当电网换相换流器高压直流输电（linecommutated converter based high voltage direct current,LCC-HVDC）逆变侧交流母线处含有静止同步补偿器（static synchronous compensator,STATCOM）时,LCC-HVDC与STATCOM均需要各自的锁相环（ph...当电网换相换流器高压直流输电（linecommutated converter based high voltage direct current,LCC-HVDC）逆变侧交流母线处含有静止同步补偿器（static synchronous compensator,STATCOM）时,LCC-HVDC与STATCOM均需要各自的锁相环（phase-locked-loop,PLL）为其控制系统提供基准。该文考虑LCC与STATCOM锁相环各自动态建立含STATCOM的LCC-HVDC系统的小干扰模型,采用经典特征根分析方法,通过对比LCC-HVDC系统与含STATCOM的LCC-HVDC系统二者之间的锁相环与控制系统参数可行域的差异,研究STATCOM对LCC-HVDC小干扰稳定裕度的影响。最后,通过理论计算,对比有无STATCOM投入时LCC-HVDC系统在不同SCR与不同PLL参数下的最大传输有功功率（maximum available power,MAP）及临界短路比（critical short circuit ratio,CSCR）的变化规律。研究结果表明,当LCC-HVDC连接较弱系统时,控制系统之间的耦合作用对LCC锁相环的稳定可行域产生负面影响,可能引发由于LCC锁相环增益过大而导致的整个混合系统的小干扰失稳现象。展开更多
电压源换流器型直流输电(voltage source converter based high voltage direct current,VSC-HVDC)可用于联接弱交流系统,但其联于弱交流系统时的运行特性仍待深入研究。该文以VSC的交流侧稳态潮流方程为基础,归纳两种不同控制方式下VS...电压源换流器型直流输电(voltage source converter based high voltage direct current,VSC-HVDC)可用于联接弱交流系统,但其联于弱交流系统时的运行特性仍待深入研究。该文以VSC的交流侧稳态潮流方程为基础,归纳两种不同控制方式下VSC稳态运行时的交流侧安全稳定性约束条件,分析安全稳定判据随短路比(short-circuit ratio,SCR)的变化规律,解释VSC联于弱交流系统时无法安全稳定运行的现象,并给出求取临界短路比(critical short-circuit ratio,CSCR)的步骤流程。在此基础上,研究各种工况因素(交流等效电动势、交流等效系统阻抗、VSC运行方式等)不同时VSC的CSCR,并和PSCAD的仿真结果进行对比验证。最后,总结VSC的CSCR的主要制约因素,并给出各种运行方式下CSCR的典型范围。展开更多
目的:通过分析中心性浆液性脉络膜视网膜病变(Central Serous Chorioretinopathy,CSCR)的吲哚青绿血管造影(Indocyanine Green Angiography,ICGA)特征,探讨该病的病理特点及治疗机理。方法:使用海德堡血管造影仪对35例临床诊断为CSCR患...目的:通过分析中心性浆液性脉络膜视网膜病变(Central Serous Chorioretinopathy,CSCR)的吲哚青绿血管造影(Indocyanine Green Angiography,ICGA)特征,探讨该病的病理特点及治疗机理。方法:使用海德堡血管造影仪对35例临床诊断为CSCR患者进行ICGA及眼底荧光血管造影(FFA)同步分析,解释和讨论造影结果。结果:35例病例中,有29例(83％)在ICEA中发现的病灶超过FFA所见病灶数,25例(71.4％)为双眼,所有FFA的病灶处均有ICGA改变,且ICGA所见病灶范围大于FFA病变。结论:脉络膜通透性改变是中浆的早期改变,由此引起其上方视网膜色素上皮(RPE)功能失代偿和缺损可能是中浆的主要发病机制。中浆的激光和药物治疗效果和原理需要进一步探讨。眼科学报1999;15:81—84。展开更多
Nowadays in the medicalfield,imaging techniques such as Optical Coherence Tomography(OCT)are mainly used to identify retinal diseases.In this paper,the Central Serous Chorio Retinopathy(CSCR)image is analyzed for vari...Nowadays in the medicalfield,imaging techniques such as Optical Coherence Tomography(OCT)are mainly used to identify retinal diseases.In this paper,the Central Serous Chorio Retinopathy(CSCR)image is analyzed for various stages and then compares the difference between CSCR before as well as after treatment using different application methods.Thefirst approach,which was focused on image quality,improves medical image accuracy.An enhancement algorithm was implemented to improve the OCT image contrast and denoise purpose called Boosted Anisotropic Diffusion with an Unsharp Masking Filter(BADWUMF).The classifier used here is tofigure out whether the OCT image is a CSCR case or not.150 images are checked for this research work(75 abnormal from Optical Coherence Tomography Image Retinal Database,in-house clinical database,and 75 normal images).This article explicitly decides that the approaches suggested aid the ophthalmologist with the precise retinal analysis and hence the risk factors to be minimized.The total precision is 90 percent obtained from the Two Class Support Vector Machine(TCSVM)classifier and 93.3 percent is obtained from Shallow Neural Network with the Powell-Beale(SNNWPB)classifier using the MATLAB 2019a program.展开更多
