academy of Sciences

Convolution integral restricted on closed hypersurfaces

DU Wenkui, YAN Dunyan

2019, 36 (5): 577-580. DOI: 10.7523/j.issn.2095-6134.2019.05.001

The classical convolution integral on Euclidean space is given as follows. For f∈L¹(Rⁿ) and g∈L^p(Rⁿ), T_f(g) is defined as
T_f(g)(x):f*g(x)=∫_Rⁿf(x-y)g(y)dy.
It has many applications in analysis and engineering. Young's inequality demonstrates that T_f:L^p(Rⁿ)→L^p(Rⁿ) is a bounded operator for 1 ≤ p ≤ ∞. In this study, we have obtained the estimation of the L^p norm of convolution integral restricted on closed hypersurfaces. More precisely, we have established Young's inequality on closed hypersurfaces.

Bulk-edge correspondence of light manipulated electrons on Shastry-Sutherland lattice

JIN Yuesu, SU Gang

2019, 36 (5): 581-589. DOI: 10.7523/j.issn.2095-6134.2019.05.002

Abstract ( 305 ) PDF (KB) ( 0 )

Electrons on Shastry-Sutherland (SS) lattice have plentiful properties. We use Floquet theory to demonstrate that a high-frequency circularly polarized light exerted on such a system generates phases including Dirac fermion, semi-Dirac fermion, quadratic band touch, SO(3) fermion gapless phases, and a gapped phase. In the presence of the spin-orbit coupling, those four gapless phases are shown to be topologically equivalent because of the opening of a gap. Through calculating the edge states of a nanoribbon, we further verify that those four gapless phases become topological insulators after the opening of gap according to the bulk-edge correspondence. Besides, we also find the bulk-edge correspondence between the bulk anisotropic dispersion of semi-Dirac fermion and its nanoribbon truncated along two different directions.

Parallel/coincident D-brane superpotentials, Ooguri-Vafa invariants, and Type II/F theory duality

JIANG Xiaotian, YANG Fuzhong

2019, 36 (5): 590-597. DOI: 10.7523/j.issn.2095-6134.2019.05.003

Abstract ( 275 ) PDF (KB) ( 11 )

The superpotential is very important physical observation in the topological string theory, and it determines the F-term of the low-energy effective theory and the string vacuum structure. Ooguri-Vafa invariants, as the counting number of BPS states, can be extracted from the superpotential, giving rise to the energy spectrum of the D-brane system. We compute the superpotentials and Ooguri-Vafa invariants for complicated D-brane system, namely double D-branes system, in the parallel and coincident phases using the Type Ⅱ/F theory duality for the first time. The coincidence of parallel D-branes leads to the enhancement of gauge symmetry U(1)×…×U(1)→U(n) in terms of gauge theory on the worldvolume of the D-branes being known as the phase transition between the parallel D-brane phase and the coincident D-brane phase. We find the difference between the Ooguri-Vafa invariants for the two phases giving rise to the distinct spectra. It can be viewed as an evidence of the phase transition.

Chiral vortical effect in Weyl semimetals

JI Xuanting, ZHU Zhen

2019, 36 (5): 598-604. DOI: 10.7523/j.issn.2095-6134.2019.05.004

Abstract ( 314 ) PDF (KB) ( 1 )

As the experiments indicate, not only the chiral anomaly but also the gravitational anomaly exist in Weyl semimetal. Gravitational anomaly induces the chiral vortical effect. Hence it is necessary to study the chiral vortical effect in Weyl semimetal. Furthermore, due to the analogy to the graphene, Weyl semimetal may also suffer strong coupling. Based on this, we study the chiral vortical conductivity in a strong coupling Weyl semimetal by AdS/CFT. Under the circumstance where only gravitational anomaly is considered, we obtain the conclusions as follows. 1)Gravitational anomaly induces the chiral vortical effect, which exists in the Weyl semimetal equipped with the chiral fermions, and it is proportional to the coupling strength. 2)Chiral vortical conductivity is proportional to square of temperature.

