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Generalized Reflection-Transmission Coefficient Method for Synthesizing Theoretical Seismograms in a Spherical Earth Model
YANG Limeng, CHEN Xiaofei
Acta Scientiarum Naturalium Universitatis Pekinensis    2025, 61 (6): 1071-1079.   DOI: 10.13209/j.0479-8023.2025.085
Abstract1018)   HTML    PDF(pc) (830KB)(263)       Save
For a spherical layered Earth model, by assuming that the medium parameters in each layer follow specific variation laws and introducing earth flattening transformation, the ordinary differential equations (ODEs) with variable coefficients in the spherical model are transformed into ODEs with constant coefficients that can be solved using the generalized reflection-transmission coefficient method (GRTCM), and the theoretical seismograms are calculated. Numerical results show that the generalized reflection-transmission coefficient method is accurate and efficient for computing theoretical seismograms at epicentral distances within 100 degrees. The error of the method will be significantly reduced as the layer thickness of spherical model is reduced. 
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Computation of Toroidal Modes in a Spherical Non-Gravity Elastic Earth Model Using a Family of Secular Functions
YANG Limeng, CHEN Xiaofei
Acta Scientiarum Naturalium Universitatis Pekinensis    2025, 61 (6): 1064-1070.   DOI: 10.13209/j.0479-8023.2025.084
Abstract881)   HTML    PDF(pc) (816KB)(253)       Save
When using the exact flattening transformation method to compute the oscillation modes, root-leakage issues can easily arise during the root-search phase. By introducing the exact flattening transformation within the framework of the generalized reflection-transmission coefficient method (GRTCM), this method can be extended to the spherical non-gravity elastic Earth model. Subsequently, using the duration function families, we calculate the toroidal modes in this model. The results of the proposed method align closely with the precise outcomes from MINEOS.
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An Overview of EMRI Data Analysis
ZOU Xiaobo, Soumya Mohanty, XIE Qunying, CHEN Xian, LUO Honggang, LIU Yuxiao, HAN Wenbiao, JIAO Jiageng, ZHANG Xuehao, ZHAO Shaodong, GUO Yiyang, WANG Hanzhi, JIN Shuzhu
Acta Scientiarum Naturalium Universitatis Pekinensis    2025, 61 (1): 181-194.   DOI: 10.13209/j.0479-8023.2024.038
Abstract1841)   HTML    PDF(pc) (5142KB)(1915)       Save
The Extreme Mass-Ratio Inspiral (EMRI) refers to binary system with a mass ratio between 104 and 106, where the smaller object loses energy as it inspirals closer to a massive black hole, emitting gravitational waves. It is estimated that there are 105 cycles during the last year before plunge, providing rich information on the evolution of gravitational wave phases. The motion of the smaller object in the strong gravitational field of the massive black hole can reflect the surrounding spacetime structure. The massive black hole is typically located at the center of a galaxy, in which the galaxy environment leaves traces in the EMRI waveform, thus EMRI can be used to constrain the gravitational theories, no-hair theorem and so on. Multiple sources can provide constraints on the mass and spin distribution of massive black holes, contributing to the understanding of cosmic and galactic evolution. Due to this significance, EMRI has become an important target for space gravitational wave missions such as LISA, Taiji, and TianQin. Consequently, the EMRI data analysis has become a crucial task. However, due to the high dimensionality and complexity of the waveform, relevant methods are still under discussion. This article initially reviews the framework and discussions regarding EMRI data analysis conducted during the Mock LISA Data Challenge (MLDC). It subsequently provides a comprehensive overview of the challenges encountered and the corresponding improvements proposed based on the authors’ research. Finally, the article offers some clues and suggestions regarding potential advancements in EMRI data analysis methods. 
