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25 May 2019, Volume 2019 Issue 3 Previous Issue    Next Issue

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Mathematics

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Existence of weak solutions for a p-Laplace equation with gradient term LI Zhong-qing 2019, 2019 (3):  1-5.  doi: 10.3969/j.issn.1000-5641.2019.03.001 Abstract ( 436 )   HTML ( 62 )   PDF (489KB) ( 412 )   Save This paper is devoted to the study of a quasi-linear elliptic equation with gradient term, where the source term f lies in the space L1. Using the relationship between the coefficient of the zero order term and the source term, the a priori L∞ estimate and the existence of weak solutions are obtained. References | Related Articles | Metrics

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Pseudo-umbilical space-like submanifolds in locally symmetric pseudo-Riemannian manifolds BAI Hui-run, LIU Jian-cheng 2019, 2019 (3):  6-12.  doi: 10.3969/j.issn.1000-5641.2019.03.002 Abstract ( 483 )   HTML ( 247 )   PDF (279KB) ( 355 )   Save In this paper, we study the pseudo-umbilical space-like submanifolds Mn which are immersed into locally symmetric pseudo-Riemannian manifolds Npn+p. When Mn is complete non-compact and has a parallel mean curvature vector field, a pinching theorem for the square length of the second fundamental form of Mn is obtained. When Mn is compact and has a parallel mean curvature vector field, then we prove that Mn is totally geodesic. References | Related Articles | Metrics

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Asymptotic behavior of solutions for the classical reaction-diffusion equation with nonlinear boundary conditions and fading memory WANG Xuan, ZHAO Tao, ZHANG Yu-bao 2019, 2019 (3):  13-23.  doi: 10.3969/j.issn.1000-5641.2019.03.003 Abstract ( 419 )   HTML ( 21 )   PDF (572KB) ( 280 )   Save In this paper, we study the asymptotic behavior of solutions for the classical reaction-diffusion equation with memory. Through the use of abstract function theory and semigroup theory, the existence of a global attractor in L2(Ω)×Lμ2(R+; H1(Ω)) is proven when the internal nonlinearity and boundary nonlinearity adhere to polynomial growth of arbitrary order as well as the balance condition. This result extends and improves some known results. References | Related Articles | Metrics

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Valuation of American continuous-installment put options CEN Yuan-jun 2019, 2019 (3):  24-34,62.  doi: 10.3969/j.issn.1000-5641.2019.03.004 Abstract ( 504 )   HTML ( 20 )   PDF (736KB) ( 300 )   Save Installment options are designed for an investor who is willing to pay a little extra for the opportunity to terminate a contract and reduce losses caused by a void investment position. Because of this extra privilege, installment options are weakly path-dependent. American continuous-installment put options are discussed in this paper. In addition to the right to terminate the contract by stopping the payments at any time, the holder also has the right to exercise the option at any time until maturity; this leads to three potential choices during the holding period:cancel, exercise, or hold on. The mathematical pricing model of this option can be formulated as a parabolic variational inequality, which is a free boundary problem. The existence and uniqueness of the solution can be solved using the penalty method and regular PDE arguments. Different from the standard American put option, this option has two free boundaries irrespective of dividends. Attention is focused on properties of the free boundaries, such as monotonicity, smoothness, and location. References | Related Articles | Metrics

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(d,1)-total labeling of lexicographic products of some classes of graphs HAN Xin-yin, YAO Min, ZUO Lian-cui, ZHOU Wei-na 2019, 2019 (3):  35-41.  doi: 10.3969/j.issn.1000-5641.2019.03.005 Abstract ( 480 )   HTML ( 15 )   PDF (274KB) ( 329 )   Save This paper focuses on (d, 1)-total labeling of the lexicographic products of path Pn and path Pm, path Pn and circle Cn, and gets the exact value of the (d, 1)-total number λdT (G) of lexicographic product Pn·Pm, Pn·Cm under certain constraints. References | Related Articles | Metrics

