Journal of University of Chinese Academy of Sciences

Stochastic dominance comparisons based on interest discount model

ZHUANG Weiwei, DU Xianyang, QIU Guoxin

2024, 41 (4): 433-441. DOI: 10.7523/j.ucas.2022.086

The sufficient conditions for interest discount models increasing in the sense of the first-order stochastic dominance, the second-order stochastic dominance, and the risk-loving stochastic dominance were first given in this paper. We also obtained the sufficient conditions for weighted interest discount models increasing in the sense of the second-order stochastic dominance, and the risk-loving stochastic dominance when the weights decrease in the sense of the majorization order.

Experimental study on the effect of gravity on the heat transfer performance of a novel high-power looped heat pipe

WANG Xinyue, LI Ji

2024, 41 (4): 442-451. DOI: 10.7523/j.ucas.2022.064

Abstract ( 254 ) PDF (0KB) ( 0 )

To solve the problem of huge energy consumption caused by data center cooling, this paper proposes a high-power air-cooled loop heat pipe that can be used for data center server cooling. The effect of gravity on the heat transfer performance of the loop heat pipe was explored through a large number of comparative experiments. The experimental results show that the gradient capillary structure and the method of re-cooling the reflux liquid proposed in this paper can effectively improve the heat transfer performance of the high-power loop heat pipe in different gravity modes. The loop heat pipe with optimized structure has a maximum heat transfer capacity of 950 W and a minimum total thermal resistance of 0.1 ℃/W in gravity-assisted mode. In addition, the high-power loop heat pipe proposed in this paper successfully operated in the anti-gravity mode.

Molecular dynamics study on irradiation damage of single crystal tungsten

LIU Songchang, YU Xin'gang

2024, 41 (4): 452-460. DOI: 10.7523/j.ucas.2022.087

Abstract ( 218 ) PDF (0KB) ( 0 )

Tungsten has been considered the most suitable plasma facing material in magnetic confinement fusion devices due to its excellent physical and chemical properties. However, studies on the defect evolution of tungsten metal under high-energy neutron irradiation are still insufficient. In this paper, the evolution of radiation damage in single crystal tungsten was simulated by using molecular dynamics method. The effects of incident energy, load, and impurity atoms on the evolution of radiation damage, as well as the effects of radiation defects on the mechanical properties of single crystal tungsten were investigated. The results show that the retention of carbon and hydrogen in the tungsten lattice increases the irradiation defects to some extent, with the effect of carbon being more significant than that of hydrogen. Compressive load has a certain inhibitory effect on irradiation defects, while tensile load has the opposite effect. Frenkel defects caused by irradiation can promote the emission of dislocations and hinder the movement of dislocations.

Materialization properties and vapor-liquid phase equilibrium for 5-chloro-2-pentanone with cyclopropyl methyl ketone

XU Lijun, LI Xiang, LI Hui, LIU Long, ZHANG Yanqiang, JIANG Renzheng

2024, 41 (4): 461-467. DOI: 10.7523/j.ucas.2023.005

Abstract ( 147 ) PDF (0KB) ( 0 )

The physical and chemical properties for 5-chloro-2-pentanone and cyclopropyl methyl ketone, including density, viscosity, molar volume, thermal expansion coefficient, and surface tension, were determined. The vapor-liquid phase equilibrium (VLE) of the binary system of 5-chloro-2-pentanone (1) + cyclopropyl methyl ketone (2) was further determined, and Van Laar equation, Wilson equation, and NRTL equation in Aspen Plus V11 were applied to correlate the experimental data. Moreover, the binary interaction parameters were also obtained by regression. The experimental results were confirmed by a thermodynamic consistency examination. This study not only complements the vapor-liquid phase balance database, but also provides thermodynamic data for the isolation of 5-chloro-2-pentanone and cyclopropyl methyl ketone.

