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YOLO11n-seg-RF: An Improved Lightweight Rock Fracture Detection and Segmentation Algorithm
JIN Ziyue, LI Haitao, YIN Haichen, YANG Guanyu, CHEN Yulong, ZHANG Haikuan, LI Xiantao, CAI Shaoyang
Acta Scientiarum Naturalium Universitatis Pekinensis    2026, 62 (2): 237-252.   DOI: 10.13209/j.0479-8023.2025.063
Abstract202)   HTML    PDF(pc) (27650KB)(49)       Save
To address the challenges of sample imbalance, insufficient learning of hard-to-classified samples, and difficulties in small target segmentation in rock fracture detection and segmentation tasks, this paper proposes YOLO11n-seg-RF, an improved lightweight algorithm based on YOLO11n-seg. The proposed method incorporates three key components: 1) a Multi-Receptive Field Joint Enhanced Convolutional Block Attention Module (JECBAM) to enhance feature representation, 2) a Grouped Channel Attention-based Feature Fusion Module (GCAConcat) for effective multi-scale feature integration, and 3) a Simplified Spatial Pyramid Pooling Fast module (SimSPPF) to optimize spatial information aggregation. Additionally, the Focaler-IoU loss function is adopted to improve segmentation accuracy for fine-grained and multi-branch fractures. Experimental results on a custom rock fracture dataset demonstrate superior performance. Detection metrics achieve 88.7% Precision (Box), 77.5% Recall (Box), 84.2% mAP0.5 (Box), and 67.3% mAP0.5:0.95 (Box). Segmentation metrics reach 78.5% Precision (Mask), 68.0% Recall (Mask), 68.0% mAP0.5 (Mask), and 27.0% mAP0.5:0.95 (Mask). The model achieves real-time inference at 144 FPS with only 2.47M parameters, outperforming baseline YOLO11n-seg and other mainstream instance segmentation models. Ablation studies confirm the effectiveness of each proposed module, showing significant improvements in detection/segmentation accuracy while reducing model complexity. Generalization experiments on public datasets (crack-seg and carparts-seg) demonstrate superior cross-domain performance, with mAP0.5 (Box) and mAP0.5 (Mask) exceeding comparative models. Practical validation in mining engineering applications reveals that the algorithm successfully identifies core fractures in borehole samples, enabling rapid estimation of uniaxial compressive strength through established porosity-compressive strength equations derived from fracture ratio analysis and uniaxial compression tests, thereby verifying the practical engineering value. To address the challenges of sample imbalance, insufficient learning of hard-to-classified samples, and difficulties in small target segmentation in rock fracture detection and segmentation tasks, this paper proposes YOLO11n-seg-RF, an improved lightweight algorithm based on YOLO11n-seg. The proposed method incorporates three key components: 1) a Multi-Receptive Field Joint Enhanced Convolutional Block Attention Module (JECBAM) to enhance feature representation, 2) a Grouped Channel Attention-based Feature Fusion Module (GCAConcat) for effective multi-scale feature integration, and 3) a Simplified Spatial Pyramid Pooling Fast module (SimSPPF) to optimize spatial information aggregation. Additionally, the Focaler-IoU loss function is adopted to improve segmentation accuracy for fine-grained and multi-branch fractures. Experimental results on a custom rock fracture dataset demonstrate superior performance. Detection metrics achieve 88.7% Precision (Box), 77.5% Recall (Box), 84.2% mAP0.5 (Box), and 67.3% mAP0.5:0.95 (Box). Segmentation metrics reach 78.5% Precision (Mask), 68.0% Recall (Mask), 68.0% mAP0.5 (Mask), and 27.0% mAP0.5:0.95 (Mask). The model achieves real-time inference at 144 FPS with only 2.47M parameters, outperforming baseline YOLO11n-seg and other mainstream instance segmentation models. Ablation studies confirm the effectiveness of each proposed module, showing significant improvements in detection/segmentation accuracy while reducing model complexity. Generalization experiments on public datasets (crack-seg and carparts-seg) demonstrate superior cross-domain performance, with mAP0.5 (Box) and mAP0.5 (Mask) exceeding comparative models. Practical validation in mining engineering applications reveals that the algorithm successfully identifies core fractures in borehole samples, enabling rapid estimation of uniaxial compressive strength through established porosity-compressive strength equations derived from fracture ratio analysis and uniaxial compression tests, thereby verifying the practical engineering value. 
