局部放电的发生伴随着电磁波的发射,电磁波在特高频段(300MHz^3GHz)的抗干扰能力很强,因此通过接受该频段的电磁波进行局部放电的检测与定位很有研究前景。近年来特高频法(ultra high frequency method,简称UHF)在局部放电的检测与定位...局部放电的发生伴随着电磁波的发射,电磁波在特高频段(300MHz^3GHz)的抗干扰能力很强,因此通过接受该频段的电磁波进行局部放电的检测与定位很有研究前景。近年来特高频法(ultra high frequency method,简称UHF)在局部放电的检测与定位工作中得到广泛推广。为改进确定时延的方法,准确定位放电源,采用了特高频法和信号传播时延来实现对局部放电源的定位。该法采用信号初始峰值法、相关法和能量最小值法求取信号传播时延,通过比较讨论3种方法的优劣,确定了一套求取时延的方案。最后用空间搜索法实现对缺陷中局部放电的定位。展开更多
Background:To evaluate the effect of three different combinations of tip designs and infusion systems in torsional phacoemulsification(INFINITI and CENTURION)in patients with cataract.According to the manufacturer,two...Background:To evaluate the effect of three different combinations of tip designs and infusion systems in torsional phacoemulsification(INFINITI and CENTURION)in patients with cataract.According to the manufacturer,two unique improvements in the Centurion are:active fluid dynamic management system and use of an intrepid balanced tip.The study specifically aimed to evaluate the beneficial effects,if any,of change in tip design and infusion system individually and in combination on both per-operative parameters as well as endothelial health over 6 months.Methods:One hundred and twenty six consenting patients of grade 4.0-6.9 senile cataract were randomized into three groups for phacoemulsification:Group A(n=42):Gravity fed infusion system and 45° Kelman miniflared ABS phaco tip;Group B(n=42):intraocular pressure(IOP)based infusion system and 45° Kelman miniflared ABS phaco tip;Group C(n=42):IOP based infusion system and 45° Intrepid balanced phaco tip.The cumulative dissipated energy(CDE),estimated fluid usage(EFU)and total aspiration time(TAT)were compared peroperatively.The endothelial parameters were followed up postoperatively for six months.Results:The three arms were matched for age(p=0.525),gender(p=0.96)and grade of cataract(p=0.177).Group C was associated with significant reductions in CDE(p=0.001),EFU(p<0.0005)as well as TAT(p=0.001)in comparison to the other groups.All three groups had comparable baseline endothelial cell density(p=0.876)and central corneal thickness(p=0.561).On post-operative evaluation,although all groups were comparable till 3 months,by 6 months,the percentage losses in endothelial cell density were significantly lower in group C as compared to the other groups.Conclusions:Use of an IOP based phacoemulsification system in association with use of the Intrepid balanced tip reduces the CDE,EFU and TAT in comparison to a gravity fed system with a mini flared tip or IOP based system with a mini flared tip while also providing better endothelial preservation thus favouring the use of an I展开更多
Background:To compare femtosecond laser-assisted versus conventional phacoemulsification in terms of visual and refractive outcomes,cumulative dissipated energy,anterior chamber inflammation and endothelial cell loss....Background:To compare femtosecond laser-assisted versus conventional phacoemulsification in terms of visual and refractive outcomes,cumulative dissipated energy,anterior chamber inflammation and endothelial cell loss.Methods:In this retrospective cohort study,records of eyes that underwent femtosecond laser-assisted cataract surgery(FLACS)or conventional phacoemulsification(CP)were reviewed.The Victus femtosecond laser(Bausch and Lomb,Germany)was used to carry out corneal incisions,anterior capsulotomy,and lens fragmentation in FLACS procedures.Manifest refraction spherical equivalence(MRSE),uncorrected distance visual acuity(UDVA),corrected distance visual acuity(CDVA),cumulative dissipated energy(CDE),postoperative cells and flare and endothelial cell count data were collected.Subgroup analysis of the visual acuity tests was performed based on the type of intraocular lens implanted(monofocal,monofocal toric,multifocal,multifocal toric,accommodating).Results:A total of 735 eyes were included in the study(296 eyes for the FLACS group and 439 eyes for the CP group).At one year follow-up,120 eyes comprised the FLACS group and 265 eyes for the CP group.MRSE in the FLACS group was−0.16±0.58 D and−0.20±0.52 D in the CP group(P=0.50).UDVA in the FLACS group was 