Multi-scale featured convolution neural network-based soybean phenotypic prediction

LIN Yutong, WANG Hong, CHAI Tuanyao

2024, 41 (4): 468-476. DOI: 10.7523/j.ucas.2023.046

Abstract ( 404 ) PDF (0KB) ( 9 )

In breeding, single nucleotide polymorphisms (SNPs) in the genome are often used to predict quantitative phenotypes to assist breeding, thereby improving breeding efficiency. The traditional statistical analysis method is limited by many factors including missing data, and its performance sometimes can not meet the requirements. In this paper, we proposed a multi-scale feature convolutional neural network model (MSF-CNN) to predict plant traits. The model extracted SNP features at three different scales through convolution and analyzed the significance of SNP sites through the weight of the SNPs input into the model. The test results showed that MSF-CNN model performed with higher accuracy than the known methods and other deep learning models in phenotype prediction on the datasets with missing genotypic data. This paper also studied the contribution of genotype to traits through saliency map, and discovered several significant SNP loci. These results showed that, compared with other known methods available at present, the deep learning model proposed in this paper can obtain more accurate prediction results of quantitative phenotypes, and can also effectively and efficiently identify SNPs associated with genome-wide association research.

Temporal and spatial variation of summer soil moisture and its driving factors in Yellow River basin during the last 20 years

ZHANG Ya'nan, SONG Xiaoning, LENG Pei, GAO Liang, YIN Dewei

2024, 41 (4): 477-489. DOI: 10.7523/j.ucas.2023.041

Abstract ( 359 ) PDF (0KB) ( 0 )

Based on the moderate resolution imaging spectroradiometer products and global land data assimilation system meteorological data from 2001 to 2020, soil moisture in summer in the Yellow River basin was retrieved based on the vegetation index/land surface temperature trapezoid feature spatial model. The spatial-temporal pattern and driving factors of soil moisture in the Yellow River basin were analyzed using the Sen slope method, Mann-Kendall method, and geographical detector. The results showed that soil moisture in the Yellow River basin had apparent spatial heterogeneity. The source and lower reaches of the Yellow River are humid, while the middle reaches are relatively dry. From 2001 to 2020, soil moisture in the Yellow River basin showed an insignificant increase and an insignificant decrease in space, accounting for 39.54% and 58.01% of the regional area, respectively. The growth rate of soil moisture in the upper reaches was the fastest. Precipitation is the dominant factor of temporal variation of soil moisture in the Yellow River basin. Temperature and elevation are the main factors affecting the spatial variation of soil moisture in the upper reaches, and normalized difference vegetation index and precipitation are the main driving factors influencing soil moisture change in the middle reaches of the Yellow River.

Remote sensing inversion of CO₂ emissions from super-large coal-fired power plants in China based on OCO-2/3 satellite

GUO Wenyue, SHI Yusheng

2024, 41 (4): 490-502. DOI: 10.7523/j.ucas.2023.050

Abstract ( 360 ) PDF (0KB) ( 0 )

Coal-fired power plants are important contributors to CO₂ emissions in China. Due to the low timeliness of statistical data and inaccurate emission factors, the existing emission inventories gradually fail to reflect the CO₂ emissions of power plants. This study provides a method to estimate CO₂ emissions from power plants based on Orbiting Carbon Observatory 2/3 (OCO-2/3) satellite data and Gaussian plume model, retrieving the images of super-large coal-fired power plants (≥5 000 MW) in China from the OCO-2 (September 6,2014-October 1, 2021) and OCO-3 (August 6, 2019-October 1, 2021) dataset, and identifying a total of seven plumes near Tuoketuo, Waigaoqiao, and Jiaxing power plants. Using a combination of three atmospheric background value determination methods, the CO₂ emissions estimated by the Gaussian plume model range from 43 to 77 kt/d, with correlation coefficients ranging from 0.50 to 0.87. The uncertainties of individual plumes varied from 8% to 32% (1σ), with wind speed being the largest uncertainty (6%-31%), followed by background values (5%-18%), enhanced values (1%-21%), and plume rise (1%-8%). The estimates are verified to be in high agreement with Carbon Monitoring for Action, Carbon Brief, and the Global Power Emissions Database (Tuoketuo: (76.48±15.75), Waigaoqiao: (55.98±6.90), Jiaxing: (64.55±15.89) kt/d). This study helps monitor and estimate important point source carbon emissions, which is not only a prerequisite for the power industry to carry out carbon reduction efforts but also helps develop specific regional carbon reduction policies, thereby reducing anthropogenic carbon emissions.