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Tidal Current Characteristics and Response of Tidal Current to Typhoon on the West Side of Hainan Island by High Frequency Radars
CHEN Xi, YANG Fan, WEI Jun
Acta Scientiarum Naturalium Universitatis Pekinensis    2025, 61 (1): 53-64.   DOI: 10.13209/j.0479-8023.2025.007
Abstract1405)   HTML    PDF(pc) (2782KB)(2881)       Save
Based on the surface flow field data from high-frequency radar on the west side of Hainan Island, harmonic analysis and some other methods were employed to investigate the tidal current characteristics and their seasonal variations in this region. The results show significant shallow-water tidal features, with the tidal currents predominantly diurnal. The northern part of the study area exhibits irregular diurnal tidal characteristics, while the southern part displays regular diurnal tidal patterns. The tidal current mainly follows a clockwise reciprocating motion, with the maximum potential tidal current velocity being stronger in the south region than that in the north region. Specifically, the maximum possible tidal current velocity is 1.2–1.8 m/s in the south and 0.25–1 m/s in the north. In addition, the impact of Typhoon “Koguma” on the tidal current was also calculated. The results indicate that the typhoon temporarily weakens the surface tidal current intensity, which generally recovers to normal intensity within seven days. Compared with semi-diurnal tides, this phenomenon is more pronounced in diurnal tides.
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Study on Influencing Factors of Hydrothermal Carbonization of Sewage Sludge
WANG Hang, LIU Yangsheng, WANG Dianchang, CHEN Xiang, LIU Feng, QIAO Xueyuan, LI Kun, WANG Xiankai
Acta Scientiarum Naturalium Universitatis Pekinensis    2024, 60 (4): 745-757.   DOI: 10.13209/j.0479-8023.2024.043
Abstract1589)   HTML    PDF(pc) (1681KB)(227)       Save
The effects of reaction temperature, time, and medium on the properties of sludge hydrochar were experimentally studied. The results demonstrated that hydrothermal carbonization (HTC) treatment enhanced sludge dewatering and volume reduction, with a higher water removal rate (42.8%–53.3%) observed under acidic conditions compared to neutral conditions (28.9%–45.2%). Notably, the highest dehydration rate was achieved after HTC at 240°C for 1 hour. Increased reaction temperatures and longer reaction times led to reduced hydrochar yield due to enhanced dehydration and decarboxylation reactions. The H/C and O/C atomic ratios gradually decreased as a result. Furthermore, the regular and compact structure of sludge was disrupted to varying degrees following HTC treatment, resulting in the formation of holes and grooves that increased the specific surface area, pore volume, and pore size of the hydrochar produced. Specifically, hydrochar obtained from HTC at 220°C for 1 hour exhibited the highest specific surface area (129.98 m2/g) and pore volume (0.66 cm3/g). The composition and crystalline structure of hydrochar were primarily influenced by factors such as reaction medium > reaction temperature > reaction time. With the increase of HTC reaction temperature and residence time, the volatile content of hydrochar decreased while the fixed carbon and ash content increased. The main exothermic range during combustion of hydrochar occured between 250–550°C.
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Process-Based Simulation of Spring Flowering and Autumn Leaf Coloration of Main Ornamental Plants in Beijing Botanical Garden
TANG Lingpei, CHEN Xiaoqiu, QIAN Siwei, MO Zhihong
Acta Scientiarum Naturalium Universitatis Pekinensis    2023, 59 (4): 649-658.   DOI: 10.13209/j.0479-8023.2023.034
Abstract1651)   HTML    PDF(pc) (985KB)(1342)       Save
Accurately simulating occurrence dates of spring flowering and autumn leaf coloration of ornamental plants is of significant importance for revealing phenological response of urban vegetation to climate change and predicting the optimum timing for flower and foliage viewing. This study employed the Unified Forcing Model (UniForc) and Unified Chilling Model (UniChill) to fit the first flowering and 50% flowering dates of 20 plant species from 1979 to 2019 in Beijing Botanical Garden, and the Low Temperature and Photoperiod Multiplicative Model (TPM) to fit the first leaf coloration and 100% coloration dates of 10 plant species. The errors of optimum models in simulation and prediction were evaluated. Results show that spring flowering of ornamental plants is mainly driven by forcing temperature during ecodormancy and growth periods, but less restricted by chilling temperature during endodormancy period. First leaf coloration of ornamental plants is mainly driven by the process of leaf senescence induced by daily minimum temperature decrease, and 100% leaf coloration is mainly driven by the process of leaf senescence induced by photoperiod shortening. The average simulated root-mean square errors (RMSE) for first flowering and 50% flowering are 3.7 days and 3.2 days, respectively, and simulated RMSEs for the two spring phenophases show good interspecific synchronization. The average simulated RMSEs for first leaf coloration and 100% leaf coloration are 9.4 days and 5.6 days, respectively, but simulated RMSEs for the two autumn phenophases do not display interspecific synchronization. Simulated RMSEs of flowering dates and leaf coloration dates of various plants correlate significantly and positively with their standard deviation of interannual variations. The simulated and extrapolating RMSEs of optimum spring and autumn process-based models are very close, indicating that the models have high robustness. 
