Journal of University of Chinese Academy of Sciences

DONG Chao, ZHANG Huai, SHI Yaolin

2019, 36 (2): 145-154. DOI: 10.7523/j.issn.2095-6134.2019.02.001

This review simply summarizes geodynamo models, including the control equations, dimensionless scheme, initial and boundary conditions, the numerical methods, the scaling laws, and so on. MoSST model is taken as an example to show the results of geodynamo numerical model. Though in the geodynamo numerical simulation there exist many problems and challenges, it is still an indispensable method to study the geomagnetic field. With the improvement in the computing power in the near future, the geodynamo numerical simulation will achieve great development and will provide powerful supports for understanding the geomagnetic field.

A powerful procedure for multiple outcomes comparison with covariate adjustment and its application to genomic data

ZHANG Shenghu, ZHU Jiayan, ZHANG Sanguo

2019, 36 (2): 155-161. DOI: 10.7523/j.issn.2095-6134.2019.02.002

Abstract ( 298 ) PDF (KB) ( 2 )

Although there are many procedures developed for handling multiple outcomes comparison in the literature, the nonparametric methodology for group comparison with covariate adjustment is still in its infancy. One can use rank-sum test, adjusted rank-sum test, or max-type test by analyzing the processed data orthogonal to the space spanned by covariates. However, the power is not satisfactory. In this work, we combine the adjusted rank-sum test and pseudo F test and then construct a MIN2 test to handle this issue. The performances of MIN2 are thoroughly explored by extensive computer simulations and a real example.

Effects of different convective conditions at cooling and heating ends on the performance of thermoelectric refrigeration

ZHOU Wuyang, WANG Yong

2019, 36 (2): 162-168. DOI: 10.7523/j.issn.2095-6134.2019.02.003

Abstract ( 374 ) PDF (KB) ( 6 )

For a given thermoelectric refrigerator, the main factor that affects the cooling efficiency is the enhanced heat dissipation modes at the cold and hot ends. In this work, the temperature variations of radiators, coolers, and cooling space with time in the states of forced convection and natural convection at the heating end and the cooling end, respectively, were experimentally studied. The experimental results show that under the natural convection at the heating end, the relative temperature of the radiator continues to rise and the relative temperature of the cooler first drops to the minimum and then rises. When the experiment lasts 600 s, the radiator relative temperature and the cooler relative temperature are 26.05℃ and -3.97℃, respectively. Under the forced convection, the radiator and cooler relative temperatures were stable at 3.2℃ and -20.00℃, respectively. There is an optimal value for the amount of the heating end air flow, which minimizes the input power consumption of the cooling fan and the thermoelectric cooling and leads to the best performance of the thermoelectric cooling. When the cooling end is under forced convection, the maximum temperature difference between the cooler and the cooling space is 2℃, while under natural convection the maximum temperature difference is 7℃,which realizes the uniformity of the temperature in cooling space.

Investigation on the concentration, source, and health risk assessment of atmospheric VOCs in urban Jinan

SANG Bo, WEI Fengxia

2019, 36 (2): 169-177. DOI: 10.7523/j.issn.2095-6134.2019.02.004

Abstract ( 239 ) PDF (KB) ( 3 )

Atmospheric VOCs samples were collected to investigate the concentrations, compositions, sources, and health risk of atmospheric VOCs in urban Jinan. Results showed that the total VOCs concentrations were comparable in 2010, 2011, 2015, and 2016, while the total VOCs concentration were lower in 2012, 2013, and 2014. Significant differences in the compositional characteristics were found among alkanes, olefins, and aromatics for each year. Main sources of atmospheric VOCs in urban Jinan during the period of the studied 7 years were determined to be motor vehicle exhaust, industrial emissions, paint and solvent using, and oil evaporation by principal factor analysis (PCA). Health risk assessment of atmospheric VOCs was carried out. The results showed that there was no presence of non-carcinogenic risks during the period of the studied 7 years, while lifetime cancer risks were close to the level of carcinogenic risks in some of the years. Attentions should be paid and measures should be taken.

