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Adsorption and migration of Li-ion in layered SnSe2: a first principle study
- FANG Lincan, HAO Kuanrong, YAN Qingbo, ZHENG Qingrong
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2018, 35 (6):
735-742.
DOI: 10.7523/j.issn.2095-6134.2018.06.004
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Abstract (
457 )
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The properties of Li-ion adsorption and migration in layered SnSe2 are systematically investigated using the first principle calculations. It is found that the Li atoms are adsorbed strongly on substrate SnSe2, and the binding energy (>3eV) is significantly higher than those on graphene, phosphorene, MoS2, and some other two-dimensional (2D) layered materials. Bader charge analysis reveals that almost the whole charge of 2s electron of the Li atom transfers to substrate SnSe2 and Li exists in the cationic state. The Li-ion migration energy barrier for monolayer SnSe2 is 0.197eV, which is significantly lower than those for graphene, MoS2, and other 2D materials. The average open-circuit voltage of 3.05V is predicted in the monolayer SnSe2-based Li-ion battery. The Li intercalation also leads to a transition from semiconductor to metallic state and gives rise to a good electrical conductivity. These findings provide insights into the Li-ion adsorption properties and migration mechanism in layered transition-metal dichalcogenide.
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Effects of crack orientations on crack stress intensity factors in a bearing
- LIU Long, SHI Junbo, DING Ning, WU Lawrence Chiman
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2018, 35 (6):
743-748.
DOI: 10.7523/j.issn.2095-6134.2018.06.005
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Abstract (
349 )
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Effects of crack orientations on stress intensity factors were studied using the finite element analysis method. We considered the angle between the crack orientation and inner ring axial direction and the angle between the crack orientation and inner ring radius direction. The results indicate that when the angle between the crack orientation and inner ring axial direction is about 10°, the crack propagation rate reaches a maximum and the equivalent stress intensity factor is 0.22MPa·m0.5. The crack propagation rate reaches a minimum and the equivalent stress intensity factor is 0.039MPa·m0.5 when the angle between the crack orientation and inner ring axial direction is about 90°. When the angle between the crack orientation and inner ring radius direction is about 10°, the crack propagation rate reaches another maximum and the equivalent stress intensity factor is 0.19MPa·m0.5. When the angle between the crack orientation and inner ring radius direction is about 80° or -80°, the crack propagation rate reaches another minimum and the equivalent stress intensity factor is about 0.15MPa·m0.5. These results indicate that the crack orientation influences the crack propagation rate significantly.
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Gradient variation of δ15N values in herbs and its indication to environmental information in the agro-pastoral ecotone in the north of China
- LIU Xianzhao, ZHANG Yong, SU Qing, LI Zhenguo, FENG Teng, SONG Yan
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2018, 35 (6):
749-760.
DOI: 10.7523/j.issn.2095-6134.2018.06.006
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Abstract (
334 )
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Nitrogen isotope signature (δ15N) in plants is an effective indicator for evaluating ecosystem nitrogen cycling and monitoring changes of climate environment. Investigation of δ15N for herbs and soils was conducted along the 400mm isoline of annual mean precipitation in the agro-pastoral ecotone in the north of China(APENC). The relationships between the δ15N values and environmental factors were analyzed. The main results are shown as follows. 1)The δ15N values of all herbs in this region ranged between -5.5‰ and -15.3‰ (the mean value:4.02‰). The C3 herbs had a wider range of the δ15N value (-5.5‰-15.0‰) and a significantly lower mean value than the C4 herbs (-2.85‰-15.3‰). The soil δ15N value varied from 1.42‰ to 9.11‰ with a mean value of 4.74‰. 2)The δ15N values of the C3 and C4 herbs and 2 eurytopic species were all positively correlated with the latitude and longitude(except the relationship between δ15N of C4 herbs and longitude), while displayed a weak relationship with the altitude. 3)The δ15N values of herbs amd soil showed obviously negative trends with temperature. The δ15N-temperature coefficients for C3 and C4 herbs were -0.41‰/℃ and -0.39‰/℃, respectively. However, the δ15N values of herbs showed a weak negative trend with precipitation. 4)Partial correlation analysis showed that the correlation between δ15N and the annual mean temperature was more significant after controlling precipitation. However, the relation between herbs δ15N and the annual mean precipitation was weaker after controlling temperature. This study indicates that the temperature may be a key factor affecting plant δ15N under the condition of little moisture change, and the δ15N value may provide an indication to temperature changes in APENC.
