A self-consistent two-dimensional （2D） collisionless fluid model is developed to sim- ulate the effects of the low-frequency （LF） power on a dual frequency （DF） capacitive sheath over an electrode with a cylindr...A self-consistent two-dimensional （2D） collisionless fluid model is developed to sim- ulate the effects of the low-frequency （LF） power on a dual frequency （DF） capacitive sheath over an electrode with a cylindrical hole. In this paper, the time-averaged potential, electric field （E- field）, ion density in the sheath, and ion energy distributions （IEDs） at the center of the cylindrical hole＇s bottom are calculated and compared for different LF powers. The results show that the LF power is crucial for determining the sheath structure. As the LF power decreases, the potential drop decreases, the sheath becomes thinner, and the plasma molding effect seems to be more significant. The existence of a radial E-field near the sidewalls of a hole may cause a significant portion of ions to strike the sidewall and lead to the phenomenon of notching.展开更多
Since processed substrates usually exhibit nonplanar surface structures in micro- electro-mechmfical-systems （MEMS） etching, a two-dimensional （2D） fluid model is developed to simulate the characteristics of the s...Since processed substrates usually exhibit nonplanar surface structures in micro- electro-mechmfical-systems （MEMS） etching, a two-dimensional （2D） fluid model is developed to simulate the characteristics of the sheath near a conductive substrate with a circular trench, which is placed in an argon discharge powered by a radio-frequency （RF） current source. The model consists of 2D time-dependent fluid equations, the Poisson equation, and a current balance equation that can self-consistently determine the instantaneous voltage oll the substrate placed on a powered electrode. The effects of both the aspect ratio （depth/width） and the structure of the trench on the characteristics of the sheath are simulated. The time-averaged potential and electric field in the sheath are calculated and compared for different discharge parameters. The results show that the radial sheath profile is not uniform and always tends to adapt to the contour of the substrate, which is believed to be the moulding effect. Affected by the structure of the substrate surface, the potential and electric field near the inner and outer sidewalls of the trench exhibit obvious non-uniforlnity, which will inevitably lead to non-uniformity in etching, such as notching. Furthermore, with a fixed amplitude of the RF current source, the potential drops and the sheath thickness decrease with an increase in aspect ratio.展开更多
A simple collisional radio frequency (rf) sheath fluid model, which is not restricted by the ratio of rf frequency to ion plasma frequency (β=ωrf/Upi), was established and solved numerically. In the ion balance equa...A simple collisional radio frequency (rf) sheath fluid model, which is not restricted by the ratio of rf frequency to ion plasma frequency (β=ωrf/Upi), was established and solved numerically. In the ion balance equation, the effect of the collision on the ion and the ion velocity is assumed to be a direct ratio to ion velocity. The ion energy distributions (IEDs) calculated in the model in comparison with the experimental data [M. A. Sobolewski, J. K. Olthoff, and Y. C. Wang, J. Appl. Phys. 85, 3966 (1999)], proved the validity of the model. And the effect of the collision on the sheath characteristic was obtained and discussed. This paper demonstrates that the collision frequency is another crucial parameter as well as the ratio β to determine the rf sheath characteristics and the shape of IEDs.展开更多
The present research investigates the influence of sheath solvent’s flow rate on the quality of electrospun ethyl cellulose (EC) nanofibers using a modified coaxial process. With 24 w/v % EC in ethanol as electrospin...The present research investigates the influence of sheath solvent’s flow rate on the quality of electrospun ethyl cellulose (EC) nanofibers using a modified coaxial process. With 24 w/v % EC in ethanol as electrospinnable core fluid and ethanol as sheath fluid, EC nanofibers generated under different sheath flow rates were generated from the modified processes. FESEM observations demonstrate that the modified process is effective in preventing the clogging of spinneret for a smooth electrospinning. The key for the modified coaxial process is the reasonable selection of a sheath flow rate matching the drawing process of core EC fluid during the electrpospinning. The EC nanofibers’ diameters (D, nm) could be manipulated through the sheath-to-core flow rate ratio (f) as D = 819-1651f (R= 0.9754) within a suitable range of 0 to 0.25. The present paper provides useful data for the implementation of the modified coaxial process controllably to obtain polymer nanofibers with high quality.展开更多
