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25 July 2018, Volume 2018 Issue 4 Previous Issue    Next Issue

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Existence of a travelling wave solution for a single population model with spatio-temporal delay YANG Gao-xiang, ZHAO Lin-long 2018, 2018 (4):  1-8.  doi: 10.3969/j.issn.1000-5641.2018.04.001 Abstract ( 334 )   HTML ( 14 )   PDF (352KB) ( 518 )   Save In this paper, the existence of a travelling wave solution for a single population model with spatio-temporal delay is investigated by employing singular perturbation. The theoretical results are validated by using a numerical method. When the time delay is very small, a wave front solution exists; however, as the time delay increases, the shape of this travelling wave solution can vary and an oscillation wake can occur. References | Related Articles | Metrics

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Spatial Turing pattern of a predator-prey system with nonlinear harvesting effect ZHANG Dao-xiang, SUN Guang-xun, HU Wei, KAI Ge 2018, 2018 (4):  9-22,31.  doi: 10.3969/j.issn.1000-5641.2018.04.002 Abstract ( 414 )   HTML ( 181 )   PDF (2601KB) ( 717 )   Save We study the formation and selection of Turing patterns for a class of predator-prey systems with nonlinear harvesting effect. Firstly, the conditions of Turing instability induced by cross-diffusion terms are given by stability theory, and the existence region of Turing patterns of the system are obtained by bifurcation theory. Secondly, the amplitude equations of the system are derived using the multi-scales analysis method, and the selection results of Turing patterns are given. Finally, Matlab is used to simulate the pattern formation and selection results of the system. The results show that the system has rich Turing patterns, such as spot, stripe, and coexistence of the two types. References | Related Articles | Metrics

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Two optimal inequalities for Neuman-Sándor means YANG Yue-ying, MA Ping 2018, 2018 (4):  23-31.  doi: 10.3969/j.issn.1000-5641.2018.04.003 Abstract ( 380 )   HTML ( 11 )   PDF (252KB) ( 559 )   Save This paper deals with the inequalities involving Neuman-Sándor means using methods of real analysis. The convex combinations of the second contra-harmonic mean D(a, b) and the harmonic root-square mean H(a, b) (or harmonic mean H(a,b)) for the Neuman-Sándor mean M(a, b) are discussed. We find the maximum values λ1, λ2 ∈ (0, 1) and the minimum values μ1, μ2 ∈ (0, 1) such that the two-sided inequalities λ1D(a, b) + (1-λ1)H(a, b) < M(a, b) < μ1D(a, b) + (1-μ1)H(a, b), λ2D(a, b) + (1-λ2)H(a,b) < M(a, b) < μ2D(a, b) + (1-μ2)H(a,b) hold for all a, b > 0 with a≠b. References | Related Articles | Metrics

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The skew-Hermitian {P,k+1} Hamiltonian solutions of a linear matrix equation YONG Jin-jun, CHEN Guo-liang, XU Wei-ru 2018, 2018 (4):  32-46,58.  doi: 10.3969/j.issn.1000-5641.2018.04.004 Abstract ( 440 )   HTML ( 9 )   PDF (414KB) ( 512 )   Save Given P ∈Cn×n and P*=-P=P k+1, we consider the necessary and sufficient conditions such that the matrix equation AX=B is consistent with the skew-Hermitian {P, k + 1} (skew-) Hamiltonian structural constraint. Then, the corresponding expressions of the constraint solutions are also obtained. For any given matrix à ∈ Cn×n, we present the optimal approximate solution ā ∈ Cn×n such that ||Ã-ā|| is minimized in the Frobenius norm sense. If the matrix equation AX=B is not consistent, its least-squares skew-Hermitian {P, k + 1} (skew-) Hamiltonian solutions are given. Under the least-square sense, we consider the best approximate solutions to any given matrix. Finally, some illustrative experiments are also presented. References | Related Articles | Metrics