Spatiotemporal variation of drought conditions based on MODIS data over the source area of Yellow River

LIU Xin, SONG Xiaoning, LENG Pei, XIA Long

2019, 36 (2): 178-187. DOI: 10.7523/j.issn.2095-6134.2019.02.005

Abstract ( 228 ) PDF (KB) ( 2 )

To determine the drought situation over the source area of Yellow River (SAYR) and to analyze the spatiotemporal patterns, the moderate resolution imaging spectroradiometer (MODIS) products, including MOD11A2(8-day land surface temperature)and MOD13A2(16-day vegetation index)in 1 km resolution, were used to obtain the temperature-vegetation drought index (TVDI) over a 10-year period from 2007 to 2016. The results are given as follows. 1) Significant correlation coefficient of 0.7 occurred in the linear fitting between TVDI and in-situ soil moisture measurements, indicating that TVDI could be recognized as an effective drought indicator over the SAYR for monitoring drought. 2) The average TVDI value over the whole study area ranged between 0.4 and 0.6 within the study period, showing a normal condition by drought classification standard. However, the southeastern region revealed various drought conditions. Moreover, grassland in different vegetation coverages in the past 10 years had serious drought conditions. Medium and low vegetation-covered areas showed the similar trend with the TVDI value varying from 0.6 to 1. Severe drought in high vegetation-covered regions was alleviated compared to those with low vegetation coverage. 3) The spatial variation of drought was significant. Severe drought occurred mostly in the northeastern and southeastern regions. The distribution trend basically corresponded to the fact that the overall soil water content in central and western regions was adequate while the regions with severe drought mainly distributed in the northeastern and southeastern regions.

Estimation of GDP based on long time series of DMSP/OLS nighttime light images

GU Pengcheng, WANG Shixin, ZHOU Yi, LIU Wenliang, SHANG Ming

2019, 36 (2): 188-195. DOI: 10.7523/j.issn.2095-6134.2019.02.006

Abstract ( 434 ) PDF (KB) ( 1 )

In this study, the DMSP/OLS nighttime satellite data of China from 1992 to 2013 were used to find the relationships between GDP and nighttime satellite data. The nighttime satellite imageries were corrected by mutual correction, saturation correction, and continuity correction based on the invariant target region method. Then the lighting information of Mainland China and 31 provincial regions were extracted and models between GDP and light information, including linear, quadratic polynomial, power function, and exponential regression models, were tested to find the optimal ones. The results are showed as follows. 1) The corrected DMSP/OLS nighttime satellite data are more stable and continuous than the uncorrected data. 2) There is a strong correlation between the corrected DMSP/OLS night light dataset and GDP. 3) Exponential model was the most suitable one for predicting GDP of Mainland China, with the R² value of 0.97 and MARE of 11.32%.4)Provincial models of long time series are better than the annual provincial administrative region models. The exponential function models were optimal for the four municipalities and the top six provincial economic entities, and the quadratic polynomial models were optimal for the other administrative regions, whose R² values are above 0.95 and MARE's are about 10%.

Three-dimensional numerical modeling of the tectonic evolution of the serial basins in the Hexi Corridor in Northwest China

LI Weilin, CHENG Huihong, ZHANG Huai, SHI Yaolin

2019, 36 (2): 196-207. DOI: 10.7523/j.issn.2095-6134.2019.02.007

Abstract ( 235 ) PDF (KB) ( 3 )

