Coupling the quasi 3D numerical simulation of electromagnetic field and the experiments with some metals such as tin, aluminum, copper and steel, the electromagnetic characteristics of continuous casting with soft con...Coupling the quasi 3D numerical simulation of electromagnetic field and the experiments with some metals such as tin, aluminum, copper and steel, the electromagnetic characteristics of continuous casting with soft contacted mould, especially the influences of power frequency, the mould structure, and the inductor position, size and current on the electromagnetic force and pressure on the billet, were analyzed. The result shows that, in continuous casting with soft contacted mould, the electromagnetic pressure on the surface of billet increases with the rising of the power frequency as a logarithmically parabolic function and, with that of inductor current as a parabolic function. The design principle of the soft contacted mould is that 1) the mould structure should be ‘more segments and thin slits’; 2) the topside of inductor should be at the same location with the meniscus of molten metal; 3) the inductor should cover the initial solidifying shell of billet.展开更多
In this paper, coupling the quasi-3D numerical simulation of electromagnetic field and the experiments of continuous casting with soft-contacted mould with some metals such as tin, aluminum, copper and steel, the elec...In this paper, coupling the quasi-3D numerical simulation of electromagnetic field and the experiments of continuous casting with soft-contacted mould with some metals such as tin, aluminum, copper and steel, the electromagnetic characteristics of continuous casting with soft-contacted mould is analyzed. It is shown that the electromagnetic pressure on the surface of billet is increasing with the rising of power frequency as a logarithmically parabolic function, with that of electric conductivity of billet as a power junction, and with that of the current in inductor as a parabolic junction.展开更多
AIM:To assess the visual correction of patients with different degrees of astigmatism with toric soft contact lenses(TSC).METHODS:It was a real-world study with prospective and single-arm design.A total of 384 patient...AIM:To assess the visual correction of patients with different degrees of astigmatism with toric soft contact lenses(TSC).METHODS:It was a real-world study with prospective and single-arm design.A total of 384 patients with astigmatism who came for TSC fitting and alignment from November 2022 to January 2023 were included.According to the difference in astigmatism,patients were divided into groups A(cylinder degree:-0.75 to-0.50 D),B(cylinder degree:-1.75 to-1.00 D)and C(cylinder degree≤-2.00 D),and followed up on the day of wear,1wk,1 and 3mo,mainly to observe visual acuity,refraction,lens fit,visual quality and comfort at 1wk after wear.The visual acuity success rate and the overall success rate of the fitting were evaluation indicators(taking into account the four dimensions of visual acuity,fitting,quality of vision and comfort).The visual acuity success rate was calculated by taking“corrected visual acuity with contact lenses is no less than 1 line or better than best spectacle-corrected visual acuity”(i.e.corrected visual acuity with contact lenses is 1 line below,equal to,one line above or more than best spectaclecorrected visual acuity)as the criterion for visual success,and the the overall success rate of the fitting was calculated by using the comprehensive indicators(visual acuity,fit,visual quality,comfort)to meet certain conditions as the judgment criteria for successful fitting.RESULTS:After 1wk of wearing TSC,the visual acuity success rates of patients were 100%(207/207),98.58%(139/141)and 97.22%(35/36)in the three groups,respectively,with residual cylinder closed to 0.The acceptability of the lens fitting was over 95%;the incidence of adverse visual symptoms was within 10%and the comfort acceptability was over 97%.The overall success rate of fitting for patients with high,medium and low astigmatism was 93.72%(194/207),90.78%(128/141)and 88.89%(32/36),respectively.CONCLUSION:TSC(model:G&G POP·CT)are effective in correcting astigmatism in patients with different degrees of astigmatism.展开更多
Coupling the quasi 3D numerical simulation of the electromagnetic field and the experiments with some metals, a series of phenomena in the processes of continuous casting with soft contacted mould was analyzed. Some t...Coupling the quasi 3D numerical simulation of the electromagnetic field and the experiments with some metals, a series of phenomena in the processes of continuous casting with soft contacted mould was analyzed. Some theoretical and experimental models were presented, from which following results were obtained. 1) The electromagnetic force is related with electric conductivity of billet as a power function to 0.4. 2) The heat transfer between billet and mould is related with the contacting pressure, and it is a linear function for tin billet approximately. 3) The distance between initial solidification point and meniscus in billet is related with the surface magnetic flux density as a fourth root function. 4) The temperature gradient in the initial solidifying shell is reduced, which can decrease the tendency of hot tearing on the surface of billet, and increase the equiaxed crystal zone in billet. 5) The stronger the magnetic flux density is, the more shallow and the thinner the oscillation mark on the surface of billet is. 6) The depth of oscillation mark on the billet cast by the soft contacted mould can be reduced to about 10% in comparison with that on the billets cast by traditional mould. 7) In non dimensional condition, the average depth of the oscillation marks on the billets cast by the soft contacted mould decreases with increasing magnetic flux density on there as a complementary error function. [展开更多