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Vector Magnetometer for Space Applications Based on a Magnetoresistance
YU Xiangqian, LI Jiawei, XIAO Chijie, HUANG Cong, LIU Si, WANG Jindong, LI Yunpeng, QU Yanan, WANG Yongfu, CHEN Hongfei, ZOU Hong, SHI Weihong, ZONG Qiugang, CHEN Xiaofei, ZHANG Xiaoxin, ZONG Weiguo, WANG Jinsong
Acta Scientiarum Naturalium Universitatis Pekinensis    2023, 59 (4): 609-616.   DOI: 10.13209/j.0479-8023.2022.111
Abstract1652)   HTML    PDF(pc) (12594KB)(571)       Save
A low-resource anisotropic magnetoresistance-based vector magnetometer for space science applications is presented. The proposed vector magnetometer can detect magnetic fields in a range of ±65000 nT, has a –3 dB bandwidth of DC to 10 Hz, and a noise power spectral density of ≤0.2 nT/Hz1/2@1 Hz. Furthermore, the device has a non-linearity error of ≤3.6%oo over the entire range and non-orthogonality error of ≤1.2%oo. The vector magnetometer was equip on a Chinese Feng-Yun meteorological satellite (FY-3E) whose orbit was a sun synchronous orbit. The first in-flight science results show that the sensor can detect transient physical signals with amplitudes of 20–60 nT.
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Characteristics of Surface Currents in Guangdong-Hong Kong-Macao Greater Bay Area in Spring Based on High Frequency Radar Observations
REN Lei, YANG Fan, YANG Lingna, CHEN Xiaofan, PAN Guangwei, WEI Jun
Acta Scientiarum Naturalium Universitatis Pekinensis    2022, 58 (5): 839-849.   DOI: 10.13209/j.0479-8023.2022.055
Abstract1961)   HTML    PDF(pc) (2588KB)(1325)       Save
Based on the sea surface currents data of Guangdong-Hong Kong-Macao Greater Bay Area (GBA) in March 2020 obtained from high frequency radar (HFR), the surface currents data from 907 densely distributed points were selected to analyze the characteristics of spatial-temporal variation. Harmonic analysis and some other methods were used to explore the characteristics of tidal currents. The results show that the irregular semidiurnal tide M2 is dominant in the sea area, and the shallow-water effect is significant. The dip angles of the main diurnal and semidiurnal tides are between 120° to 160°. The direction of maximum flow rate is WN-ES, which shows the trend of shore offshore flow. As the distance to the shoreline increases, the tidal current pattern coefficient and the effect of shallow water constituents coefficient gradually increase, and the offshore area in the south of the research area shows the characteristics of irregular diurnal tide. The ranges of probable maximum current velocity and measured maximum current velocity were 0.33 cm/s to 71.01 cm/s and 58.63 cm/s to 149.99 cm/s, respectively, with the upper-end values distributed in the northwest and south of the study area.
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A Category Hybrid Embedding Based Approach for Power Text Hierarchical Classification
CHEN Xiaona, GAO Pengfei, LIANG Yue, MA Yinglong
Acta Scientiarum Naturalium Universitatis Pekinensis    2022, 58 (1): 77-82.   DOI: 10.13209/j.0479-8023.2021.104
Abstract1837)   HTML    PDF(pc) (473KB)(994)       Save
Aiming at the problem that the current power text classification methods ignore the latent semantic association between category labels and therefore lead to low classification performance, a hierarchical multi-label power text classification method is proposed. Firstly, a power multi-label text dataset is built using automatic information extraction based on power unstructured texts, and the hierarchical structural relationships between categories are constructed by leveraging relevant domain knowledge. Secondly, a text classification method HONLSTM-BERT is proposed based on hybrid embeddings of category structure and label semantics for hierarchically classifying power texts in a top-down manner. At last, experiments were made in comparison with some popular text classification methods, and the experimental results show that proposed HONLSTM-BERT method achieves superior classification accuracy, and can efficiently improve the performance of automatic text classification.