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Shape changes of Bohai Sea since the early 1940s
- SONG Yang, ZHANG Hua, HOU Xiyong
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2018, 35 (6):
761-770.
DOI: 10.7523/j.issn.2095-6134.2018.06.007
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Abstract (
395 )
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China has experienced several booms in sea reclamation since the mid-20th century. The reclamation in Bohai Rim expanded dramatically in a scale much larger than in other coastal zones in China, especially since 2 000. Therefore, based on topographic maps, nautical charts, and multi-temporal remote sensing imageries, the two-dimensional centroid, three-dimensional centroid, shoreline, low tide line, depth contour, bay area, and water volume of Bohai Sea since the 1940s were extracted and analyzed to reveal the tendencies, characters, and driving factors of long-term shape changes of Bohai Sea. The results indicate that, during the past 70 years, the area of Bohai Sea decreased continuously and that shoreline, low tide line, and 5 m isobaths shifted toward the sea in most coastal areas. Consequently, the two-dimensional centroid of Bohai Sea moved northeastward significantly, while the perimeter increased remarkably and the geometric shape became complicated. During the past 50 years, overall, the volume of Bohai Sea declined and the three-dimensional centroid dived significantly. The development of estuary delta and sea reclamation were the fundamental driving forces of long-term shape changes of Bohai Sea. However, the human forces have gradually exceeded the natural forces.
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A method for surface soil moisture estimation based on the DTR-FVC space
- RU Chen, DUAN Sibo, JIANG Xiaoguang, LENG Pei, GAO Maofang, HUO Hongyuan, LI Zhaoliang
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2018, 35 (6):
771-781.
DOI: 10.7523/j.issn.2095-6134.2018.06.008
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Abstract (
384 )
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Soil moisture is a key parameter for the studies of climatology, hydrology, and ecology. The commonly used remotely sensed approach is based on the land surface temperature-vegetation index (LST-VI) space. With the Meteosat Second Generation-Spinning Enhanced Visible and Infrared Imager (MSG-SEVIRI) data, the study is conducted over Ibérian Peninsula. In this study, we use the diurnal temperature range (DTR), instead of surface temperature, to compose a diurnal temperature range-fraction vegetation coverage (DTR-FVC) space. Based on the DTR-FVC space, the soil moisture retrieval model is established to estimate soil moisture with the soil texture data. The results are validated by in situ measurements from 19 meteorological stations in Spain, and the root mean square error (RMSE) is about 0.05m3/m3. Compared with the LST-VI space, the DTR-FVC space reduces the retrieval error caused by the uncertainty of instantaneous land surface temperature, and thus the accuracy of soil moisture is improved.
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Automatic extraction of urban road information based on mobile laser scanning data
- ZHAO Haipeng, XI Xiaohuan, WANG Cheng, LEI Zhao
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2018, 35 (6):
782-787.
DOI: 10.7523/j.issn.2095-6134.2018.06.009
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Abstract (
328 )
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Extracting accurate road information is of vital importance in urban planning and digital city mapping. We used high-density point clouds collected by mobile laser scanning(MLS) systems, and proposed a novel approach based on road boundary detection in curb missing areas. First, the road was roughly extracted by using plane detection algorithm. Next, we analyzed the difference in laser reflection intensity and geometry attribution between road boundary and two sides of surface and retrieved the point clouds of boundary by setting reasonable threshold. Finally, the road surface was accurately extracted based on curve fitting of discrete points. To evaluate the performance of the proposed method, experiments were conducted using urban point clouds data. The extraction method achieves correctness, completeness, and quality rates of above 90%, which indicates that the proposed method effectively detects road boundary and extracts road surface accurately in curb missing urban areas.
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Very high resolution (VHR) SAR image simulation for buildings
- REN Miaomiao, PAN Zhuo, XU Xianghui, SU Haitao
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2018, 35 (6):
788-794.
DOI: 10.7523/j.issn.2095-6134.2018.06.010
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Abstract (
325 )
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In this study a very high resolution SAR (VHR SAR) simulation method is proposed based on the geometrical signatures of buildings. Firstly, the imaging scene model is constructed,and an improved Phong Shading model is used as approximate scattering model. Then, the scattering and coordinate information is obtained by tracing rays in the scene. To make the simulation images more realistic, a post process is completed. Finally, a real VHR SAR building image is obtained by two-dimensional imaging. Analysis and simulation results validate that the proposed method describes the geometrical and radiant signatures correctly and efficiently in SAR image. The simulated images provide effective database for understanding SAR images.