Heat transfer and deformation of initial solidification shell in soft contact continuous casting mold under high frequency electromagnetic field were analyzed using numerical simulation method; the relative electromag...Heat transfer and deformation of initial solidification shell in soft contact continuous casting mold under high frequency electromagnetic field were analyzed using numerical simulation method; the relative electromagnetic parameters were obtained from the previous studies. Owing to the induction heating of a high frequency electromagnetic field (20 kHz), the thickness of initial solidification shell decreases, and the temperature of strand surface and slit copper mold increases when compared with the case without the electromagnetic filed. The viscosity of flux de- creases because of the induction heating of the high frequency electromagnetic field, and the dimension of the flux channel increases with electromagnetic pressure; thus, the deformation behavior of initial solidification shell was different before and after the action of high frequency electromagnetic field. Furthermore, the abatement mechanism of oscillation marks under high frequency electromagnetic field was explained.展开更多
Roadways excavated in soft rocks at great depth are difficult to be maintained due to large deformation of surrounding rocks, which greatly influences the safety and efficiency of deep resources exploitation. During t...Roadways excavated in soft rocks at great depth are difficult to be maintained due to large deformation of surrounding rocks, which greatly influences the safety and efficiency of deep resources exploitation. During the excavation process of a deep soft rock tunnel, the rock wall may be compacted due to large deformation. In this paper, the technique to address this problem by a two-dimensional (2D) finite element software, large deformation engineering analyses software (LDEAS 1.0), is provided. By using the Lagrange multiplier method, the kinematic constraint of non-penetrating condition and static constraint of Coulomb friction are introduced to the governing equations in the form of incremental displacement. The numerical example demonstrates the efficiency of this technology. Deformations of a transportation tunnel in inclined soft rock strata at the depth of 1 000 m in Qishan coal mine and a tunnel excavated to three different depths are analyzed by two models, i.e. the additive decomposition model and polar decomposition model. It can be found that the deformation of the transportation tunnel is asymmetrical due to the inclination of rock strata. For extremely soft rock, large deformation can converge only for the additive decomposition model. The deformation of surrounding rocks increases with the increase in the tunnel depth for both models. At the same depth, the deformation calculated by the additive decomposition model is smaller than that by the polar decomposition model.展开更多
Using molten Pb-Sn-Bi alloy, the meniscus shape under high frequency magnetic field of φ100 mm round billet caster was investigated. The effect of some parameters on meniscus shape was studied. The results show that ...Using molten Pb-Sn-Bi alloy, the meniscus shape under high frequency magnetic field of φ100 mm round billet caster was investigated. The effect of some parameters on meniscus shape was studied. The results show that for a mold with 12 segments, the meniscus shape is relatively stable. With increasing power input, the menis- cus height increases with intensification of fluctuation. For the given caster, the reasonable power input is about 70 kW. The coil should be near to the top of mold and/or the initial meniscus should be near to the center of the coil. The lower the frequency, the higher is the meniscus height. With increasing frequency, the free surface is more flattened and meniscus becomes more stable. In practice, the power input should be increased simultaneously with frequency. The optimal frequency is about 20 kHz.展开更多
AIMTo determine the effect of pH, osmolality, and buffering system on the oxygen permeability (Dk) of soft contact lenses.METHODSTwo hydrogel lenses (nelfilcon A and etafilcon A) and 2 silicone hydrogel lenses (lotraf...AIMTo determine the effect of pH, osmolality, and buffering system on the oxygen permeability (Dk) of soft contact lenses.METHODSTwo hydrogel lenses (nelfilcon A and etafilcon A) and 2 silicone hydrogel lenses (lotrafilcon A and balafilcon A) were used in the study. These lenses were incubated in phosphate-buffered saline (PBS) and borate-buffered saline (BBS) solutions adjusted by 0.8 pH increments to a pH in the range of 5.8-9.0 or in hypotonic (280 mOsmol/kg), isotonic (310 mOsmol/kg) and hypertonic (380 mOsmol/kg) PBS solutions. Polarographic method was used for measuring the Dk and lenses were stacked as 4 layers to correct the boundary effect.RESULTSDk values of all contact lenses measured in BBS solutions were more stable than those in PBS solutions. Especially the etafilcon A lens showed a relative big change compared with other types of contact lenses at the same conditions. When the osmolality of PBS solution increased from hypotonic to hypertonic, Dk of all contact lenses decreased. Variations in Dk existed depending on lens materials, etafilcon A lens was the most affected and nelfilcon A was the least affected by osmolality.CONCLUSIONFrom the result obtained, it is revealed that Dk of contact lenses is changed by the pH, osmolality, and buffering condition of tear. Thus, Dk of contact lens can be varied by the lens wearers' physiological and/or pathological conditions.展开更多