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Simulation of a queuing model with backup waiters and impatient customers PAN Heng-yi 2019, 2019 (3):  42-54,62.  doi: 10.3969/j.issn.1000-5641.2019.03.006 Abstract ( 473 )   HTML ( 13 )   PDF (1068KB) ( 464 )   Save There are many factors that affect the performance of a queuing system. Under certain assumptions, the number of waiters determines the service efficiency while the presence of impatient customers will affect the service earnings. Traditional queuing theory primarily analyzes queuing models with different time distribution types, while a Monte Carlo simulation model can adapt to the queuing processes of different time distribution types simultaneously. In this paper, several queuing models under common conditions were constructed and simulated by a Monte Carlo simulation; in particular, some commonly used indicators were analyzed. Through a comparison and analysis of the simulation results from these models, it is shown that if the number of waiters is adjusted based on the customer queuing circumstances, it can not only improve service efficiency, but also avoid excessive waste of idle resources and loss of customers. Meanwhile, the simulation results can be used as the basis for setting up queue types and model parameters, as well as a reference for decision making. References | Related Articles | Metrics

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A q-analogy of a nonterminating 7F6-series summation CHEN Ting, WANG Chen-ying 2019, 2019 (3):  55-62.  doi: 10.3969/j.issn.1000-5641.2019.03.007 Abstract ( 408 )   HTML ( 12 )   PDF (280KB) ( 349 )   Save The modified Abel lemma on summation by parts with a "remainder term" was employed to establish a nonterminating basic hypergeometric series transformation which can be seen as a q-analogy of a known 7F6-series summation formula. References | Related Articles | Metrics

Computer Science

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Research on a commodity recommendation algorithm based on reverse furthest neighbor WANG Kai, LI Bo-han, WAN Shuo, ZHANG An-man, GUAN Dong-hai 2019, 2019 (3):  63-77.  doi: 10.3969/j.issn.1000-5641.2019.03.008 Abstract ( 507 )   HTML ( 19 )   PDF (923KB) ( 415 )   Save Effective recommendation algorithms can help maximize the value of a product. By studying the user's preferences, we can recommend underlying contents for the user from mass merchandise information. However, most recommendation systems focus on popular products, ignoring those products that are currently not popular but have huge potential. Our recommendation system, based on reverse furthest neighbor (RFN) queries, uses the idea of mining popular products in niche markets. We improve the traditional collaborative filtering recommendation algorithm and adopt a collaborative filtering algorithm based on expert users. The modified algorithm can recommend products with potential value based on the power law, which makes the distribution of minority mined products more visible to users. Experimental results show that the quality of the proposed algorithm is high and is suitable for partially addressing the long tail problem. References | Related Articles | Metrics

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Recognition of mathematical formulas based on support vector machines LIU Ting-ting, CHENG Tao, JIN Gang-zeng, WANG Xi-kun, GAO Ming 2019, 2019 (3):  78-85.  doi: 10.3969/j.issn.1000-5641.2019.03.009 Abstract ( 526 )   HTML ( 88 )   PDF (902KB) ( 408 )   Save The recognition of mathematical formulas has been widely used in intelligent education applications, such as searching for answers to questions in image format, automatic marking, and constructing a database of questions. Mathematical formulas often exist in the form of images in many applications; hence, identifying the formulas in these images is an important research topic in the field of intelligent education. Given the complex structure of mathematical formulas, however, recognizing their presence within images is far more complicated than a general optical character recognition task. This paper decomposes formula recognition into three steps:character segmentation, character recognition, and formula reconstruction. First, the characters are separated from an image by using a combination of projection and connected-domain methods. Second, the features of characters are extracted based on the proportion of pixels in a single character relative to pixels in all characters, and a supervised learning model is established to identify each character. Finally, the mathematical formula is reconstructed based on the location of each character in the formula. Experimental results on a real data set show the proposed mathematical formula recognition method can achieve an accuracy of up to 98.0%. References | Related Articles | Metrics