Background and Objective:Subthreshold laser therapy has emerged as a therapeutic alternative to traditional laser photocoagulation for certain ophthalmic diseases including central serous chorioretinopathy(CSCR),diabe...Background and Objective:Subthreshold laser therapy has emerged as a therapeutic alternative to traditional laser photocoagulation for certain ophthalmic diseases including central serous chorioretinopathy(CSCR),diabetic macular edema(DME),macular edema secondary to branch retinal vein occlusion(BRVO),and age-related macular degeneration(AMD).The objective of this paper is to review and discuss the clinical applications of subthreshold laser and the mechanisms of different subthreshold laser techniques including subthreshold micropulse laser(SMPL),selective retina therapy(SRT),subthreshold nanosecond laser(SNL),endpoint management(EpM),and transpupillary thermotherapy(TTT).Methods:A narrative review of English literature and publicly available information published before November 2021 from literature databases and computerized texts.We discuss the currently available subthreshold laser systems and the advancements made to perform different subthreshold laser techniques for various ophthalmic diseases.We highlight various clinical studies and therapeutic techniques that have been conducted to further understand the effectiveness of subthreshold laser in the clinical setting.We conclude the article by covering emerging subthreshold laser systems that are currently being developed for future clinical use.The PubMed database was utilized for peer-reviewed articles and pertinent information on subthreshold systems was cited from publicly available online websites covering specific systems.Key Content and Findings:Various subthreshold laser systems have been developed to treat certain retinal diseases.Several systems are currently in development for future clinical applications.Conclusions:While conventional laser photocoagulation has been effective in treating various retinal diseases,subthreshold laser systems aim to provide a therapeutic effect without visible signs of damage to the underlying tissue.This technology may be particularly effective in treating macular disorders.Further clinical studies are needed to evaluate their role in the management of retinal diseases.展开更多
Pregnancy requires several changes in the body of the mother to successfully carry and deliver a child.Multiple alterations occur,including changes in cardiovascular system to meet the increased demands of the mother ...Pregnancy requires several changes in the body of the mother to successfully carry and deliver a child.Multiple alterations occur,including changes in cardiovascular system to meet the increased demands of the mother and placenta,the tilting of the hypercoagulable status to a more pro-coagulable state to prevent excessive blood loss post-delivery,and immunologic manipulations to protect the mother and fetus and decreasing the risk of a fatal immunologic response to the allogeneic fetus.These alterations are physiologically normal and expected,but can become pathologic when thresholds are crossed.Pregnancy may cause or exacerbate underlying retinal vascular diseases,a class of disorders compromised predominantly of retinal vein occlusion(RVO),retinal artery occlusion(RAO),central serous retinopathy(CSR),diabetic retinopathy,and hypertensive-related retinopathy,which includes pre-eclampsia,eclampsia,and hemolysis,elevated liver enzymes,and low platelets(HELLP)syndrome.The majority of the literature on retinal changes associated with pregnancy has focused on diabetic retinopathy,while the knowledge regarding the pathogenesis and treatment options of other pregnancy-related vascular diseases remains scarce.Understanding the implications pregnancy has on these rare,but severe,retinal vascular complications can help guide clinical management and potential treatment modalities.This paper aims to serve as a review of the retinal manifestations of diseases outside of diabetic retinopathy.展开更多