The distribution of the magnetic flux density in a soft-contact electromagnetic continuous casting (EMCC) rectangular mold was investigated. The experimental results show that with an increase in electric power, the...The distribution of the magnetic flux density in a soft-contact electromagnetic continuous casting (EMCC) rectangular mold was investigated. The experimental results show that with an increase in electric power, the magnetic flux density increases. The position where the maximum magnetic flux density appears will shift up when the coil moves to the top of the mold. At the same time, the maximum magnetic flux density will increase and the effective acting range of electromagnetic pressure will widen. As a result, in practice, the coil should be placed near the top part of the mold. The meniscus should be controlled near the top part of the coil, as this not only remarkably improves the billet surface quality but also saves energy. With the same electric power input, the higher the frequency, the lower the magnetic flux density.展开更多
Purpose: Reasons for the lack of success for contact lens patients range from poor fit, to discomfort or to a less than optimum wearing schedule. This project was a preliminary investigation of customized soft toric c...Purpose: Reasons for the lack of success for contact lens patients range from poor fit, to discomfort or to a less than optimum wearing schedule. This project was a preliminary investigation of customized soft toric contact lenses as an alternative for unsuccessful contact lens patients or potential drop-outs. Methods: Fifteen healthy non-compromised, previously unsuccessful contact lens wearing patients (13 women, 2 men) with ages from 21 to 33 years (25.1 ± 2.7 years) were the subjects for this study. They were empirically fitted with 15 astigmatic and 5 spherical customized SpecialEyes soft contact lenses. Visual acuities, comfort, lens movement, and rotation were evaluated. Results: Patients fitted with customized SpecialEyes soft contact lenses had statistically significant better visual acuities than with Phoropter Manifest Refraction. The lenses used in this study centered well and moved no more than 1 mm upon each blink. Lens rotation was less than 10 degrees for all toric lenses. Patients gave very positive vision and comfort ratings. Conclusion: This preliminary study supports the application of a software program to empirically design and manufacture Special Eyes custom soft lenses based upon corneal topographical parameters and subjective manifest refraction for those patients who either have challenging corneal parameters, high sphero-cylindrical prescriptions, or are currently dissatisfied with their contact lenses and are potential drop-outs.展开更多
Purpose: The purpose of this study was to evaluate the change in corneal wavefront aberrations in young adults who have been fit with multifocal soft contact lenses for myopia progression control. Findings have been a...Purpose: The purpose of this study was to evaluate the change in corneal wavefront aberrations in young adults who have been fit with multifocal soft contact lenses for myopia progression control. Findings have been analyzed for statistical significance and clinical relevance and compared to reportedly successful Orthokeratology outcomes. Methods: The dominant eye of 40 participants (27 women, 13 men;mean age 27.3 ± 3.2 years;range 23 to 39 years) was fit with Proclear Multifocal center distance lenses (Coopervision, Pleasanton, USA) having a variety of distance powers and reading additions. Refractive errors were limited to a range of –6.00 D up to +1.00 D of sphere, and no greater than –1.00 D of cylinder. Corneal wavefront measurements were performed over 6 mm diameters with a Zeiss Atlas 9000 corneal topographer (Zeiss Meditec, Dublin, USA) prior to, and following lens fitting. Data were converted into rectangular Fourier optics terms M, J0, J45 and RMS values for each reading addition were statistically analyzed. Following evaluation of statistical significance and clinical relevance, results were compared to published data from successful Orthokeratology treatments. Results: Statistically significant changes in higher order aberrations were detected for lenses of all reading additions. Lens groups with higher Add-powers demonstrated stronger changes with increased significance. Final RMS values relating to 2nd, 3rd and 4th Zernike Orders reached clinical significance with a wavefront error of 0.10 μm, the equivalent of 0.25D. Moreover, as Add-powers increased, 3rd and 4th order aberrations likewise showed an increase. Pre-fitting astigmatism values accounted for the highest recorded aberrations and remained predominantly unchanged. Conclusion: Proclear Multifocal center-distance contact lenses were found to increase higher order wavefront aberrations in a manner dependent on their Add-power. In comparison to successful Orthokeratology outcomes, the amounts of resulting aberrations are notably different.展开更多
