Objective:To explore the implementation of gastrointestinal endoscopy technology and endoscopic narrow-band imaging(NBI)in the early screening of gastric cancer and to observe and study their application effects.Metho...Objective:To explore the implementation of gastrointestinal endoscopy technology and endoscopic narrow-band imaging(NBI)in the early screening of gastric cancer and to observe and study their application effects.Methods:During the period from March 2023 to August 2023,312 patients who received gastroscopy in the Kunming Guandu District People’s Hospital were selected,and they underwent both conventional gastroscopy and endoscopic NBI,with clinicopathological tissue biopsy serving as the gold standard.The application value for early screening of gastric cancer was observed and analyzed.Results:The scoring data showed that the clarity of gastric mucosal glandular tube structure,microvascular structure clarity,and lesion contour scoring data of conventional gastroscopy were lower than those of the NBI technology(P<0.05).The screening rate of pathological biopsy in 312 patients was 18.59%(58 cases).Conventional gastroscopy showed a screening rate of 11.53%(36 cases),while NBI technology examined a screening rate of 17.63%(55 cases),and the two-by-two comparison of the screening rate data of the three groups was not statistically significant(P>0.05).The sensitivity,specificity,accuracy,positive predictive value,and negative predictive value of conventional gastroscopy appeared to be lower than those of NBI technology(P<0.05).Conclusion:In the early screening of gastric cancer,endoscopic NBI technology can be applied to patients.Compared with conventional gastroscopy,it provides a clearer visualization of the structure of the gastric mucosal glandular structure and microvascular structure,with a certain screening rate.Additionally,its sensitivity,specificity,accuracy,positive predictive value,and negative predictive value are higher,demonstrating outstanding effectiveness.展开更多
We propose a novel approach for generating a high-density,spatially periodic narrow electron beam comb(EBC)from a plasma grating induced by the interference of two intense laser pulses in subcritical-density plasma.We...We propose a novel approach for generating a high-density,spatially periodic narrow electron beam comb(EBC)from a plasma grating induced by the interference of two intense laser pulses in subcritical-density plasma.We employ particle-in-cell(PIC)simulations to investigate the effects of cross-propagating laser pulses with specific angles overlapping in a subcritical plasma.This overlap results in the formation of a transverse standing wave,leading to a spatially periodic high-density modulation known as a plasma grating.The electron density peak within the grating can reach several times the background plasma density.The charge imbalance between electrons and ions in the electron density peaks causes mutual repulsion among the electrons,resulting in Coulomb expansion and acceleration of the electrons.As a result,some electrons expand into vacuum,forming a periodic narrow EBC with an individual beam width in the nanoscale range.To further explore the formation of the nanoscale EBC,we conduct additional PIC simulations to study the dependence on various laser parameters.Overall,our proposed method offers a promising and controlled approach to generate tunable narrow EBCs with high density.展开更多
Narrow bipolar events(NBEs)are intriguing intra-cloud discharge that have attracted enormous interest in the lightning community.They come with two polarities that dominate at different altitudes in thunderclouds.The ...Narrow bipolar events(NBEs)are intriguing intra-cloud discharge that have attracted enormous interest in the lightning community.They come with two polarities that dominate at different altitudes in thunderclouds.The sources of negative NBEs are usually located near the top of thunderclouds;those of positive NBEs are at the middle levels.NBEs may occur at the onset of lightning.The electrical properties of NBEs remain poorly understood.We present here the first comparative study of the electrical characteristics of negative and positive NBEs.To derive electrical parameters from the fast electric field change waveforms of 1673 positive NBEs and 364 negative NBEs recorded by the Jianghuai Area Sferic Array(JASA)in China,we use an improved method based on the transmission line model.This approach concludes that negative NBEs occurring at high altitudes tend to produce a narrower current pulse and take a shorter time to traverse the channel than their positive counterparts.Moreover,compared to positive NBEs,a larger portion of negative NBEs are associated with slightly greater peak current moments but smaller overall charge moments.The differences reported herein between electrical properties of negative and positive NBEs suggest that charge distribution in NBE-producing thunderstorms tends to vary systematically with altitude.展开更多