The Hexi Corridor, located in the northeastern margin of Qinghai-Tibet Plateau, is the leading edge of northeastern expanding of Qinghai-Tibet Plateau. In the northeastern thrusting of Qinghai-Tibet Plateau, there forms the landscape of basins and mountains in the Hexi Corridor, which is an ideal area for studying the tectonic evolution of the Cenozoic basins. The four basins, Wuwei, Zhangye, Jiuquan, and Yumen basins, lay in the Hexi Corridor from the east to the west. Based on the Late Cenozoic tectonic environment in the Hexi Corridor and its adjacent areas, the geometric structure of the present basins and fault zones, GPS, and historical seismic data, we establish a three-dimensional visco-elastic-plastic finite element model to describe the tectonic evolution process of the serial basins in the Hexi Corridor dynamically and explore the effects of lateral inhomogeneity of the crust on the tectonic deformation in this area. The results of the simulation are shown as follows. 1) The hard secondary blocks in the Hexi Corridor form four basins in a sequence of left echelon arrangement in the model and they are separated by the NNW-NW faults. 2) Compared with other regions, the Qilian Mountains and the junction areas of the Hexi Corridor with the Qilian Mountains and the Alashan block generally uplift fast and the uplifting speed of the Northern Qilian Mountains is higher than that of the Southern Qilian Mountains. 3) Under the overall compression-torsion, there appears an approximate "pull-point tectonic structure" gap on the Elm Shan fault in the northern Qilian fault zone where the uplifting speed is slower than in the adjacent part on the fault. 4) In the Tarim and Alashan blocks, the upper crust sinks correspondingly and squeezes lower blocks, and thus the tectonic framework between the basins and the mountains forms. The results of the modeling reflect the evolution of the serial basins in the Hexi Corridor, explain the distribution of the current river network in the Qilian Mountains area, and reveal the potential power source of the northeastern thrusting of the northeastern Tibetan Plateau.

Structure-controlled karst development in Middle-Upper Proterozoic strata in the Zhangfang area in Beijing

LIU Jianming, ZHANG Yuxiu, ZENG Lu, JU Yiwen, RUI Xiaoping, QIAO Xiaojuan

2019, 36 (2): 208-217. DOI: 10.7523/j.issn.2095-6134.2019.02.008

Abstract ( 201 ) PDF (KB) ( 4 )

The Zhangfang karst area, located in the southwest of the Zhoukoudian structural province in Beijing, is featured by widespread classic North China type karst. In this study, we analyse the characteristics of the Middle-Late Proterozoic stratigraphic distribution and structural deformation in the Zhangfang area, and we discuss the relationship among the structural evolution, stratigraphic distribution, and karst development. In the Zhangfang area, there mainly exposed the subhorizontal Middle-Late Proterozoic carbonate rocks interbeded with fine clastic rocks and siliceous rocks. This area is characterized by the complex folds, faults, structural fractures, and karst landforms as the products of multiphase structural deformations, including the Indosinian (or earlier) solid-state rheological deformation, the Yanshanian thrust-fold deformation, and the postmagmatic extensional deformation related to the Fangshan pluton. The development of large karst cave systems is mainly related to the Middle-Late Proterozoic lithostratigraphic distribution, the Mesozoic thrust-fold systems, and the Cenozoic extensional faults. With the main controlling factors of different sedimentary rocks, subhorizontal strata, and multiphase structural deformation, there developed four stages of paleokarst in Mesoproterozoic, Paleozoic, Mesozoic, and Cenozoic eras in the Zhangfang area. We document there are three erosion types of karst development including structural uplift, structural inversion, and multiphase uplift.

Scene-independent sound event detection based on multi-state transition model

WANG Jianfei, ZHANG Weiqiang, LIU Jia

2019, 36 (2): 218-225. DOI: 10.7523/j.issn.2095-6134.2019.02.009

Abstract ( 269 ) PDF (KB) ( 7 )

We designed the multi-state transition model for different types of sound events, and combined two kinds of deep neural network to achieve the improvement of the traditional framework. The performance evaluated on the DCASE2017 task2 development dataset showed that the improved DNN-HMM system outperformed the baseline and achieved 19% absolutely lower error rate (ER) and 8.9% relatively higher F-score. The state clustering convolutional neural network (SC-CNN) system based on multi-state transition model also achieved 18% relatively higher F-score and 30% absolutely lower ER, which has reached the international advanced level.