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Application of 3D Raman Imaging and Quantitative Analysis in Geological Fluid: A Case Study of Fluid Inclusions in Eclogite from the Western Tianshan
QI Ning, ZHANG Lijuan, ZHANG Lifei, LI Xiaoguang
Acta Scientiarum Naturalium Universitatis Pekinensis    2026, 62 (1): 101-113.   DOI: 10.13209/j.0479-8023.2025.016
Abstract451)   HTML    PDF(pc) (22424KB)(258)       Save
This study applies confocal Raman microscopy to conduct 3D imaging of methane-bearing fluid inclusions in eclogites from the Chinese Western Tianshan high-pressure/ultrahigh-pressure metamorphic belt, precisely delineating the morphology and spatial distribution of distinct phases. Based on the imaging data, ImageJ software was employed to perform volumetric quantification and mass calculations of the inclusion components. We present a comprehensive practical guide encompassing instrument operation, data processing, parameter optimization, and quantitative calculation workflows. These protocols offer a valuable resource for researchers investigating 3D Raman quantitative methods, thereby facilitating the acquisition of precise quantitative data in geological fluid research.
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Screening, Whole Genome Analysis, and Enzyme Production Optimization of Alginate Lyase-Producing Strain Cobetia marina 29
QIAN Xiangyu, LIU Zhixiang, TANG Wenzhu, LI Xianzhen
Acta Scientiarum Naturalium Universitatis Pekinensis    2025, 61 (6): 1025-1038.   DOI: 10.13209/j.0479-8023.2025.101
Abstract716)   HTML    PDF(pc) (3416KB)(344)       Save
This study successfully isolated and screened a microbial strain with efficient alginate-degrading capability from seaweed, utilizing alginate as the sole carbon source in a selective culture medium. The strain was systematically identified and subjected to bioinformatics analysis through physiological and biochemical characterization, 16S rDNA sequence analysis, and whole-genome sequencing to uncover potential alginate lyase-related genes. Additionally, the enzyme production conditions for the strain were optimized using single-factor experiments, Plackett-Burman design, and response surface methodology. Morphological observations, physiological and biochemical trait analysis, and 16S rDNA gene sequence identification confirmed the strain to be of the genus Cobetia. The full length of the strain’s genome is 4136490 base pairs, with a GC content of 62.48%. Genome prediction encoded 3454 protein-coding genes, 70 tRNA genes, and 12 rRNA genes. Nucleotide consistency analysis was subsequently performed and it was named Cobetia marina 29. Nucleotide consistency analysis was subsequently performed and it was named Cobetia marina 29. Functional annotation using the GO, KEGG, COG, and CAZy databases yielded 2487, 2271, 2910, and 145 annotated functional genes, respectively. Among these, three genes encoded alginate lyases and were classified into the PL17 and PL7 families. Finally, the cultivation parameters were refined, and under the optimal conditions for enzyme production, the enzyme activity was enhanced to 179.29 U/mL, which represented a 53.6% increase compared with the levels prior to optimization. The findings of this study provided a new microbial resource for the biodegradation of alginate and laid the foundation for subsequent industrial applications.
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Risk Assessment of Hydrogen Sulfide Oil Wells in Bonan Sag
LI Xiaohui, LIU Yisu, SHI Yongmin, SHI Xiang, XU Lei, CAO Weidong, XU Haotian, CAO Yunjiang
Acta Scientiarum Naturalium Universitatis Pekinensis    2025, 61 (3): 501-507.   DOI: 10.13209/j.0479-8023.2025.008
Abstract2145)   HTML    PDF(pc) (1078KB)(3364)       Save
To solve the prevention and control of hydrogen sulfide in the well block area, a comprehensive analysis was conducted using core samples, drilling data, logging data, well testing data, and seismic data. The quantile classification method was employed to assess the risk levels of hydrogen sulfide wells in the Bonan Sag. Using a 1:2:4:2:1 hundred-digit classification method, the study area was divided into five levels of hydrogen sulfide environmental zones, and the high-risk sulfur-containing area in the Bonan Sag was identified. Vertically, the concentration of hydrogen sulfide gradually increases with terrain from low to high. Horizontally, the source of hydrogen sulfide in the carbonate rocks of the upper Sha 4th member exhibits characteristics of “rich gypsum, rich limestone, hydrocarbon generation, and high pressure”, representing a typical “self-generated” type of hydrogen sulfide. The sag and slope areas lack material supply, but carbonate rocks are widely distributed. The coexistence of gypsum and limestone in the southern slope zone provides reservoir space for hydrogen sulfide, while fault development creates conditions for its migration, and high-pressure sealing ensures its preservation. Medium-low risk areas are distributed between high-risk and medium-high risk zones. 