MHD flow feature, heat transfer, and structural mechanical behaviors in the U-shaped channel

LIANG Siyuan, NI Mingjiu, ZHANG Nianmei

2019, 36 (5): 605-613. DOI: 10.7523/j.issn.2095-6134.2019.05.005

Abstract ( 302 ) PDF (KB) ( 1 )

In the fusion reactor blanket module, a U-shaped channel was investigated. Numerical simulations based on the finite volume method and finite element method were carried out to study magnetohydrodynamic features, heat transfer, and structure mechanical behaviors. The influences caused by flow velocity, magnetic field strength, and structural electrical conductivity were considered. Results suggest that stronger magnetic field and higher inlet velocity lead to higher outlet fluid temperature. With larger flow channel insert conductivity, ‘M-shaped’ velocity profiles were observed. Considering structural thermal stresses, the most dangerous area is near the side wall in the bend segment. Thermal deformation of the flow channel insert increases with the magnetic field magnitude, and thermal stresses decrease with the increase of inlet velocity. The electrical conductivity has little effect on structural stresses and strains. This work provides valuable information for the design of blanket modules.

Structure design of power feeding nozzle for wide-band laser cladding and investigation of powder flow

CHEN Ru, YU Gang, HE Xiuli, ZHANG Yue, LI Shaoxia

2019, 36 (5): 614-619. DOI: 10.7523/j.issn.2095-6134.2019.05.006

Abstract ( 240 ) PDF (KB) ( 1 )

In this work, we designed a new structure of powder feeding nozzle for wide-band laser cladding and effectively solved the problem of excessive divergence angle in the scanning direction by using multi-channel exits. The powder flow concentration in the vertical scanning direction was adjusted by adding an internal cylinder. Discrete phase model was built for investigation of the particle mass concentration. The cylinder diameter was optimized to obtain wide-band powder flow with uniform concentration distribution and wide-band coating with uniform thickness.

Structures and photophysical properties of four copper(I) complexes based on cyclic thiourea

CHAI Ke, GAO Yueze, ZHANG Jing

2019, 36 (5): 620-625. DOI: 10.7523/j.issn.2095-6134.2019.05.007

Abstract ( 252 ) PDF (KB) ( 1 )

Cyclic thiourea copper(I) complexes, 1-Cu(TU)I, 2-Cu(TU)₂I, 3-[Cu(TU)₂](BF₄), and 4-[Cu(TU)₂](PF₆), were successfully prepared by solvothermal method. By adjusting the molar ratio of the ligand to the cuprous salt and the anion in the cuprous salt, we got four coordination complexes and characterized their structures by X-ray single crystallography. The photophysical properties of these four complexes were measured. Complex 1 exhibited modest SHG response of 1.1 times response of potassium dihydrogen phosphate(KDP). Under excitation at either 392 or 335 nm, complexes 3 and 4 showed the phosphorescence at 517 and 520 nm, respectively, and high quantum yields in solid state at room temperature.

The main factors influencing urban living resource consumption and pollution emission in China

YANG Xiaojiao, WANG Xiaoke

2019, 36 (5): 626-632. DOI: 10.7523/j.issn.2095-6134.2019.05.008

Abstract ( 286 ) PDF (KB) ( 1 )

The guarantee of the resource and environment directly affects the speed and quality of China's urbanization and restricts the sustainable development of urbanization. Based on the correlation analysis and redundancy analysis, we studied the main factors influencing urban living resource consumption and pollution emission. The results are showed as follows.1) The main influencing factors on the consumption of living resource in China's provincial capital cities were climate (the explained variation being 0.40), followed by economic development level (0.14) and urban scale (0.11). 2)The urban scale was the main influencing factor on pollution emission (the explained variation being 0.21), followed by economic development level (0.17) and climate (0.16). Therefore, it is of great significance to the sustainable development of China's cities to formulate appropriate policies of resource development and environmental governance in view of the factors affecting urban resource consumption and pollution emission.