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A public opinion analysis model based on Danmu data monitoring and sentiment classification YE Jian, ZHAO Hui 2019, 2019 (3):  86-100.  doi: 10.3969/j.issn.1000-5641.2019.03.010 Abstract ( 643 )   HTML ( 87 )   PDF (2640KB) ( 526 )   Save With the rapid development of online video platforms, Danmu has gradually become an important way for people to express their opinions, and it is particularly welcomed by young people. Unlike conventional texts, Danmu texts are generally short, unstructured, and involve Internet slang as well as conventional stop words to express emotions. In this paper, a public opinion analysis model based on Danmu data is proposed. According to the data generation and storage characteristics of Danmu, a hotspot detection-based loop algorithm is proposed for Danmu data collection. Moreover, the sentiment dictionary to distinguish emotional tendencies is expanded to include network vocabularies commonly appearing in Danmu. Finally, based on the convolutional neural network (CNN), we build a classification model to distinguish positive and negative emotions. Experiments show that the public opinion analysis model of this paper can effectively demonstrate public opinion analysis of Danmu data. References | Related Articles | Metrics

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Vital nodes identification by the hybrid K-shell method based on vertex strength WANG Huan, ZHU Min 2019, 2019 (3):  101-109.  doi: 10.3969/j.issn.1000-5641.2019.03.011 Abstract ( 514 )   HTML ( 16 )   PDF (1359KB) ( 577 )   Save In complex networks, evaluating the importance of individual nodes is of great significance to studying the structure of the network and the propagation process. Based on the location of nodes, the K-shell decomposition algorithm can identify key nodes well; however, it results in many nodes with the same K-shell (Ks) value. Meanwhile, most other algorithms only consider local or global indicators, which can lead to a single factor in judging the importance of a node. In order to better identify key nodes, we propose the extended K-shell and degree of neighbors (EKSDN) algorithm, which considers the global index weighted kernel value of the node and the local index degree of the node comprehensively. A comparison of our experimental results with results from the SIR (Susceptible-Infectious-Recovered) model on real complex networks, show that the proposed algorithm can better quantify the influence of a node. References | Related Articles | Metrics

Physics and Electronics

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Dissociative ionization of allyl bromide in 800 nm and 400 nm intense femtosecond laser fields LIU Yang, LIU Bo-tong, YANG Yan, SUN Zhen-rong 2019, 2019 (3):  110-119.  doi: 10.3969/j.issn.1000-5641.2019.03.012 Abstract ( 415 )   HTML ( 13 )   PDF (1551KB) ( 458 )   Save Using a homemade time-of-flight mass spectrometer, the ionization and dissociation of gaseous molecular allyl bromide in 800 nm and 400 nm femtosecond laser fields were studied. By analyzing the dependence of ion fragment yields and laser intensity, combined with calculation of the Keldysh parameter, it was shown that multi-photon ionization dominates the ionization process involved in our experiment. Based on a theoretical calculation with the Gaussian 09 software package, flexible force constants and appearance energies of different fragment ions were calculated and dissociation channels were identified. Meanwhile, the results demonstrate that non-resonant multi-photon absorption will lead to simultaneous cleavage of multi-chemical bonds; moreover, the charge distribution of parent ions will steer the reaction pathway. References | Related Articles | Metrics

Life Science

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Differences in biodiversity of diurnal and nocturnal waterbirds between natural and artificial wetlands: A case study from Caohai Nature Reserve and Yangwanqiao Reservoir, Guizhou Province LUO Zu-kui, LI Yang, LIU Wen, LI Xing-yuan 2019, 2019 (3):  120-130.  doi: 10.3969/j.issn.1000-5641.2019.03.013 Abstract ( 548 )   HTML ( 19 )   PDF (663KB) ( 382 )   Save In order to compare diurnal and nocturnal differences in waterbird biodiversity between Caohai Nature Reserve (natural wetland) and Yangwanqiao Reservoir (artificial wetland), we investigated waterbirds primarily using the line transect method during the wintering period from 2010 to 2016. The results from daylight hours indicated that avian abundance, richness, unique species, and the G-F index in Caohai Nature Reserve were all significantly higher than those observed in Yangwanqiao Reservoir, both in spring and winter. The results from nighttime indicated that avian abundance, richness, unique species, and G-F index in Caohai Nature Reserve were all significantly higher than those observed in Yangwanqiao Reservoir in winter. However, there were not significant differences in avian abundance, richness, and unique species observed between the two wetlands in spring. Birds with both different foraging ways and different body sizes varied significantly between the wetlands during daytime and nighttime. The size of mudflats, anthropological disturbances, cement banks, and emerging lake aquatic plants are the main factors that bring about differences in the waterbird community between the two wetlands. The status of habitat exploitation by waterbirds in a plot can be shown if avian distribution is observed both during daytime and nighttime. References | Related Articles | Metrics