Background: The burden of cataract and glaucoma has been increasing. Primary angle closure occurs as a result of crowded anterior segment anatomy causing appositional contact between peripheral iris and trabecular mes...Background: The burden of cataract and glaucoma has been increasing. Primary angle closure occurs as a result of crowded anterior segment anatomy causing appositional contact between peripheral iris and trabecular meshwork. Lens extraction has been proposed as a method of deepening anterior chamber and managing intraocular pressure. Purpose: To assess changes in anterior chamber depth after phacoemulsification with intraocular lens implantation in narrow angle eyes. Design: Prospective controlled trial (before-after) study. Method: The study was conducted from March 2015 to August 2017 among the patients of department of Ophthalmology of BSMMU who were diagnosed as cataract with narrow angles. Anterior chamber angle grading of 2 or less (Shaffer grading) in 3 or more quadrants was considered narrow angle (NA). The purposive type sampling technique was applied to collect sample from the study population, as per inclusion and exclusion criteria. Complete clinical evaluation including history, physical examination, relevant ocular examinations and systemic examinations were performed. In this prospective study, subjects underwent phacoemulsification with foldable lens implantation. A scan ultrasonography was performed preoperatively and 10<sup>th</sup> and 30<sup>th</sup> postoperative days of surgery. Results: Thirty eyes of 29 patients included in the study, male: female ratio was 1:1, with an overall mean age of 62.03 ± 8.95 years. The mean preoperative central ACD was 2.95 ± 0.35 mm. At 10<sup>th</sup> and 30<sup>th</sup> POD mean central ACD were 3.94 ± 0.32, and 3.92 ± 0.28 mm respectively. Mean of increase in central ACD at final follow-up was 0.96 mm (p Conclusion: Phacoemulsification with posterior chamber in bag lens implantation can deepen the anterior chamber depth in patients with narrow angles. Based on these findings, it is concluded that phacoemulsification with foldable intraocular lens implantation is an effective tool in deepening the anterior chamber.展开更多
Spectrally-selective photodetection plays a crucial role in various applications,including target imaging and environmental monitoring.Traditional deep-ultraviolet(DUV)narrowband photodetection systems consist of broa...Spectrally-selective photodetection plays a crucial role in various applications,including target imaging and environmental monitoring.Traditional deep-ultraviolet(DUV)narrowband photodetection systems consist of broadband photodetectors and filters,which complicates the architecture and constrains imaging quality.Here,we introduce an electronic-grade diamond single-crystal photodetector exhibiting an exceptionally narrow spectral response in the DUV range with a full width at half maximum of 8 nm.By examining diamond photodetectors with varying dislocation densities,we propose that mitigating the defect-induced trapping effect to achieve charge collection narrowing,assisted by free exciton radiative recombination,is an effective strategy for narrowband photodetection.The superior performance of this device is evidenced through the imaging of DUV light sources,showcasing its capability to differentiate between distinct light sources and monitor human-safe sterilization systems.Our findings underscore the promising potential applications of electronicgrade diamond in narrowband photodetection and offer a valuable technique for identifying electronic-grade diamond.展开更多