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Pricing of lookback options under a mixed fractional Brownian movement CHEN Hai-zhen, ZHOU Sheng-wu, SUN Xiang-yan 2018, 2018 (4):  47-58.  doi: 10.3969/j.issn.1000-5641.2018.04.005 Abstract ( 352 )   HTML ( 6 )   PDF (589KB) ( 461 )   Save This paper studied the pricing of European lookback options when the underlying asset followed a mixed fractional Brownian movement and the transaction costs were considered. Firstly, the nonlinear partial differential equation and its boundary condition were obtained using the hedging principle under the model. Secondly, the partial differential equation was reduced using variable substitution. Next, we found its numerical solution by constructing a Crank-Nicolson format. Lastly, the convergence of the numerical scheme was discussed. We also discussed the influence of the transaction fee ratio, Hurst index, and so on. References | Related Articles | Metrics

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A strategy for real-time trajectory privacy protection LIAO Chun-he, HUA Jia-xun, TIAN Xiu-xia, QIN Bo, JIN Che-qing 2018, 2018 (4):  59-69,108.  doi: 10.3969/j.issn.1000-5641.2018.04.006 Abstract ( 449 )   HTML ( 11 )   PDF (1956KB) ( 639 )   Save Real-time trajectory privacy protection is a key research topic in the field of location-based services (LBS). Dummy trajectory technology is a popular privacy protection method which generates multiple fake trajectories similar to real ones. However, existing schemes take into account neither the real environment nor the relationship between adjacent positions carefully; with the help of this ancillary information, the real trajectory can be inferred easily. Hence we integrate entropy and constraints on location reachability into our proposed schemes, named dummy-based trajectory generating (DTG) and enhanced-DTG (EnDTG). Experimental results show that both schemes offer a higher privacy level than existing ones. References | Related Articles | Metrics

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An algorithm for natural language generation via text extracting AI Li-si, TANG Wei-hong, FU Yun-bin, DONG Qi-min, ZHENG Jian-bing, GAO Ming 2018, 2018 (4):  70-79.  doi: 10.3969/j.issn.1000-5641.2018.04.007 Abstract ( 456 )   HTML ( 73 )   PDF (922KB) ( 571 )   Save The aim of natural language generation is to achieve a state where machines can generate text automatically. This would reduce the workload of human language workers and helps us deliver real-time, concise news coverage to readers. It could be applied to many applications, such as question and answers systems, automatic news writing, incident reporting, and so on. The challenge has been one of the open problems for both academia and industry. In this paper, we model the issue as a keyword covering problem and propose an unsupervised approach to extract text for natural language generation.The experimental results illustrate that the algorithm is effective for large-scale corpus; the text coverage is more comprehensive and the generated text is closer to the manual text produced by an individual. References | Related Articles | Metrics

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Incorporating Bayesian inference with random walk for friend recommendations YANG Qing, WANG Hai-yang, BIAN Meng-yang, ZHANG Jing-wei, LIN Yu-ming, ZHANG Hui-bing, ZHANG Hai-tao 2018, 2018 (4):  80-89.  doi: 10.3969/j.issn.1000-5641.2018.04.008 Abstract ( 408 )   HTML ( 9 )   PDF (643KB) ( 485 )   Save Random walk is an effective strategy for dealing with a large user base as well as data sparsity in recommendation problems. However, the current work on recommendation problems do not take full account of the impact implied by both the intimacy difference between users and the reverse social influence. This paper presents an optimized friend recommendation model based on random walk, which introduces frequent pattern mining to capture user intimacy and to optimize the transition probability matrix,and is combined with local reverse search to implement recommendations. In order to make full use of users' attribute information, a Bayesian inference model is proposed for analyzing users' potential friend relationships and combined with random walk to provide better recommendation services. Experiments on real datasets demonstrated the effectiveness of the proposed method. References | Related Articles | Metrics