Sedimentary facies and detrital provenance evolution of the Sinian Sugetebulak Formation from northern margin of Tarim Basin: a case study of XH1 well in Tabei uplift

ZHANG Wei, HU Juncheng, ZHANG Yuxiu

2024, 41 (4): 503-516. DOI: 10.7523/j.ucas.2022.073

Abstract ( 177 ) PDF (0KB) ( 0 )

The Tabei uplift from the north of Tarim Basin lacks Sinian outcrops, resulting in a lack of understanding of the Sinian stratigraphic development and provenance evolution. In this study, the detrital components, heavy minerals, detrital zircon U-Pb-Hf isotopic and REE data for the sandstone of the Neoproterozoic Sugetebulak Formation, were studied based on the XH1 well from the Tabei uplift. According to the logging curves, core facies transformation and heavy mineral indexes, it is concluded that the Sinian Sugetebulak Formation in Tabei uplift deposited in tidal flat environment. The U-Pb ages of detrital zircons are divided into four groups: 2 900-2 400, 2 300-1 600, 1 100-900， and 750-580 Ma. The maximum depositional age of the Sugatebulak Formation is no earlier than 572 Ma. The heavy minerals and detrital zircons indicate that the parent rocks are mainly acidic magmatic rocks with small amount of basic-ultrabasic rocks. The provenance is mainly from the Kuruqtage area and its vicinity, the eastern basement of the Tarim Basin and the West Kunlun area, with a small amount from the central Tianshan microcontinent. Paleoproterozoic zircons yield Hf model ages (T_DMC) range from 3 474 Ma to 2 360 Ma, and some Paleoproterozoic zircons show positive ε_Hf(t) values, indicating zircons were derived from juvenile mantle-derived material at those periods. However, most Paleoproterozoic zircons show negative ε_Hf(t) values, suggesting the crustal reworking was the dominant process from Archaean to Paleoproterozoic. The Neoproterozoic detrital zircons have negative ε_Hf(t) values and yield Hf model ages (T_DMC) range from 4 032 Ma to 1 485 Ma, which suggest that the Neoproterozoic detrital zircons were derived from reworking of the ancient Archaean to middle Proterozoic. Based on the data of this study and previous data, it is considered that the northern margin of Tarim Basin was the collision background during the Sugetebulak period.

Regional differences in the flowering phenology of plants in Beijing based on airborne pollen data

SUN Aizhi, WU Shuangshuang, LI Xueyin, YE Caihua

2024, 41 (4): 517-523. DOI: 10.7523/j.ucas.2023.011

Abstract ( 198 ) PDF (0KB) ( 0 )

Airborne pollen is a strong corroboration of phenological events at different spatial and temporal latitudes. Airborne pollen was collected from March 1 to May 31, 2020, using umbrella pollen samplers at two research sites in Beijing (Huairou District, Shijingshan District), with the aim of studying the regional characteristics of flowering phenology of spring-flowering plants from the perspective of airborne pollen, and analyzing the relationship between first flowering time, flowering duration of plants and temperature. The results showed that：1) There are some regional differences in the airborne pollen types and content between Huairou and Shijingshan districts. The airborne pollen in Huairou District belongs to 18 families and genera, with the highest content being Cupressaceae pollen (65%), followed by Populus, Pinus, Ulmus, Rosaceae. The airborne pollen in Shijingshan District belongs to 16 families and genera, with Cupressaceae pollen dominating (41%) but lower than that in Huairou District, followed by Fabaceae, Ulmus and Oleaceae. 2) There are some differences in the first flowering time and flowering duration of spring flowering plants in two areas. The first flowering times in Shijingshan District, which exhibits higher spring temperatures, are earlier than those in Huairou District, except for Populus (2 days later), ranging from 2 to 16 days earlier, with an average of about 7 days. 3) Airborne pollen monitoring data indicates that the first flowering time of spring flowering plants also shows a clear trend of advancement with increasing temperatures in different periods in the same area. These results are basically consistent with the previous results based on plant phenology observation, which indicates that the monitoring results of airborne pollen can also reflect the time and the state of plant flowering phenology, and can provide a multi-disciplinary supplement and reference for the study of plant flowering phenology.