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Influence of Preparation Methods for Bamboo-Based Biochar on Its Benzene Adsorption Performance
ZENG Ziruo, LI Kai, LI Xiaokang, YANG Xinyu, GONG Yuanjun, LI Yuan, WANG Fei, NING Ping
Acta Scientiarum Naturalium Universitatis Pekinensis    2025, 61 (2): 335-342.   DOI: 10.13209/j.0479-8023.2024.112
Abstract2509)   HTML    PDF(pc) (5555KB)(2802)       Save
Using the stems of Dendrocalamus membranaceus Munro as raw materials, pyrolysis char BC-700 and hydrochar HBC-190/700 were prepared by the high-temperature pyrolysis method and the hydrothermal roasting method, respectively. Then, their benzene adsorption performance was evaluated at 55°C. The results showed that the adsorption effect of biochar HBC-190/700 on benzene was three times that of BC-700. Furthermore, the influence of preparation methods on the physical and chemical properties of the adsorbents was investigated using characterization techniques such as BET, XRD, SEM, Raman and FT-IR. SEM results indicated that many carbon microspheres were accumulated on the surface of hydrothermal carbon HBC-190/700, resulting in the formation of crevice pores. BET analysis showed that the hydrothermal carbon HBC-190/700 presented a hierarchical pore distribution of micropores and mesopores, which was conducive to the mass transfer of benzene. In addition, FT-IR analysis revealed that the aromatic functional groups of HBC-190/700 were the key factors for benzene adsorption. 
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Construction of Emission Inventory and Temporal-Spatial Distribution of Soil Fugitive Dust in Typical Oasis Cities
BAI Wenyu, LI Xiaofang, ZHANG Hongbin, WANG Jing, ZHAO Xueyan, LAI Xiaoshan, HONG Wen, JIANG Yan
Acta Scientiarum Naturalium Universitatis Pekinensis    2025, 61 (2): 217-226.   DOI: 10.13209/j.0479-8023.2024.115
Abstract1734)   HTML    PDF(pc) (2418KB)(4495)       Save
To evaluate the contribution of soil wind erosion to the particulate matter emissions of oasis cities, based on collected activity levels and emission factors related to soil fugitive dust, a 3 km×3 km-gridded emission inventory of PM2.5 and PM10 from soil fugitive dust in Xinjiang typical oasis cities (Altay City, Yizhou District of Hami City, and Kashgar City) in 2021 was developed in combination with Emission Factors and GIS technology. The results showed that the total emissions of PM10 from soil fugitive dust in Altay City, Kashgar City, and Yizhou District of Hami City were estimated to be 40983.79, 6541.97, and 1974362.24 t, respectively. The total emissions of PM2.5 were estimated to be 7069.69, 1090.49, and 326187.68 t, respectively. The particulate matter emission of Yizhou District of Hami City was the highest among the study areas, and the emission of PM10 is 302 times and 48 times higher than that of Kashgar and Altay. Due to factors such as soil type, location in the sand source area, and high wind speed, the emission intensity of particulate matter from soil wind erosion in Yizhou District of Hami City was also significantly higher than that of the other two cities. The temporal distribution characteristics in Yizhou District of Hami City showed a unimodal pattern, with the highest occurring in May. Kashgar City and Altay City both showed a bimodal pattern, with Kashgar City’s peaks occurring in June and August, and Altay City’s peaks occurring in May and July. 
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Responses of Soil Dissolved Organic Carbon to Climate Warming: A Review
QIN Wenkuan, LI Xiaojie, WANG Xudong, ZHU Biao
Acta Scientiarum Naturalium Universitatis Pekinensis    2024, 60 (4): 758-766.   DOI: 10.13209/j.0479-8023.2024.028
Abstract2227)   HTML    PDF(pc) (6269KB)(418)       Save
This review focuses on the characteristics of soil dissolved organic carbon (DOC) and its response and potential mechanisms to climate warming. The properties of soil DOC are described, and its sampling and analyzing methods are summarized. Soil DOC is mainly derived from soil organic carbon (SOC) dissolution, root exudates, microbial products and necromass, and the concentration and composition of soil DOC varies along soil profile and over time. Multiple sampling (e.g. tension lysimeter) and analyzing (e.g. Fourier transform ion cyclotron resonance mass spectrometry) methods of soil DOC were applied to investigate the responses and mechanisms of soil DOC to experimental warming. Based on previous studies, this review also discussed the effects of plants, microorganisms, and soil properties on soil DOC characteristics. Experimental warming may not only directly alter soil DOC concentration, but also indirectly change soil DOC properties via affecting plant, soil and microbial properties. Future studies should pay more attention to the vertical transport and temporal dynamics of DOM to further improve the SOC models and strengthen the prediction accuracy of global carbon cycle under climate warming in future.
