Numerical Simulation of Heat Transfer and Deformation of Initial Shell in Soft Contact Continuous Casting Mold Under High Frequency Electromagnetic Field

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.

Oxygen permeability of soft contact lenses in different pH, osmolality and buffering solution

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.

Distribution of Magnetic Flux Density in Soft-Contact EMCC Rectangular Mold

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.

Effectiveness of toric soft contact lenses for vision correction in patients with different degrees of astigmatism: a real-world study

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.

An experimental study on fractural features of concrete samples containing hard inclusion

The final fractural forms and variation status of hard inclusion samples under biaxial compression have been primarily studied in this paper. The lateral fractural forms of samples are mainly compressive shear fracture, two kinds appear on surface: one is strike slip fault with reversed thrust, and another is thrust. Some hard inclusions rupture and some do not while hard contact serves between hard inclusions and sample; main fracture bypasses hard inclusion while soft contact serves. Finally, process of stress concentration, yield, softening until failure for hard inclusions have been analysed under a certain condition.

Visual quality of juvenile myopes wearing multifocal soft contact lenses

Background:It is unclear whether multifocal soft contact lenses(MFSCLs)affect visual quality when they are used for myopia control in juvenile myopes.The aim of this study was,therefore,to investigate the effect of MFSCLs on visual quality among juvenile myopia subjects.Methods:In a prospective,intervention study,thirty-three juvenile myopes were enrolled.Visual perception was assessed by a quality of vision(QoV)questionnaire with spectacles at baseline and after 1 month of MFSCL wear.At the one-month visit,the high(96%)contrast distance visual acuity(distance HCVA)and low(10%)contrast distance visual acuity(distance LCVA)were measured with single vision spectacle lenses,single vision soft contact lenses(SVSCLs)and MFSCLs in a random order.Wavefront aberrations were measured with SVSCLs,with MFSCLs,and without any correction.Results:Neither distance HCVA(p>0.05)nor distance LCVA(p>0.05)revealed any significant difference between MFSCLs,SVSCLs and single vision spectacle lenses.The overall score(the sum of ten symptoms)of the QoV questionnaire did not show a statistically significant difference between spectacles at baseline and after 1 month of MFSCL wear(p=0.357).The results showed that the frequency(p<0.001),severity(p=0.001)and bothersome degree(p=0.016)of halos were significantly worse when wearing MFSCLs than when wearing single vision spectacle lenses.In contrast,the bothersome degree caused by focusing difficulty(p=0.046)and the frequency of difficulty in judging distance or depth perception(p=0.046)were better when wearing MFSCLs than when wearing single vision spectacle lenses.Compared with the naked eye,MFSCLs increased the total aberrations(p<0.001),higher-order aberrations(p<0.001),trefoil(p=0.023),coma aberrations(p<0.001)and spherical aberrations(SA)(p<0.001).Compared with the SVSCLs,MFSCLs increased the total aberrations(p<0.001),higher-order aberrations(p<0.001),coma aberrations(p<0.001)and SA(p<0.001).The direction of SA was more positive(p<0.001)with the MFSCLs and more negative(p=0.001)with the SVSCLs compared with the naked eye.Conclusions:Wearing MFSCLs can provide satisfactory corrected visual acuity(both distance HCVA and distance LCVA).Although the lenses increased the aberrations,such as total aberrations and higher-order aberrations,there were few adverse effects on the distance HCVA,distance LCVA and visual perception after 1 month of MFSCL use.

Frictional behaviors of rough soft contact on wet and dry pipeline surfaces:With application to deepwater pipelaying

Elastic rubbers are widely used in nature and engineering.In order to better understand soft rough contact under dry and wet conditions during deepwater pipelaying process,various polyurethane(PU)discs both in PU-pipe and PU-steel sliding combinations have been investigated by using self-developed tribometer.The tribological test results show that the friction coefficient can be clearly seen:PU90<PU80<PU70,under dry conditions.Experimental results also indicate that the two dramatic increases of the frictional coefficient exist in the rough soft PU-pipe contact.The potential influence of asperities and thin liquid film is discussed.