Comparative analysis on the benefits of cultivated land use between the reclamation areas and rural areas in western part of Heilongjiang Province

PAN Xiaohui, ZHANG Pingyu, LIU Shiwei, CHU Nanchen

2019, 36 (5): 633-641. DOI: 10.7523/j.issn.2095-6134.2019.05.009

Abstract ( 239 ) PDF (KB) ( 1 )

The benefit of cultivated land use is closely connected with the land management models. Based on the data on the cultivated land use of the reclamation area and rural area in western Heilongjiang Province from 2006 to 2015, the evaluation index system of the cultivated land use was constructed to measure the economic-social-ecological benefits of cultivated land use by the entropy method. Based on the coupling coordination degree model, the coupling phases and coordination types were divided to make the comparative analysis on the benefit differences in cultivated land use between the reclamation areas and rural areas in western Heilongjiang Province. The results are given as follows. 1) The benefits of cultivated land use in the reclamation areas slowly increased from 2006 to 2015, while the benefits fluctuated and declined in the rural areas. The economic and social benefits were higher than the ecological benefits in both the reclamation areas and rural areas. 2) In 2015, the economic, social, and comprehensive benefits of cultivated land use in the reclamation areas were higher than in the rural areas, while the ecological benefits in the reclamation areas were lower than in the rural areas. The coupling degrees among the economic, social, and ecological benefits in both the reclamation and rural areas showed rivalries. The coordination degrees in the reclamation areas were relatively coordinate, while in the slight disorder in the rural areas. 3) Different land management models led to differences in the benefit of cultivated land use between these two types of areas. In the process of utilizing the cultivated land, it is suggested to explore land management models and to emphasize the coordinated development among the economic, social, and ecological benefits.

Development of foreign trade between Xinjiang of China and Central Asia over the past decade

HE Shuling, DU Hongru

2019, 36 (5): 642-649. DOI: 10.7523/j.issn.2095-6134.2019.05.010

Abstract ( 345 ) PDF (KB) ( 0 )

This study makes a comparative analysis of the changes of foreign trade between Xinjiang of China and the countries in Central Asia from 2005 to 2014. The dynamic changes of bilateral trade, trade unions, trade balance, and trade development environment on the time scale are explored. The study results are shown as follows. 1) The trade volume between Xinjiang and countries in Central Asia has increased in the past years. However, in terms of trade with Central Asian countries, Xinjiang's dominant position in China has decreased gradually in the past years. 2) The bilateral trade has a high degree of integration, while the degree of dependence on trade is decreasing year by year. 3) There is a large surplus in the trade of Xinjiang with the countries in Central Asia, and the difference is expanding. 4) The trade development environment in Xinjiang is superior to those in Central Asian countries, and bilateral trade environment has been improved in recent years. In order to optimize the trade between the two sides, we put forward the suggestions for the trade development as follows. 1) The development of processing trade in Xinjiang should be strengthened to improve the digestion capacity of imported raw materials. 2) The imports from Central Asian countries should also be strengthened to balance the trade gap. 3) The bilateral free trade areas should be constructed to offer new chances to develop the trade cooperation among the countries.

The first flush effect of urban rainfall runoff based on MFF₃₀ method

LI Qi, ZHANG Na, LUO Yingjie, WANG Xin, JING Yongcai

2019, 36 (5): 650-662. DOI: 10.7523/j.issn.2095-6134.2019.05.011

Abstract ( 251 ) PDF (KB) ( 0 )

It is of great significance to reasonably discriminate the first flush effect of rainfall runoff, scientifically evaluate the flushing strength, and explore the factors influencing the first flush effect. In the present study, the corrected five-level classification criteria of MFF₃₀ (the ratio of cumulative pollution load ratio to cumulative runoff ratio when the top 30% of surface runoff occurs) were developed. Overland flow processes and runoff water quality were measured within the seven different subcatchments during the seven rainfall events in Beijing, and the factors that influenced the TSS, COD, and TN flushing strengths were analyzed. The results showed that the first flush effects could be explicitly quantified and compared by using the corrected MFF₃₀ method. If other precipitation or underlying surface conditions were similar, antecedent dry days, dynamic variation in rainfall intensity, surface slope and width of the subcatchment, and traffic flow greatly made the impact on the first flush effect.