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Reducing Multi-model Biases for Robust Visual Question Answering
ZHANG Fengshuo, LI Yu, LI Xiangqian, XU Jin’an, CHEN Yufeng
Acta Scientiarum Naturalium Universitatis Pekinensis    2024, 60 (1): 23-33.   DOI: 10.13209/j.0479-8023.2023.072
Abstract3135)   HTML    PDF(pc) (5709KB)(888)       Save
In order to enhance the robustness of the visual question answering model, a bias reduction method is proposed. Based on this, the influence of language and visual information on bias effect is explored. Furthermore, two bias learning branches are constructed to capture the language bias, and the bias caused by both language and images. Then, more robust prediction results are obtained by using the bias reduction method. Finally, based on the difference in prediction probabilities between standard visual question answering and bias branches, samples are dynamically weighted, allowing the model to adjust learning levels for samples with different levels of bias. Experiments on VQA-CP v2.0 and other data sets demonstrate the effectiveness of the proposed method and alleviate the influence of bias on the model.
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Efficient Combined Simulation Research of Finite Element Analysis for Bolt Assembly Process
LI Xiang, SHEN Chao, LIU Zhao, LIU Caishan, LIU Yan, LIU Chao
Acta Scientiarum Naturalium Universitatis Pekinensis    2023, 59 (6): 923-933.   DOI: 10.13209/j.0479-8023.2023.087
Abstract1433)   HTML    PDF(pc) (16629KB)(277)       Save
Current finite element (FE) simulating methods for pre-tightening process of thread fasteners have some shortcomings. In order to ensure the accuracy and efficiency simultaneously, the interference fit method and the direct torsion method are combined via ANSYS APDL to form a new pre-tightening means. Firstly, FE models of the thread pair structure before and after simulating the necking plastic forming process are obtained. Further assembly process simulation of the necking anti-loosening nuts is realized. Via different pre-tightening methods for simulating the assembly process, the thread pair load distribution, the contact stress state and the torsion-tension relationship can be obtained. Via comparing the numerical results of the zero closure amount nuts with some theoretical solutions, the reliabilities of the FE models and the simulation process are verified. Furthermore, the calculation time and numerical results of different pre-tightening methods are compared to prove the combined pre-tightening method is reliable and effective. 
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Impact of Urbanization and Industrial Collaborative Agglomeration on Land Use Efficiency of Resource-Based Cities in the Yellow River Basin, China
LI Xiaojing, HAO Jianhua, CAI Yinfei, SUN Yanan
Acta Scientiarum Naturalium Universitatis Pekinensis    2023, 59 (4): 681-694.   DOI: 10.13209/j.0479-8023.2023.009
Abstract2706)   HTML    PDF(pc) (1337KB)(1041)       Save
Based on the panel data of 41 prefecture-level resource-based cities in the Yellow River Basin from 2000 to 2019 and the relationship between urbanization and industrial collaborative agglomeration on land use efficiency, this paper uses spatial autocorrelation analysis and spatial Durbin model to analyze the spatial spillover effect of urbanization and industrial collaborative agglomeration on land use efficiency. The threshold regression model is used to discuss the threshold characteristics of industrial collaborative agglomeration in resource-based cities, and the crowding effect matrix table is innovatively constructed. The results show that the land use efficiency among resource-based cities in the Yellow River Basin is geographically correlated with the same high agglomeration or the same low agglomeration in space, and the spatial spillover inhibitory effect of urbanization accounts for 70% of the total inhibitory effect, showing an inhibitory effect. The spatial spillover growth effect of industrial collaborative agglomeration accounts for 70% of the total growth effect, and the spatial spillover inhibitory effect accounts for 20% of the total inhibitory effect, which shows the role of rapid promotion and gradual inhibition. After 2014, the agglomeration effect of some resource-based cities in the Yellow River Basin has accelerated to the threshold, among which Luoyang, Shizuishan, Shuozhou, Wuhai and Jinchang perform well and have the best agglomeration. Baotou and Ordos form a collaborative relationship between cities. The industrial agglomeration of most resource-based cities is still insufficient or crowded, and the future development should combine the characteristics of the city itself to play a synergistic role between adjacent cities.
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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
Abstract2188)   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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Basic Supply Service Model of Beijing-Tianjin-Hebei Region Based on LUCC-ESs Matrix
LI Xiaojing, GAO Yang, LI Shuangcheng
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (5): 950-958.   DOI: 10.13209/j.0479-8023.2020.064
Abstract2012)   HTML    PDF(pc) (2252KB)(432)       Save
As the traditional ecosystem service evaluation methods have the disadvantageous as high subjectivity and low comparability, a LUCC-ESs matrix evaluation method is improved. Based on the land use/cover types, the proposed method calculates the ecosystem service units, then builds the LUCC-ESs matrix to evaluate the ecosystem services. This method can avoid different outcomes obtained by different calculation methods, and make these test results comparable and practical. The application of the basic supply service in the Beijing-Tianjin-Hebei region indicates that the spatial pattern of the basic supply services is regional and highly connected with resource reserves and land productivities. The spatial pattern of the demand service appears the same movement and aggregation characteristics as that of the population, which decreases from the city center to suburban. The basic services both inside and outside Beijing-Tianjin-Hebei region converge to the urban center. 