Background:Cerebrospinal fluid(CSF)-diversion procedures have traditionally been the standard of treatment for patients with medically refractive idiopathic intracranial hypertension(IIH).However,dural venous sinus st...Background:Cerebrospinal fluid(CSF)-diversion procedures have traditionally been the standard of treatment for patients with medically refractive idiopathic intracranial hypertension(IIH).However,dural venous sinus stent(VSS)placement has been described as a safe and effective procedure for the management of medically refractive IIH.We performed a meta-analysis comparing outcomes and complications of CSF-diversion procedures,VSS and optic nerve sheath fenestration(ONSF)for the treatment of medically refractive IIH.Methods:Electronic searches were performed using six databases from 1988 to January 2017.Data was extracted and meta-analysed from the identified studies.Results:From 55 pooled studies,there were 538 CSF-diversion cases,224 dural venous stent placements,and 872 ONSF procedures.Similar improvements were found in terms of postoperative headaches(CSF vs.VSS vs.ONSF:84%vs.78%vs.62%,P=0.223),papilledema(CSF vs.VSS vs.ONSF:71%vs.86%vs.77%,P=0.192),whilst visual acuity changes favored venous stenting(CSF vs.VSS vs.ONSF:55%vs.69%vs.44%,P=0.037).There was a significantly lower rate of subsequent procedures with venous stent placement(CSF vs.VSS vs.ONSF:37%vs.13%vs.18%,P<0.001),but other complication rates were similar(CSF vs.VSS vs.ONSF:13%vs.8%vs.14%,P=0.28).Subgroup analysis of lumbar-peritoneal vs.ventriculoperitoneal shunts found no differences in symptom improvements,complications and subsequent procedure rates.Conclusions:Our findings suggest that dural venous sinus stenting may be a viable alternative to traditional surgical interventions in patients who are refractory to medical treatment.展开更多
基金supported by Handan Science and Technology Research and Development Project of China(No.1121120069-5)the Scientific Research Start-up Funds of Doctor and Master of Handan College of China(No.2010005)+1 种基金National Natural Science Foundation of China(Nos.11335004 and 11375040)the Important National Science and Technology Specific Project of China(No.2011ZX02403-001)
文摘A self-consistent two-dimensional （2D） collisionless fluid model is developed to sim- ulate the effects of the low-frequency （LF） power on a dual frequency （DF） capacitive sheath over an electrode with a cylindrical hole. In this paper, the time-averaged potential, electric field （E- field）, ion density in the sheath, and ion energy distributions （IEDs） at the center of the cylindrical hole＇s bottom are calculated and compared for different LF powers. The results show that the LF power is crucial for determining the sheath structure. As the LF power decreases, the potential drop decreases, the sheath becomes thinner, and the plasma molding effect seems to be more significant. The existence of a radial E-field near the sidewalls of a hole may cause a significant portion of ions to strike the sidewall and lead to the phenomenon of notching.
基金supported by National Natural Scienee Foundation of China (Nos. 10635010, 10975030)the Science Resemrch Foundation of Dalian University of Technology of China
文摘Since processed substrates usually exhibit nonplanar surface structures in micro- electro-mechmfical-systems （MEMS） etching, a two-dimensional （2D） fluid model is developed to simulate the characteristics of the sheath near a conductive substrate with a circular trench, which is placed in an argon discharge powered by a radio-frequency （RF） current source. The model consists of 2D time-dependent fluid equations, the Poisson equation, and a current balance equation that can self-consistently determine the instantaneous voltage oll the substrate placed on a powered electrode. The effects of both the aspect ratio （depth/width） and the structure of the trench on the characteristics of the sheath are simulated. The time-averaged potential and electric field in the sheath are calculated and compared for different discharge parameters. The results show that the radial sheath profile is not uniform and always tends to adapt to the contour of the substrate, which is believed to be the moulding effect. Affected by the structure of the substrate surface, the potential and electric field near the inner and outer sidewalls of the trench exhibit obvious non-uniforlnity, which will inevitably lead to non-uniformity in etching, such as notching. Furthermore, with a fixed amplitude of the RF current source, the potential drops and the sheath thickness decrease with an increase in aspect ratio.
