This work deals with determining the optimum thickness of the lamella wafer of silicon solar cell. The (p) base region makes up the bulk of the thickness of the wafer. This thickness has always been a factor limiting ...This work deals with determining the optimum thickness of the lamella wafer of silicon solar cell. The (p) base region makes up the bulk of the thickness of the wafer. This thickness has always been a factor limiting the performance of the solar cell, as it produces the maximum amount of electrical charges, contributing to the photocurrent. Determining the thickness of the wafer cannot be only mechanical. It takes into account the internal physical mechanisms of generation-diffusion-recombination of excess minority carriers. They are also influenced by external factors such as temperature and magnetic field. Under these conditions, magneto transport equation is required to be applied on excess minority carrier in lamella base silicon solar cell. It yields maximum diffusion coefficient which result on Lorentz law and Umklapp process. Then from photocurrent, back surface recombination velocity expressions are derived, both maximum diffusion coefficient and thickness dependent. The plot of the back surface recombination calibration curves as function of lamella width, leads to its maximum values, trough intercept points. Lamella optimum width is then obtained, both temperature and magnetic field dependent and expressed in relationships to show the required base thickness in the elaboration process.展开更多
This paper analyzes the characteristic of matching efficiency between the fundamental mode of two kinds of optical waveguides and its Gaussian approximate field.Then, it presents a new method where the mode-field half...This paper analyzes the characteristic of matching efficiency between the fundamental mode of two kinds of optical waveguides and its Gaussian approximate field.Then, it presents a new method where the mode-field half-width of Caussian approximation for the fundamental mode should be defined according to the maximal matching efficiency method. The relationship between the mode-field half-width of the Gaussian approximate field obtained from the maximal matching efficiency and normalized frequency is studied; furthermore, two formulas of mode-field half-widths as a function of normalized frequency are proposed.展开更多
AIM：To determine the Bruch＇s membrane opening-minimum rim width（BMO-MRW） tipping point where corresponding visual field（VF） damages become detectable.METHODS：A total of 85 normal subjects and 83 glaucoma patie...AIM：To determine the Bruch＇s membrane opening-minimum rim width（BMO-MRW） tipping point where corresponding visual field（VF） damages become detectable.METHODS：A total of 85 normal subjects and 83 glaucoma patients（one eye per participant） were recruited for the study.All of the patients had VF examinations and spectral-domain optical coherence tomography to measure the BMO-MRW.Total deviation values for 52 VF points were allocated to the corresponding sector according to the Garway-Heath distribution map.To evaluate the relationship between VF loss and BMOMRW measurements,a ＂broken-stick＂ statistical model was used.The tipping point where the VF values started to sharply decrease as a function of BMO-MRW measurements was estimated and the slopes above and below this tipping point were compared.RESULTS：A 25.9% global BMO-MRW loss from normative value was required for the VF loss to be detectable.Sectorally,substantial BMO-MRW thinning in inferotemporal sector（33.1%） and relatively less BMO-MRW thinning in the superotemporal sector（8.9%） were necessary for the detection of the VF loss.Beyond the tipping point,the slopes were close to zero throughout all of the sectors and the VF loss was unrelated to the BMO-MRW loss.The VF loss was related to the BMO-MRW loss below the tipping point.The difference between the two slopes was statistically significant（P≤0.002）.CONCLUSION：Substantial BMO-MRW loss appears to be necessary for VF loss to be detectable in patients with open angle glaucoma with standard achromatic perimetry.展开更多