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Analysis of Bi-directional Reranking Model for Uyghur-Chinese Neural Machine Translation
ZHANG Xinlu, LI Xiao, YANG Yating, WANG Lei, DONG Rui
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (1): 31-38.   DOI: 10.13209/j.0479-8023.2019.093
Abstract2947)   HTML    PDF(pc) (899KB)(935)       Save
The fitting training of neural machine translation is easy to fall into a local optimal solution on a lowresource corpus such as Uyghur to Chinese, resulting in the translation result of a single model may not be a global optimal solution. In order to solve this problem, the probability distribution predicted by multiple models is effectively integrated through the ensemble strategy, and multiple translation models are taken as a whole. At the same time, the translation models with opposite decoding directions are integrated by the reordering method based on cross entropy, and the candidate translation with the highest comprehensive score is selected as the output. The experiment on CWMT2015 Uighur-Chinese parallel corpus shows that proposed method has 4.82 BLEU values improvement compared with a single transformer model.
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Research on Transformer Oil Aging by Nuclear Magnetic Resonance Spectroscopy of Relaxation Time
LI Xiaonan, LIU Guoqiang, ZHANG Laifu, WANG Zhipeng, DING Guangxin, ZHAO Shilong, XIA Hui
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (5): 865-870.   DOI: 10.13209/j.0479-8023.2019.068
Abstract1867)   HTML    PDF(pc) (2398KB)(639)       Save
According to the limitations of conventional thermal aging detection of transformer oil insulation (not accurate or complicated process), a low field nuclear magnetic resonance relaxation time spectrum detection method is proposed. Based on the principle that hydrocarbon compounds in oil are cracked in high-pressure discharge environment and the molecular structure of hydrogen-containing molecules is changed, a transverse NMR relaxation spectrum detection system for thermal aging of transformer oil is designed. An algorithm for obtaining relaxation time spectrum based on inversion is described by using the peak point of time domain signal of oil samples collected by spin echo sequence. With the oil samples from the 110 kV power station in Changzhi City, the aging factor was detected by the nuclear magnetic resonance relaxation spectroscopy. The oil samples were used for 1, 10 and 20 year, individually. The results show that, in a 17.173 MHz condition, the relaxation time is 203.83, 145.82 and 141.95 ms, respectively. The detection time is controlled within 1 minute. The decreasing trend of relaxation time indicates that the high temperature causes the breaking of molecular chemical bonds and the precipitation of small hydrocarbon gases.
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Research on Sentiment Analysis Based on Representation Learning
LI Xiaojun, SHI Hanxiao, CHEN Nannan, LIU Hong, ZOU Yi
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (1): 105-112.   DOI: 10.13209/j.0479-8023.2018.066
Abstract3402)   HTML    PDF(pc) (931KB)(2135)       Save

The authors propose C&W-SP model — a text sentiment analysis model based on the representation learning. Firstly, an improved training model based on C&W model is proposed which can integrate emotional information and part of speech information in the training process of word embedding. The evaluation of data sets of NLP&CC’2013 is used to compare experimental results with different models. The experimental results show that the C&W-SP model which combines emotion information and part of speech information has the best performance and confirm the effectiveness of the proposed method.

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Accumulation Process and Control Factors of Jurassic-Cretaceous Distant-Source and Secondary-Filled Reservoirs in the Hinterland of Junggar Basin
MA Weijiao, WEI Yanzhao, LI Xia, TAO Shizhen, LI Yongguang, ZHAO Zhengya
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (6): 1195-1204.   DOI: 10.13209/j.0479-8023.2018.073
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Homogenization temperature of fluid inclusions, stratigraphic burial-thermal history, paeleostructure of accumulation period, known reservoirs and geochemical index are analyzed. Hydrocarbon accumulation periods, hydrocarbon transport system, trap-forming conditions of the Jurassic-Cretaceous in the hinterland of Junggar Basin are discussed. Thus, the dynamic accumulation process of the distant sourced, secondary-accumulated reservoirs is revealed. Results show that there are two periods of oil and gas charging in the Jurassic and cretaceous reservoirs in the hinterland of Junggar Basin, which are primary reservoirs formed in the early Cretaceous and secondary-filled reservoirs formed in the late paleogene till now. Both the primary reservoirs and sencondary accumulated reservoirs are widely spread in the hinterland area. Faults-sand bodies-unconformities act as three dimensional transporting systems for hydrocarbon migration and accumulation. The formation of primary reservoirs is controlled by paleostructure of accumulation period. During the later dissolution of paleostructure, primary reservoirs are destroyed and oil and gas migrate towards the north. Reservoirs types are decided by trap conditions on the migration pathways. At present, low-amplitude anticline, fault block and litho-stratigraphic reservoirs are the most discovered.