Soft machine refers to a kind of mechanical system made of soft materials to complete sophisticated missions, such as handling a fragile object and crawling along a narrow tunnel corner, under low cost control and act...Soft machine refers to a kind of mechanical system made of soft materials to complete sophisticated missions, such as handling a fragile object and crawling along a narrow tunnel corner, under low cost control and actuation. Hence, soft machines have raised great challenges to computational dynamics. In this review article, recent studies of the authors on the dynamic modeling, numerical simulation, and experimental validation of soft machines are summarized in the framework of multibody system dynamics. The dynamic modeling approaches are presented first for the geometric nonlinearities of coupled overall motions and large deformations of a soft component, the physical nonlinearities of a soft component made of hyperelastic or elastoplastic materials, and the frictional contacts/impacts of soft components, respectively. Then the computation approach is outlined for the dynamic simulation of soft machines governed by a set of differential-algebraic equations of very high dimensions, with an emphasis on the efficient computations of the nonlinear elastic force vector of finite elements. The validations of the proposed approaches are given via three case studies, including the locomotion of a soft quadrupedal robot, the spinning deployment of a solar sail of a spacecraft, and the deployment of a mesh reflector of a satellite antenna, as well as the corresponding experimental studies. Finally, some remarks are made for future studies.展开更多
We theoretically study the indentation response of a compressible soft electroactive material by a rigid punch. The half-space material is assumed to be initially subjected to a finite deformation and an electric bias...We theoretically study the indentation response of a compressible soft electroactive material by a rigid punch. The half-space material is assumed to be initially subjected to a finite deformation and an electric biasing field. By adopting the linearized theory for incremental fields, which is established on the basis of a general nonlinear theory for electroelasticity, the appropriate equations governing the perturbed infinitesimal elastic and electric fields are derived particularly when the material is subjected to a uniform equibiaxial stretch and a uniform electric displacement. A general solution to the governing equations is presented, which is concisely expressed in terms of four quasi-harmonic functions. By adopting the potential theory method, exact contact solutions for three common perfectly conducting rigid indenters of fiat-ended circular, conical and spherical geometries can be derived, and some explicit relations that are of practical importance are outlined.展开更多
In order to avoid any possible effect of separating procedures from intact cell on morphologic structure of the chromosomes, cultivated Hep-2 tumor cells were treated with colchicine and observed by soft X-ray contact...In order to avoid any possible effect of separating procedures from intact cell on morphologic structure of the chromosomes, cultivated Hep-2 tumor cells were treated with colchicine and observed by soft X-ray contact microscopy for the first time. The fine structures of chromosomes are more clear with stereo features. The thread-like and coarse granular structures twine and tangle up together within chromosome masses which can not easily be revealed in Wright’s stained sample by light microscope or osmium stained sample by transmission electron展开更多
Purpose: To investigate the efficacy and complications of continuous wear of etafilcon A for therapeutic use. Materials and Methods: The subjects were 228 eyes of 219 outpatients prescribed contact lens (CL) for one w...Purpose: To investigate the efficacy and complications of continuous wear of etafilcon A for therapeutic use. Materials and Methods: The subjects were 228 eyes of 219 outpatients prescribed contact lens (CL) for one week of continuous therapeutic wear during 10 years. The reason for prescription of CLs, the primary disease, the duration of CL wear and the complications were assessed retrospectively. Results: The predominant reason for prescription of CLs was relief of pain or a foreign-body sensation (62.3%) and protection of the corneal epithelium (20.6%). The primary disease was post-penetrating keratoplasty (36.8%), followed by corneal epithelial erosion (14.5%), post-lamellar keratoplasty (14.0%) and bullous keratopathy (12.2%). The average duration of wearing single lens was 6.5 ± 3.2 days. The average duration of wearing CLs in total was 9.2 ± 10.7 months. The most frequent problem associated with continuous wear of CLs was their dropping out of CLs (12.3%). The complications associated with CLs included conjunctivitis with papillary hyperplasia, corneal erosion and superficial punctate keratitis, but corneal ulcer and corneal infiltrates were not found. Conclusion: Serious complications were not shown changing the lenses every week to keep to the prescribed time limit for continuous therapeutic wear, even if corneal epithelial barrier function is impaired.展开更多