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Social spatial structure of Urumqi City during the period of Republic of China
- JIA Xiaoting, LEI Jun, ZHANG Xiaolei
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2018, 35 (6):
795-804.
DOI: 10.7523/j.issn.2095-6134.2018.06.011
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Abstract (
452 )
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Based on the developing process of urban space of Urumqi City, this work reveals the evolution characteristics of the socio-spatial structure during the period of Republic of China. In the early period, Urumqi was divided into five social areas:Manchu soldiers residential area, Han businessmen residential area, Uygur and Hui residential area, Russian immigrants residential area, and agricultural population residential area. In the late period, inside the city there were government area and Han businessmen residential area, but outside the city there were Uygur and Hui residential area and agricultural population residential area. In the context of warlord rule, the surrounding powerful nationstates, and immigration,urban social space of Urumqi started to show overall difference between the inside and outside of the city in races, social class, and culture. The powers of government and military were the leading factors for the evolution of urban social spatial structure of Urumqi. The multi-culture and multi-ethnic history was the fundamental factor for the evolution of Urumqi socio-spatial structure. The ethnic policy, the development of urban business, and the population urbanization are the direct factors for the evolution of Urumqi socio-spatial structure.
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A supervisory game model for village committees' behavior in the marketilization of rural commercial collective-owned construction land
- LIU Jingyu, YIN Qi, TANG Hong, ZHANG Zhan
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2018, 35 (6):
805-813.
DOI: 10.7523/j.issn.2095-6134.2018.06.012
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Abstract (
242 )
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In order to suppress the village committees' rent-seeking behavior effectively, this study establishes a supervision game model between the local supervisory authorities and village committees, and analyzes the factors that affect the rent-seeking and supervising behavior of rural collective management land in China. The results show that the probability of selecting a rent-seeking strategy by the village committees is affected by the cost of the local supervisory authority, the probability of strict supervision, the probability of detection (the probability of no strict monitor), and the effects of distortion and punishment. The probability of strict monitor by the local supervisory authorities is affected by the probability of detection (the probability of no strict monitor/strict monitor) and the punishment. Therefore, this study suggests that a combination model of national and social supervision is needed to smooth the channels of public supervision and reduce the monitoring cost of the local supervisory authorities. At the same time, the network monitoring should be improved by the national administrative legislation. Finally, the punishment from the political and economic aspects should be strengthened.
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Establishment of the relationship between contamination concentration and electrical resistivity in shallow aquifer based on groundwater numerical modeling
- ZHAO Shaohua, DONG Yanhui, LI Xuelan, WANG Liheng
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2018, 35 (6):
814-821.
DOI: 10.7523/j.issn.2095-6134.2018.06.013
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Abstract (
480 )
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Geophysical method is an important technique in groundwater contamination investigation. The geoelectrical method is capable of mapping both low and high resistivity and has been commonly used to explore concentration of contamination in groundwater. How to convert apparent resistivity of groundwater into concentration distribution of contamination in groundwater should be first considered carefully. Therefore, it is necessary to establish a relationship between electrical resistivity and contamination concentration for concentration estimation using geoelectrical information. We present a method for establishing this relationship based on groundwater numerical model. In this method, the relationship of electrical information and concentration information is obtained by comparing the contamination data from solute transport model with the electrical resistivity data from geophysical forward and inverse modeling. The results show that there is a clear relationship between the electrical resistivity and contamination concentration, which also has a spatial heterogeneity. The applications of the relationships established using linear fitting and polynomial fitting both are better than that by converting electrical resistivity data to concentration directly using Archie's law. In addition, the relationship established using polynomial fitting is better than that using linear fitting in some cases. The method proposed in this work has great potential for estimating the concentration of groundwater concentration based on geoeletrical data.
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A fast factorized back-projection approach based on chirp modulation
- LIN Jianhe, LÜ Xiaolei
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2018, 35 (6):
822-831.