Analysis of lunar irradiance model based on the SeaWiFS lunar observations

ZENG Xiangzhao, TANG Lingli

2019, 36 (5): 663-670. DOI: 10.7523/j.issn.2095-6134.2019.05.012

Abstract ( 323 ) PDF (KB) ( 0 )

As the unique natural satellite of the Earth, the Moon has been studied for a long time. Since the lunar reflectance is very stable due to the absence of water and atmosphere, the Moon is very suitable as a reference standard for radiometric calibration of on-orbit sensors. Based on the Earth-based lunar observations, the lunar irradiance models were developed. However, the precisions of the current models are limited. Based on the SeaWiFS lunar observations, the influence factors on lunar reflective property and the current models, ROLO and MT2009, are analyzed for improving the current models.

The method of aerosol retrieval using Himawari-8 satellite data and its application in monitoring haze process

NIU Xiaojun, TANG Jiakui, ZHANG Zili, CUI Linli, XING Weipeng, SONG Yi

2019, 36 (5): 671-681. DOI: 10.7523/j.issn.2095-6134.2019.05.013

Abstract ( 516 ) PDF (KB) ( 0 )

Haze disaster is characterized by spatio-temporally dynamic changes.Himawari-8 is a new generation of geostationary meteorological satellite launched by Japan Meteorological Agency, and it is very suitable for haze process dynamic monitoring due to its observational ability in wide range, high frequency, and high spatial resolution. A new algorithm was proposed to retrieve aerosol optical thickness using the ratio of Himawari-8 visible band surface reflectivity, and the retrieval evaluation experiments were carried out on May 17, 2017 and May 18, 2017, the two haze days, in Beijing area. The retrieval results showed that the proposed method is the best in retrieval accuracy, retrieval effective spatial and temporal ranges, and spatial resolution by comparing the results with the observation data of the three international AERONET sites of Beijing, Beijing-CAMS, and Beijing-PKU, the Himawari-8 official aerosol products, and the MODIS official aerosol products. Finally, based on the analysis of hourly-level AOD retrieval results on the two haze dates, temporal changes of the haze process in Beijing area were discussed. Based on the retrieval images of the time series, we clearly observe the moving direction of the pollution center and the increasingly or decreasingly dynamic changes of the haze, which shows that the proposed Himawari-8 algorithm has potential application for the dynamic monitoring of haze process.

PolSAR remote sensing image method for building extraction based on polarization and texture characteristics

MA Xiaoxiao, CHENG Bo, LIU Yueming, CUI Shiai, LIANG Chenbin

2019, 36 (5): 682-693. DOI: 10.7523/j.issn.2095-6134.2019.05.014

Abstract ( 376 ) PDF (KB) ( 0 )

Polarimetric synthetic aperture radar (PolSAR) plays an important role in the field of building extraction because of its multi-parameter, multi-channel, multi-polarization, and rich information records. Taking Radarsat-2 image of Suzhou in 2017 as an example,19 polarization features and 8 texture features are extracted by polarization non-coherent decomposition methods and GLCM, respectively. Based on the analysis of features, we obtain the results of building extraction by PCA feature fusion and SVM algorithm. The results show that the extraction accuracies based on polarization features and texture feature are 92.4% and 88.9%, respectively. The accuracy is 93.7% when the polarization and texture features are used together. The combination of polarization and texture features improves the accuracy and the PCA feature fusion increases both efficiency and precision.