Large-area patterned films of boron nanowires（BNWs） are fabricated at various densities by chemical vapor deposition（CVD）. Different widths of unit-cell of Mo masks are used as templates. The widths of unit-cell o...Large-area patterned films of boron nanowires（BNWs） are fabricated at various densities by chemical vapor deposition（CVD）. Different widths of unit-cell of Mo masks are used as templates. The widths of unit-cell of Mo masks are100 μm, 150 μm, and 200 μm, respectively. The distance between unit cells is 50 μm. The BNWs have an average diameter of about 20 nm and lengths of 10 μm–20 μm. High-resolution transmission electron microscopy analysis shows that each nanowire has a β-tetragonal structure with good crystallization. Field emission measurements of the BNW films show that their turn-on electric fields decrease with width of unit-cell increasing.展开更多
Magnetic mirror used as an efficient tool to confine plasma has been widely adopted in many different areas especially in recent cusped field thrusters. In order to check the influence of magnetic mirror effect on the...Magnetic mirror used as an efficient tool to confine plasma has been widely adopted in many different areas especially in recent cusped field thrusters. In order to check the influence of magnetic mirror effect on the plasma distribution in a cusped field thruster, three different radii of the discharge channel(6 mm, 4 mm, and 2 mm) in a cusped field thruster are investigated by using Particle-in-Cell Plus Monte Carlo(PIC-MCC) simulated method, under the condition of a fixed axial length of the discharge channel and the same operating parameters. It is found that magnetic cusps inside the small radius discharge channel cannot confine electrons very well. Thus, the electric field is hard to establish. With the reduction of the discharge channel’s diameter, more electrons will escape from cusps to the centerline area near the anode due to a lower magnetic mirror ratio. Meanwhile, the leak width of the cusped magnetic field will increase at the cusp. By increasing the magnetic field strength in a small radius model of a cusped field thruster, the negative effect caused by the weak magnetic mirror effect can be partially compensated. Therefore, according to engineering design, the increase of magnetic field strength can contribute to obtaining a good performance, when the radial distance between the magnets and the inner surface of the discharge channel is relatively big.展开更多
The domains are of fundamental interest for engineering a ferroelectric material. The domain wall and its width control the ferroelectric behavior to a great extent. The stability of polarization in the context of Lan...The domains are of fundamental interest for engineering a ferroelectric material. The domain wall and its width control the ferroelectric behavior to a great extent. The stability of polarization in the context of Landau-Ginzburg free energy functional has been worked out in a previous work by a perturbation approach, where two limits of domain wall width were estimated within the stability zone and they were also found to correspond well with the data on lithium niobate and lithium tantalate. In the present work, it is shown that this model is valid for a wide range of ferroelectric materials and also for a given ferroelectric, such as lithium niobate with different levels of impurities, which are known to affect the domain wall width.展开更多
With rapid growth of power demand, transmission capacity is also in urgent need of upgrading. In some cases, converting existing AC transmission lines to DC lines can Improve the transmission capacity and reduce the c...With rapid growth of power demand, transmission capacity is also in urgent need of upgrading. In some cases, converting existing AC transmission lines to DC lines can Improve the transmission capacity and reduce the construction investment. In this paper, the upstream finite element method was expanded to calculate the total electric field of same tower multi-circuit DC lines converted from double-circuit AC lines, and the validity of the algorithm was confirmed by experiments. Taking a DC line converted