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Estimation of Shadow Price of Major Pollutants in China’s Chemical Firms: An Empirical Analysis Based on Directional Distance Function
CHEN Xing, XU Jintao
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (2): 341-350.   DOI: 10.13209/j.0479-8023.2021.008
Abstract1781)   HTML    PDF(pc) (1279KB)(1078)       Save
This study estimated the shadow price of two air pollutants (sulfur dioxide and nitrogen oxides) and carbon dioxide in 867 chemical firms from 2007 to 2012 using a parameterized directional distance function to measure the marginal abatement cost of pollutants. The result is as follows. 1) The average shadow prices of SO2, NOx and CO2 in the sample chemical firms were 59.8 yuan/kg equivalent, 388.13 yuan/kg equivalent and 164 yuan/ton equivalent, respectively. 2) The shadow prices of the three pollutants showed an upward and fragmented trend, implying that traditional target-bound emission reductions policies during the 11th Five-Year-Plan had not been economically effective. 3) By plotting the marginal abatement cost curve (MACC) of chemical industry, we find that in order to achieve the pollution reduction targets set by the 13th Five-Year Plan, the effective environmental tax rate should be much higher than the current environmental tax rate or the average carbon price in the carbon market, which means that the current environmental tax may require some adjustment. The shadow price of nitrogen oxides is much higher than that of sulfur dioxide, therefore the tax rate of nitrogen oxides may need a certain degree of adjustment. The results can provide some reference for the future establishment of a more complete system of environmental tax.
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Spatial Pattern and Driving Factors of Soil Microbial Biomass Carbon in Grassland in Northern Agro-Pastoral Transition Zone
CHEN Xinyue, YAO Xiaodong, ZENG Wenjing, WANG Wei
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (2): 250-260.   DOI: 10.13209/j.0479-8023.2021.003
Abstract2158)   HTML    PDF(pc) (1079KB)(1021)       Save
 In order to explore spatial pattern of soil microbial biomass carbon (MBC) and its environmental driving forces in grassland surface layer (0?10 cm) and subsurface layer (10?20 cm) in the agro-pastoral transition zone in northern China, 456 soil samples (57 sample sites, two soil layers and four replicates) were selected for investigation from Inner Mongolia-Liaoning plain, Bashang on the north of Beijing, the northern foot of Yinshan Mountain and Ningxia-Shaanxi Loess Plateau. The results showed that the spatial pattern of MBC was consistent between the surface and subsurface layer, which increased with latitude and had no significant change with longitude and elevation. With the increase of degradation degree, the reduction of soil microbial biomass in the subsurface layer was smaller than that in the surface layer. The difference of soil pH between the two layers decreased with the degree of degradation. The difference in soil MBC between surface and subsurface soils was regulated by the change of soil pH. The smaller the difference in pH between the two soil layers, the smaller the difference in MBC. Climate, vegetation and soil factors could affect the spatial variation of MBC, and soil factors were the main driving forces for MBC at the regional scale. The main influencing factor of MBC was soil total carbon at surface layer, and soil total nitrogen at subsurface layer. In the context of climate change and the intensification of human activities, the results were useful for predicting the response of soil microorganisms at the regional scale and maintaining and restoring ecological functions of degraded grasslands.
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Review of Regionalization and Remote Sensing Based Method for Hydrological Model Parameters Calibration in Ungauged Basins
JIANG Lulu, WU Huan, Lorenzo Alfieri, LI Xiaomeng, John S. Kimball, CHEN Xiuwan
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (6): 1152-1164.   DOI: 10.13209/j.0479-8023.2020.076
Abstract2187)   HTML    PDF(pc) (4416KB)(799)       Save
Challenges in calibration of hydrological model parameters in ungauged basins were discussed, and the latest advances in regionalization method and remote sensing based method were summarized. First, the common problems in the hydrological model calibration (derivation of hydrographic parameters, construction of objective function and selection of optimization method) and their influences on the results of parameter optimization) were analyzed and leading-edge solutions were then provided. Next, fundamental principles and study progress of regionalization method were introduced, and the importance of stream gauge network density of donor catchments for the streamflow prediction was emphasized. The advance of remote sensing based hydrological model calibration method was discussed in terms of model spatial domain, model structure, satellite data source, and
calibration target. Finally, the advantages and disadvantages and the future development prospect between regionalization method and remote sensing based method were compared and analyzed, and potential practical strategies for continuous streamflow prediction in ungauged basins in China are suggested.