20/25(mean logMAR 0.12±0.13)and 20/25(mean logMAR 0.11±0.13)in the CP group(P=0.48).CDVA was 20/20(mean logMAR 0.03±0.07)in the FLACS group and 20/20(mean logMAR 0.02±0.06)in the CP group(P=0.15).No statistically significant trend was seen for FLACS versus CP by intraocular type for visual acuity.CDE for the different cataract grades ranged from 6.97±5.74 to 29.02±16.07 in the FLACS group and 7.59±6.42 to 35.69±18.30 in the CP group.The FLACS group was significantly lower for post-operative central corneal edema(P=0.05),cells and flare(P=0.01),and endothelial cell loss(P=0.04).Conclusions:Femtosecond laser-assisted cataract surgery and conventional phacoemulsification had similar refractive and visual outcomes.Phacoemulsification energy,anterior ch展开更多
变电设备内部有时会存在多个缺陷的局部放电,其放电模式识别及危险度评估的难度大大增加,为更有效地诊断设备绝缘状况,该文提出了一种基于累积能量函数特征参量优化提取的多源局放分离技术。利用时频域累积能量函数表征脉冲电流脉冲或...变电设备内部有时会存在多个缺陷的局部放电,其放电模式识别及危险度评估的难度大大增加,为更有效地诊断设备绝缘状况,该文提出了一种基于累积能量函数特征参量优化提取的多源局放分离技术。利用时频域累积能量函数表征脉冲电流脉冲或特高频(UHF)信号的时频域变化,并采用数学形态学梯度运算提取了时频域累积能量的上升陡度参量。提出了以上升陡度参量的标准差作为分离性能评价指标,优化选取数学形态学梯度运算中的结构元素长度,提取此时的上升陡度参量,达到最优分离效果的目标。最后在实验室252k V GIS模型内建立了3种典型多缺陷模型,将所提出的多源放电分离技术应用于该混合缺陷放电UHF信号的分离,进而将该方法成功应用于一起现场1100k V GIS多源局放案例。结果表明,特征参量优化提取分离方法适用于内外置UHF传感器信号,在多源放电混合UHF信号分离中具有良好的应用效果。展开更多
In order to investigate the fatigue performance of orthotropic anisotropic steel bridge decks,this study realizes the simulation of the welding process through elastic-plastic finite element theory,thermal-structural ...In order to investigate the fatigue performance of orthotropic anisotropic steel bridge decks,this study realizes the simulation of the welding process through elastic-plastic finite element theory,thermal-structural sequential coupling,and the birth-death element method.The simulated welding residual stresses are introduced into the multiscale finite element model of the bridge as the initial stress.Furthermore,the study explores the impact of residual stress on crack propagation in the fatigue-vulnerable components of the corroded steel box girder.The results indicate that fatigue cracks at the weld toe of the top deck,the weld root of the top deck,and the opening of the transverse diaphragm will not propagate under the action of a standard vehicle load.However,the inclusion of residual stress leads to the propagation of these cracks.When considering residual stress,the fatigue crack propagation paths at the weld toe of the transverse diaphragm and the U-rib weld toe align with those observed in actual bridges.In the absence of residual stress,the cracks at the toe of the transverse diaphragm with a 15%mass loss rate are categorized as type I cracks.Conversely,when residual stress is considered,these cracks become I-II composite cracks.Residual stress significantly alters the cumulative energy release rate of the three fracturemodes.Therefore,incorporating the influence of residual stress is essential when assessing the fatigue performance of corroded steel box girders in long-span bridges.展开更多
Raveling is a common distress of asphalt pavements,defined as the removal of stones from the pavement surface.To predict and assess raveling quantitatively,a cumulative damage model based on an energy dissipation appr...Raveling is a common distress of asphalt pavements,defined as the removal of stones from the pavement surface.To predict and assess raveling quantitatively,a cumulative damage model based on an energy dissipation approach has been developed at the meso level.To construct the model,a new test method,the pendulum impact test,was employed to determine the fracture energy of the stone-mastic-stone meso-unit,while digital image analysis and dynamic shear rheometer test were used to acquire the strain rate of specimens and the rheology property of mastic,respectively.Analysis of the model reveals that when the material properties remain constant,the cumulative damage is directly correlated with loading time,loading amplitude,and loading frequency.Specifically,damage increases with superimposed linear and cosine variations over time.A higher stress amplitude results in a more rapidly increasing rate of damage,while a lower load frequency leads to more severe damage within the same loading time.Moreover,an example of the application of the model has been presented,showing that the model can be utilized to estimate failure life due to raveling.The model is able to offer a theoretical foundation for the design and maintenance of anti-raveling asphalt pavements.展开更多