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Sublink elimination and optimization in data storage and processing separation architecture WANG Yan-zhao, HU Hui-qi, ZHANG Zhao, LIU Xiao-bing, DUAN Hui-chao 2018, 2018 (4):  90-98.  doi: 10.3969/j.issn.1000-5641.2018.04.009 Abstract ( 338 )   HTML ( 12 )   PDF (741KB) ( 434 )   Save This paper implemented a sublink elimination optimizer in NewSQL RDBMS (Relational Database Management System). The purpose of the optimizer is to make complex SQL so that it can be executable in New SQL systems, and achieve auto-tuning of complex SQL to reduce the cost of migrating from a centralized database to a distributed database; this would make the NewSQL DBMS (Database Management System) available to telecomunications and banking industries. We also provide a method to minimize data transmission between servers after sublink promotion. Experiments show that the optimization effect of the query optimizer is notable and can replace manual optimization and reduce the workload of application migration. References | Related Articles | Metrics

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Data calculation and performance optimization of dairy traceability based on Hadoop/Hive ZHU Shu-xin, LI Yue, YUAN Pei-sen, XU Huan-liang, WANG Kang, XIE Zhong-hong 2018, 2018 (4):  99-108.  doi: 10.3969/j.issn.1000-5641.2018.04.010 Abstract ( 418 )   HTML ( 20 )   PDF (1550KB) ( 477 )   Save In order to enhance the performance of traditional dairy traceability systems for the production data of large-scale enterprise, this paper analyzed the supply chain process of dairy enterprises, key traceability units and traceability information; combining Hadoop/Hive big data technology and distributed database technology, the paper designed and constructed a dairy products traceability framework based on Hadoop/Hive. We built a simulated large-scale data environment and used actual production data to test the system performance. The experimental results showed that after the introduction of the Hadoop/Hive technology system, the average data storage speed, the average data access speed, and the average data exchange rate increased by 87.43%, 27.10% and 58.16%, respectively. The improved traceability system for dairy products is superior to the traditional dairy traceability system in storing and processing large-scale data. References | Related Articles | Metrics

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High performance computing in quantum chemistry WANG Tao 2018, 2018 (4):  109-119.  doi: 10.3969/j.issn.1000-5641.2018.04.011 Abstract ( 386 )   HTML ( 20 )   PDF (402KB) ( 596 )   Save High performance computing is widely used for chemical simulations. This paper reviews the current state of parallel computation methods in quantum chemistry; discusses the features, software technology and parallel implements of various quantum chemistry methods; and considers the prospects for the future. References | Related Articles | Metrics

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Collaborative filtering recommendation algorithm based on the self-similarity matrix ZHANG Wei, ZHENG Jun, PANG Jiao-na, BAI Yue 2018, 2018 (4):  120-128,146.  doi: 10.3969/j.issn.1000-5641.2018.04.012 Abstract ( 384 )   HTML ( 11 )   PDF (721KB) ( 527 )   Save A collaborative filtering recommendation algorithm based on self-similar matrices is put forward for the noise problem in the proposed system. In this paper, self-similar matrices are selected as primitive matrices, and the sliding window is chosen as the row vector and column vector of the score. The new score matrix is obtained to preprocess the original scoring matrix to establish the linear relationship between the scoring value and the self-similar matrices. The new scoring matrix preserves the original matrix of scoring information, while weakening the impact of noise data on the recommended system. Experiments show that the pre-processing of the original matrix effectively alleviates the impact of noise in the scoring matrix and improves the performance of the proposed system. References | Related Articles | Metrics

