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25 March 2018, Volume 2018 Issue 2 Previous Issue    Next Issue

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Existence and non-existence of global solutions for the wave equations JIN Shou-bo, ZHANG Zu-feng 2018, 2018 (2):  1-10.  doi: 10.3969/j.issn.1000-5641.2018.02.001 Abstract ( 485 )   HTML ( 20 )   PDF (299KB) ( 808 )   Save In this paper we investigated the initial boundary value problem for a class of higher order wave equations with two opposite source terms. Firstly, we introduced the latest research progress of the wave equations and defined some important generalized functionals and sets, then the properties of the functionals were discussed. Secondly, it was proved that these sets were invariant under the wave equation. Finally, we proved the existence of global weak solutions by the combination of Galerkin approximation method and potential well method, and obtained the conditions of the non-existence of global weak solutions by using the potential well method and the convexity. The optimal threshold results were given for the existence and non-existence of global weak solutions. References | Related Articles | Metrics

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Global attractors for the coupled damped suspension bridge equations with linear memory HUANG Shang-shang, MA Qiao-zhen 2018, 2018 (2):  11-22.  doi: 10.3969/j.issn.1000-5641.2018.02.002 Abstract ( 505 )   HTML ( 135 )   PDF (315KB) ( 624 )   Save In this paper, we investigate the long-time dynamical behavior of coupled suspension bridge equations with linear memory. We obtain the existence of the global attractors in the weak Hilbert space by using methods of energy estimates and contractive function. References | Related Articles | Metrics

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Exploring equivalent definitions of eulerian graphs SUN Hui, YAO Bing 2018, 2018 (2):  23-30,40.  doi: 10.3969/j.issn.1000-5641.2018.02.003 Abstract ( 414 )   HTML ( 10 )   PDF (739KB) ( 670 )   Save From the topic of equivalent propositions of eulerian graph to start our study, we try to dig the topology of eulerian graph, and to describe eulerian graph from the view of different insights. Finally, we obtain four new equivalent propositions of eulerian graph by the technique of "concentration" and "dilution" operations, which can be transformed into two feasible algorithms. References | Related Articles | Metrics

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Approximation properties of the left quasi-interpolants Gamma operators in Orlicz spaces HAN Ling-xiong 2018, 2018 (2):  31-40.  doi: 10.3969/j.issn.1000-5641.2018.02.004 Abstract ( 383 )   HTML ( 10 )   PDF (291KB) ( 541 )   Save In order to reach better approximation degree, people start to study the quasiinterpolants of operators. In this paper, approximation properties of left quasi-interpolants Gamma operators are discussed by the tools of Ditizan-Totik modulus, K-functional, Hölder's inequality, Cauchy-Schwarz's inequality and Laguerre polynomials and so on. Then we obtain the direct, inverse and equivalence theorems which generalize the results of left quasi-interpolants Gamma operators in Lp space and improve the approximation properties of Gamma operators in Orlicz spaces. References | Related Articles | Metrics

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Efficient verifiable privacy-preserving recommendation system SONG Chun-zhi, DONG Xiao-lei, CAO Zhen-fu 2018, 2018 (2):  41-51,62.  doi: 10.3969/j.issn.1000-5641.2018.02.005 Abstract ( 479 )   HTML ( 16 )   PDF (633KB) ( 676 )   Save To address the problem of privacy disclosure in traditional personalized recommendation systems, this paper proposes an efficient verifiable privacy-preserving recommendation system, which can provide user the way to verify the correctness of the resulting model of cloud computing under the premise of protecting user's data privacy. This paper uses ridge regression to find the best-fit linear curve of user's input data, and implements Yao's garbled circuit to realize the computation and the correctness verification of the recommendation model. The user and the cloud use a newly-devised privacy preserving data aggregation method named AGG (Aggregation) to replace public key homomorphic encryption used in most existing work, which can reduce the computational overhead of the user and the cloud, thus making the system more efficient. The security analysis and the efficiency analysis of the scheme are given at the end of the article. References | Related Articles | Metrics