Effective enhanced model for a large deformable soft pneumatic actuator

Soft pneumatic actuators have been widely used for implementing sophisticated and dexterous movements,due to numerous fascinating features compared with their rigid counterparts.Relatively speaking,modeling and analysis of an entire soft pneumatic actuator considering contact interaction between two adjacent air chambers is extremely rare,which is exactly what we are particularly interested in.Therefore,in order to establish an accurate mechanical model and analyze the overall configuration and stress distribution for the soft pneumatic actuator with large deflection,we consider the contact interaction of soft materials rather than hard materials,to produce an effective enhanced model for soft contact of a large deformable pneumatic actuator.In this article,a multiple-point contact approach is developed to circumvent the mutual penetration problem between adjacent air chambers of the soft actuator that occurs with the single-point contact approach employed in linear elastic rigid materials.In contrast to the previous simplified rod-based model that did not focus on contact interaction which was adopted to clarify the entire deformation of the actuator,the present model not only elaborates nonlinear large deformation and overall configuration variations,but also accurately delineates stress distribution law inside the chamber structure and the stress concentration phenomenon.By means of a corresponding static experiment,a comparison of the simulation results with experimental data validates the effectiveness and accuracy of this model employing a multiple-point contact approach.Excellent simulation of the actual bending deformation of the soft actuator is obtained,while mutual penetration is successfully circumvented,whereas the model with single-point contact cannot achieve those goals.Finally,as compared with the rod-based model,the results obtained using the proposed model are more consistent with experimental data,and simulation precision is improved.

Visual quality of juvenile myopes wearing multifocal soft contact lenses

Background:It is unclear whether multifocal soft contact lenses(MFSCLs)affect visual quality when they are used for myopia control in juvenile myopes.The aim of this study was,therefore,to investigate the effect of MFSCLs on visual quality among juvenile myopia subjects.Methods:In a prospective,intervention study,33 juvenile myopes were enrolled.Visual perception was assessed by a quality of vision(QoV)questionnaire with spectacles at baseline and after one month of MFSCL wear.At the one month visit,the high(96%)contrast distance visual acuity(distance HCVA)and low(10%)contrast distance visual acuity(distance LCVA)were measured with single-vision spectacle lenses,single-vision soft contact lenses(SVSCLs)and MFSCLs in a random order.Wavefront aberrations Were measured with SVSCLs,MFSCLs and,without anycorrection.Results:Neither distance HCVA(P>0.05)nor distance LCVA(P>0.05)revealed any significant difference between MFSCLs,SVSCLs and single-vision spectacle lenses.The overall score(the sum of ten symptoms)of the QoV questionnaire did not show a statistically significant difference between spectacles at baseline and after one month of MFSCL wear(P=0.357).The results showed that the frequency(P<0.001),severity(P=0.001)and bothersome degree(P=0.016)of halos were significantly worse when wearing MFSCLs than when wearing single-vision spectacle lenses.In contrast,the bothersome degree caused by focusing difficulty(P=0.046)and the frequency of difficulty in judging distance or depth perception(P=0.046)were better when wearing MFSCLs than when wearing single-vision spectacle lenses.Compared with the naked eye,MFSCLs increased the total aberrations(P<0.001),higher-order aberrations(P<0.001),trefoil(P=0.023),coma aberrations(P<0.001)and spherical aberrations(SA)(P<0.001).Compared with the SVSCLs,MFSCLs increased the total aberrations(P<0.001),higher-order aberrations(P<0.001),coma aberrations(P<0.001)and SA(P<0.001).The direction of SA was more positive(P<0.001)with the MFSCLs and more negative(P=0.001)with the SVSCLs compared with the naked eye.Conclusions:Wearing MFSCLs can provide satisfactory corrected visual acuity(both distance HCVA and distance LCVA).Although the lenses increased the aberrations,such as total aberrations and higher-order aberrations,there were few adverse effects on the distance HCVA,distance LCVA and visual perception after one month of MFSCL Wear.

Exploring the relevance between load-bearing capacity and surface friction behavior based on a layered hydrogel cartilage prototype

Cartilage is well lubricated over a lifetime and this phenomenon is attributed to both of the surface hydration lubrication and the matrix load-bearing capacity.Lubricious hydrogels with a layered structure are designed to mimic cartilage as potential replacements.While many studies have concentrated on improving surface hydration to reduce friction,few have experimentally detected the relationship between load-bearing capacity of hydrogels and their interface friction behavior.In this work,a bilayer hydrogel,serving as a cartilage prototype consisted of a top thick hydrated polymer brush layer and a bottom hydrogel matrix with tunable modulus was designed to investigate this relationship.The coefficient of friction(COF,μ)is defined as the sum of interfacial component(μInt)and deformation/hysteresis component(μHyst).The presence of the top hydration layer effectively dissipates contact stress and reduces the interface interaction(μInt),leading to a stable and low COF.The contribution of mechanical deformation(μHyst)during the sliding shearing process to COF can be significantly reduced by increasing the local mechanical modulus,thereby enhancing the load-bearing capacity.These results show that the strategy of coupling surface hydration layer with a high load-bearing matrix can indeed enhance the lubrication performance of hydrogel cartilage prototypes,and implies a promising routine for designing robust soft matter lubrication system and friction-control devices.