基金The project supported by the National Nature Science Function of China (Nos. 10175013, 10010760807, and 10160420799)
文摘A simple collisional radio frequency (rf) sheath fluid model, which is not restricted by the ratio of rf frequency to ion plasma frequency (β=ωrf/Upi), was established and solved numerically. In the ion balance equation, the effect of the collision on the ion and the ion velocity is assumed to be a direct ratio to ion velocity. The ion energy distributions (IEDs) calculated in the model in comparison with the experimental data [M. A. Sobolewski, J. K. Olthoff, and Y. C. Wang, J. Appl. Phys. 85, 3966 (1999)], proved the validity of the model. And the effect of the collision on the sheath characteristic was obtained and discussed. This paper demonstrates that the collision frequency is another crucial parameter as well as the ratio β to determine the rf sheath characteristics and the shape of IEDs.
文摘The present research investigates the influence of sheath solvent’s flow rate on the quality of electrospun ethyl cellulose (EC) nanofibers using a modified coaxial process. With 24 w/v % EC in ethanol as electrospinnable core fluid and ethanol as sheath fluid, EC nanofibers generated under different sheath flow rates were generated from the modified processes. FESEM observations demonstrate that the modified process is effective in preventing the clogging of spinneret for a smooth electrospinning. The key for the modified coaxial process is the reasonable selection of a sheath flow rate matching the drawing process of core EC fluid during the electrpospinning. The EC nanofibers’ diameters (D, nm) could be manipulated through the sheath-to-core flow rate ratio (f) as D = 819-1651f (R= 0.9754) within a suitable range of 0 to 0.25. The present paper provides useful data for the implementation of the modified coaxial process controllably to obtain polymer nanofibers with high quality.
文摘Background:Cerebrospinal fluid(CSF)-diversion procedures have traditionally been the standard of treatment for patients with medically refractive idiopathic intracranial hypertension(IIH).However,dural venous sinus stent(VSS)placement has been described as a safe and effective procedure for the management of medically refractive IIH.We performed a meta-analysis comparing outcomes and complications of CSF-diversion procedures,VSS and optic nerve sheath fenestration(ONSF)for the treatment of medically refractive IIH.Methods:Electronic searches were performed using six databases from 1988 to January 2017.Data was extracted and meta-analysed from the identified studies.Results:From 55 pooled studies,there were 538 CSF-diversion cases,224 dural venous stent placements,and 872 ONSF procedures.Similar improvements were found in terms of postoperative headaches(CSF vs.VSS vs.ONSF:84%vs.78%vs.62%,P=0.223),papilledema(CSF vs.VSS vs.ONSF:71%vs.86%vs.77%,P=0.192),whilst visual acuity changes favored venous stenting(CSF vs.VSS vs.ONSF:55%vs.69%vs.44%,P=0.037).There was a significantly lower rate of subsequent procedures with venous stent placement(CSF vs.VSS vs.ONSF:37%vs.13%vs.18%,P<0.001),but other complication rates were similar(CSF vs.VSS vs.ONSF:13%vs.8%vs.14%,P=0.28).Subgroup analysis of lumbar-peritoneal vs.ventriculoperitoneal shunts found no differences in symptom improvements,complications and subsequent procedure rates.Conclusions:Our findings suggest that dural venous sinus stenting may be a viable alternative to traditional surgical interventions in patients who are refractory to medical treatment.