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Balancing travel satisfaction algorithm for multi-day trip planning XU Kan, ZHENG Jun 2018, 2018 (2):  52-62.  doi: 10.3969/j.issn.1000-5641.2018.02.006 Abstract ( 414 )   HTML ( 10 )   PDF (588KB) ( 643 )   Save Location-based service is a kind of service that obtains the location of mobile user and provides it according to location. Among them, one of the active topics is trip planning. People can make different trip planning to meet their multiple requirements by location-based service. However, in most studies, trip planning only focus on searching one route in many locations according to user's demands. When people are trying to visit the city more than one day, the travel satisfaction of the routes provided by previous researches would reduce by day. Hence, the previous work cannot meet the requirement of multi-day trip planning. To improve the satisfaction stability of multi-day trip planning, we use trip day as one of the multi-day travel planning parameters. We acquire points of interest (POIs) information (e.g., location, scoring, category, etc.) and construct a POI network model, obtain optimal trip routes through heuristic algorithm, develop an effective multi-day travel planning. The experimental results demonstrate that our proposed method can plan a multi-day trip with high quality and more balanced route. References | Related Articles | Metrics

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Detection of fake plate vehicles based on traffic data stream LI Min-xi, MAO Jia-li, YUAN Pei-sen, JIN Che-qing 2018, 2018 (2):  63-76,100.  doi: 10.3969/j.issn.1000-5641.2018.02.007 Abstract ( 608 )   HTML ( 76 )   PDF (1763KB) ( 818 )   Save Since vehicles using fake plate violate traffic laws and regulations, infringe the rights of legal license owners and harm social benefits, it is therefore of great urgency to solve this social problem. In current detection methods, unified speed threshold is used to detect fake plate vehicles. Once an inappropriate threshold was set, it would lead to misjudgements and omissions, and thereby results in a low judgement accuracy. To solve this problem, we propose a two-phase fake plate vehicles detection framework. In the offline part, we train a distributed speed model based on sparse traffic trajectory data to calculate time-dependent thresholds for different roads. In the online part, we apply a sliding-window method to monitor whether a car is an outlier. If a car is continually detected as an outlier, it will be judged as a fake, and vice versa. We then use a real dataset to evaluate our method. The results demonstrate negative influences of noise data can be avoided by our method, so the accuracy of fake plate vehicles detection can be improved significantly. References | Related Articles | Metrics

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Woodpecker: Fine-grained contention simulation database testing framework LI Jie-ying, LI Yu-ming, ZHANG Xiao-lei, ZHANG Rong 2018, 2018 (2):  77-88.  doi: 10.3969/j.issn.1000-5641.2018.02.008 Abstract ( 445 )   HTML ( 9 )   PDF (695KB) ( 601 )   Save With the rich and the growing peformance requirement of applications, various database developments appear, such as row-based, column-based, main memory database and so on. Hence database testing becomes more and more important. Existing automated testing frameworks of database have some problems in flexibility of test, integrality of function and the granularity of test. Firstly they can't support functional test, performance test and DBMS functional test at the same time. Secondly popular benchmark TPC-C simulates workload contention by warehouse which can't quantify contention and maybe execution is different with expectation. Finally the use of test case is static, they can't organize and run test case dynamically. As a consequence this paper presents a flexible database testing framework which is called Woodpecker, its test task descriptive language has abundant primitives, easy-to-use and could write test case efficiently. Woodpecker is the first test framework that can mix three above-mentioned tests in one test case, and simulates workload contention in fine granularity which include read-write contention and write-write contention. We use a simple case in auto increment testing to show the descriptive language's advantage, last we verify the capacity of mixing three tests in Woodpecker, and besides, we show the results of workload contention simulation in performance test. References | Related Articles | Metrics

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Design and implementation of PK answer based on WebSocket ZHU Xiang, DONG Qi-wen, YU Ke-ren 2018, 2018 (2):  89-100.  doi: 10.3969/j.issn.1000-5641.2018.02.009 Abstract ( 467 )   HTML ( 29 )   PDF (892KB) ( 1007 )   Save The development of the Internet has brought great convenience to people's life and work, at the same time, people have more demand for Internet applications. How to help students answer questions onlineis increasingly becoming a reality demand for primary and secondary schools as well as online education platforms. From this realistic demand, an online PK (Player Killing) answer function is proposed. Through the online PK answer, students' interest in learning and their ability to grasp knowledgecan be enhanced. References | Related Articles | Metrics

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Electrical manipulation of Rashba spin-orbit coupling in the two-dimensional transition metal dichalcogenide YAO Qun-fang, CAI Jia, GONG Shi-jing 2018, 2018 (2):  101-108.  doi: 10.3969/j.issn.1000-5641.2018.02.010 Abstract ( 494 )   HTML ( 15 )   PDF (1090KB) ( 1411 )   Save Using the first-principles density functional theory calculations, we investigate the Rashba spin-orbit coupling of the transition metal dichalcogenide (TMD) monolayers MX2(M=Mo, W; X=S, Se, Te) induced by the external electric field. It is found that the anions X play an important role on the Rashba spin-orbit coupling effect. With the increase of the atomic number of X, Rashba spin-orbit splitting around the Γ point increases more distinctively, and the external electric field can hardly influence the cations because of the coverage by the anions. Thus the strength of the Rashba spin-orbit coupling follows the sequence:WTe2 > MoTe2 > WSe2 > MoSe2 > WS2 > MoS2. Furthermore, the distribution of the spin polarization along the high symmetry line Γ-K/K' turns from the vertical direction to the two-dimensional plane under the external electric fields, and the in-plane spin polarization distribution rises with the increase of the external electric field. References | Related Articles | Metrics