文摘局部放电的发生伴随着电磁波的发射,电磁波在特高频段(300MHz^3GHz)的抗干扰能力很强,因此通过接受该频段的电磁波进行局部放电的检测与定位很有研究前景。近年来特高频法(ultra high frequency method,简称UHF)在局部放电的检测与定位工作中得到广泛推广。为改进确定时延的方法,准确定位放电源,采用了特高频法和信号传播时延来实现对局部放电源的定位。该法采用信号初始峰值法、相关法和能量最小值法求取信号传播时延,通过比较讨论3种方法的优劣,确定了一套求取时延的方案。最后用空间搜索法实现对缺陷中局部放电的定位。
文摘Background:To evaluate the effect of three different combinations of tip designs and infusion systems in torsional phacoemulsification(INFINITI and CENTURION)in patients with cataract.According to the manufacturer,two unique improvements in the Centurion are:active fluid dynamic management system and use of an intrepid balanced tip.The study specifically aimed to evaluate the beneficial effects,if any,of change in tip design and infusion system individually and in combination on both per-operative parameters as well as endothelial health over 6 months.Methods:One hundred and twenty six consenting patients of grade 4.0-6.9 senile cataract were randomized into three groups for phacoemulsification:Group A(n=42):Gravity fed infusion system and 45° Kelman miniflared ABS phaco tip;Group B(n=42):intraocular pressure(IOP)based infusion system and 45° Kelman miniflared ABS phaco tip;Group C(n=42):IOP based infusion system and 45° Intrepid balanced phaco tip.The cumulative dissipated energy(CDE),estimated fluid usage(EFU)and total aspiration time(TAT)were compared peroperatively.The endothelial parameters were followed up postoperatively for six months.Results:The three arms were matched for age(p=0.525),gender(p=0.96)and grade of cataract(p=0.177).Group C was associated with significant reductions in CDE(p=0.001),EFU(p<0.0005)as well as TAT(p=0.001)in comparison to the other groups.All three groups had comparable baseline endothelial cell density(p=0.876)and central corneal thickness(p=0.561).On post-operative evaluation,although all groups were comparable till 3 months,by 6 months,the percentage losses in endothelial cell density were significantly lower in group C as compared to the other groups.Conclusions:Use of an IOP based phacoemulsification system in association with use of the Intrepid balanced tip reduces the CDE,EFU and TAT in comparison to a gravity fed system with a mini flared tip or IOP based system with a mini flared tip while also providing better endothelial preservation thus favouring the use of an I
文摘Background:To compare femtosecond laser-assisted versus conventional phacoemulsification in terms of visual and refractive outcomes,cumulative dissipated energy,anterior chamber inflammation and endothelial cell loss.Methods:In this retrospective cohort study,records of eyes that underwent femtosecond laser-assisted cataract surgery(FLACS)or conventional phacoemulsification(CP)were reviewed.The Victus femtosecond laser(Bausch and Lomb,Germany)was used to carry out corneal incisions,anterior capsulotomy,and lens fragmentation in FLACS procedures.Manifest refraction spherical equivalence(MRSE),uncorrected distance visual acuity(UDVA),corrected distance visual acuity(CDVA),cumulative dissipated energy(CDE),postoperative cells and flare and endothelial cell count data were collected.Subgroup analysis of the visual acuity tests was performed based on the type of intraocular lens implanted(monofocal,monofocal toric,multifocal,multifocal toric,accommodating).Results:A total of 735 eyes were included in the study(296 eyes for the FLACS group and 439 eyes for the CP group).At one year follow-up,120 eyes comprised the FLACS group and 265 eyes for the CP group.MRSE in the FLACS group was−0.16±0.58 D and−0.20±0.52 D in the CP group(P=0.50).UDVA in the FLACS group was 20/25(mean logMAR 0.12±0.13)and 20/25(mean logMAR 0.11±0.13)in the CP group(P=0.48).CDVA was 20/20(mean logMAR 0.03±0.07)in the FLACS group and 20/20(mean logMAR 0.02±0.06)in the CP group(P=0.15).No statistically significant trend was seen for FLACS versus CP by intraocular type for visual acuity.CDE for the different cataract grades ranged from 6.97±5.74 to 29.02±16.07 in the FLACS group and 7.59±6.42 to 35.69±18.30 in the CP group.The FLACS group was significantly lower for post-operative central corneal edema(P=0.05),cells and flare(P=0.01),and endothelial cell loss(P=0.04).Conclusions:Femtosecond laser-assisted cataract surgery and conventional phacoemulsification had similar refractive and visual outcomes.Phacoemulsification energy,anterior ch