This paper investigates to what extent and why the key Action 1 of the Erasmus+ programme, namely learning mobility of individuals, can be considered a soft power’s instrument on European neighbourhood countries. The...This paper investigates to what extent and why the key Action 1 of the Erasmus+ programme, namely learning mobility of individuals, can be considered a soft power’s instrument on European neighbourhood countries. The core assumption is that due to people-to-people contact, Erasmus participants are most likely to become EU informal ambassadors, in the sense that they become carriers of EU soft power leading to changes in cultural and social perceptions. However, what will the place of Erasmus+ be in the ongoing debate on international cultural relations’ strategy? Erasmus+ can play a major role in this new strategy considering the huge growth of mobility flows between EU and ENP countries, since the new programme was launched. Moreover, EU institutions are looking for new strategic tools of public diplomacy. Have they realised that the external dimension of Erasmus+ lends itself to being one of these? Therefore, the topic of this work is of high interest because it is closely related to the debate about both the means and the ends of the EU external policy. For the sake of this research, three case studies, from different geographical regions neighbouring the EU, have been chosen: Tunisia, Ukraine, and Georgia. A comparison among these three countries will reveal under which conditions Erasmus+ can be considered a soft power’s instrument. Hence, the identification of conditions applicable to all EU partner countries in order to evaluate whether the EU can spread its soft power through Erasmus+, represents the paper’s added value which opens new avenues for further research on the topic.展开更多
文摘Coupling the quasi 3D numerical simulation of electromagnetic field and the experiments with some metals such as tin, aluminum, copper and steel, the electromagnetic characteristics of continuous casting with soft contacted mould, especially the influences of power frequency, the mould structure, and the inductor position, size and current on the electromagnetic force and pressure on the billet, were analyzed. The result shows that, in continuous casting with soft contacted mould, the electromagnetic pressure on the surface of billet increases with the rising of the power frequency as a logarithmically parabolic function and, with that of inductor current as a parabolic function. The design principle of the soft contacted mould is that 1) the mould structure should be ‘more segments and thin slits’; 2) the topside of inductor should be at the same location with the meniscus of molten metal; 3) the inductor should cover the initial solidifying shell of billet.
文摘In this paper, coupling the quasi-3D numerical simulation of electromagnetic field and the experiments of continuous casting with soft-contacted mould with some metals such as tin, aluminum, copper and steel, the electromagnetic characteristics of continuous casting with soft-contacted mould is analyzed. It is shown that the electromagnetic pressure on the surface of billet is increasing with the rising of power frequency as a logarithmically parabolic function, with that of electric conductivity of billet as a power junction, and with that of the current in inductor as a parabolic junction.
基金Supported by Key R&D Plan of Shaanxi Province:Key Industrial Innovation Chain(Cluster)-Social Development Field(No.2022ZDLSF03-10).
文摘AIM:To assess the visual correction of patients with different degrees of astigmatism with toric soft contact lenses(TSC).METHODS:It was a real-world study with prospective and single-arm design.A total of 384 patients with astigmatism who came for TSC fitting and alignment from November 2022 to January 2023 were included.According to the difference in astigmatism,patients were divided into groups A(cylinder degree:-0.75 to-0.50 D),B(cylinder degree:-1.75 to-1.00 D)and C(cylinder degree≤-2.00 D),and followed up on the day of wear,1wk,1 and 3mo,mainly to observe visual acuity,refraction,lens fit,visual quality and comfort at 1wk after wear.The visual acuity success rate and the overall success rate of the fitting were evaluation indicators(taking into account the four dimensions of visual acuity,fitting,quality of vision and comfort).The visual acuity success rate was calculated by taking“corrected visual acuity with contact lenses is no less than 1 line or better than best spectacle-corrected visual acuity”(i.e.corrected visual acuity with contact lenses is 1 line below,equal to,one line above or more than best spectaclecorrected visual acuity)as the criterion for visual success,and the the overall success rate of the fitting was calculated by using the comprehensive indicators(visual acuity,fit,visual quality,comfort)to meet certain conditions as the judgment criteria for successful fitting.RESULTS:After 1wk of wearing TSC,the visual acuity success rates of patients were 100%(207/207),98.58%(139/141)and 97.22%(35/36)in the three groups,respectively,with residual cylinder closed to 0.The acceptability of the lens fitting was over 95%;the incidence of adverse visual symptoms was within 10%and the comfort acceptability was over 97%.The overall success rate of fitting for patients with high,medium and low astigmatism was 93.72%(194/207),90.78%(128/141)and 88.89%(32/36),respectively.CONCLUSION:TSC(model:G&G POP·CT)are effective in correcting astigmatism in patients with different degrees of astigmatism.