In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on out...In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on output power and voltage ratio. The DAB converters operate with hard switching at light loads, it is difficult to achieve high efficiency. Fortunately, WBG power semiconductor devices have excellent hard switching characteristics and can increase efficiency compared to silicon (Si) devices. In particular, WBG devices can achieve ZVS at low load currents due to their low parasitic output capacitance (C<sub>o,tr</sub>) characteristics. Therefore, in this paper, the ZVS operating resion is analyzed based on the characteristics of Si, silicon carbide (SiC) and gallium nitride (GaN). Power semiconductor devices. WBG devices with low C<sub>o,tr</sub> operate at ZVS at lower load currents compared to Si devices. To verify this, experiments are conducted and the results are analyzed using a 3 kW DAB converter. For Si devices, ZVS is achieved above 1.4 kW. For WBG devices, ZVS is achieved at 700 W. Due to the ZVS conditions depending on the switching device, the DAB converter using Si devices achieves a power conversion efficiency of 91% at 1.1 kW output. On the other hand, in the case of WBG devices, power conversion efficiency of more than 98% is achieved under 11 kW conditions. In conclusion, it is confirmed that the WBG device operates in ZVS at a lower load compared to the Si device, which is advantageous in increasing light load efficiency.展开更多
目的 探讨通过窄带成像(narrow band imaging,NBI)电子喉镜下观察喉黏膜上皮内的毛细血管袢形态,能否指导喉白斑患者治疗方法的选择。方法 选取2019年6月~2021年9月临床诊断为喉白斑的68例患者为研究对象,根据NBI电子喉镜的诊断结果,将...目的 探讨通过窄带成像(narrow band imaging,NBI)电子喉镜下观察喉黏膜上皮内的毛细血管袢形态,能否指导喉白斑患者治疗方法的选择。方法 选取2019年6月~2021年9月临床诊断为喉白斑的68例患者为研究对象,根据NBI电子喉镜的诊断结果,将患者分为两组:良性病变组(52/68)和恶性病变组(16/68)。比较NBI喉镜诊断与病理检查结果的一致性。结果良性病变组中病理确诊为鳞状上皮增生伴角化35例(67.31%),轻度不典型增生9例(17.31%),中度不典型增生3例(5.77%),原位癌5例(9.62%),恶性病变组中病理确诊为中度不典型增生2例(12.50%),重度不典型增生1例(6.25%),原位癌9例(56.25%),浸润癌4例(25.00%)。采用Kappa一致性检验法,k=0.687,P<0.001,说明NBI电子喉镜诊断结果和病理检查结果存在一致性。结论 NBI电子喉镜能很好的分辨喉白斑的性质,对喉白斑治疗方法的选择和随访观察喉白斑的进展有较高的指导意义。展开更多
脉冲熔化极气体保护焊(pulsed gas metal arc welding,P-GMAW)起弧过程易产生不稳定现象,会严重影响电弧传感焊缝跟踪精度.针对这一问题,对摆动电弧窄间隙P-GMAW不稳定起弧过程的成因进行了研究,发现送丝速度对起弧过程稳定性具有重要影...脉冲熔化极气体保护焊(pulsed gas metal arc welding,P-GMAW)起弧过程易产生不稳定现象,会严重影响电弧传感焊缝跟踪精度.针对这一问题,对摆动电弧窄间隙P-GMAW不稳定起弧过程的成因进行了研究,发现送丝速度对起弧过程稳定性具有重要影响.通过对电弧图像与电信号特征进行对比分析,提取了表征电弧稳定性的电信号特征变量;为减小变量冗余性和过拟合,采用最大似然估计法筛选并提取了8个变量,并通过主成分分析法(principal component analysis,PCA)对变量进行融合,提取了方差贡献率最高的前两个主成分;根据因子载荷发现,相比熔滴过渡阶段和基值阶段,脉冲峰值阶段是电弧更易发生不稳定现象的阶段.结合提取的主成分变量与二分类Logistic回归模型建立了起弧过程电弧稳定性判别模型.通过受试者工作特征(receiver operating characteristic,ROC)曲线得到了模型的最佳阈值.结果表明,该模型对脉冲稳定性判别准确率达到了80%以上,表明模型具有良好的判别性能.该模型对提高窄间隙高低跟踪精度、保证焊接质量具有一定应用价值.展开更多
文摘Objective:To explore the implementation of gastrointestinal endoscopy technology and endoscopic narrow-band imaging(NBI)in the early screening of gastric cancer and to observe and study their application effects.Methods:During the period from March 2023 to August 2023,312 patients who received gastroscopy in the Kunming Guandu District People’s Hospital were selected,and they underwent both conventional gastroscopy and endoscopic NBI,with clinicopathological tissue biopsy serving as the gold standard.The application value for early screening of gastric cancer was observed and analyzed.Results:The scoring data showed that the clarity of gastric mucosal glandular tube structure,microvascular structure clarity,and lesion contour scoring data of conventional gastroscopy were lower than those of the NBI technology(P<0.05).The screening rate of pathological biopsy in 312 patients was 18.59%(58 cases).Conventional gastroscopy showed a screening rate of 11.53%(36 cases),while NBI technology examined a screening rate of 17.63%(55 cases),and the two-by-two comparison of the screening rate data of the three groups was not statistically significant(P>0.05).The sensitivity,specificity,accuracy,positive predictive value,and negative predictive value of conventional gastroscopy appeared to be lower than those of NBI technology(P<0.05).Conclusion:In the early screening of gastric cancer,endoscopic NBI technology can be applied to patients.Compared with conventional gastroscopy,it provides a clearer visualization of the structure of the gastric mucosal glandular structure and microvascular structure,with a certain screening rate.Additionally,its sensitivity,specificity,accuracy,positive predictive value,and negative predictive value are higher,demonstrating outstanding effectiveness.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.12174410,11991072,11991074,12225411,and 12105353)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR060)the State Key Laboratory Program of the Chinese Ministry of Science and Technology,and the CAS Youth Innovation Promotion Association(Grant Nos.Y201952 and 2022242).