from a typical same tower 500 kV double-circuit AC transmission line as an example, the surface electric field and the ground total electric field in different pole conductor arrangement schemes were calculated and analyzed, and the critical height of pole conductors for DC lines in residential and non-residential area were determined. Then, the corridor width of DC and AC lines at critical height in residential and non-residential areas before and after AC-DC line transformation were compared. The results indicate that for DC lines converted from common 500 kV double-circuit AC lines, the ground total electric field can meet the requirements of corresponding standard with appropriate pole conductor arrangement schemes.展开更多
目的探讨鼻咽癌(NPC)在螺旋断层放射治疗计划系统中采用不同铅门宽度的剂量学差异,研究其与机器参数、治疗时间的关系,为NPC制定螺旋断层放疗计划提供参考依据。方法选择16例NPC患者,其中男性15例,女性1例;年龄20~69岁,中位年龄46岁;病...目的探讨鼻咽癌(NPC)在螺旋断层放射治疗计划系统中采用不同铅门宽度的剂量学差异,研究其与机器参数、治疗时间的关系,为NPC制定螺旋断层放疗计划提供参考依据。方法选择16例NPC患者,其中男性15例,女性1例;年龄20~69岁,中位年龄46岁;病理诊断均为低分化鳞癌,按照美国癌症联合委员会(AJCC)第八版分期标准,其中Ⅱ期3例,Ⅲ期8例,Ⅳ期5例。采用3种铅门宽度(1.0 cm、2.5 cm和5.0 cm)分别进行治疗计划设计,对靶区的适形度指数(CI)、均匀性指数(HI)和危及器官的最大剂量(D_(max))、平均剂量(D_(mean))等各项指标的分析,比较3种治疗计划的剂量学分布差异,评估治疗计划的治疗时间、机器出束量、机架旋转圈数和旋转周期,对3种治疗计划数据进行多配对样本Friedman非参数检验。结果3种不同铅门宽度下,靶区计划原发肿瘤区(PGTV)nx、PGTVnd、计划靶区(PTV)1、PTV2的剂量参数CI、HI,差异有统计学意义(CI 0.81±0.04 vs 0.80±0.03 vs 0.72±0.03、0.81±0.05 vs 0.78±0.04 vs 0.72±0.07、0.77±0.07 vs 0.73±0.07 vs 0.69±0.07、0.72±0.09 vs 0.68±0.11 vs 0.67±0.14,HI 0.05±0.09 vs 0.06±0.11 vs 0.08±0.19、0.04±0.11 vs 0.05±0.09 vs 0.06±0.11、0.18±0.03 vs 0.21±0.04 vs 0.28±0.06、0.10±0.01 vs 0.12±0.02 vs 0.15±0.01)(P<0.05)。3种不同铅门宽度下,危及器官中双侧晶状体、双侧视神经、视交叉、双侧内耳、脑干、脊髓的D_(max)、D_(mean)的差异有统计学意义(P<0.05),双侧腮腺的V_(30)、口腔的V_(30)、V_(40)和D_(mean)的差异均具有统计学意义(P<0.05)。物理参数中治疗时间、机器跳数、机架旋转圈数和旋转周期,3种铅门宽度(1.0 cm、2.5 cm和5.0 cm)的差异均有统计学意义[(1095.70±163.64)s vs(447.10±71.80)s vs(231.50±40.15)s、(14854.50±2217.75)MU vs(6031.00±939.00)MU vs(3136.25±624.00)MU、47.95±7.90 vs 21.49±1.48 vs 12.15±0.83、22.80±2.00 vs 20.10±2.30 vs 18.90±2.58](P<0.05)。结论在保证靶区剂量CI和HI较好及危及器官受量达到临床要求、提高治疗效率的前提下综合考虑,建议在NPC螺旋断层放射治疗计划系统中采用2.5 cm铅门宽度进行计划设计。展开更多
文摘This work deals with determining the optimum thickness of the lamella wafer of silicon solar cell. The (p) base region makes up the bulk of the thickness of the wafer. This thickness has always been a factor limiting the performance of the solar cell, as it produces the maximum amount of electrical charges, contributing to the photocurrent. Determining the thickness of the wafer cannot be only mechanical. It takes into account the internal physical mechanisms of generation-diffusion-recombination of excess minority carriers. They are also influenced by external factors such as temperature and magnetic field. Under these conditions, magneto transport equation is required to be applied on excess minority carrier in lamella base silicon solar cell. It yields maximum diffusion coefficient which result on Lorentz law and Umklapp process. Then from photocurrent, back surface recombination velocity expressions are derived, both maximum diffusion coefficient and thickness dependent. The plot of the back surface recombination calibration curves as function of lamella width, leads to its maximum values, trough intercept points. Lamella optimum width is then obtained, both temperature and magnetic field dependent and expressed in relationships to show the required base thickness in the elaboration process.
基金Project supported by Natural Science Foundation of the Department of Science & Technology of Fujian Province of China (GrantNo 2007F5040)
文摘This paper analyzes the characteristic of matching efficiency between the fundamental mode of two kinds of optical waveguides and its Gaussian approximate field.Then, it presents a new method where the mode-field half-width of Caussian approximation for the fundamental mode should be defined according to the maximal matching efficiency method. The relationship between the mode-field half-width of the Gaussian approximate field obtained from the maximal matching efficiency and normalized frequency is studied; furthermore, two formulas of mode-field half-widths as a function of normalized frequency are proposed.