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Coherent acoustic phonon inmagnetic thin films excited by femtosecond laser YAN Jia-qi, LI Wei, LOU Shi-tao, ZHANG Xiao-lei 2018, 2018 (2):  109-114.  doi: 10.3969/j.issn.1000-5641.2018.02.011 Abstract ( 641 )   HTML ( 11 )   PDF (576KB) ( 581 )   Save The interaction between the femtosecond laser pulse and the MnIr layer in the magnetic thin film excites the coherent acoustic phonon with an initial phase of 90° and a propagation velocity of 4 300 m/s. The vibration frequency of the acoustic phonon is independent of the laser energy density and is inversely proportional to the total thickness of the magnetic thin film. And the acoustic phono can propagate in the adjacent metal layers due to the high lattice matching. The electron temperature in the magnetic thin film increases sharply absorbing by femtosecond laser pulse, then an decreasing electron temperature gradient with increasing depth is generated instantaneously by the absorption of the laser which lead to the lattice oscillate coherently in the depth direction, that is, the acoustic phonon. In addition, the frequency of the acoustic phonon changes caused by the applied magnetic field is within the experimental error range, indicating that the magnetic interaction is very weak compared to the electrical interaction in the lattice. References | Related Articles | Metrics

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Luminescence characteristics of Eu2+-activated white-emitting phosphor prepared from solar cell cutting Si powder YU Xin-yang, CAI Ya-guo, SUN Zhuo, PIAO Xian-qing 2018, 2018 (2):  115-124.  doi: 10.3969/j.issn.1000-5641.2018.02.012 Abstract ( 454 )   HTML ( 9 )   PDF (1454KB) ( 667 )   Save Eu2+-activated white-emitting phosphors were synthesized by the process of ammonia nitridation at high temperature with the raw material of silicon powder from crystalline silicon solar cells cutting sludge. The effect of Eu2+ doping concentrations on structural and luminescent properties of phosphors was studied in detail. It turns out that the principal crystalline phase of the sample is the mixture of Ca2SiO4, CaSiO3 and Ca2Si5N8. These phosphors can be effectively excited in the range of 300~450 nm, showing intense absorption in ultraviolet to near-ultraviolet region. In addition, they exhibit intense white emissions with CIE (Commission Internationale de L'Eclairage) coordinates of (0.327 5, 0.386 6) under 370 nm excitation with color temperature of 5 705 K(5 431.85℃). There are two luminescence centers in the host, which locate at 470 nm and 570 nm, respectively. With the increase of the doping concentration of Eu2+, the emission reaches an intensity saturation and the optimum doping content of Eu2+ is 10.0 mol% due to the interaction among the activator ions which result in an concentration quenching. Using such a single phosphor, a white light output can be directly achieved combined with UV chip. References | Related Articles | Metrics

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Research progress of the target proteins by proteasome activator REGγ in human cancers CHEN Shao-jun, LI Xiao-tao, ZHENG Jun-hua 2018, 2018 (2):  125-130,159.  doi: 10.3969/j.issn.1000-5641.2018.02.013 Abstract ( 675 )   HTML ( 14 )   PDF (615KB) ( 561 )   Save The proteasome activator REGγ, which is a member of REG (11 S) proteasome activator family, can stimulate the proteolytic activity of the 20 S core proteasome to degrade proteins independent of ubiquitination and ATP. In recent years, more and more studies show that REGγ is dysregulated in various human cancers and closely related to the oncogenesis and development of cancers. The potential mechanism by which REGγ exerts its role in cancer development is degradation of various target proteins. We now review the target proteins of REGγ in human cancers in order to further understand the mechanism by which REGγ exerts its role in cancer development, and to uncover the potential of REGγ to serve as a new marker for diagnosis and a novel target for treatment in human cancers. References | Related Articles | Metrics