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Differences in Exhaled VOCs from Patients with Upper Respiratory Tract Infection and Healthy Ones
WANG Jue, ZHENG Yunhao, LIU Zhaorong, YAO Maosheng, LI Xiaoguang, ZHUANG Jia, PENG Wangyuan
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (4): 807-814.   DOI: 10.13209/j.0479-8023.2017.191
Abstract2632)   HTML    PDF(pc) (757KB)(2656)       Save

Analysis of exhaled VOCs from health and patients may help building association between VOCs and different diseases condition, which could offer a possibility of noninvasive monitoring of disease. VOCs were collected in 30 healthy subjects and 60 patients with upper respiratory tract infection. Analysis of 97 VOCs was
performed by gas chromatography and mass spectrometry (GC-MS). The concentration of alkanes, alkenes, halogenated hydrocarbon, oxygenated hydrocarbons and aromatic hydrocarbons in health and patients breath was analyzed. Analysis of variance (ANOVA), principal component analysis (PCA) were used to analyze the VOC differences from patients and healthy ones. The results show that the concentration of isoprene differ among patients, healthy ones and indoor air (P<0.05). Patients show higher concentration of n-pentane compared to healthy ones (P<0.05). Patients with bacterial upper respiratory tract infection show higher concentration of propanal compared to healthy ones. The results of PCA show that there were significant VOC differences between patients with upper respiratory tract infection and healthy ones (P=0.019), but no differences between bacterial and non-bacterial upper respiratory tract infection.

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Research of Carrying Capacity on Resource and Environment in Core Cities of Central Henan Urban Agglomeration
YU Yang, HAN Peng, YANG Nan, LI Xiaolei, GUO Yunhao
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (2): 407-414.   DOI: 10.13209/j.0479-8023.2017.160
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By analyzing the characteristic of urban agglomeration areas, proposing that considering the mobility of resource is essential in researching carrying capacity, the research used core cities of Central Henan urban agglomeration as cases to study, referencing press-state-response model to build the target system of carrying capacity, considering resource supply and consumption & environmental pollution and treatment, using AHP method to evaluate. Reliant exponential is used to evaluate the dependence severity. The result shows that according to the comparison of two results considering resource fluidity or not in Zhengzhou in 2004?2014, only considering resource fluidity can reflect the real condition of an area. Core cities of Central Henan urban agglomeration are short of water and energy resources but are enough to use with the supply of external resources. The orders of the carrying capacity index on resource and environment are Luohe, Xuchang, Xinxiang, Zhengzhou, Jiyuan, Jiaozuo, Luoyang, Pingdingshan and Kaifeng. According to the reliant exponential of external resources, grain resources in these nine cities are self-sufficiency. External energy resources are needed in Kaifeng, Xinxiang, etc. External water resources are needed in Zhengzhou, Kaifeng, etc. More external water resources are needed than external water resources.

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Geometry and Tectonic Evolution of the Laojunmiao Break-Thrust Belt in the Northern Margin of Qilian Mountain
XIAO Yuxiang, DU Wenbo, ZHANG Bo, ZHANG Jinjiang, HOU Xiulin, WANG Wei, HE Xin, LI Xiaojun, YIN Congyuan
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (5): 891-901.   DOI: 10.13209/j.0479-8023.2016.054
Abstract3139)   HTML    PDF(pc) (6159KB)(2465)       Save

On the base of the 3D seismic profile interpretations, combined with the previous findings, geometry and tectonic evolution across and along the Laojunmiao break-thrust belt in the northern margin of the Northern Qilian belt are deciphered. The Laojunmiao belt is a bi-layer thrust system, consisting of a trishear faultpropagation fold system in the upper part, wedge-shaped thrust in the lower part. The Laojunmiao thrust system is linked with the NE-SW striking-slip 134 fault in the western segment, which forms a unified system of fracture on the Laojunmiao belt. Thrusting sheet above the hanging wall of the 134-Laojunmiao fault system is folded under nearly E-S compressive stress field, which results in the N-S striking folding to superpose on the Cenozoic bedding.