文摘变电设备内部有时会存在多个缺陷的局部放电,其放电模式识别及危险度评估的难度大大增加,为更有效地诊断设备绝缘状况,该文提出了一种基于累积能量函数特征参量优化提取的多源局放分离技术。利用时频域累积能量函数表征脉冲电流脉冲或特高频(UHF)信号的时频域变化,并采用数学形态学梯度运算提取了时频域累积能量的上升陡度参量。提出了以上升陡度参量的标准差作为分离性能评价指标,优化选取数学形态学梯度运算中的结构元素长度,提取此时的上升陡度参量,达到最优分离效果的目标。最后在实验室252k V GIS模型内建立了3种典型多缺陷模型,将所提出的多源放电分离技术应用于该混合缺陷放电UHF信号的分离,进而将该方法成功应用于一起现场1100k V GIS多源局放案例。结果表明,特征参量优化提取分离方法适用于内外置UHF传感器信号,在多源放电混合UHF信号分离中具有良好的应用效果。
基金supported by a grant from the Key Technologies Research and Development Program(No.2021YFF0602005)Jiangsu Key Research and Development Plan(Nos.BE2022129,BE2022134)the Fundamental Research Funds for the Central Universities(Nos.2242022k30031,2242022k30033),which are gratefully acknowledged.
文摘In order to investigate the fatigue performance of orthotropic anisotropic steel bridge decks,this study realizes the simulation of the welding process through elastic-plastic finite element theory,thermal-structural sequential coupling,and the birth-death element method.The simulated welding residual stresses are introduced into the multiscale finite element model of the bridge as the initial stress.Furthermore,the study explores the impact of residual stress on crack propagation in the fatigue-vulnerable components of the corroded steel box girder.The results indicate that fatigue cracks at the weld toe of the top deck,the weld root of the top deck,and the opening of the transverse diaphragm will not propagate under the action of a standard vehicle load.However,the inclusion of residual stress leads to the propagation of these cracks.When considering residual stress,the fatigue crack propagation paths at the weld toe of the transverse diaphragm and the U-rib weld toe align with those observed in actual bridges.In the absence of residual stress,the cracks at the toe of the transverse diaphragm with a 15%mass loss rate are categorized as type I cracks.Conversely,when residual stress is considered,these cracks become I-II composite cracks.Residual stress significantly alters the cumulative energy release rate of the three fracturemodes.Therefore,incorporating the influence of residual stress is essential when assessing the fatigue performance of corroded steel box girders in long-span bridges.
基金The authors gratefully acknowledge the financial supports by the National Natural Science Foundation of China(Grant No.51278203)the Natural Science Fund of Guangdong Province(No.2019A1515011965).
文摘Raveling is a common distress of asphalt pavements,defined as the removal of stones from the pavement surface.To predict and assess raveling quantitatively,a cumulative damage model based on an energy dissipation approach has been developed at the meso level.To construct the model,a new test method,the pendulum impact test,was employed to determine the fracture energy of the stone-mastic-stone meso-unit,while digital image analysis and dynamic shear rheometer test were used to acquire the strain rate of specimens and the rheology property of mastic,respectively.Analysis of the model reveals that when the material properties remain constant,the cumulative damage is directly correlated with loading time,loading amplitude,and loading frequency.Specifically,damage increases with superimposed linear and cosine variations over time.A higher stress amplitude results in a more rapidly increasing rate of damage,while a lower load frequency leads to more severe damage within the same loading time.Moreover,an example of the application of the model has been presented,showing that the model can be utilized to estimate failure life due to raveling.The model is able to offer a theoretical foundation for the design and maintenance of anti-raveling asphalt pavements.