Multi-region and multi-physics coupled 3D numerical simulation of enhanced geothermal system

DING Junfeng, WANG Shimin

2019, 36 (5): 694-701. DOI: 10.7523/j.issn.2095-6134.2019.05.015

Abstract ( 331 ) PDF (KB) ( 0 )

Studies on enhanced geothermal system (EGS) are important for developing geothermal power generation. As an EGS typically involves multi-regional and multi-physical coupling and the in-well flows are turbulent, it is necessary in EGS numerical simulation to handle regional coupling correctly, represent in-well turbulence reasonably, and achieve sufficient computational accuracy and efficiency. In this study, the processes of porous flow and heat transfer associated with EGS are systematically investigated based on a multi-region and multi-physics coupled 3D finite element model. The obtained results are given as follows. 1) The natural coupling of temperature, pressure, and velocity fields between different EGS regions can be successfully realized in terms of correctly posed connection conditions. 2) Different turbulence models for in-well flows predict essentially consistent in-well pressure variation. The turbulence pressure drop across the well depth is predicted to be about 4 times as large as the laminar pressure drop but 3 orders of magnitude smaller than the overall pressure drop from the injection well to the production well, resulting in insignificant influence of in-well turbulence on the EGS heat extraction process. 3) With the vertical variations of EGS structure and thermophysical properties, the natural convection inside the reservoir, and the effects of in-well turbulence all being negligible, an EGS is dominated by horizontal porous flow and horizontal convective heat transfer, and thus may be approximately simulated by 2D modeling.

An improved ICP method using Gaussian curvature

WANG Feipeng, XIAO Jun, WANG Ying, WANG Yunbiao

2019, 36 (5): 702-708. DOI: 10.7523/j.issn.2095-6134.2019.05.016

Abstract ( 496 ) PDF (KB) ( 0 )

As one of basic topics of computer vision, 3-D point cloud registration has been studied for decades. Among the works, ICP (iterative closest point) is the most well-known algorithm for its simplicity and accuracy. However, due to its iteratively greedy strategy, ICP is time consuming, prone to local minima, and hence susceptible to noise and outliers. In the work, we present a method to improve the performance of ICP in terms of both efficiency and robustness. Firstly, the method estimates Gaussian curvature of each point in the point clouds. Secondly, the method filters out those points which are considered to be trivial points, outliers, and noise. Then, the method applies ICP to the remaining points. The results demonstrate that our method improves both efficiency and resilience against outliers and noise of ICP without causing accuracy degeneration.

Synthesis and aggregation induced emission of quinoline-based oligoamide helical foldamers capped with bromobenzene

WANG Wentao, LIU Yanwei, MU Wenjing, QI Ting

2019, 36 (5): 709-715. DOI: 10.7523/j.issn.2095-6134.2019.05.017

Abstract ( 214 ) PDF (KB) ( 22 )

Two bromobenzene-capped quinoline-based oligoamide foldamers with different lengths and different side chains are designed and synthesized. The compounds have been characterized by UV-Vis, fluorescence spectra, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The results show that the side chains have no effects on the morphology of the aggregated state and the different aggregated morphologies have great influence on the fluorescence intensity. The photoluminescence behavior of the compounds in THF-H₂O binary solvent system and films has been studied, and these compounds display aggregation-induced emissions (AIE). They hardly emit light in the solution state, whereas the photoluminescence intensity in the solid state is several dozen times higher than that in THF-H₂O binary solvent system. This AIE phenomenon is caused by the stable helical structure of foldamers which restricts the intramolecular random rotation of single bonds and intermolecular closest packing. Moreover, the AIE effect of the foldamers is strongly affected by solvents.

1D barcode fast localization technology based on image processing

JI Qinqin, HUANG Lu

2019, 36 (5): 716-720. DOI: 10.7523/j.issn.2095-6134.2019.05.018

Abstract ( 588 ) PDF (KB) ( 0 )

In this paper we demonstrate the implementation of the fast localization of 1D-barcode based on digital image processing techniques. First, we conduct the edge detection and binary quantization on the input image. Then, we use digital morphological processing to obtain the candidate region of the barcode and adopt the gradient feature to extract the edge line of the region. Finally, we select the area of the barcode by utilizing the fact that the blank areas are parallel to each other. The algorithm is tested on two barcode data sets:WWU Muenster and ArTe-Lab. The results show that our algorithm is faster than the existing algorithms and therefore is more suitable for real-time applications.

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