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New Word Detection Based on an Improved PMI Algorithm for Enhancing Segmentation System
DU Liping, LI Xiaoge, YU Gen, LIU Chunli, LIU Rui
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (1): 35-40.   DOI: 10.13209/j.0479-8023.2016.024
Abstract3120)   HTML    PDF(pc) (401KB)(2320)       Save

This paper presents an unsupervised method to identify internet new words from the large scale web corpus, which combines with an improved Point-wise Mutual Information (PMI), PMIk algorithm, and some basic rules. This method can recognize internet new words with length from 2 to n (n is any number as needed). Experimented based on 257 MB Baidu Tieba corpus, the precision of proposed system achieves 97.39% when the parameter value of PMIk algorithm is equal to 10, and the precision increases 28.79%, compared to PMI method. The results show that proposed system is significant and efficient for detecting new word from the large scale web corpus. Compiling the results of new word discovery into user dictionary and then loading the user dictionary into ICTCLAS (Institute of Computing Technology, Chinese Lexical Analysis System), experimented with 10 KB Baidu Tieba corpus, the precision, the recall and F-measure were promoted 7.93%, 3.73% and 5.91% respectively, compared with ICTCLAS. The result show that new word discovery could improve the performance of segmentation for web corpus significantly.

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Calculation of Full Carbon Emission and Evaluation of Carbon Emission Performance
ZHANG Xuehua;LI Xiang;YE Wenhu;ZHANG Baoan
   2015, 51 (4): 639-646.   DOI: 10.13209/j.0479-8023.2015.073
Abstract3293)      PDF(pc) (495KB)(2945)       Save
A full carbon emission calculation method is proposed, whose accounts include energy consumption carbon emission, potential carbon consumption of biomass resource consumption, and potential carbon consumption of waste emission. The solar emergy is used as a tool of the same normalized dimension for calculating the amount of full carbon emission. Based on the full carbon emission calculation, population carrying capacity of one unit carbon emission, economic output of one unit carbon emission, and per capita disposable income of one unit carbon emission are considered into one package to construct an index to evaluate the carbon efficiency and development coordination level of a region, and the index is named carbon emission performance integrated index. Taking Beijing and Chongqing as examples, an assessment is made from 2001 to 2011 with the result that the proportion of energy consumption carbon emission in the full carbon emission of the two cities is raised continuously, which indicates that even in the view of full carbon emission, energy consumption is still the main factor affecting carbon emission; however, the effects from modes of both life and production on carbon emission also cannot be neglected. Compared with the traditional carbon efficiency evaluation with only energy carbon emission and carbon production rate considered, the carbon integrated performance evaluation based on “full carbon emission calculation” can fairly and objectively reflect carbon performance of a region, thus it provides a scientific method to identify the responsibility of regional carbon emission reduction.
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An Online Content Analysis on Honeymoon Destination Choice by Chinese Market
WANG Fei;SONG Meng;XIN Xin;LI Xiaodan;WU Bihu
Acta Scientiarum Naturalium Universitatis Pekinensis    DOI: 10.13209/j.0479-8023.2014.157
Methodology and Case Study of Sea Level Prediction Based on Secular Tide Gauge Data
DUAN Xiaofeng,XU Xuegong,CHEN Manchun,LI Xiang
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1299)      PDF(pc) (548KB)(568)       Save
Based on the periodic, trending, and stochasticcharacteristics of secular tide gauge data, a predictive methodology using stochastic-dynamic model was present to the sea level change research. The periodic term was resolved by wavelet and spectrum analysis. Stepwise regression was applied to the trending term analysis. The residual sequence was fitted by autoregression moving average model. Least-squares iteration method was applied for parameter estimation ofthe superposition model, which was composed of significant period model, trending term model and the residual sequenceautoregression moving average model. The stochasticdynamic model is applied to 57 years’monthly mean sea level data from Tanggu tide gauge for case study. The results show that the predictive methodology based on stochastic-dynamic model is feasible and efficient in sea level change prediction. Considering the high accuracy of modeling and predicting, this methodology can be used as a reference for future studies in sea level change.
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Research on Speech Synthesis for Large-Scale Corpora
YU Yansuo,ZHU Fengyun,LI Xiangang,LIU Yi,WU Xihong
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1340)      PDF(pc) (419KB)(1124)       Save
Aiming at roughly labeled corpora with several hundred hours of speech, a novel approach of constructing text-to-speech system is proposed. This approach realizes automatically cleaning and labeling of large-scale corpora by means of speech recognition, text alignment and syntactic parsing. Furthermore, in order to solve the problems of memory space expansion and time consumption for acoustic model training of large-scale corpora, a fast training method, which can ensure the accuracy of acoustic model, is realized through the optimization of conventional process of model training. Subjective evaluations show that the exploitation of large-scale corpora with rough transcription can achieve significant improvement at 0.5 MOS score in contrast with small-scale corpora with exact transcription.
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A Single Device Clock Loaded Contention Constrained RAM Latch Design
JIA Song,LIU Li,LI Tao,LI Xiayu,WANG Yuan,ZHANG Ganggang
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1215)      PDF(pc) (417KB)(380)       Save
A new structure of RAM type latch is proposed in which parallel charging branches are used to solve the contradiction of the switching current and the charging speed. Compared with the conventional structure, new latch can maintain a relatively high rate of charging and reduce the short-circuit power. Furthermore only one MOS transistor is needed as clock load, saving the power consumption of clocking. HSPICE simulation results show that the proposed RAM n-Latch and p-Latch exhibits 12.8% and 25.5% speed improvement, 19.8% and 26.9% PDP (power-delay product) reduction compared to reported structure.