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Studies of seasonal variation on genetic toxicity of typical fine particulate matter samples in Shanghai ZHANG Ying, YANG Jing, CHEN Xiao-qian, YANG He-xing, YIN Hao-wen 2018, 2018 (2):  131-140.  doi: 10.3969/j.issn.1000-5641.2018.02.014 Abstract ( 427 )   HTML ( 13 )   PDF (835KB) ( 619 )   Save To explore the genetic toxicity on different components of PM2.5 in Huinan and Pudong during winter and summer, the SOS chromotest is used to detect the genetic toxicity of the total particulate, the organic extract and the water-soluble component. Results shows that tests of the genetic toxicity on the total particulate in Huinan are positive at the highest concentration of 2 mg·mL-1 both in winter and summer, also are positive in Pudong respectively at the concentration of 1 mg·mL-1 in winter and at the highest concentration of 2 mg·mL-1 in summer. Tests of the genetic toxicity at two stations both in winter and summer on the water-soluble component are positive at the highest concentration of 2 mg·mL-1and negative on the the organic extract in the range of 0.000 2 mg·mL-1and 2 mg·mL-1. To further compare the genetic toxicity of the PM2.5 in Huinan and Pudong during winter and summer when exposed to the same volume air, the genetic toxicity of the different components are expressed as the content of the 4-nitroquinoline oxide (4-NQO) per cubic meter of air. Results indicat that the genetic toxicity of the fine particulate matter in Shanghai Puding and Huinan is seasonal and higher in summer than in winter. Furthermore the genotoxic component and the concentration of the total particulate and the water-soluble during winter and summer may be different. It, combined with the result of existing studies that pollutants concentration or components of fine particulate matter were generally higher in winter than in summer at multiple sites in Shanghai, is speculated that the genetic toxicity of atmospheric particulates in every part of Shanghai has similar seasonal change rule. The genotoxic effect of the organic extract is not significant. The main source of the genetic toxicity in the fine particulate matter may be the water-soluble component. The atmospheric pollution at Pudong stationwas continuously serious and equivalent to Huinan stationon the pollution level and the genetic toxicity in same seasons. It is speculated that the genotoxic chemical compositions of atmospheric particulate matter at Pudong station and Huinan station are similar. References | Related Articles | Metrics

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Pollution effects of atmospheric deposition on heavy metals in leafy vegetables and its health risks ZHOU Xiao-xiao, BI Chun-juan, WANG Meng, ZHOU Ya, CHEN Zhen-lou 2018, 2018 (2):  141-150.  doi: 10.3969/j.issn.1000-5641.2018.02.015 Abstract ( 465 )   HTML ( 11 )   PDF (666KB) ( 555 )   Save In order to study the pollution effects of heavy metals in atmospheric deposition on leafy vegetables and health risks via consuming vegetables, this research chooses a farmland near the suburban Shanghai as a study area, makes comparative analysis of heavy metal contents in vegetables samples, including Shanghai Green cabbage, leaf lettuce, amaranth and water spinach, both in outdoor and greenhouses, and makes the health risk assessment of the edible parts of vegetables using the target hazard quotient (THQ). The results show that the heavy metal contents of the vegetables in outdoor are higher than those in greenhouses. The average contents of Zn, Cr, Cu, Pb, Cd, Hg, and As in outdoor vegetables are 7.32, 0.91, 0.52, 0.007, 0.029, 0.002, and 0.014 mg·kg-1, respectively; among which, the contents of Zn, Cr, Cu, Cd, and Hg are 26.4%, 28.4%, 83.3%, 33.9%, and 14% higher than those in greenhouses, respectively. The enrichment factors of greenhouse vegetables are higher than those of outdoor vegetables, showing that the heavy metals of outdoor vegetables are greatly influenced by atmospheric deposition. Different vegetables have different enrichment capacity of heavy metals. Amaranth has the strongest enrichment capacity for Zn, Hg, As and Cu; while water spinach has the most powerful enrichment capacity for Pb. TotalTarget Hazard Quotient (TTHQ)values ofvegetables in outdoor are between 1.41 to 2.99 with an average of 2.29; while those in greenhouses are between 1.10 to 2.19 with an average of 1.85, which is 23.4% lower than the outdoor values. There is a threat for the health of adult and children. The risk of consuming vegetables in outdoor is higher than that in greenhouses. Atmospheric deposition is one of the important sources of heavy metals in vegetables. Hence, we suggest to avoid outdoor cultivating vegetables in high risk areas with atmospheric pollution of heavy metals, thus reducing the impact of atmospheric deposition on enrichment of heavy metals in vegetables. References | Related Articles | Metrics