文摘Coupling the quasi 3D numerical simulation of the electromagnetic field and the experiments with some metals, a series of phenomena in the processes of continuous casting with soft contacted mould was analyzed. Some theoretical and experimental models were presented, from which following results were obtained. 1) The electromagnetic force is related with electric conductivity of billet as a power function to 0.4. 2) The heat transfer between billet and mould is related with the contacting pressure, and it is a linear function for tin billet approximately. 3) The distance between initial solidification point and meniscus in billet is related with the surface magnetic flux density as a fourth root function. 4) The temperature gradient in the initial solidifying shell is reduced, which can decrease the tendency of hot tearing on the surface of billet, and increase the equiaxed crystal zone in billet. 5) The stronger the magnetic flux density is, the more shallow and the thinner the oscillation mark on the surface of billet is. 6) The depth of oscillation mark on the billet cast by the soft contacted mould can be reduced to about 10% in comparison with that on the billets cast by traditional mould. 7) In non dimensional condition, the average depth of the oscillation marks on the billets cast by the soft contacted mould decreases with increasing magnetic flux density on there as a complementary error function. [
基金Item Sponsored by National Natural Science Foundation of China (59734080)
文摘Heat transfer and deformation of initial solidification shell in soft contact continuous casting mold under high frequency electromagnetic field were analyzed using numerical simulation method; the relative electromagnetic parameters were obtained from the previous studies. Owing to the induction heating of a high frequency electromagnetic field (20 kHz), the thickness of initial solidification shell decreases, and the temperature of strand surface and slit copper mold increases when compared with the case without the electromagnetic filed. The viscosity of flux de- creases because of the induction heating of the high frequency electromagnetic field, and the dimension of the flux channel increases with electromagnetic pressure; thus, the deformation behavior of initial solidification shell was different before and after the action of high frequency electromagnetic field. Furthermore, the abatement mechanism of oscillation marks under high frequency electromagnetic field was explained.
基金Supported by the Fundamental Research Funds for the Central Universities of China (2009QL05)
文摘Roadways excavated in soft rocks at great depth are difficult to be maintained due to large deformation of surrounding rocks, which greatly influences the safety and efficiency of deep resources exploitation. During the excavation process of a deep soft rock tunnel, the rock wall may be compacted due to large deformation. In this paper, the technique to address this problem by a two-dimensional (2D) finite element software, large deformation engineering analyses software (LDEAS 1.0), is provided. By using the Lagrange multiplier method, the kinematic constraint of non-penetrating condition and static constraint of Coulomb friction are introduced to the governing equations in the form of incremental displacement. The numerical example demonstrates the efficiency of this technology. Deformations of a transportation tunnel in inclined soft rock strata at the depth of 1 000 m in Qishan coal mine and a tunnel excavated to three different depths are analyzed by two models, i.e. the additive decomposition model and polar decomposition model. It can be found that the deformation of the transportation tunnel is asymmetrical due to the inclination of rock strata. For extremely soft rock, large deformation can converge only for the additive decomposition model. The deformation of surrounding rocks increases with the increase in the tunnel depth for both models. At the same depth, the deformation calculated by the additive decomposition model is smaller than that by the polar decomposition model.
文摘Using molten Pb-Sn-Bi alloy, the meniscus shape under high frequency magnetic field of φ100 mm round billet caster was investigated. The effect of some parameters on meniscus shape was studied. The results show that for a mold with 12 segments, the meniscus shape is relatively stable. With increasing power input, the menis- cus height increases with intensification of fluctuation. For the given caster, the reasonable power input is about 70 kW. The coil should be near to the top of mold and/or the initial meniscus should be near to the center of the coil. The lower the frequency, the higher is the meniscus height. With increasing frequency, the free surface is more flattened and meniscus becomes more stable. In practice, the power input should be increased simultaneously with frequency. The optimal frequency is about 20 kHz.
文摘AIMTo determine the effect of pH, osmolality, and buffering system on the oxygen permeability (Dk) of soft contact lenses.METHODSTwo hydrogel lenses (nelfilcon A and etafilcon A) and 2 silicone hydrogel lenses (lotrafilcon A and balafilcon A) were used in the study. These lenses were incubated in phosphate-buffered saline (PBS) and borate-buffered saline (BBS) solutions adjusted by 0.8 pH increments to a pH in the range of 5.8-9.0 or in hypotonic (280 mOsmol/kg), isotonic (310 mOsmol/kg) and hypertonic (380 mOsmol/kg) PBS solutions. Polarographic method was used for measuring the Dk and lenses were stacked as 4 layers to correct the boundary effect.RESULTSDk values of all contact lenses measured in BBS solutions were more stable than those in PBS solutions. Especially the etafilcon A lens showed a relative big change compared with other types of contact lenses at the same conditions. When the osmolality of PBS solution increased from hypotonic to hypertonic, Dk of all contact lenses decreased. Variations in Dk existed depending on lens materials, etafilcon A lens was the most affected and nelfilcon A was the least affected by osmolality.CONCLUSIONFrom the result obtained, it is revealed that Dk of contact lenses is changed by the pH, osmolality, and buffering condition of tear. Thus, Dk of contact lens can be varied by the lens wearers' physiological and/or pathological conditions.