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Volcanic Debris Flow: A New Type of Lower Cretaceous Reservoir in Hailar-Tamtsag Basin
LI Xiaomin,SHI Yongmin,JIANG Hongfu,WANG Lei,QIN Xiaoshuang,WU Wenjuan,CHAI Zhi
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1139)      PDF(pc) (7884KB)(475)       Save
The lower cretaceous oil-bearing reservoir of Hailar-Tamtsag basin is composed of several NNE trending volcanic rift basin group during the early cretaceous. In the early phase, large-scale volcanic debris flow sediment filled in the lacustrine basin center where the source was prolific, which then caused the formation of endogenous volcanic debris flow oil and gas reservoirs that became a new and major reservoir type in the basin. The petrology experiments suggest that the combination of lithology in this reservoir is different from the usual pyroclastic rock such as “tuffaceous sandstone” and “tuff glutenite”. Its mixed facies are caused by rapid accumulation of volcanic debris flow with specific sedimentary origin and paleogeographic environment, which is also a new type of reservoir sedimentary origin on which there is less domestic and international research. The characteristics of this reservoir includes mélange accumulation of tuff and normal glutenite, complex types of pore space, strong water-sensitivity, low permeability, fast change of facies, strong heterogeneity. Since the reservoir is a special type of reservoir with unstable physics and chemistry, it has strong sensibilities and weak cementation, which likely causes strong water-sensitivity, speed-sensitivity, casing damages and deformations, sand productions, and the development is difficult. The investigation of the genetic mechanism of volcanic debris flow reservoir will provide the theoretical basis for optimizing the development method, making rational policy and exploiting economically and effectively.
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A Dynamic Density-Based Clustering Algorithm Appropriate to Large-Scale Text Processing
LI Xia,JIANG Shengyi,ZHANG Qiansheng,ZHU Jing
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1166)      PDF(pc) (524KB)(456)       Save
Because of the high time complexity and complicated parameter setting in traditional density-based clustering algorithm, a new density definition is proposed, which just needs one parameter and can find clusters with different densities. The authors also expand the algorithm to a two-stage dynamic density-based clustering algorithm, which can process large-scale text corpus data. Experiments on synthetic dataset, large-scale dataset from UCI, English text corpus and Chinese text corpus show that TSDDBCA algorithm has the characteristic of easy parameter setting and high clustering efficiency, and can be applied to clustering process to large-scale text data.
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Theory and Application of Numerical Simulation of Asymmetric Hydraulic Fractures in Ultra-Low Permeability Reservoirs
WU Wenjuan,SHI Yongmin,WANG Xiaojun,LIU Hongtao,QIN Xiaoshuang,WANG Lei,CHAI Zhi,LI Xiaomin
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1368)      PDF(pc) (1679KB)(677)       Save
Based on Chang-6 formation of Yanchang group in Erdos basin, built the geology, 3D rock mechanics and 3D stress field models with core and logging data, and obtained the properties of any point between wellbores. With the fracturing principle, the actual geometry of the fractures can be calculated, and the asymmetry fractures model can be built, including the length, height, width and the direction of the fractures. With the analysis of production history, the residual oil distribution can be obtained, and the multiple fracturing procedure can be designed. With the guidance of the asymmetric fracture models, the daily increase of production is more than 4 ton.
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Analysis of Predominant Factors of Volcanic Reservoirs in Carboniferous of Junggar Basin
QIN Xiaoshuang,SHI Yongmin,WU Wenjuan,KOU Yu,WANG Lei,LI Xiaomin,CHAI Zhi
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract1255)      PDF(pc) (6688KB)(631)       Save
According to the core observation and statistics of physical properties, it is found that weathering, tectonism, lithology and litho-facies are the predominant factors of volcanic reservoirs in Carboniferous of Junggar Basin. The reservoir space includes primary fractures, primary porosity, secondary porosity and secondary fractures. The permeability is mostly controlled by fractures. Weathering crust is the main reservoir of volcanic rock in Carboniferous. High quality reservoirs are mainly located 250 m from the top of weathering crust. Among all the high quality reservoirs, the paleohigh around the depression is the better position. As the distance from the top of weathering crust increases, the filling degree of fractures as well as porosity becomes higher and this degrades the reservoir quality.
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Life Cycle Greenhouse Gas Emission Assessment of Fuel Ethanol Based on EIO-LCA
LI Xiaohuan,JI Junping,MA Xiaoming,WANG Jingtian