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A Long Dialogue Summary Model Integrating Salience Discourse Context Window Sampling Methods
WU Jie, WANG Pengming, XIONG Zhengkun
Acta Scientiarum Naturalium Universitatis Pekinensis    2024, 60 (1): 53-61.   DOI: 10.13209/j.0479-8023.2023.078
Abstract90)   HTML    PDF(pc) (856KB)(47)       Save
A long dialogue summary generation model with integrated salience discourse context window sampling method (SDCWS) is proposed according to the characteristics of dialogue corpus. The model is divided into two modules. 1) The salience discourse context window sampling module (CWS) evaluates the dialogue discourse for salience, uses the salient discourse as the sampling anchor point, and then sets the sampling window to extract the discourse adjacent to the left and right of the sampling anchor point together as fragments, containing richer discourse relations. 2) The inter-fragment information fusion summary generation module (IF) uses the transformer block to fuse information from mutually independent fragments, enhancing the semantic relationships between fragments and assigning blended weights to fragments during summary generation. The loss-of-consistency mechanism is used to encourage the salience discourse context window sampling module to determine better sampling anchors. Experimental results on the publicly available query-based long conversation summary dataset QMSum show that scores of the proposed model are significantly higher than the best existing model on the ROUGE evaluation metric.
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Research on the Fast-Response Air Pressure Sensor and Spectral Characteristics of the Pressure Fluctuations in the Turbulent Atmosphere
WEI Zhuorui, ZHANG Hongsheng, LI Qianhui, REN Yan, KANG Ling, WANG Pengfei, LIU Haibo
Acta Scientiarum Naturalium Universitatis Pekinensis    2022, 58 (1): 186-194.   DOI: 10.13209/j.0479-8023.2021.122
Abstract539)   HTML    PDF(pc) (5161KB)(168)       Save
Based on the observational data of a self-developed fast-response air pressure sensor at the Atmospheric Boundary Layer and Atmospheric Environment Comprehensive Experimental Station in the Horqin area, Inner Mongolia in the summer of 2019, the characteristic parameters of the pressure fluctuations were calculated, and the spectral characteristics of the pressure fluctuations and the characteristics of the pressure standard deviation were studied. The results show that the self-developed fast-response air pressure sensor can reflect the rapid fluctuations of pressure, and the frequency response is close to 1 Hz. The variance spectra of the pressure fluctuations satisfy the n-2 scaling law in the frequency range from 0.0006 to 0.5 Hz, and the peak frequency is lower than that of the wind speed and temperature. The normalized variance spectra of pressure fluctuations under different atmospheric stabilities merge into a single line in the high-frequency range and distribute around the stability parameter in the low-frequency range. The contribution of pressure fluctuations to turbulent energy is mainly at larger scales, while that of the wind speed and temperature is mainly at smaller scales. The standard deviation and fluctuation intensity of the pressure have obvious diurnal variation characteristics, which is strong during the daytime and weak during the nighttime.
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Vertical Distribution Characteristics of Raindrop Size Distribution at Lower Atmospheric Boundary Layer in Beijing
TANG Jishun, LIU Xiaoyang, LIU Junhui, LI Aiguo, WANG Pengfei
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (6): 1045-1057.   DOI: 10.13209/j.0479-8023.2021.085
Abstract727)   HTML    PDF(pc) (1621KB)(207)       Save
Based on three laser optical Parsivel disdrometers installed at different heights on meteorological tower, the vertical distribution characteristics of raindrop size distribution (DSD) and the influences on rainfall measurement by radar in the lower atmospheric boundary layer were investigated, during 31 precipitation episodes in Beijing from June to August 2020. The results show that the break-up process is dominant from 280 m to 140 m, which leads to the decrease of large scale raindrops and the increase of small scale raindrops. Whereas, from 140 m to ground, the collision-coalescence process is dominant on the falling path of raindrops, which leads to the decrease of large and small scale raindrops and the increase of medium scale raindrops. Because of the great influence on DSD by break up, large scale raindrops in convection rain decrease rapidly with height. The DSD of convective rain in Beijing is different from oceanic-like cluster and continental-like cluster. Due to the change of DSD with height, characteristic parameters of rainfall vary nonlinerly. A Z-R mismatch error would be caused when using ground precipitation data for correction of the meteorological radar rainfall estimation, which is heavier in stratiform and light rain.