Background: To report the outcomes of external drainage of subretinal fluid(SRF) in exudative retinal detachment secondary to central serous chorioretinopathy(CSCR).Methods: Retrospective observational analysis of six...Background: To report the outcomes of external drainage of subretinal fluid(SRF) in exudative retinal detachment secondary to central serous chorioretinopathy(CSCR).Methods: Retrospective observational analysis of six eyes with exudative retinal detachment secondary to CSCR who underwent external drainage of SRF between 2004 and 2014 was performed. Collected data included demographics, steroid usage, surgical details, and visual acuity preoperatively and postoperative visual acuity and clinical examination data were collected. Results: Six eyes of six subjects were included with mean age of 45 years(range, 32 to 61 years). All subjects were male. Mean duration of symptoms was 4.6 months(range, 3 to 8 months). The pre-operative bestcorrected visual acuity(BCVA) ranged from perception of light to 20/60. Four eyes were treated with conventional external drainage and two underwent Chandelier-assisted external drainage. Three cases had laser treatment before drainage and one case underwent photodynamic therapy(PDT) after drainage. The BCVA at last follow-up ranged from 20/2,000(counting fingers at 2 feet) to 20/20. No recurrences were noted in any of the cases till the last follow-up. Mean duration of follow-up was 38 months. Conclusions: Our study demonstrates successful management of exudative retinal detachment secondary to CSCR with external SRF drainage without any complications.展开更多
文摘当电网换相换流器高压直流输电（linecommutated converter based high voltage direct current,LCC-HVDC）逆变侧交流母线处含有静止同步补偿器（static synchronous compensator,STATCOM）时,LCC-HVDC与STATCOM均需要各自的锁相环（phase-locked-loop,PLL）为其控制系统提供基准。该文考虑LCC与STATCOM锁相环各自动态建立含STATCOM的LCC-HVDC系统的小干扰模型,采用经典特征根分析方法,通过对比LCC-HVDC系统与含STATCOM的LCC-HVDC系统二者之间的锁相环与控制系统参数可行域的差异,研究STATCOM对LCC-HVDC小干扰稳定裕度的影响。最后,通过理论计算,对比有无STATCOM投入时LCC-HVDC系统在不同SCR与不同PLL参数下的最大传输有功功率（maximum available power,MAP）及临界短路比（critical short circuit ratio,CSCR）的变化规律。研究结果表明,当LCC-HVDC连接较弱系统时,控制系统之间的耦合作用对LCC锁相环的稳定可行域产生负面影响,可能引发由于LCC锁相环增益过大而导致的整个混合系统的小干扰失稳现象。
文摘电压源换流器型直流输电(voltage source converter based high voltage direct current,VSC-HVDC)可用于联接弱交流系统,但其联于弱交流系统时的运行特性仍待深入研究。该文以VSC的交流侧稳态潮流方程为基础,归纳两种不同控制方式下VSC稳态运行时的交流侧安全稳定性约束条件,分析安全稳定判据随短路比(short-circuit ratio,SCR)的变化规律,解释VSC联于弱交流系统时无法安全稳定运行的现象,并给出求取临界短路比(critical short-circuit ratio,CSCR)的步骤流程。在此基础上,研究各种工况因素(交流等效电动势、交流等效系统阻抗、VSC运行方式等)不同时VSC的CSCR,并和PSCAD的仿真结果进行对比验证。最后,总结VSC的CSCR的主要制约因素,并给出各种运行方式下CSCR的典型范围。
文摘目的:通过分析中心性浆液性脉络膜视网膜病变(Central Serous Chorioretinopathy,CSCR)的吲哚青绿血管造影(Indocyanine Green Angiography,ICGA)特征,探讨该病的病理特点及治疗机理。方法:使用海德堡血管造影仪对35例临床诊断为CSCR患者进行ICGA及眼底荧光血管造影(FFA)同步分析,解释和讨论造影结果。结果:35例病例中,有29例(83％)在ICEA中发现的病灶超过FFA所见病灶数,25例(71.4％)为双眼,所有FFA的病灶处均有ICGA改变,且ICGA所见病灶范围大于FFA病变。结论:脉络膜通透性改变是中浆的早期改变,由此引起其上方视网膜色素上皮(RPE)功能失代偿和缺损可能是中浆的主要发病机制。中浆的激光和药物治疗效果和原理需要进一步探讨。眼科学报1999;15:81—84。
文摘Nowadays in the medicalfield,imaging techniques such as Optical Coherence Tomography(OCT)are mainly used to identify retinal diseases.In this paper,the Central Serous Chorio Retinopathy(CSCR)image is analyzed for various stages and then compares the difference between CSCR before as well as after treatment using different application methods.Thefirst approach,which was focused on image quality,improves medical image accuracy.An enhancement algorithm was implemented to improve the OCT image contrast and denoise purpose called Boosted Anisotropic Diffusion with an Unsharp Masking Filter(BADWUMF).The classifier used here is tofigure out whether the OCT image is a CSCR case or not.150 images are checked for this research work(75 abnormal from Optical Coherence Tomography Image Retinal Database,in-house clinical database,and 75 normal images).This article explicitly decides that the approaches suggested aid the ophthalmologist with the precise retinal analysis and hence the risk factors to be minimized.The total precision is 90 percent obtained from the Two Class Support Vector Machine(TCSVM)classifier and 93.3 percent is obtained from Shallow Neural Network with the Powell-Beale(SNNWPB)classifier using the MATLAB 2019a program.