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Effect of egg yolk immunoglobulin on an experimental periodontitis model induced by Porphyromonas gingivalis WANG Fang, XU Xiao-chen, WU Wen-hui 2019, 2019 (3):  131-137.  doi: 10.3969/j.issn.1000-5641.2019.03.014 Abstract ( 540 )   HTML ( 167 )   PDF (1651KB) ( 384 )   Save This study evaluates the therapeutic effects of egg yolk Immunoglobulin (IgY) on periodontitis in an established rat periodontitis model through the growth inhibition of Porphyromonas gingivalis. Experimental periodontitis was induced in mice by ligation of their second molar with medical thread and oral infection with Porphyromonas gingivalis. Periodontitis rats were randomly divided into control, high-dose, and low-dose groups. Each group was comprised of eight rats. The gingival index (GI), plaque index (PI), and bleeding on probing (BOP) were evaluated, the levels of IL-6 and TNF-α were examined, and an X-ray image and histomorphological section were observed after 28 days. Compared with the control, the scores for PI, GI, and BOP and the levels of IL-6 and TNF-α were significantly decreased in the IgY-treated groups. X-ray images showed that the tooth gap narrowed considerably. Pathological observation, furthermore, showed that periodontal fibers were neatly arranged, a small amount of inflammatory cells were infiltrated, the alveolar ridge was not absorbed, and alveolar bone increased. In conclusion, specific IgY can treat periodontitis induced by P.gingivalis in an established rat periodontitis model. References | Related Articles | Metrics

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Variation in germination rates of moss spores using a cryopreservation technique: A case study of spores from six moss species SUN Li-wei, GAO Xue-di, XU Dan-er, Wang Shu-qin, YANG Zhuo-jun, WANG Jian 2019, 2019 (3):  138-143,154.  doi: 10.3969/j.issn.1000-5641.2019.03.015 Abstract ( 545 )   HTML ( 12 )   PDF (1006KB) ( 423 )   Save To evaluate the applicability of cryopreservation for bryophyte spores, this study explored the effect of dehydration time and low temperature pretreatment; the study was used to identify the optimal conditions for six moss spores collected from different habitats. In addition, varying time periods (1 d, 15 d, 30 d, 90 d, 180 d) of spore cryopreservation were studied under the optimal pretreatment conditions identified. The results showed that:①After dehydration and low temperature pretreatment, the highest germination rates of spores from the six moss species were maintained (87.25%~96.21%). ②Compared to low temperature pretreatment, dehydration seems to be the key point of success for spore cryopreservation. The average spore germination rates ranged from 74.97% to 96.21% when treated with dehydration alone; in comparison, germination rates ranged from 21.73% to 90.94% when pretreated with low temperature alone. ③The average germination rates of spores from five moss species maintained their respective highest level (87.25%~96.21%) after cryopreservation for 1 d and then decreased with the prolongation of storage time; nevertheless, the germination rates still remained at relatively high levels (73.69%~86.60%).④ The average germination rates of spores from Funaria hygrometrica, Pohlia elongate, and Trematodon longicollis after storage for 30 d were 86.49%, 86.60%, and 84.98%, respectively. The germination rates of spores from Bryum blindii and B. caespiticium reached 73.69% and 84.17%, respectively, after storage for 180 d. The study indicates that the procedure for spore cryopreservation could be a simple, stable, and efficient method for storage of bryophyte species in conservation programs. References | Related Articles | Metrics