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Effects of Air Temperature and Soil Moisture on Common Brown-Down Date of Taraxacum mongolicum in Eastern China’s Temperate Zone
XUE Tingting, ZHAO Yuan, CHEN Xiaoqiu, JIANG Mengdi, LIANG Boyi
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (1): 173-183.   DOI: 10.13209/j.0479-8023.2019.127
Abstract2963)   HTML    PDF(pc) (1051KB)(882)       Save
In order to reveal temporal variations of autumn phenology of herbaceous plants and their climatic attributions, we analyzed changing trend of the common brown-down date of Taraxacum mongolicum and simulated interannual variation of the common brown-down date using plant phenological and meteorological data at 47 phenological stations in eastern China’s temperate zone from 1992 to 2012 and statistical methods. Results show that 1) the common brown-down date of Taraxacum mongolicum was delayed at 34 stations from 1992 to 2012, of which significant delaying trends were observed at 22 stations. By contrast, the common brown-down date of Taraxacum mongolicum advanced at 13 stations, of which significant advancing trends were detected at five stations. 2) The common brown-down date of Taraxacum mongolicum at individual stations correlates mainly negative with average temperature during the growing season (the period from leaf unfolding to common browndown) but positive with relative soil moisture and daily minimum temperature in autumn. 3) Among the 30 effective optimal models at individual stations (p<0.05), the common brown-down date of Taraxacum mongolicum was influenced by relative soil moisture at 22 stations, by daily minimum temperature at 19 stations and by average temperature during the growing season at 21 stations. Moreover, simulation accuracy of the model was significantly affected by interannual variation of the common brown-down date of Taraxacum mongolicum, namely, the smaller the interannual variation of the common brown-down date at a station, the higher the simulation accuracy of the model.
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Quantitative Analysis of Potential Tsunami Hazard in the South China Sea
XU Liwen, CHEN Xiuwan, YANG Ting, LI Fei
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (3): 445-450.   DOI: 10.13209/j.0479-8023.2019.015
Abstract2230)   HTML    PDF(pc) (941KB)(1692)       Save
The COMCOT model was used to analyze the potential hazards of the tsunami source in Manila Trench. By changing the information of the two tsunami initial fields — magnitude and source depth, the quantitative relationship between the first wave amplitude and the two is revealed when the tsunami landed in China’s coastal areas. The results show that the influence amplitude of different focal depths on the amplitude of the first wave can reach 50%. With the different magnitude of earthquake, the influence of the focal depth on the amplitude of the first wave is also different. The amplitude of the first wave of the tsunami landing basically increases with the magnitude. However, during the process of the tsunami spreading to the near shore, the tsunami wave will overlap with the reflection wave near the shore, which may cause the first wave landing amplitude to decrease abnormally. When the magnitude reach Mw 8.6, the tsunami level is 1 and some coastal areas will be threatened by tsunami.
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Loop Corrections to the Decuplet-Octet Baryon Transition Axial Charges
LENG Changzhi, CHEN Xiaolin
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (3): 411-421.   DOI: 10.13209/j.0479-8023.2019.027
Abstract2145)   HTML    PDF(pc) (552KB)(1251)       Save
The authors calulate chiral corrections to the decuplet-octet baryon transition axial charges through O(p3) using heavy baryon chiral perturbation theory (HBCPT). Theoretical predictions are presented. Chiral symmetry breaking, vertex correctiongs, wavefunction renormalization are included. The contributions from both the intermediate decuplet and octet baryon states are taken into account in the loops. The results show reasonably good convergence of the chiral expansion and agreement with the known experimental data.
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Simulation and Experimental Study on the Effect of Large Granular Rocks in Lunar Soil on Drilling Load
PANG Yong, FENG Yajie, SUN Qichen, LAI Xiaomin, WANG Haiyuan, CHEN Xibao, LIANG Jieneng, LIU Tianxi
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (3): 397-404.   DOI: 10.13209/j.0479-8023.2019.008
Abstract2116)   HTML    PDF(pc) (12383KB)(773)       Save
The dynamics of auger drilling into lunar soil with large granular rocks was studied by discrete element method (DEM) simulation and experiment, in which the large granular rocks with different configurations were arranged at different locations. The result of simulation and experiment indicate that the surface morphology is the key factor which controls whether the granular rocks could be removed in drilling process. The result would be an important support for China’s deep space exploration mission.