Target recognition performance analysis based on multi-aspect composite SAR images

ZOU Hao, LIN Yun, HONG Wen

2019, 36 (2): 226-234. DOI: 10.7523/j.issn.2095-6134.2019.02.010

Abstract ( 361 ) PDF (KB) ( 2 )

Synthetic aperture radar (SAR) receives the backscatter of target within only a small range of azimuth during the synthetic aperture accumulation time, which makes the SAR image extremely sensitive to the change in observation azimuth. In this study, an SAR image with more obvious features is composed of multiple SAR images obtained at different azimuths by means of non-coherent composition, and then 2DPCA is used to extract features and the k-nearest neighbor method is used for target recognition.Finally the recognition performance is analyzed on two different datasets. The experimental results show that the multi-aspect SAR has a higher recognition rate than the single aspect, and has strong robustness to the change in depression angle.

Multi-rotor UAV's micro-Doppler characteristic analysis and feature extraction

MA Jiao, DONG Yongwei, LI Yuan, LI Lingxiao, YANG Jiefang

2019, 36 (2): 235-243. DOI: 10.7523/j.issn.2095-6134.2019.02.011

Abstract ( 487 ) PDF (KB) ( 2 )

In order to solve the problem of multi-rotor UAV target recognition, a micro-Doppler feature extraction algorithm based on Gabor transform is proposed by combining the instantaneous frequency estimation and fast Fourier transform(FFT). Firstly, the echo model of multi-rotor UAV is established, and the analysis of the influences of number of blades, rotor speed, and initial phase on the micro-Doppler characteristics is made by simulation. Then, Gabor transform is adopted to obtain time-frequency feature. Based on this, micro-Doppler frequency is extracted by the instantaneous frequency maximum value method, and the FFT of instantaneous frequency is used to extract rotor number and rotational frequency. With the above information, the length of the blade is calculated. Finally, the measured data for "Phantom 3S" show that the proposed algorithm extracts the micro-Doppler parameters accurately, indicating the effectiveness of the algorithm.

ISAR sparse imaging algorithm based on generalized minimax concave penalty

YANG Li, WEI Zhonghao, ZHANG Bingchen, LU Xiaojun

2019, 36 (2): 244-250. DOI: 10.7523/j.issn.2095-6134.2019.02.012

Abstract ( 419 ) PDF (KB) ( 3 )

A sparse imaging algorithm of ISAR based on generalized minimax concave (GMC) penalty is deseribed in this paper. The penalty of the algorithm is different from that of the L₁ norm regularization. The penalty function not only maintains the convexity of the least squares cost function to be minimized but also avoids the systematic underestimation characteristic of the L₁ norm regularization. This work illustrates the amplitude preservation characteristics of GMC algorithm in ISAR imaging by simulation experiments and imaging results of real data of Yak-42 aircraft. The results show that GMC algorithm has obvious advantages in imaging accuracy and has better imaging effect.

A new phase unwrapping algorithm of time series InSAR for large bridges

DUAN Wei, LÜ Xiaolei

2019, 36 (2): 251-258. DOI: 10.7523/j.issn.2095-6134.2019.02.013

Abstract ( 293 ) PDF (KB) ( 3 )

Time series InSAR technique can be used to obtain the deformation of buildings, and its application in the bridge deformation monitoring is important to bridge health monitoring due to many profits of space remote sensing. However, the present phase unwrapping methods of time series InSAR make many errors in deformation monitoring of the cable-stayed bridge. Thus it is difficult to acquire the reasonable deformation results of the bridge. This work proposes a new phase unwrapping algorithm based on bipartite graph matching with partitioned residues. After generating the constrained Delaunay triangulation network, the found residues are then partitioned. Finally, the bipartite graph matching algorithm is used to get the optimal connection of positive and negative residues, and the unwrapped phase is acquired by integration of wrapped phase gradient field. The results, tested on real SAR images of the Dongtinghu Bridge, confirm the effectiveness and reliability of the algorithm.