DOI: 10.7523/j.issn.2095-6134.2018.06.014
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Abstract (
334 )
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The inefficiency of the BP algorithm greatly limits its application in wide range scenarios and occasions of high real-time requirements. In this work, we propose a fast factorized back-projection approach based on chirp modulation, which combines the two kinds of fast BP algorithms based on the concept of the equivalent distance. On one hand, the proposed algorithm reduces the length of equivalent synthetic aperture by the chirp modulated back projection (CMBP) algorithm. On the other hand, the proposed algorithm reduces the number of synthetic aperture by the fast factorized back projection (FFBP) algorithm. We argue that the physical meaning of the polar angle of the equivalent distance remains the same, and points within a range of pixel space still have approximately equal equivalent distances. Therefore, the FFBP algorithm can be realized through the equivalent distance. Simulation and experimental data validate the effectiveness of the algorithm.
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Preparation of nano-TiO2 dispersion solution and its photocatalytic activity
- WU Zhijiao, ZHAI Yanqing, GUO Rui, CAO Baosheng, PIAO Lingyu
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2018, 35 (6):
832-838.
DOI: 10.7523/j.issn.2095-6134.2018.06.015
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Abstract (
692 )
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In this work, a kind of nano-TiO2 dispersion solution with excellent dispersity and stability was prepared and its photocatalytic activity was studied. The TiO2 nanoparticles (NPs) with particle size of 30nm were prepared using a combined method of precipitation and solvothermal. The morphology, structure, and surface state of TiO2 NPs were characterized by transmission electron microscope (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectra (FT-IR), and X-ray photoelectron spectroscopy (XPS). The results show that the TiO2 NPs are of anatase type with uniform particle size and good dispersion. Without surface modification, the prepared TiO2 dispersion solution keeps transparent after aged for 180 days at room temperature. Under UV irradiation, the dispersion shows excellent photocatalytic activity on degradation of rhodamine B. The aluminum substrates exhibit good self-cleaning ability after modification by the prepared dispersion.
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Dissociation and physical properties of methyl iodide in external electric field
- ZHANG Xiangyun, LIU Yuzhu, MA Xinyu, QIN Chaochao
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2018, 35 (6):
839-844.
DOI: 10.7523/j.issn.2095-6134.2018.06.016
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Abstract (
348 )
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As a kind of toxic methylation reagent and disinfectant, methyl iodide (CH3I) is widely used. It is important to study the basic physical properties of methyl iodide and to use effective measures to degrade it. The ground states of methyl iodide in different electric fields from 0 to 0.04a.u.(atomic unit) are optimized using the B3LYP calculation with the LANL2DZ basis set. Optimized parameters, total energies, bond lengths, dipole moments, the highest occupied molecular orbital energies, the lowest unoccupied molecular orbital energies, energy gaps, infrared spectra, and dissociation potential energy surface (PES) are obtained. The obtained results show that when the external electric field gradually increases from 0 to 0.04a.u. along the molecular axis Z (the C-I bond direction), the total energy decreases while the dipole moment increases. The C-I and C-H bond lengths increase gradually. The energy gap first increases and then decreases with the external electric field. Further studies show that when the external electric field increases from 0 to 0.04 a.u., the dissociation PES along the C-I bond becomes unbound with the potential energy barrier disappearing. The external electric field of 0.04 a.u. is sufficient to induce the degradation of methyl iodide with the C-I bond breaking. This work provides an important support for the degradation of methyl iodide in the external electric field.
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Effects of particle sizes and C/N ratios on the nitrogen removal performance in CANON system
- LI Jinqing, HAN Xiaoyu, HUANG Jing, ZHANG Shujun, LIU Honghui, LIU Xinchun
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2018, 35 (6):
845-850.
DOI: 10.7523/j.issn.2095-6134.2018.06.017
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Abstract (
311 )
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4
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High ammonia nitrogen wastewater was treated in an integrated anaerobic ammonia oxidation SBR reactor. Effects of particle sizes (R1:0.2-0.5mm,R2:0.5-1mm,R3:>1mm) and C/N ratios on the nitrogen removal from granular sludge were studied. The results showed that the AOB activities of R1, R2 and R3 decreased in turn; R2 had the highest NOB activity, followed by R1, and R3 had the lowest; and R2 had the highest activity of ANAMMOX, followed by R1, and R3 had the lowest. When the C/N ratio increased, the granular sludge morphology changed obviously, and microscopic examination showed that the middle red part gradually reduced and peripheral yellow encirclement occurred. The total nitrogen removal load reduced from 0.59kg/(m3·d) to 0.34kg/(m3·d), and the total nitrogen removal rate increased from 94.75% to 95.07% and then decreased to 87.55%. The results showed that the C/N ratio should not exceed 1.5 in CANON process.