Ecological and Environmental Science

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A discussion on river network vulnerability in Shanghai based on the PSR model CHENG Rui-hui, FAN Qun-jie, WANG Yu-kun, LIU Yao-yi, CHE Yue 2019, 2019 (3):  144-154.  doi: 10.3969/j.issn.1000-5641.2019.03.016 Abstract ( 496 )   HTML ( 9 )   PDF (777KB) ( 334 )   Save This paper combines the concept of vulnerability with a study of river network systems. Shanghai, a typical river network area, is selected as the research area. Based on the PSR model, river network vulnerability is evaluated using 13 indicators for human activity and the river network environment; the aim of this study was to explore vulnerability characteristics and driving mechanisms for regional river networks. The results show that:①Urbanization has caused distinct differences in water system characteristics between Shanghai's regions. The river networks in Pudong and Qingpu are densely distributed, but sparse in the central urban area. ②The overall river network vulnerability in Shanghai is intermediate. Extreme and severe vulnerability areas, accounting for 24.64% of the city's total area, are concentrated in the central urban area and the main urban areas of suburbs. The moderate and mild vulnerability areas account for 22.71% and 31.93%, respectively. ③River network vulnerability features spatial clustering with clear heterogeneity; distribution patterns typically show only "high" or "low" aggregation. ④There is significant correlation between the four land use patterns and river network vulnerability, and construction is the main driving factor driving changes in river network vulnerability. References | Related Articles | Metrics

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Research on service requirements and management strategies for urban parks with extended opening hours in Shanghai LIU Na-na, GUO Xue-yan, CUI Yi-chong, ZHANG Hong, LU Jun-yao, DA Liang-jun 2019, 2019 (3):  155-163.  doi: 10.3969/j.issn.1000-5641.2019.03.017 Abstract ( 496 )   HTML ( 15 )   PDF (768KB) ( 331 )   Save Based on increasing demand for extended opening hours of urban parks at night, this study explores the satisfaction and service requirements of parks, via questionnaires, from the perspective of visitors and park managers. Based on an analysis of facility status, use characteristics, and park management and maintenance, the study puts forward countermeasures to meet the diverse demands of visitors, strengthen safety, and improve management policies, leveraging the management experience of gate-free urban parks in China and abroad. This study, furthermore, aims to provide a valuable reference for improving the quality of urban parks with extended opening hours. References | Related Articles | Metrics

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Community structure and gene expression analysis for nitrifier enrichment cultures YU Chen-di, HOU Li-jun, ZHENG Yan-ling, LIU Min, YIN Guo-yu, GAO Juan, LIU Cheng, CHANG Yong-kai 2019, 2019 (3):  164-173.  doi: 10.3969/j.issn.1000-5641.2019.03.018 Abstract ( 615 )   HTML ( 13 )   PDF (1293KB) ( 430 )   Save Nitrifiers were enriched from the tidal sediments of the Yangtze Estuary. Four kinds of nitrifying groups (accounting for 34.7% of the total reads) were detected based on metagenomics, including the recently discovered complete ammonia oxidizers (comammox), strictly nitrite-oxidizing Nitrospira, β-proteobacterial ammonia-oxidizing bacteria, and ammonia-oxidizing archaea. Comammox accounted for 48% of the detected nitrifiers. In addition, gene expression patterns of the nitrifier group (according to the classification in Evolutionary genealogy of genes:Non-supervised Orthologous Groupsdatabase) were analyzed based on metatranscriptomics. The present study showed the community structure and gene expression characteristics of nitrifiers enriched from the tidal sediments, especially the newly discovered comammox. Results enriched our knowledge about the nitrifying communities of estuarine environment, which have great significance to the further molecular ecology research of the nitrification processes. References | Related Articles | Metrics

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State of marine microplastic pollution research and the limitations LI Dao-ji, Zhu Li-xin, CHANG Si-yuan, ZHANG Feng, WANG Lu 2019, 2019 (3):  174-185.  doi: 10.3969/j.issn.1000-5641.2019.03.019 Abstract ( 848 )   HTML ( 43 )   PDF (1724KB) ( 886 )   Save Microplastics (less than 5 mm in diameter) are ubiquitously distributed throughout the world's oceans. Marine microplastic pollution has become a global research hotspot and a new frontier in ecological and environmental sciences. The issue has increasingly attracted the attention of scientists, government agencies, and NGOs worldwide. Although the problem of marine plastic pollution was first discovered in the 1970s, it didn't gain attention in the international arena until recent years. Since then, microplastic research has progressed rapidly both globally and in China. However, there are still many problems with the research and response to marine microplastics, requiring further clarification and solutions. This paper first briefly reviews the chronological development of marine microplastic research as well as the role and significance of key events. Thereafter, the paper discusses the state of marine microplastic pollution research and the mitigation efforts in China and abroad, highlighting the current limitations in the research and response to marine plastic and microplastic pollution. References | Related Articles | Metrics