An improved SIFT algorithm for SAR image registration

CHI Yingpeng, LIU Chang

2019, 36 (2): 259-266. DOI: 10.7523/j.issn.2095-6134.2019.02.014

Abstract ( 360 ) PDF (KB) ( 3 )

In view of the features of SAR images, we propose an improved SIFT algorithm based on the traditional SIFT algorithm combined with the ROEWA and OTSU algorithms. The algorithm firstly detects the edge region and shadow area of the image by using ROEWA and OTSU algorithms, respectively. Then, the feature points are fused by using SIFT algorithm to find the matching points and calculate the transformation matrix for image registration. Compared with the original algorithm, this method eliminates the influences of the edge response of the DoG operator and the shadow, makes the extraction of feature points more accurate, and enhances the correct matching rate, the stability of the algorithm, and the accuracy of image registration.

A method of hyperspectral remote sensing image classification based on spectral clustering

YANG Suixin, GENG Xiurui, YANG Weitun, ZHAO Yongchao, LU Xiaojun

2019, 36 (2): 267-274. DOI: 10.7523/j.issn.2095-6134.2019.02.015

Abstract ( 487 ) PDF (KB) ( 3 )

As common unsupervised clustering methods, K-means and spectral clustering methods have some disadvantages and limitations in clustering hyperspectral remote sensing image. Aiming at these problems, a new clustering method of hyperspectral image is proposed in this study. In this method, based on the feature reduction dimension of hyperspectral image data, K-means algorithm is first used to make rough clustering of images. Then spectral clustering method is used to cluster the results of coarse clustering with high precision. Compared with K-means clustering algorithm, this method effectively improves the classification accuracy of hyperspectral image clustering. Experiments on simulated data and real hyperspectral data show that this method has good clustering performance compared with K-means and spectral clustering methods.

Effect of DNA on the oxidase mimetic activity of CeO₂ nanowires

YANG Dingding, YAO Xin

2019, 36 (2): 275-279. DOI: 10.7523/j.issn.2095-6134.2019.02.016

Abstract ( 238 ) PDF (KB) ( 2 )

The CeO₂ nanowires were synthesized by the hydrothermal method. The sample was characterized by transmission electron microscopy, X-ray diffractometer, and Raman spectrometer. Fourier transform infrared spectrometer and UV-Vis spectrophotometer were used to analyze the interaction between DNA and CeO₂ nanowires. The effect of DNA on the oxidase mimetic activity of CeO₂ nanowires was further studied by UV-Vis spectrophotometry. The impact of pH on the system and specificity experiment were also studied. The results show that DNA inhibits the oxidase activity of CeO₂ nanowires, and the inhibition is specific. This work further promotes the practical application of CeO₂ nanowires.

A fast evaluation method of channel imbalance of polarimetric SAR based on common distributed targets

JIANG Sha, QIU Xiaolan, HAN Bing, HU Wenlong, LU Xiaojun

2019, 36 (2): 280-288. DOI: 10.7523/j.issn.2095-6134.2019.02.017

Abstract ( 277 ) PDF (KB) ( 2 )

There are a variety of algorithms in which the calibrated field and calibrator are used to calculate the channel imbalance, but they do not meet the need of normalized quality monitoring because of the limitations to area and revisit frequency. In this work, based on the statistical properties of ground objects' scattering, a fast evaluation method of channel imbalance of polarimetric SAR based on common distributed targets is proposed. The requirements of the method on the scattering characteristics of ground objects are deduced, and the statistical calculation methods are adopted to reduce the requirements. This method achieves the convenient and normalized evaluation of channel imbalance. The experiments of semi-physical simulation and of GF-3 measured data verify the effectiveness of the method.

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