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在不影响Er3+-Tm3+共掺石英光纤超宽带放大特性的前提下,提出了利用串联的方式提高系统功率增益的方法,并模拟仿真了两级串联此种石英光纤的工作特性。仿真结果表明:两级串联的Er3+-Tm3+共掺石英光纤的功率增益可达20 dB,基本上解决了其宽带放大但只具有低功率增益的特性。通过与现阶段其它宽带光放大器比较,可以看出采用此种方式的Er3+-Tm3+共掺石英光纤放大器无论在系统复杂度还是在成本方面都具有明显优势。

Copyright of Science Technology & Engineering is the property of Chinese Society of Technology Economics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Anhui Agricultural Sciences is the property of Journal of Anhui Agricultural Sciences Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Rehabilitation Medicine is the property of China Association of Rehabilitation Medicine, China-Japan Friendship Hospital and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Henan University of Technology Natural Science Edition is the property of Henan University of Technology Journal Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To understand the effects of Feizhusan on the growth performance, serum biochemical indexes, antioxidant levels, and growth hormone levels of fattening pigs, a total of 160 fattening pigs were divided into four groups in this experiment. The control group was fed with basic feed, group 1, 2, and 3 added 1%, 2%, and 4% Feizhusan to the feed. The experimental period was 35 days. During the experiment, the growth of fattening pigs were recorded, and serum biochemical indexes, antioxidant levels, and growth hormone levels were measured on days 0 and 35. The results showed that compared with the control group, the weight gain and average daily weight gain of group1, group 2, and group 3 increased significantly (P<0.01), average daily feed in‐ take of group 2 and group 3 increased significantly (P<0.05). There were no significant difference in feed conversion ratio among the groups (P>0.05). Serum urea nitrogen significantly decreased (P<0.05), serum glucose extremely significantly increased (P<0.01), superoxide dismutase showed an upward trend (0.05< P<0.10), and cortisol significantly decreased (P<0.05). In summary, adding Feizhusan to the feed for fat‐ tening pigs has the effect of improving growth performance, improving serum biochemical indexes, in‐ creasing antioxidant and growth hormone levels，and the recommended dosage is 2%. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Engineering Management & Technology Discussion is the property of Omniscient Pte. Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Science Technology & Engineering is the property of Chinese Society of Technology Economics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Xinyang Normal University Natural Science Edition is the property of Journal of Xinyang Normal University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Modern Medicine & Health is the property of Journal of Modern Medicine & Health and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Computational Mechanics / Jisuan Lixue Xuebao is the property of Chinese Journal of Computational Mechanics Editorial Office, Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the daily precipitation grid data and NECP/NCAR reanalysis data from 1961 to 2018 in Gansu Province, and based on the "east-west reverse" distribution mode of annual precipitation changes, Gansu was divided into two regions with 104 °E as the boundary to conduct research on precipitation event changes of different intensities and analyze their causes. The results showed that the proportion of moderate precipitation events in summer precipitation in both regions exceeded 46%, accounting for the dominant role; the frequency of strong and moderate precipitation events in the western region showed an upward trend, while the frequency of various intensity precipitation events in the eastern region showed a downward trend. The analysis of weather causes showed that when the precipitation in the eastern and western regions tential in the mid latitude region promoted the enhancement of cold and warm air and its convergence in the Gansu region. The development of of Gansu was relatively strong, the South Asian high pressure abnormally strengthened, providing good conditions for high-altitude divergence. The subtropical high pressure in the western Pacific was relatively strong, northward or westward, and the abnormal height of the "+-+" pothe fluctuation trough in the westerly belt, combined with the low vortex on the eastern side of the near surface plateau, will relay low latitude water vapor to the northwest, leading to precipitation. Compared to the eastern region, the summer monsoon system of precipitation in the western region was more anomalous, with significant fluctuations in the westerly belt and a negative anomaly position in the geopotential height towards the north. [ABSTRACT FROM AUTHOR]

Promoting the coordinated development of "population-land-industry" in resource-based shrinking cities is the difficulty and challenge to realize regional high-quality development. This research constructed the evaluation index system of population, land and industrial development level, and used the coupling coordination model to analyze the "population-land-industry" coordinated development of 26 resource-based Shrinking Cities in China in 2008, 2013 and 2018. The results show that: (1) The development level of industrial system in resource-based cities is high, the development of land system is at the middle level, and the development of population system is low. The coordination degree of "population-land-industry" in each city is at the level of near imbalance and slight imbalance, but most cities have an upward trend; (2) There are obvious differences in the development level and coordination degree of population, land, and industry of different types of resource-based shrinking cities. From the development stage, the development level of grown-up cities is the highest, while that of recessionary cities is the lowest. In 2008 and 2013, the average coordination degree ranked as growing city > grownup city > regenerative city > recessionary city, and in 2018, it is growing city> regenerative city > grown-up city > recessionary city. From the perspective of leading industries, the development level of oil&gas-based cities is the highest, while that of coal-based cities is the lowest. In the three years, the order of the average coordination degree is oil&gas-based city > nonmetalbased city > ferrous metal-based city > forestry-based city > coal-based cities. (3) The coordinated development model of "population-land-industry" in resource-based shrinking cities is dominated by population lag and land lag. [ABSTRACT FROM AUTHOR]

Copyright of School Administrators is the property of School Administration Research Association, R.O.C. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new feedback-free jet oscillator component with a splitter is numerically simulated and studied. In order to solve the governing equations, the commercial software ANSYS CFX 19. 2 is used as well as a turbulence model based on the Reynolds-averaged Navier-Strokes (RANS) is used. The study looks into the effect of 5 geo-metric parameters on the oscillation performance including splitter distance, splitter angle, distance between outlet nozzles, splitter radius, and splitter shape. The results show that the frequency can be observed to increase by 1. 46 times by changing the splitter distance, and the effective oscillation is generated within the range of 3. 7-4. 6 mm. It is also found that the increase in the splitter angle, the distance between outlet nozzles and splitter radius initially causes an increase in the frequency then it is followed by a reduction. The simulation results for the splitter shape show that the convex shape makes it easier to oscillate at the same splitting distance. In the later stage, the developed flow control element was applied to the flotation experiment of removing silica from gold ore. The results show that the conversion of the stable intake mode to the oscillating intake mode can significantly improve the flotation recovery rate of silica fine particles, which provides a theoretical basis and technical support for future research of fine and coarse particle flotation. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of School Administrators is the property of School Administration Research Association, R.O.C. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Science Technology & Engineering is the property of Chinese Society of Technology Economics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

牙周炎是发生在牙周支持组织的慢性感染性疾病。牙菌斑中的机会致病菌作为牙周炎发生、发展的启动 因子，在受到局部因素或全身因素刺激后引起牙周组织的免疫防御反应，激活宿主免疫细胞并产生炎症因子、前列 腺素、基质金属蛋白酶及活性氧等细胞因子。其中大量活性氧的产生使得体内抗氧化系统失衡，在杀灭病原体的同 时亦会对牙周组织造成破坏。抗氧化剂是一类能清除自由基，达到消除或抑制氧化反应效果的物质，根据来源可分 为内源性抗氧化剂和外源性抗氧化剂。其中外源性抗氧化剂根据其结构不同可分为维生素及衍生物、天然色素类、 黄酮类、多酚类、纳米材料及其他材料等，多表现出良好的清除活性氧和治疗牙周炎潜力。 [ABSTRACT FROM AUTHOR]

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