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Combining GPM DPR with S-Band Radar to Retrieve RSD
CHEN Xintao, LIU Xiaoyang
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (2): 227-236.   DOI: 10.13209/j.0479-8023.2019.009
Abstract2414)   HTML    PDF(pc) (5170KB)(679)       Save

For solving the dual-value problem of RSD raindrop size distribution retrieval algorithm using GPMCO DPR data, a solution is put forward: combining the observation data of S-band weather radar and GPM-CO DPR to provide determinant for the dual-value problem. On the basis of completing the retrieval algorithm, the radar simulation program, Quickbeam, is utilized to validate the algorithm, and actual observation data is utilized to validate the algorithm as well. The results of theoretical validation show that the correlation coefficients between retrieved data and input data are over 0.99, and the results of validation with actual observation data show that the retrieved RSD can reflect the raindrop distribution situation of the rainfall process. The algorithm can help to solve the dual-value problem to o certain degree.

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Stability and Bifurcation for a Type of Non-autonomous Generalized Birkhoffian Systems
CAO Qiupeng, CHEN Xiangwei
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (4): 653-657.   DOI: 10.13209/j.0479-8023.2016.067
Abstract2484)   HTML    PDF(pc) (357KB)(1364)       Save

Bifurcation for a type of non-autonomous generalized Birkhoffian systems is studied. Gradient representations for this type of non-autonomous generalized Birkhoffian systems are given. The stability of equilibrium point of these systems is discussed by the characteristic of the gradient system. Further the systems which contain some parameter are studied. The stability and the number of equilibrium point will change along with the change of the parameter to produce the bifurcation phenomenon.

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A New Method of Estimating Soil Moisture Content Using GNSS-R Technology Based on Lookup Table
PENG Xuefeng;CHEN Xiuwan;WAN Wei et al
Acta Scientiarum Naturalium Universitatis Pekinensis    2015, 51 (5): 879-887.  
Abstract1145)      PDF(pc) (4339KB)(1551)       Save
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Elevation Applicability Study of the Zenith Hydrostatic Delay Models
CAO Yanfeng,CHEN Xiuwan,LI Wei,XIAO Han,LI Huayu
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1403)      PDF(pc) (871KB)(1171)       Save
In order to study the three general models of ZHD, i.e. Saastamoinen model, Hopfield model and Black model, a Radiosonde method based on the radiosonde data is constructed to calculate the true value of ZHD. The elevation applicability of the three general models is studied by comparing the ZHD calculated by the Radiosonde method and three general models in the real and standard summer atmospheric conditions respectively at mid-northern latitudes of North American. It was found that three general models are all applicable to the height of 0-30 km; Black model and Saastamoinen model are in the same high precision level and Hopfield model has the worst accuracy. Finally, a localized ZHD-P model in high pressure range is discovered and constructed.
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Shortest Time Path Algorithm Based on Shared Location Data
ZHU Han,LI Huaiyu,XIAO Han,CHEN Xiuwan,WANG Tingting
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1425)      PDF(pc) (15075KB)(489)       Save
In order to meet the need of reaching destination through a shortest time, while distributing flow reasonably, using public resources plenty, easing urban traffic jam during work peak period, the authors propose a shortest time target optimal path algorithm based on LBPSS (location based participatory sensing service) data. The algorithm is supposed to solve the lack of traffic information, road network coverage shortage, hysteresis traffic data update and data inconformity with reality. Then the goal of route navigation combining real-time traffic information can be achieved. Finally combining the ArcGIS and Android platform, using great methods of database as quick query, indexes and collections, the authors bring about an application example of shortest time path algorithm based on LBPSS data. Compared with recently popular algorithms, the feasibility and effectiveness of proposed algorithm are verified. The result shows that the algorithm proposed has more practical value in distributing traffic flow reasonably, in easing urban traffic jam during work peak period effectively and saving travel time wisely.
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Location Based Participatory Sensing Service
LI Huaiyu,ZHU Han,XIAO Han,CHEN Xiuwan,TAO Li
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1172)      PDF(pc) (1886KB)(770)       Save
Based on the core idea of sharing, a novel extensible Location Based Service (LBS) named the Location Based Participatory Sensing Service (LBPSS) is proposed. It is designed to solve the current LBS problems, such as the delay of POI (point of interest) update, the difficulty of data collection, the low viscosity of the users and so on. The architecture of the LBPSS system is described in detail and the advantages and characteristics of LBPSS compared to LBS are selectively analyzed. For the implementation of LBPSS, five key technologies like privacy protection, incentive of participation, data validation, mining and visualization, are presented. The users of LBPSS can provide the data based on the location and get the data and services at the same time, achieving the purpose of more diverse data collection and the wide data sharing usage. Finally, integrated with ArcGIS Server and Android platform, the application of LBPSS in air quality monitoring is realized to verify the feasibility and validity of the LBPSS.