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A study of approximate analytical solutions of a kind of typical second-order nonlinear different equation LOU Zhi-mei, WANG Yuan-bin, WANG Peng 2018, 2018 (4):  129-137.  doi: 10.3969/j.issn.1000-5641.2018.04.013 Abstract ( 474 )   HTML ( 12 )   PDF (329KB) ( 511 )   Save In a non-inertial rotational reference frame, the motion of a system can be governed by a kind of second-order nonlinear differential equation, in which the numerator and denominator both contain nonlinear terms; in this context, it is hard to obtain an approximate solution for this strongly nonlinear equation. In this paper, we study the approximate solution of the second-order nonlinear differential equation by the Adomian decomposition method. Comparisons between the approximate solution and the numerical solution by using two other methods are also made. The results show that, in the first quarter period, the approximate solutions obtained by the Adomian decomposition method is in good agreement with the numerical solutions and the error of the approximate solutions are smaller than the other solutions obtained by the homotopy asymptotic method. References | Related Articles | Metrics

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Study and investigation of Lejeuneaceae species diversity in Anhui Province SHI Xue-qin, TANG Xia, WEI Yu-mei, WANG Jian 2018, 2018 (4):  138-146.  doi: 10.3969/j.issn.1000-5641.2018.04.014 Abstract ( 457 )   HTML ( 9 )   PDF (466KB) ( 496 )   Save This paper studies the diversity of Lejeuneaceae species in Anhui Province based on field data collections and literature review. Our study reveals the occurrence of 46 species in 11 genera of Lejeuneaceae in Anhui Province, including one newly recorded genus (Myriocoleopsis Schiffn.) and 10 newly recorded species. The genus with the largest number of species is Lejeunea (12 spp.) and the second largest genus is Cololejeunea (10 spp.). Floristic analysis shows that tropical elements are the most prevalent among Anhui Lejeuneaceae flora with 27 species, accounting for approximately 58.7% of the Lejeuneaceae species in Anhui Province. East Asian elements, the second most prevalent group, with 13 species accounts for approximately 28.3% of the total number of species. The optimal habitat conditions for most Lejeuneaceae are low mountainous and ravine areas below 400 m as well as alpine areas above 1 600 m. Four epiphyllous liverwort species are newly reported from Guniujiang Nature Reserve in Shitai County. The distribution of epiphyllous liverworts in Eastern China therefore extends north of latitude 30°N. We also analyzed the status of epiphyllous liverworts in this area. References | Related Articles | Metrics

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A study on spatial-temporal differences and factor decomposition of the ecological footprint of Zhejiang Province LI Guo-zhi 2018, 2018 (4):  147-158.  doi: 10.3969/j.issn.1000-5641.2018.04.015 Abstract ( 342 )   HTML ( 8 )   PDF (553KB) ( 496 )   Save Using an ecological footprint model, this paper calculated the ecological footprint and ecological carrying capacity of Zhejiang Province, and further decomposed the ecological footprint using an IPAT model. The results showed that the ecological footprint increased from 7.852×107 ghm2 to 1.5484×108 ghm2 from 2002 to 2015, and that the ecological pressure was significant. At the same time, the ecological efficiency improved rapidly, and the capacity for economic sustainable development improved. The ecological footprint and ecological carrying capacity varied greatly in different regions. Lishui City was the only region with ecological surplus; the ecological efficiency was 1.04×104 yuan/ghm2 in 2015, the highest among all the regions in Zhejiang Province. The results of factor decomposition showed that economic growth was the inhibiting factor for the ecological footprint, and it reduced the ecological footprint to 8.164×107 ghm2 across the whole province. The level of economic development and population size were driving factors, and they increased the ecological footprint by 1.2987×108 ghm2 and 2.810×107 ghm2, respectively, across the whole province. References | Related Articles | Metrics