基金ItemSponsored by National Natural Science Foundation of China (50274203) , National High Technology Research andDevelopment Programof China (2001AA337040) and National Fundamental Research and Development Plan of China(G1998061510)
文摘The distribution of the magnetic flux density in a soft-contact electromagnetic continuous casting (EMCC) rectangular mold was investigated. The experimental results show that with an increase in electric power, the magnetic flux density increases. The position where the maximum magnetic flux density appears will shift up when the coil moves to the top of the mold. At the same time, the maximum magnetic flux density will increase and the effective acting range of electromagnetic pressure will widen. As a result, in practice, the coil should be placed near the top part of the mold. The meniscus should be controlled near the top part of the coil, as this not only remarkably improves the billet surface quality but also saves energy. With the same electric power input, the higher the frequency, the lower the magnetic flux density.
文摘Purpose: Reasons for the lack of success for contact lens patients range from poor fit, to discomfort or to a less than optimum wearing schedule. This project was a preliminary investigation of customized soft toric contact lenses as an alternative for unsuccessful contact lens patients or potential drop-outs. Methods: Fifteen healthy non-compromised, previously unsuccessful contact lens wearing patients (13 women, 2 men) with ages from 21 to 33 years (25.1 ± 2.7 years) were the subjects for this study. They were empirically fitted with 15 astigmatic and 5 spherical customized SpecialEyes soft contact lenses. Visual acuities, comfort, lens movement, and rotation were evaluated. Results: Patients fitted with customized SpecialEyes soft contact lenses had statistically significant better visual acuities than with Phoropter Manifest Refraction. The lenses used in this study centered well and moved no more than 1 mm upon each blink. Lens rotation was less than 10 degrees for all toric lenses. Patients gave very positive vision and comfort ratings. Conclusion: This preliminary study supports the application of a software program to empirically design and manufacture Special Eyes custom soft lenses based upon corneal topographical parameters and subjective manifest refraction for those patients who either have challenging corneal parameters, high sphero-cylindrical prescriptions, or are currently dissatisfied with their contact lenses and are potential drop-outs.
文摘Purpose: The purpose of this study was to evaluate the change in corneal wavefront aberrations in young adults who have been fit with multifocal soft contact lenses for myopia progression control. Findings have been analyzed for statistical significance and clinical relevance and compared to reportedly successful Orthokeratology outcomes. Methods: The dominant eye of 40 participants (27 women, 13 men;mean age 27.3 ± 3.2 years;range 23 to 39 years) was fit with Proclear Multifocal center distance lenses (Coopervision, Pleasanton, USA) having a variety of distance powers and reading additions. Refractive errors were limited to a range of –6.00 D up to +1.00 D of sphere, and no greater than –1.00 D of cylinder. Corneal wavefront measurements were performed over 6 mm diameters with a Zeiss Atlas 9000 corneal topographer (Zeiss Meditec, Dublin, USA) prior to, and following lens fitting. Data were converted into rectangular Fourier optics terms M, J0, J45 and RMS values for each reading addition were statistically analyzed. Following evaluation of statistical significance and clinical relevance, results were compared to published data from successful Orthokeratology treatments. Results: Statistically significant changes in higher order aberrations were detected for lenses of all reading additions. Lens groups with higher Add-powers demonstrated stronger changes with increased significance. Final RMS values relating to 2nd, 3rd and 4th Zernike Orders reached clinical significance with a wavefront error of 0.10 μm, the equivalent of 0.25D. Moreover, as Add-powers increased, 3rd and 4th order aberrations likewise showed an increase. Pre-fitting astigmatism values accounted for the highest recorded aberrations and remained predominantly unchanged. Conclusion: Proclear Multifocal center-distance contact lenses were found to increase higher order wavefront aberrations in a manner dependent on their Add-power. In comparison to successful Orthokeratology outcomes, the amounts of resulting aberrations are notably different.