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Geochemical characteristics of the peat profile in the Yangbajing basin, Tibetan, China and its paleoenvironmental implications MENG Qing-hao, NIU Rui, ZHENG Xiang-min, Zhou Li-min, SUN Cheng-cheng, WANG Lin 2018, 2018 (2):  151-159.  doi: 10.3969/j.issn.1000-5641.2018.02.016 Abstract ( 448 )   HTML ( 9 )   PDF (1371KB) ( 646 )   Save The peat contains abundant information about climate change.In this study, the ratios of characteristic elements in the Yangbajing basin, Tibetan Plateau, are found to be an good indicator for evaluating the regional sedimentary environment (e.g., the change of wet and dry stages), according to the analytical results of special element rations (Fe/Mn, Ba/Sr, K2O/Na2O), humification and mercury (Hg) records in the peat cores. The paleoclimate evolution in the Yangbajing basin is classified as three stages as revealed by the elemental geochemical records:Temperature fluctuates and shows an overall increasing trend between 9.1~7.6 cal ka BP. The sedimentary environment is relatively wet during this period. Significant and frequent fluctuation of temperature is observed between 7.6~4.5 cal ka BP. The sedimentary environment tends to be dry; the temperature fluctuats less and shows a decreasing upward trend 4.5~3.5 cal ka BP. The sedimentary environment tends to be warm and wet. A total of four drying events are recorded in the peat profile, which occurs at approximately 5.8, 6.1, 8.2 and 8.8～8.5 cal ka BP, respectively. The four events recorded in the peat core in the Yangbajing basin are consistent with the regional and global climate records. References | Related Articles | Metrics

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Analyses of saltwater intrusion at the water intake of Qingcaosha reservoir in the Changjiang Estuary in dry season from 2015 to 2017 LI Guo-ping, ZHU Jian-rong 2018, 2018 (2):  160-169.  doi: 10.3969/j.issn.1000-5641.2018.02.017 Abstract ( 437 )   HTML ( 13 )   PDF (4723KB) ( 642 )   Save Based on the measured salinity at the upper and lower water gate of Qingcaosha reservoir from January to Match from 2015 to 2017, and combined the measured river discharge at Datong station, wind at weather station at Chongming eastern shoal, water level at Baozhen hydrologic station and salinity at Chongxi hydrologic station, the frequency and source of saltwater intrusion at the water intake of Qingcaosha reservoir in the last three years were analyzed. The frequencies at the water intake of the reservoir from January to March in 2015, 2016 and 2017 were three, one and one of saltwater intrusion, respectively. Only one time of saltwater intrusion in the dry season of 2016 and 2017 occurred due to the higher river discharge. Among the total five times of saltwater intrusion happened at the water intake from January to March in the last three years, only one of saltwater source was from upstream, i.e., the saltwater-spilling-over from the North Branch into the South Branch, which took about 3 days for the saltwater moving from the Chongxi hydrologic station to the water intake of the reservoir; Four times of saltwater source were from downstream, i.e., the saltwater intrusion through the North Channel, which appeared in neap tide or medium tide after neap tide, was weaker under general wind speed, and was stronger under strong north wind. In view of the saltwater intrusion at the water intake of Qingcaosha reservoir in the last three years, the frequencies of saltwater intrusion coming from the downstream of the North Channel were increased distinctly, and the saltwater intrusion would be severe if strong north wind occurs in neap tide. References | Related Articles | Metrics

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Study of the ebb sediment diversion ratios during wet season in the South and North Passage, Changjiang Estuary YANG Wan-lun, DAO Fu-hai, LUAN Hua-long, GE Jian-zhong, DING Ping-xing 2018, 2018 (2):  170-180.  doi: 10.3969/j.issn.1000-5641.2018.02.018 Abstract ( 510 )   HTML ( 17 )   PDF (1399KB) ( 666 )   Save This study investigates the characteristics of the ebb water and sediment diversion ratios during wet season in the North Passage, Changjiang Estuary and the reasons for the differences within neap-spring tidal cycles based on field measurements. The results of the measurements indicate that the averaged ebb flow diversion ratios of the North Passage in spring and neap tide are 41.9% and 43.1%, respectively, while the averaged ebb sediment diversion ratios of the North Passage in spring and neap tide are 35.1% and 39%,the averaged ebb sediment diversion ratios of the North Passage in spring can approximate representatively ebb sediment diversion status. The ebb sediment diversion ratio of the North Passage is dependent on the ratios of mean flow velocity, suspended sediment concentration and section areas of the North and South Passage. And these parameters show minor changes within neap-spring tidal cycles. Therefore, it can be concluded that the differences of ebb flow and sediment diversions of the North Passage within neap-spring tidal cycles are limited. References | Related Articles | Metrics