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Dynamic characteristics and influencing mechanisms of suspended sediment discharge at the outlet of Dongting Lake YU Ya-wen, DAI Zhi-jun, MEI Xue-fei, WANG Jie, WEI Wen 2018, 2018 (4):  159-170.  doi: 10.3969/j.issn.1000-5641.2018.04.016 Abstract ( 413 )   HTML ( 11 )   PDF (2788KB) ( 449 )   Save Dongting Lake's storage capacity is of vital significance to the Changjiang River. The changes in suspended sediment discharge (SSD) from Dongting Lake to the Changjiang River are closely linked to both the lake's evolution and the lake-river relationship. Based on long-term hydrologic data from 1951-2015, the dynamic characteristics of SSD at theDongting Lake outlet and associated controlling factors were analyzed by using percentile, coefficient of variation, and wavelet analysis. The results showed that the SSD time series (1951-2015) could be divided into three sub-periods, namely 1951-1970,1971-2002, and 2003-2015. Specifically, SSD of the first two periods exhibited decreasing trends, while SSD during the 2003-2015 period displayed on upward tendency. Apparent seasonal fluctuations were observed in SSD with a majority of sediment transported in March-December and in March-August during 1951-1970 and 1971-2015, respectively. However, the peak monthly SSD shifted from April in 1951-2002 to May in 2003-2015. Moreover, periodic 44-year and 24-year oscillations were detected across the entire SSD data set. The variation in SSD at the outlet of Dongting Lake can be explained by runoff, water conservancy projects, and the lake's erosion-deposition pattern. It was found that runoff at the outlet of Dongting Lake was the important factor induced the seasonal fluctuation and primary periodic oscillation of SSD. The Jingjiang Cut-off Project is likely responsible for the significant SSD decrease during the period 1971-2002. Annual average SSD over the period 2003-2015 decreased by 30.1% in comparison with 1971-2002 following opening of the Three Gorges Dam. In addition, the SSD series showed an increasing trend after 2007 as the Dongting Lake basin shifted from a deposition state into an erosion state. References | Related Articles | Metrics

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Water mass transport and its controlling mechanisms between the Changjiang Estuary and Subei Coastal Water during the summer ZHU Ping, WU Hui 2018, 2018 (4):  171-183.  doi: 10.3969/j.issn.1000-5641.2018.04.017 Abstract ( 413 )   HTML ( 13 )   PDF (2153KB) ( 503 )   Save The objective of this study was to investigate summertime water movement and its response to wind and tidal forces between the Changjiang Estuary and the Subei coastal area based on a high-resolution, three-dimensional numerical model. The volumetric flux and the freshwater transport from the Changjiang River and the Subei local rivers were quantified across a number of cross-shelf sections. The results indicated that, under the studied climatologic conditions, the net transport in the Subei Coastal Water is generally northward. The velocity of this northward transport reaches 10 cm/s in the shallow area. Offshore transport occurs in the vicinity of the Sheyang Estuary, with a net transport velocity of circa 7 cm/s along the 40 m isobaths. The sectional water flux is related to the tidal range, which reaches a low point in neap tide and a high point in spring tide, respectively. The tide has great impact on water movement in this area. Without the tide, the net water transport is entirely northward north of the Changjiang River Estuary and the southeastward transport along the 40 m isobaths vanishes. On the other hand, the monsoon has no significant influence on the water movement; it only adjusts the water transport in a few local areas. References | Related Articles | Metrics

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Characteristics of sea surface temperature in the Changjiang Estuary and adjacent waters based on a Self-Organizing Map BAI Mei, WU Hui 2018, 2018 (4):  184-194.  doi: 10.3969/j.issn.1000-5641.2018.04.018 Abstract ( 387 )   HTML ( 22 )   PDF (1860KB) ( 509 )   Save Sea surface temperature (SST) in the Changjiang Estuary and adjacent waters is affected by multiple dynamic processes, which show complex spatiotemporal variability. In this study, the SST variability was investigated by analyzing modeled results with a Self-Organizing Map (SOM) method. The SST variations were clustered on seasonal, spring-neap, and intra-tidal timescales. It was found that the SST pattern remains stable during the winter and summer seasons but highly variable during the spring and autumn seasons. A cold water band is present south of the Changjiang River mouth in the winter season, due to the southward along-shore extension of the Changjiang River plume. A cold water patch occurs near the Zhoushan Islands, caused by upwelling in the Zhejiang coastal water. In the Subei coastal water, the cold water patch and tongues were most significant during the winter and spring seasons. References | Related Articles | Metrics