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Correction of Measured Speed of OTT-Parsivel on Unstable Platform
LIU Junhui, LIU Xiaoyang, TANG Jishun, LI Aiguo, WANG Pengfei
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (6): 1035-1044.   DOI: 10.13209/j.0479-8023.2021.075
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Aiming at the problem that the measurement results of OTT-Parsivel in elevated environment are prone to error due to the influence of ambient air flow, the authors propose the detection test of OTT-Parsivel on unstable platform, proposes the quality control method under different levels of wind speed, gives the measurement speed correction model, and gives simulation and error analysis. Based on the summer precipitation process in Beijing in 2020, several precipitation cases are analyzed by using the measured data of OTT-Parsivel, three-dimensional ultrasonic wind thermometer and dynamic inclination sensor at 280 meters. The results show that the proposed model has a good correction effect on the vertical falling velocity of raindrops, the velocity distribution of each dimension tends to be normal distribution, and the number of effective particles can increased by 6%. When the horizontal wind speed exceeds 8 m/s, the availability of OTT-Parsivel raindrop spectrometer measurement data is improved.
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Effect of Environment Wind on Measurement of Optical Disdrometer
ZHENG Zheng, LIU Xiaoyang, ZHOU Shougen, WANG Pengfei
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (5): 824-834.   DOI: 10.13209/j.0479-8023.2020.055
Abstract602)   HTML    PDF(pc) (2598KB)(103)       Save
To analyze the data detected by optical disdrometer under the influence of environment wind, this paper uses data measured by OTT-Parsivel and ultrasonic anemometer during several precipitation processed in 2018 in Beijing, and studies how horizontal and vertical wind affect the measurement of disdrometer respectively. When horizontal wind speed is less than 10 m/s and vertical wind speed is less than 0.4 m/s, more than 80% vertical wind speed estimated by velocity of hydrometeors from OTT-Parsivel are consistent with that given by anemometer. While the correction of velocity of hydrometeors brings significant change to raindrop whose diameter is about 1 mm, thereby affects other parameters. Moreover, this paper defines two feature parameters calculated from size and velocity of hydrometeors: the average of standard deviation and the ratio of outlier, which can distinguish more than 80% samples with horizontal wind speed more than 10 m/s. 
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Dynamics Analogy of Thin Elastic Rod and Schrödinger Particle Wave
WANG Peng, XUE Yun
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (4): 676-680.   DOI: 10.13209/j.0479-8023.2016.073
Abstract1052)   HTML    PDF(pc) (533KB)(591)       Save

The Schrödinger analogy of thin elatic rod is studied. Compared with the Kirchhoff dynamics analogy, the Schrödinger analogy is proposed. By the new analogy, the Kirchhoff equation of elastic rod can be written as curvature equation which is similar to nonlinear Schrödinger equation. Thus, the Jacobi elliptic function solution of Schrödinger equation can be taken into elastic rod equation. The space configurations of the elastic rod described by the solution are given. Schrödinger analogy reveals the relations between the quantum state of wave function and the geometry configuration of elastic rod, and gives a new way to solve the Kirchhoff equation.

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Generation of kHz Pulsed Molecular Beams and Its Application in Experimental Research of Strong Field Atomic and Molecular Physics
XU Shaohua;WANG Peng;YANG Hong;WU Chengyin
   2015, 51 (4): 591-595.   DOI: 10.13209/j.0479-8023.2015.014
Abstract1137)      PDF(pc) (2062KB)(536)       Save
The authors successfully generated pulsed molecular beams with high repetition rate by using a cantilever piezo valve, and the highest repetition rate could reach 3 kHz. The interaction between intense femtosecond laser fields and nitrogen molecular beams were studied, in which the molecular beams were produced by cantilever piezo valve. Strong fluorescence emissions, which could be assigned to N2 +(B-X), were observed. The performance of pulse valve was characterized based on the measurement of the fluorescence emission as a function of the repetition rate and the time delay of the pulsed valve. The results demonstrate that pulsed molecular beams can be generated with high quality and high repetition rate. The combination of such pulsed molecular beams and high-frequency kHz femtosecond lasers will promote the experimental study of molecular dynamics driven by intense femtosecond laser fields.
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Adaptive Grid Technique and Its Application to Shock Problems
KANG Hongwen,WANG Pengyun,XU Xiangde
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract633)            Save
Adaptive grid techniques through a variational approach are applied to two shock problems with exact solutions. More grid points are redistributed in the shock regions in response to numerical solution and thus the shock can be captured successfully. The results show the techniques have excellent qualities in improving accuracy of numerical solution and reducing CPU time.
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