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光纤通信产品的激光安全等级认证是国际市场准入的强制要求，但其执行标准为通用激光产品安全标准，操作性不强。针对光纤通信产品的激光安全分级评估，文章根据其激光特性及应用场景，结合国际激光安全通用标准的要求，在测量几何学、激光安全分级、自动降低光功率技术、激光安全分级的评估方法和安全设计要求等方面进行了综合探讨，并提出了两种用于测量光纤通信系统中自动降低光功率激活时间及最大时间间隔内辐射量的方法。该研究可为光纤通信产品的激光安全设计、分级、测试和激光安全等级认证等提供参考。

Copyright of Bearing is the property of Bearing 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 Bearing is the property of Bearing 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 Bearing is the property of Bearing 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.)

The detailed model of the back-to-back converter of the permanent magnet direct drive wind power system contains multiple power electronic devices, and the use of pulse width modulation technology will inevitably increase the mathematical calculation of the simulation system. In view of the problem, a mean value model is proposed to simplify the system so that the wind power system can operate quickly and stably. For the converter mean value model, the controlled power supply is used to replace the converter in structure, and its higher harmonics are ignored in principle, and only the fundamental wave component is retained. In addition, from the perspective of system control, the control strategy of the system is improved by removing the PWM modulation process. Finally, a permanent magnet direct drive wind power system simulation model is built in MATLAB/Simulink, and the system response of the mean model and the detailed model are compared. The simulation results show that the mean value model can not only meet the system accuracy requirements, but also speed up the system simulation speed, greatly improve the system stability, which verifies the rationality of the control strategy. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING 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.)

Objective: To analyze the risk factors of deep venous thrombosis (DVT) in lower extremities, and to explore the clinical efficacy of catheter-contact thrombolysis in the treatment of DVT. Methods: 126 cases of DVT in lower extremities patients who were treated in Beijing Jishuitan Hospital from December 2015 to December 2018 were selected as the case group of this study, and 60 volunteers for physical examination in our hospital during the same period selected as control group . The risk factors of DVT in lower extremities were analyzed by multivariate logistic regression analysis. The case group was randomly divided into two subgroups: systemic thrombolysis group (treated with systemic thrombolysis) and catheter thrombolysis group (treated with catheter-contact thrombolysis), with 63 cases in each group. The curative effect of two groups were evaluated, and the circumference difference of lower limbs and venous patency score of two groups before treatment and 1 month after treatment were observed. The treatment time, hospitalization time, the dosage of urokinase and the occurrence of adverse reactions were recorded and compared between the two groups. Results: There were significant differences in age, body mass index (BMI), red blood cell count (RBC) and surgical trauma history between the case group and the control group (P<0.05). Multivariate logistic regression analysis showed that age, BMI, RBC and surgical trauma history were independent risk factors for DVT in lower extremities (P<0.05). The cure rate of catheter thrombolysis group was 57.14% (36/63), which was higher than that of systemic thrombolysis group 33.33% (21/63) (P<0.05). 1 month after treatment, the bilateral thigh circumference difference, circumference difference of bilateral calf and venous patency scores of the two groups were significantly reduced, and the above indexes of catheter thrombolysis group were significantly lower than those of systemic thrombolysis group. The treatment time and urokinase dosage in catheter thrombolysis group were significantly lower than those of systemic thrombolysis group, but the hospitalization time was significantly longer than that of systemic thrombolysis group (P<0.05). There was no significant difference in incidence of adverse reactions between the two groups (P>0.05). Conclusion: Age, BMI, RBC and history of surgical trauma were independent risk factors for DVT in lower extremities, the efficacy of catheter-contact thrombolysis for DVT in lower extremities is significantly, which has good safety [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing 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.)

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Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays 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 Shandong Medical Journal is the property of Shandong Medical Health Newspapers 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 Shandong Medical Journal is the property of Shandong Medical Health Newspapers 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.)

目的观察动脉腔内裸支架及Viabahn覆膜支架植入治疗长段股浅动脉闭塞的临床效果。方法选取长段股浅动脉闭塞患者33例,均进行腔内治疗,28例开通股浅动脉,其中采用裸支架植入22例、采用Viabahn覆膜支架植入6例。采用多普勒超声检测28例开通股浅动脉者术前及术后2天下肢动脉压力,计算并比较踝肱指数(ABI);检测跛行距离;术后1年行下肢动脉CTA检查,检测闭塞股浅动脉通畅情况。结果 28例开通股浅动脉患者术后即刻DSA检查显示动脉血流均通畅,残留狭窄<30%;术后2天ABI为0.95±0.10,明显高于术前的0.51±0.08(P<0.05);术后2天跛行距离为(703.6±228.5)m,明显高于术前的(205.4±101.2)m,P<0.05;裸支架植入者、Viabahn覆膜支架植入者术后ABI、跛行距离较术前均增加(P均<0.05),但二者术后比较均无统计学差异(P均>0.05)。术后1年CTA检查显示,裸支架植入者股浅动脉通畅率为72.7%(16/22),Viabahn覆膜支架植入者通畅率为100%,两者比较P<0.05。结论动脉腔内裸支架及Viabahn覆膜支架植入治疗长段股浅动脉闭塞近期效果均较好,但Viabahn覆膜支架植入术后1年血管通畅率好于裸支架。 [ABSTRACT FROM AUTHOR]