文摘We propose a novel approach for generating a high-density,spatially periodic narrow electron beam comb(EBC)from a plasma grating induced by the interference of two intense laser pulses in subcritical-density plasma.We employ particle-in-cell(PIC)simulations to investigate the effects of cross-propagating laser pulses with specific angles overlapping in a subcritical plasma.This overlap results in the formation of a transverse standing wave,leading to a spatially periodic high-density modulation known as a plasma grating.The electron density peak within the grating can reach several times the background plasma density.The charge imbalance between electrons and ions in the electron density peaks causes mutual repulsion among the electrons,resulting in Coulomb expansion and acceleration of the electrons.As a result,some electrons expand into vacuum,forming a periodic narrow EBC with an individual beam width in the nanoscale range.To further explore the formation of the nanoscale EBC,we conduct additional PIC simulations to study the dependence on various laser parameters.Overall,our proposed method offers a promising and controlled approach to generate tunable narrow EBCs with high density.
基金The authors would acknowledge financial support from the National Key Laboratory on Electromagnetic Environmental Effects and Electro-optical Engineering(NO.JCKYS2022LD6)the National Natural Science Foundation of China(42005068 and 42375074)+1 种基金the Project of Stable Support for Youth Team in Basic Research Field CAS(YSBR-018)the Joint Open Fund of Mengcheng National Geophysical Observatory(MENGO-202208).
文摘Narrow bipolar events(NBEs)are intriguing intra-cloud discharge that have attracted enormous interest in the lightning community.They come with two polarities that dominate at different altitudes in thunderclouds.The sources of negative NBEs are usually located near the top of thunderclouds;those of positive NBEs are at the middle levels.NBEs may occur at the onset of lightning.The electrical properties of NBEs remain poorly understood.We present here the first comparative study of the electrical characteristics of negative and positive NBEs.To derive electrical parameters from the fast electric field change waveforms of 1673 positive NBEs and 364 negative NBEs recorded by the Jianghuai Area Sferic Array(JASA)in China,we use an improved method based on the transmission line model.This approach concludes that negative NBEs occurring at high altitudes tend to produce a narrower current pulse and take a shorter time to traverse the channel than their positive counterparts.Moreover,compared to positive NBEs,a larger portion of negative NBEs are associated with slightly greater peak current moments but smaller overall charge moments.The differences reported herein between electrical properties of negative and positive NBEs suggest that charge distribution in NBE-producing thunderstorms tends to vary systematically with altitude.
文摘Background: The burden of cataract and glaucoma has been increasing. Primary angle closure occurs as a result of crowded anterior segment anatomy causing appositional contact between peripheral iris and trabecular meshwork. Lens extraction has been proposed as a method of deepening anterior chamber and managing intraocular pressure. Purpose: To assess changes in anterior chamber depth after phacoemulsification with intraocular lens implantation in narrow angle eyes. Design: Prospective controlled trial (before-after) study. Method: The study was conducted from March 2015 to August 2017 among the patients of department of Ophthalmology of BSMMU who were diagnosed as cataract with narrow angles. Anterior chamber angle grading of 2 or less (Shaffer grading) in 3 or more quadrants was considered narrow angle (NA). The purposive type sampling technique was applied to collect sample from the study population, as per inclusion and exclusion criteria. Complete clinical evaluation including history, physical examination, relevant ocular examinations and systemic examinations were performed. In this prospective study, subjects underwent phacoemulsification with foldable lens implantation. A scan ultrasonography was performed preoperatively and 10<sup>th</sup> and 30<sup>th</sup> postoperative days of surgery. Results: Thirty eyes of 29 patients included in the study, male: female ratio was 1:1, with an overall mean age of 62.03 ± 8.95 years. The mean preoperative central ACD was 2.95 ± 0.35 mm. At 10<sup>th</sup> and 30<sup>th</sup> POD mean central ACD were 3.94 ± 0.32, and 3.92 ± 0.28 mm respectively. Mean of increase in central ACD at final follow-up was 0.96 mm (p Conclusion: Phacoemulsification with posterior chamber in bag lens implantation can deepen the anterior chamber depth in patients with narrow angles. Based on these findings, it is concluded that phacoemulsification with foldable intraocular lens implantation is an effective tool in deepening the anterior chamber.