Geography

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HIRAS channel selection for atmospheric CO2 retrievals LI Lu-han, SHU Jiong, YIN Qiu, ZHAGN Lei, LIU Yan-an 2019, 2019 (3):  186-198.  doi: 10.3969/j.issn.1000-5641.2019.03.020 Abstract ( 547 )   HTML ( 14 )   PDF (4564KB) ( 508 )   Save The Hyperspectral Infrared Atmospheric Sounder (HIRAS) instrument onboard the Feng Yun-3D (FY-3D) satellite, launched on November 15, 2017, can be employed to retrieve column concentration of CO2 with strong absorption band sat 15 μm and 4.3 μm. The HIRAS contributes to monitoring constellations for global CO2 observation by comparison with data of other greenhouse gas sensors. Thus, the selection of a band which is concurrently sensitive to CO2 changes and resistant to interference from other parameters is one of the most critical tasks to enable use of the satellite for practical applications. First, based on the line-by-line radiative transfer model, the HIRAS radiance in the hyperspectral 15 μm band was simulated for five standard atmospheric models,and the responses of given channels to the perturbation of CO2 and other atmospheric components (H2O, O3, surface temperature, and emissivity) were analyzed. Second,using the signal-to-interference ratio,the CO2 response, and the Jacobian profiles as criteria, five different sets of channels for each condition were selected by the Optimal Sensitivity Profile (OSP) method; this was accompanied by a discussion of channel differences for different atmosphere stratification. Third, experiments involving different levels of instrumental noise showed that the lower the instrument's noise, the more helpful it is to select a CO2 sensitive height in the stratosphere. The results of the channel selection in this paper present references for instrument design in the future. References | Related Articles | Metrics

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A study on the inversion of atmospheric temperature and humidity profiles by using CrIS infrared hyperspectral satellite data SHEN Zhen-xiang, LIU Chao-shun 2019, 2019 (3):  199-210.  doi: 10.3969/j.issn.1000-5641.2019.03.021 Abstract ( 619 )   HTML ( 15 )   PDF (2185KB) ( 477 )   Save Atmospheric temperature and humidity profile data are basic inputs for numerical weather prediction and climate change assessments, and they are considered indispensable for other scientific research. Improving weather forecast and climate prediction ability by using high spectral satellite data to accurately and quantitatively invert high precision temperature and humidity profiles is of great significance. This paper uses hyperspectral infrared radiation data from the next generation cross-track infrared detector CrIS (Cross-track Infrared Sounder) on the Suomi-NPP (National Polar-orbiting Partnership) satellite as well as reanalysis data of temperature and humidity profiles from the ECMWF (European Centre for Medium-Range Weather Forecasts). In this paper, the D-R (Dual-Regression) inversion algorithm is used to study the inversion of high temperature and humidity profiles. Then, it is compared with measured temperature and humidity profile data from June to Septemberof each year between 2014 and 2016 at the Shanghai Baoshan site and the official temperature and humidity product inversion by NOAA (National Oceanic and Atmospheric Administration)'s official NUCAPS (NOAA Unique Combined Atmospheric Processing System) algorithm. The results show that the total BIAS of the atmospheric temperature profiles retrieved by the D-R algorithm, based on the background field using ECMWF's temperature and humidity reanalysis data, is basically within 1K, and the RMSE (root mean square error) is basically within 2 K, which is equivalent to the NUCAPS algorithm's inversion accuracy. In the lowest layer of the atmosphere, the inversion accuracy of the D-R algorithm remains within 2 K, which is better than the NUCAPS algorithm (RMSE index). The relative humidity at an inversion height below 300 hPa is of the same accuracy as the NUCAPS algorithm, when the RMSE is less than 20% and the BIAS is less than 10%; hence, the inversion result is good and stable. However, when the height is above 300 hPa, the error of the inversion D-R algorithm increases to 30% and the inversion accuracy is reduced. References | Related Articles | Metrics