Background: Narrow band imaging (NBI) is reported to improve the diagnostic importance of nasopharyngeal cancer. The purpose of this review was to evaluate the diagnostic significance of NBI in the literature and comp...Background: Narrow band imaging (NBI) is reported to improve the diagnostic importance of nasopharyngeal cancer. The purpose of this review was to evaluate the diagnostic significance of NBI in the literature and compare it to the conventional white light endoscopy. The use of narrow band imaging (NBI) and further technological achievements concerning the resolution and magnification of endoscopic images have in the past 15 years. With the use of NBI, superficial mucosal lesions, which may be missed by standard WLI endoscopy, can be identified easily by their neoangiogenic pattern. Objective:?To assess diagnostic value of the narrow band imaging and white light endoscopy in nasopharyngeal carcinoma and compare diagnostic values (sensitivity, specificity, positive predictive value and negative predictive value) with white light endoscopy. Search Methods: From 2010 to 2020, data was searched from electronic databases such as PubMed, web of science. We used narrow band imaging as a key word accordance with diagnostic modalities such as sensitivity, specificity, PPV and NPV and data were collected. Results: We have found mainly 6 studies have discussed about diagnostic value of endoscopy in nasopharyngeal carcinoma in the total of 2746 suspected patients. Among them, 5 studies have compared diagnostic values such as sensitivity, specificity, positive predictive value and negative predictive value between NBI and WLE. Among 5 studies, 4 studies have found higher sensitivity in NBI, 2 studies found higher 1 equal to WLE specificity in NBI. 3 studies have compared PPV and NPV between NBI and WLE. Among them, all the studies found higher PPV and NPV in NBI than WLE. Conclusion: Recently?developed narrow band imaging has a great significance in the diagnosis of nasopharyngeal carcinoma. Although NBI has also encountered some problem such as contact bleeding and darker image. So, further evaluation should be done.展开更多
When a renewable energy station(RES)connects to the rectifier station(RS)of a modular multilevel converterbased high-voltage direct current(MMC-HVDC)system,the voltage at the point of common coupling(PCC)is determined...When a renewable energy station(RES)connects to the rectifier station(RS)of a modular multilevel converterbased high-voltage direct current(MMC-HVDC)system,the voltage at the point of common coupling(PCC)is determined by RS control methods.For example,RS control may become saturated under fault,and causes the RS to change from an equivalent voltage source to an equivalent current source,making fault analysis more complicated.In addition,the grid code of the fault ride-through(FRT)requires the RES to output current according to its terminal voltage.This changes the fault point voltage and leads to RES voltage regulation and current redistribution,resulting in fault response interactions.To address these issues,this study describes how an MMC-integrated system has five operation modes and three common characteristics under the duration of the fault.The study also reveals several instances of RS performance degradation such as AC voltage loop saturation,and shows that RS power reversal can be significantly improved.An enhanced AC FRT control method is proposed to achieve controllable PCC voltage and continuous power transmission by actively reducing the PCC voltage amplitude.The robustness of the method is theoretically proven under parameter variation and operation mode switching.Finally,the feasibility of the proposed method is verified through MATLAB/Simulink results.展开更多
文摘Background: Narrow band imaging (NBI) is reported to improve the diagnostic importance of nasopharyngeal cancer. The purpose of this review was to evaluate the diagnostic significance of NBI in the literature and compare it to the conventional white light endoscopy. The use of narrow band imaging (NBI) and further technological achievements concerning the resolution and magnification of endoscopic images have in the past 15 years. With the use of NBI, superficial mucosal lesions, which may be missed by standard WLI endoscopy, can be identified easily by their neoangiogenic pattern. Objective:?To assess diagnostic value of the narrow band imaging and white light endoscopy in nasopharyngeal carcinoma and compare diagnostic values (sensitivity, specificity, positive predictive value and negative predictive value) with white light endoscopy. Search Methods: From 2010 to 2020, data was searched from electronic databases such as PubMed, web of science. We used narrow band imaging as a key word accordance with diagnostic modalities such as sensitivity, specificity, PPV and NPV and data were collected. Results: We have found mainly 6 studies have discussed about diagnostic value of endoscopy in nasopharyngeal carcinoma in the total of 2746 suspected patients. Among them, 5 studies have compared diagnostic values such as sensitivity, specificity, positive predictive value and negative predictive value between NBI and WLE. Among 5 studies, 4 studies have found higher sensitivity in NBI, 2 studies found higher 1 equal to WLE specificity in NBI. 3 studies have compared PPV and NPV between NBI and WLE. Among them, all the studies found higher PPV and NPV in NBI than WLE. Conclusion: Recently?developed narrow band imaging has a great significance in the diagnosis of nasopharyngeal carcinoma. Although NBI has also encountered some problem such as contact bleeding and darker image. So, further evaluation should be done.
基金supported in part by the National Key Research and Development Program of China(No.2020YFF0305800)State Grid Science Technology Project(No.520201210025)。
文摘When a renewable energy station(RES)connects to the rectifier station(RS)of a modular multilevel converterbased high-voltage direct current(MMC-HVDC)system,the voltage at the point of common coupling(PCC)is determined by RS control methods.For example,RS control may become saturated under fault,and causes the RS to change from an equivalent voltage source to an equivalent current source,making fault analysis more complicated.In addition,the grid code of the fault ride-through(FRT)requires the RES to output current according to its terminal voltage.This changes the fault point voltage and leads to RES voltage regulation and current redistribution,resulting in fault response interactions.To address these issues,this study describes how an MMC-integrated system has five operation modes and three common characteristics under the duration of the fault.The study also reveals several instances of RS performance degradation such as AC voltage loop saturation,and shows that RS power reversal can be significantly improved.An enhanced AC FRT control method is proposed to achieve controllable PCC voltage and continuous power transmission by actively reducing the PCC voltage amplitude.The robustness of the method is theoretically proven under parameter variation and operation mode switching.Finally,the feasibility of the proposed method is verified through MATLAB/Simulink results.