A predistortion correction method for quadrature modulation amplitude and phase imbalance of SAR excitation signal

JIA Yingxin, WANG Yanfei

2024, 41 (4): 524-532. DOI: 10.7523/j.ucas.2022.079

Abstract ( 263 ) PDF (0KB) ( 0 )

Analog I/Q modulation technology is one of the most commonly used and important technical means in broadband synthetic aperture radar (SAR) exciter design. With the increasing instantaneous bandwidth of radar system, the amplitude-phase consistency of analog I/Q modulation can not be completely guaranteed by the symmetrical characteristics of devices, and the spurious distortion caused by the IQ imbalance in broadband radar transmission system will deteriorate progressively. This paper proposes a digital predistortion method which can extract all amplitude-phase errors on the whole transmission channel， mainly including IQ imbalance， by modeling the system error and building a test system, map the amplitude-phase errors to the IQ branch of digital baseband signal output, and compensate the amplitude-phase distortion of the transmission channel. Finally, combined with the actual radar transmitting system, the distortion of the whole transmitting link is corrected by using the predistortion method. The test results before and after correction are given， demonstrating the effectiveness of the method.

A ViSAR-GMTI algorithm based on low-rank sparse decomposition and target trajectory region extraction

YIN Zhongzheng, REN Yuwei, ZHENG Mingjie

2024, 41 (4): 533-540. DOI: 10.7523/j.ucas.2022.082

Abstract ( 196 ) PDF (0KB) ( 0 )

Different observation angles cause changes in the backscattering coefficients of objects resulting in dynamic backgrounds in video synthetic aperture radar (ViSAR)，which is not conducive to the detection of moving objects in complex scenes. A ViSAR moving target detection method based on low-rank sparse decomposition and motion trajectory region extraction is proposed. First, considering the spatial continuity of the target and many interference factors in complex scenes, the conventional RPCA model is improved, and the structured sparsity-inducing norm and robust structure for dynamic background are applied in the model to obtain a better decomposition effect. Secondly, the setting of the local adaptive threshold is optimized, and the composite segmentation method is used to extract the motion trajectory area to further eliminate the interference. The mean background modeling method is used to complete the moving object detection in the trajectory area of the foreground image. Finally, the experimental results based on Qilu-1 data show the effectiveness of the proposed method, and the detection performance of the method is verified by comparative experiments.

Interference avoidance strategy for LEO satellite based on transmit beam sidelobe nulling

WANG Haiwang, ZOU Cheng, CHANG Jiachao, SHAO Fengwei, JIANG Quanjiang, LI Guotong

2024, 41 (4): 541-549. DOI: 10.7523/j.ucas.2022.068

Abstract ( 454 ) PDF (0KB) ( 0 )

With the rapid development of broadband low-orbit satellite systems, communication frequency bands such as Ku and Ka tend to be saturated gradually, and non-geostationary orbit (NGSO) satellites will inevitably cause interference to geostationary orbit (GSO) satellites operating at the same frequency. At present, a spatial isolation strategy is often adopted to avoid interference. NGSO satellites always produce the strongest interference to the collinear area. Increasing the isolation angle can reduce the interference, but it will greatly lose the coverage of the LEO satellite. This paper proposes an interference avoidance strategy based on sidelobe nulling of the transmit beam. The antenna array is divided into row and column elements by establishing the LEO satellite coordinate system. In the dimension of column elements, the robust LCMV algorithm is used to realize wide nulling. In the dimension of row elements, it is expanded in combination with beam direction, and finally forms a “null band” in the direction of the collinear area. Through simulation analysis, the proposed strategy can effectively reduce the interference avoidance isolation area of LEO satellites while avoiding collinear interference. The algorithm has low complexity and is easy to implement on satellites.