文摘Background and Objective:Subthreshold laser therapy has emerged as a therapeutic alternative to traditional laser photocoagulation for certain ophthalmic diseases including central serous chorioretinopathy(CSCR),diabetic macular edema(DME),macular edema secondary to branch retinal vein occlusion(BRVO),and age-related macular degeneration(AMD).The objective of this paper is to review and discuss the clinical applications of subthreshold laser and the mechanisms of different subthreshold laser techniques including subthreshold micropulse laser(SMPL),selective retina therapy(SRT),subthreshold nanosecond laser(SNL),endpoint management(EpM),and transpupillary thermotherapy(TTT).Methods:A narrative review of English literature and publicly available information published before November 2021 from literature databases and computerized texts.We discuss the currently available subthreshold laser systems and the advancements made to perform different subthreshold laser techniques for various ophthalmic diseases.We highlight various clinical studies and therapeutic techniques that have been conducted to further understand the effectiveness of subthreshold laser in the clinical setting.We conclude the article by covering emerging subthreshold laser systems that are currently being developed for future clinical use.The PubMed database was utilized for peer-reviewed articles and pertinent information on subthreshold systems was cited from publicly available online websites covering specific systems.Key Content and Findings:Various subthreshold laser systems have been developed to treat certain retinal diseases.Several systems are currently in development for future clinical applications.Conclusions:While conventional laser photocoagulation has been effective in treating various retinal diseases,subthreshold laser systems aim to provide a therapeutic effect without visible signs of damage to the underlying tissue.This technology may be particularly effective in treating macular disorders.Further clinical studies are needed to evaluate their role in the management of retinal diseases.
文摘Pregnancy requires several changes in the body of the mother to successfully carry and deliver a child.Multiple alterations occur,including changes in cardiovascular system to meet the increased demands of the mother and placenta,the tilting of the hypercoagulable status to a more pro-coagulable state to prevent excessive blood loss post-delivery,and immunologic manipulations to protect the mother and fetus and decreasing the risk of a fatal immunologic response to the allogeneic fetus.These alterations are physiologically normal and expected,but can become pathologic when thresholds are crossed.Pregnancy may cause or exacerbate underlying retinal vascular diseases,a class of disorders compromised predominantly of retinal vein occlusion(RVO),retinal artery occlusion(RAO),central serous retinopathy(CSR),diabetic retinopathy,and hypertensive-related retinopathy,which includes pre-eclampsia,eclampsia,and hemolysis,elevated liver enzymes,and low platelets(HELLP)syndrome.The majority of the literature on retinal changes associated with pregnancy has focused on diabetic retinopathy,while the knowledge regarding the pathogenesis and treatment options of other pregnancy-related vascular diseases remains scarce.Understanding the implications pregnancy has on these rare,but severe,retinal vascular complications can help guide clinical management and potential treatment modalities.This paper aims to serve as a review of the retinal manifestations of diseases outside of diabetic retinopathy.
文摘Background: To report the outcomes of external drainage of subretinal fluid(SRF) in exudative retinal detachment secondary to central serous chorioretinopathy(CSCR).Methods: Retrospective observational analysis of six eyes with exudative retinal detachment secondary to CSCR who underwent external drainage of SRF between 2004 and 2014 was performed. Collected data included demographics, steroid usage, surgical details, and visual acuity preoperatively and postoperative visual acuity and clinical examination data were collected. Results: Six eyes of six subjects were included with mean age of 45 years(range, 32 to 61 years). All subjects were male. Mean duration of symptoms was 4.6 months(range, 3 to 8 months). The pre-operative bestcorrected visual acuity(BCVA) ranged from perception of light to 20/60. Four eyes were treated with conventional external drainage and two underwent Chandelier-assisted external drainage. Three cases had laser treatment before drainage and one case underwent photodynamic therapy(PDT) after drainage. The BCVA at last follow-up ranged from 20/2,000(counting fingers at 2 feet) to 20/20. No recurrences were noted in any of the cases till the last follow-up. Mean duration of follow-up was 38 months. Conclusions: Our study demonstrates successful management of exudative retinal detachment secondary to CSCR with external SRF drainage without any complications.