文摘AIM：To determine the Bruch＇s membrane opening-minimum rim width（BMO-MRW） tipping point where corresponding visual field（VF） damages become detectable.METHODS：A total of 85 normal subjects and 83 glaucoma patients（one eye per participant） were recruited for the study.All of the patients had VF examinations and spectral-domain optical coherence tomography to measure the BMO-MRW.Total deviation values for 52 VF points were allocated to the corresponding sector according to the Garway-Heath distribution map.To evaluate the relationship between VF loss and BMOMRW measurements,a ＂broken-stick＂ statistical model was used.The tipping point where the VF values started to sharply decrease as a function of BMO-MRW measurements was estimated and the slopes above and below this tipping point were compared.RESULTS：A 25.9% global BMO-MRW loss from normative value was required for the VF loss to be detectable.Sectorally,substantial BMO-MRW thinning in inferotemporal sector（33.1%） and relatively less BMO-MRW thinning in the superotemporal sector（8.9%） were necessary for the detection of the VF loss.Beyond the tipping point,the slopes were close to zero throughout all of the sectors and the VF loss was unrelated to the BMO-MRW loss.The VF loss was related to the BMO-MRW loss below the tipping point.The difference between the two slopes was statistically significant（P≤0.002）.CONCLUSION：Substantial BMO-MRW loss appears to be necessary for VF loss to be detectable in patients with open angle glaucoma with standard achromatic perimetry.
基金supported by the National Basic Research Program of China(Grant Nos.2013CB933604)the National Natural Science Foundation of China(Grant No.51572290)the Fund from the Chinese Academy of Sciences(Grant Nos.1731300500015 and XDB07030100)
文摘Large-area patterned films of boron nanowires（BNWs） are fabricated at various densities by chemical vapor deposition（CVD）. Different widths of unit-cell of Mo masks are used as templates. The widths of unit-cell of Mo masks are100 μm, 150 μm, and 200 μm, respectively. The distance between unit cells is 50 μm. The BNWs have an average diameter of about 20 nm and lengths of 10 μm–20 μm. High-resolution transmission electron microscopy analysis shows that each nanowire has a β-tetragonal structure with good crystallization. Field emission measurements of the BNW films show that their turn-on electric fields decrease with width of unit-cell increasing.
基金supported by the National Natural Science Foundation of China(Grant No.51006028)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.51121004)
文摘Magnetic mirror used as an efficient tool to confine plasma has been widely adopted in many different areas especially in recent cusped field thrusters. In order to check the influence of magnetic mirror effect on the plasma distribution in a cusped field thruster, three different radii of the discharge channel(6 mm, 4 mm, and 2 mm) in a cusped field thruster are investigated by using Particle-in-Cell Plus Monte Carlo(PIC-MCC) simulated method, under the condition of a fixed axial length of the discharge channel and the same operating parameters. It is found that magnetic cusps inside the small radius discharge channel cannot confine electrons very well. Thus, the electric field is hard to establish. With the reduction of the discharge channel’s diameter, more electrons will escape from cusps to the centerline area near the anode due to a lower magnetic mirror ratio. Meanwhile, the leak width of the cusped magnetic field will increase at the cusp. By increasing the magnetic field strength in a small radius model of a cusped field thruster, the negative effect caused by the weak magnetic mirror effect can be partially compensated. Therefore, according to engineering design, the increase of magnetic field strength can contribute to obtaining a good performance, when the radial distance between the magnets and the inner surface of the discharge channel is relatively big.
文摘The domains are of fundamental interest for engineering a ferroelectric material. The domain wall and its width control the ferroelectric behavior to a great extent. The stability of polarization in the context of Landau-Ginzburg free energy functional has been worked out in a previous work by a perturbation approach, where two limits of domain wall width were estimated within the stability zone and they were also found to correspond well with the data on lithium niobate and lithium tantalate. In the present work, it is shown that this model is valid for a wide range of ferroelectric materials and also for a given ferroelectric, such as lithium niobate with different levels of impurities, which are known to affect the domain wall width.