基金supports from Natural Science Foundation of Guangdong Province for Distinguished Young Scholars(Grant No.2021B1515020105).
文摘Spectrally-selective photodetection plays a crucial role in various applications,including target imaging and environmental monitoring.Traditional deep-ultraviolet(DUV)narrowband photodetection systems consist of broadband photodetectors and filters,which complicates the architecture and constrains imaging quality.Here,we introduce an electronic-grade diamond single-crystal photodetector exhibiting an exceptionally narrow spectral response in the DUV range with a full width at half maximum of 8 nm.By examining diamond photodetectors with varying dislocation densities,we propose that mitigating the defect-induced trapping effect to achieve charge collection narrowing,assisted by free exciton radiative recombination,is an effective strategy for narrowband photodetection.The superior performance of this device is evidenced through the imaging of DUV light sources,showcasing its capability to differentiate between distinct light sources and monitor human-safe sterilization systems.Our findings underscore the promising potential applications of electronicgrade diamond in narrowband photodetection and offer a valuable technique for identifying electronic-grade diamond.
文摘In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on output power and voltage ratio. The DAB converters operate with hard switching at light loads, it is difficult to achieve high efficiency. Fortunately, WBG power semiconductor devices have excellent hard switching characteristics and can increase efficiency compared to silicon (Si) devices. In particular, WBG devices can achieve ZVS at low load currents due to their low parasitic output capacitance (C<sub>o,tr</sub>) characteristics. Therefore, in this paper, the ZVS operating resion is analyzed based on the characteristics of Si, silicon carbide (SiC) and gallium nitride (GaN). Power semiconductor devices. WBG devices with low C<sub>o,tr</sub> operate at ZVS at lower load currents compared to Si devices. To verify this, experiments are conducted and the results are analyzed using a 3 kW DAB converter. For Si devices, ZVS is achieved above 1.4 kW. For WBG devices, ZVS is achieved at 700 W. Due to the ZVS conditions depending on the switching device, the DAB converter using Si devices achieves a power conversion efficiency of 91% at 1.1 kW output. On the other hand, in the case of WBG devices, power conversion efficiency of more than 98% is achieved under 11 kW conditions. In conclusion, it is confirmed that the WBG device operates in ZVS at a lower load compared to the Si device, which is advantageous in increasing light load efficiency.
文摘脉冲熔化极气体保护焊(pulsed gas metal arc welding,P-GMAW)起弧过程易产生不稳定现象,会严重影响电弧传感焊缝跟踪精度.针对这一问题,对摆动电弧窄间隙P-GMAW不稳定起弧过程的成因进行了研究,发现送丝速度对起弧过程稳定性具有重要影响.通过对电弧图像与电信号特征进行对比分析,提取了表征电弧稳定性的电信号特征变量;为减小变量冗余性和过拟合,采用最大似然估计法筛选并提取了8个变量,并通过主成分分析法(principal component analysis,PCA)对变量进行融合,提取了方差贡献率最高的前两个主成分;根据因子载荷发现,相比熔滴过渡阶段和基值阶段,脉冲峰值阶段是电弧更易发生不稳定现象的阶段.结合提取的主成分变量与二分类Logistic回归模型建立了起弧过程电弧稳定性判别模型.通过受试者工作特征(receiver operating characteristic,ROC)曲线得到了模型的最佳阈值.结果表明,该模型对脉冲稳定性判别准确率达到了80%以上,表明模型具有良好的判别性能.该模型对提高窄间隙高低跟踪精度、保证焊接质量具有一定应用价值.