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Integration of the GIS with Criminal Probability Model and Its Application
XIAO Han,DU Yonghui,XU Jinze,CHEN Xiuwan
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1426)      PDF(pc) (648KB)(651)       Save
By considering the influencing factors such as time and distance, crime rate, population, police, geography and environment, victims’ occupation, etc, the authors use mathematical modeling to establish the evaluation function of crime probability in the research area, calculate the probability of crime, and then combine it with GIS-related technology to get the most likely crime areas, namely, the geographic portrait of crime. The authors conduct method validation and analysis through examples. This new probabilistic crime model could provide geospatial data for detecting serial criminal cases and narrow down the scope of police surveillance. This new investigative technique with high precision is suitable for various geographic regions and helpful for detecting serial criminal cases.
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Sensitivity of Risk Explicit Interval Linear Programming (REILP) Solutions to Constraint Risk Preferences: Numerical Analysis and Implications
CHEN Xing,ZOU Rui,LIU Yong,SHENG Hu,GUO Huaicheng
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1343)      PDF(pc) (832KB)(646)       Save
The authors study the solution robustness of the Risk Explicit Interval Linear Programming (REILP) model using numerical experimentations, investigating whether optimal solutions of a REILP would vary under various preferences to different constraints. The first numerical experiment deals with an optimal land use planning subject to nutrient loading constraints. The second one deals with an optimal water resource allocation subject to pollutant loading constraints. The results show that REILP solutions have different sensitivities to constraint preferences in different cases. This phenomenon suggests that in practice it is necessary to conduct thorough analysis on the robustness of REILP solutions to constraint preferences before reaching reliable decision support. In addition, the variability of REILP solutions with regard to various constraint preferences makes it possible to efficiently generate alternative management schemes within the frame work of REILP.
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Cell-ID Positioning Method Based on Linear Weight
WAN Jiahuan,ZHUANG Chunhua,CHEN Xiuwan,ZHANG Weiyi,WAN Wei
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1035)      PDF(pc) (1326KB)(1796)       Save
A kind of Cell-ID positioning method is put forward based on linear weight and Google base station database. All of the signal strength and position of the base stations received by the mobile terminal are utilized and it only needs to update the software of the terminal. The result shows that the accuracy is less than 150 m under 2s circumstances and it is more suitable for LBS.
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Team Conflict, Team Trust and Organizational Citizenship Behavior: The Mediation Effect of Organizational Justice
Aiqin,SHI Junqi,LIU Yihao,SHEN Xiuqin,SU Yonggang,CHEN Xiaoyang
Acta Scientiarum Naturalium Universitatis Pekinensis   
Factors Affecting Soil Organic Carbon Density (SOCD) and Total Nitrogen Density (TND) in Inner Mongolian Steppe
CHEN Xi,LIU Hongyan
Acta Scientiarum Naturalium Universitatis Pekinensis   
Risk Assessment on Food Crops Supply-Demand Balance under Climate Change in China
ZHOU Qiaofu,DAI Erfu,WU Shaohong,PAN Tao,CHEN Xiwei
  
Overview of Heavy Molecular States
SHEN Leilei,CHEN Xiaolin
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1015)            Save
Many new hadron states were observed by the BaBar, Belle, CDF, D0 collaborations in recent years, some of which did not fit into the quark model easily. We reviewed our groups systematic work on the heavy molecular states especially X ( 3872) , Y ( 4260) and Z+ ( 4430) and discussed the difficulties and challenges in this field and the possible improvement in the future.
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Effect of Spin Polarization on the Conductance of the Quantum Dot System
CHEN Xing,GUO Wei
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1267)            Save
By using non-degenerate Anderson model, the influence of local spin polarization on the conductance of quantum dot system was study. Based on the truncate approximation and non-condenced condition, the equation of motion gave the approximate solution of Green's functions. Then the power siries expansion of the Green's functions with respect to the splitting of local spin energy was got. Finally, local level splitting dependence of conductance from Landauer formula was obtained.
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