文摘With rapid growth of power demand, transmission capacity is also in urgent need of upgrading. In some cases, converting existing AC transmission lines to DC lines can Improve the transmission capacity and reduce the construction investment. In this paper, the upstream finite element method was expanded to calculate the total electric field of same tower multi-circuit DC lines converted from double-circuit AC lines, and the validity of the algorithm was confirmed by experiments. Taking a DC line converted from a typical same tower 500 kV double-circuit AC transmission line as an example, the surface electric field and the ground total electric field in different pole conductor arrangement schemes were calculated and analyzed, and the critical height of pole conductors for DC lines in residential and non-residential area were determined. Then, the corridor width of DC and AC lines at critical height in residential and non-residential areas before and after AC-DC line transformation were compared. The results indicate that for DC lines converted from common 500 kV double-circuit AC lines, the ground total electric field can meet the requirements of corresponding standard with appropriate pole conductor arrangement schemes.
文摘目的探讨鼻咽癌(NPC)在螺旋断层放射治疗计划系统中采用不同铅门宽度的剂量学差异,研究其与机器参数、治疗时间的关系,为NPC制定螺旋断层放疗计划提供参考依据。方法选择16例NPC患者,其中男性15例,女性1例;年龄20~69岁,中位年龄46岁;病理诊断均为低分化鳞癌,按照美国癌症联合委员会(AJCC)第八版分期标准,其中Ⅱ期3例,Ⅲ期8例,Ⅳ期5例。采用3种铅门宽度(1.0 cm、2.5 cm和5.0 cm)分别进行治疗计划设计,对靶区的适形度指数(CI)、均匀性指数(HI)和危及器官的最大剂量(D_(max))、平均剂量(D_(mean))等各项指标的分析,比较3种治疗计划的剂量学分布差异,评估治疗计划的治疗时间、机器出束量、机架旋转圈数和旋转周期,对3种治疗计划数据进行多配对样本Friedman非参数检验。结果3种不同铅门宽度下,靶区计划原发肿瘤区(PGTV)nx、PGTVnd、计划靶区(PTV)1、PTV2的剂量参数CI、HI,差异有统计学意义(CI 0.81±0.04 vs 0.80±0.03 vs 0.72±0.03、0.81±0.05 vs 0.78±0.04 vs 0.72±0.07、0.77±0.07 vs 0.73±0.07 vs 0.69±0.07、0.72±0.09 vs 0.68±0.11 vs 0.67±0.14,HI 0.05±0.09 vs 0.06±0.11 vs 0.08±0.19、0.04±0.11 vs 0.05±0.09 vs 0.06±0.11、0.18±0.03 vs 0.21±0.04 vs 0.28±0.06、0.10±0.01 vs 0.12±0.02 vs 0.15±0.01)(P<0.05)。3种不同铅门宽度下,危及器官中双侧晶状体、双侧视神经、视交叉、双侧内耳、脑干、脊髓的D_(max)、D_(mean)的差异有统计学意义(P<0.05),双侧腮腺的V_(30)、口腔的V_(30)、V_(40)和D_(mean)的差异均具有统计学意义(P<0.05)。物理参数中治疗时间、机器跳数、机架旋转圈数和旋转周期,3种铅门宽度(1.0 cm、2.5 cm和5.0 cm)的差异均有统计学意义[(1095.70±163.64)s vs(447.10±71.80)s vs(231.50±40.15)s、(14854.50±2217.75)MU vs(6031.00±939.00)MU vs(3136.25±624.00)MU、47.95±7.90 vs 21.49±1.48 vs 12.15±0.83、22.80±2.00 vs 20.10±2.30 vs 18.90±2.58](P<0.05)。结论在保证靶区剂量CI和HI较好及危及器官受量达到临床要求、提高治疗效率的前提下综合考虑,建议在NPC螺旋断层放射治疗计划系统中采用2.5 cm铅门宽度进行计划设计。