基金supported in part by the National Natural Science Foundation of China (Grants 11290150 and 11290151)
文摘Soft machine refers to a kind of mechanical system made of soft materials to complete sophisticated missions, such as handling a fragile object and crawling along a narrow tunnel corner, under low cost control and actuation. Hence, soft machines have raised great challenges to computational dynamics. In this review article, recent studies of the authors on the dynamic modeling, numerical simulation, and experimental validation of soft machines are summarized in the framework of multibody system dynamics. The dynamic modeling approaches are presented first for the geometric nonlinearities of coupled overall motions and large deformations of a soft component, the physical nonlinearities of a soft component made of hyperelastic or elastoplastic materials, and the frictional contacts/impacts of soft components, respectively. Then the computation approach is outlined for the dynamic simulation of soft machines governed by a set of differential-algebraic equations of very high dimensions, with an emphasis on the efficient computations of the nonlinear elastic force vector of finite elements. The validations of the proposed approaches are given via three case studies, including the locomotion of a soft quadrupedal robot, the spinning deployment of a solar sail of a spacecraft, and the deployment of a mesh reflector of a satellite antenna, as well as the corresponding experimental studies. Finally, some remarks are made for future studies.
基金supported by the National Natural Science Foundation of China(10832009 and 11090333)the Fundamental Research Funds for Central Universities(2011XZZX002)
文摘We theoretically study the indentation response of a compressible soft electroactive material by a rigid punch. The half-space material is assumed to be initially subjected to a finite deformation and an electric biasing field. By adopting the linearized theory for incremental fields, which is established on the basis of a general nonlinear theory for electroelasticity, the appropriate equations governing the perturbed infinitesimal elastic and electric fields are derived particularly when the material is subjected to a uniform equibiaxial stretch and a uniform electric displacement. A general solution to the governing equations is presented, which is concisely expressed in terms of four quasi-harmonic functions. By adopting the potential theory method, exact contact solutions for three common perfectly conducting rigid indenters of fiat-ended circular, conical and spherical geometries can be derived, and some explicit relations that are of practical importance are outlined.
基金The Project Supported by National Natural Science Foundation of China
文摘In order to avoid any possible effect of separating procedures from intact cell on morphologic structure of the chromosomes, cultivated Hep-2 tumor cells were treated with colchicine and observed by soft X-ray contact microscopy for the first time. The fine structures of chromosomes are more clear with stereo features. The thread-like and coarse granular structures twine and tangle up together within chromosome masses which can not easily be revealed in Wright’s stained sample by light microscope or osmium stained sample by transmission electron
文摘Purpose: To investigate the efficacy and complications of continuous wear of etafilcon A for therapeutic use. Materials and Methods: The subjects were 228 eyes of 219 outpatients prescribed contact lens (CL) for one week of continuous therapeutic wear during 10 years. The reason for prescription of CLs, the primary disease, the duration of CL wear and the complications were assessed retrospectively. Results: The predominant reason for prescription of CLs was relief of pain or a foreign-body sensation (62.3%) and protection of the corneal epithelium (20.6%). The primary disease was post-penetrating keratoplasty (36.8%), followed by corneal epithelial erosion (14.5%), post-lamellar keratoplasty (14.0%) and bullous keratopathy (12.2%). The average duration of wearing single lens was 6.5 ± 3.2 days. The average duration of wearing CLs in total was 9.2 ± 10.7 months. The most frequent problem associated with continuous wear of CLs was their dropping out of CLs (12.3%). The complications associated with CLs included conjunctivitis with papillary hyperplasia, corneal erosion and superficial punctate keratitis, but corneal ulcer and corneal infiltrates were not found. Conclusion: Serious complications were not shown changing the lenses every week to keep to the prescribed time limit for continuous therapeutic wear, even if corneal epithelial barrier function is impaired.
文摘This paper investigates to what extent and why the key Action 1 of the Erasmus+ programme, namely learning mobility of individuals, can be considered a soft power’s instrument on European neighbourhood countries. The core assumption is that due to people-to-people contact, Erasmus participants are most likely to become EU informal ambassadors, in the sense that they become carriers of EU soft power leading to changes in cultural and social perceptions. However, what will the place of Erasmus+ be in the ongoing debate on international cultural relations’ strategy? Erasmus+ can play a major role in this new strategy considering the huge growth of mobility flows between EU and ENP countries, since the new programme was launched. Moreover, EU institutions are looking for new strategic tools of public diplomacy. Have they realised that the external dimension of Erasmus+ lends itself to being one of these? Therefore, the topic of this work is of high interest because it is closely related to the debate about both the means and the ends of the EU external policy. For the sake of this research, three case studies, from different geographical regions neighbouring the EU, have been chosen: Tunisia, Ukraine, and Georgia. A comparison among these three countries will reveal under which conditions Erasmus+ can be considered a soft power’s instrument. Hence, the identification of conditions applicable to all EU partner countries in order to evaluate whether the EU can spread its soft power through Erasmus+, represents the paper’s added value which opens new avenues for further research on the topic.