Compatible strategy of VDES heterogeneous constellation based on DQN

WANG Xuefan, LI Zongwang, LIANG Xuwen

2024, 41 (4): 550-557. DOI: 10.7523/j.ucas.2022.071

Abstract ( 200 ) PDF (0KB) ( 0 )

As heterogeneous VHF data exchange system (VDES) constellations use the same communication frequency and time division multiple access (TDMA) communication mechanism, a large number of co-channel interference is caused by slot conflicts in the overlapping areas of constellations，reducing the communication quality. To tackle this problem, an inter-constellation compatibility strategy for deep Q-network (DQN) is proposed. Based on the VDES communication process, the ship station is set as the resource information transfer node, which enables the satellite to perceive the communication environment. On this basis, the resource allocation problem in the heterogeneous constellation scenario is modeled as a reinforcement learning (RL) problem, and a DQN-based slot resource allocation algorithm is proposed. By reconstructing the historical and current resource information, the optimal slot resource allocation scheme is planned and the algorithm is iteratively optimized according to the results. Simulation results show that the proposed strategy can effectively enhance communication performance.

Calculation method of time-varying meshing stiffness of helical gear pair based on tooth surface friction

MO Shuai, WANG Dongdong, HU Xiaosong, LIU Zhipeng

2024, 41 (4): 558-565. DOI: 10.7523/j.ucas.2022.069

Abstract ( 266 ) PDF (0KB) ( 0 )

Helical gears are widely used in high-speed and heavy-duty situations due to their smooth transmission and many other advantages. When helical gear pair meshing, it is inevitablely affected by friction, so it is necessary to take tooth surface friction into account when calculating the time-varying meshing stiffness(TVMS) of helical gear pair. Firstly, the helical gear is cut into micro-element slices of spur gear by the slicing method, and then the meshing stiffness of micro-element slices is calculated by the energy method. Finally, the accurate TVMS of helical gear pair is obtained by integral accumulation along the tooth width direction. The change rule of TVMS of helical gear pair under zero friction, constant friction, and time-varying friction is studied. The action mechanism of tooth surface roughness, torque, speed, tooth width, and other parameters on TVMS of helical gear pair under time-varying friction are revealed. The results show that the TVMS of helical gear pair will change under the action of friction; Under constant friction, the TVMS of helical gear pair will decrease, and the greater the constant friction coefficient, the smaller TVMS; Under the action of time-varying friction, the TVMS of helical gear pair will decrease with the increase of tooth surface roughness, increase with the increase of input torque, speed, and tooth width, respectively.

A calculation method and test analysis research of all fresh air ventilation load based on large-scale nursery piggery

WANG Bin, HU Zhiru, YANG Qizhi, WANG Yong, WANG Jinyong

2024, 41 (4): 566-576. DOI: 10.7523/j.ucas.2023.004

Abstract ( 185 ) PDF (0KB) ( 0 )

In order to solve the problems of high energy consumption, challenging load calculation and cross-infection caused by traditional ventilation environmental control method of piggery, this paper takes nursery pigs as the research object and establishes the load calculation model of all fresh air ventilation. The difference in load calculation results between this model and the traditional time-by-time cold load method is less than 5%, which can be applied to simplify the calculation of engineering.Based on the model, the dynamic regulation method of piggery environmental control parameters, considering different outdoor meteorological conditions, is proposed. Experimental results show that, the average relative error between the measured and theoretical values of the piggery temperature under its regulation strategy is 3.4%, and it meets the requirements of temperature, wind speed control value, and uniformity of the summer piggery.When the regulation method is applied to winter operating conditions, only 150 m³/h air volume per pen is required to meet the air quality requirements in the piggery.Under theoretical air supply parameters, the average air temperature in the piggery is measured to be about 26 ℃, the average daily temperature difference is 5 ℃, and the concentration of pollutants such as CO₂, NH₃, and PM_2.5 are far below the national standard limits. The load calculation model and dynamic regulation method can provide reference for the research of thermal and sanitary environment in large-scale nursery piggery.

Current Issue