AIM:To compare the subjective refraction data with non-cycloplegic auto-refraction findings in the geriatric population above 60 years of age according to the different crystalline lens conditions.METHODS:This report ...AIM:To compare the subjective refraction data with non-cycloplegic auto-refraction findings in the geriatric population above 60 years of age according to the different crystalline lens conditions.METHODS:This report is a part of the Tehran Geriatric Eye Study(TGES)that was conducted from January 2019 to January 2020 on elderly population 60 years of age and above in Tehran.The samples were selected by multistage stratified random cluster sampling.Of 3791 individual invitees,3310(response rate:87.3%)participated in this study.All study participants underwent non-cycloplegic autorefraction(auto-refractometer/keratometer Nidek ARK-510)and subjective refraction.RESULTS:Regarding the sphere,eyes with mixed cataract had the worst limits of agreement(LoA:-1.24 to 0.87)and the best agreement was related to the pseudophakic eyes(LoA:-0.83 to 0.54).The highest(0.27±0.31 D)and lowest(0.21±0.27 D)differences between the two methods regarding the cylinder power were observed in eyes with cortical cataract and normal eyes,respectively.The worst LoA between the two methods in measuring the cylinder power was related to the eyes with mixed cataract(LoA:-0.44 to 0.96).Regarding the J0(horizontal/vertical components of astigmatism),the mean values of J0 obtained by auto-refraction were tended more toward against the rule direction in all crystalline lens conditions,and the two methods had the greatest difference in cortical cataract cases(0.05±0.17 D).Regarding the J45(oblique components of astigmatism),the lowest(0±0.11 D)and highest(-0.01±0.12 D)differences were observed in normal eyes and eyes with cortical cataract,respectively.CONCLUSION:The auto-refractometer/keratometer Nidek ARK-510 results in the elderly with different phakic and pseudophakic conditions do not correspond well with subjective refraction findings.This discrepancy in spherical findings is more pronounced in individuals with mixed cataract than in other cases.展开更多
We investigate the electromagnetic properties of a four-level dense atomic gas medium with Doppler effect.It is shown that the relative permittivity and relative permeability of the medium can be negative simultaneous...We investigate the electromagnetic properties of a four-level dense atomic gas medium with Doppler effect.It is shown that the relative permittivity and relative permeability of the medium can be negative simultaneously with low absorption in the same detuning interval on account of electromagnetically induced transparency.Furthermore,with the suitable parameters,the nonreciprocal negative refraction can be obtained due to the Doppler effect,and the nonreciprocity frequency band can be regulated by adjusting the temperature,the intensity of the control field and the atomic density in this hot atomic medium.展开更多
AIM:To investigate the differences in retinal refraction difference values(RDVs)of adult patients with myopic anisometropia compared with those without myopic anisometropia,and to investigate the relationship between ...AIM:To investigate the differences in retinal refraction difference values(RDVs)of adult patients with myopic anisometropia compared with those without myopic anisometropia,and to investigate the relationship between ocular biometric measurements and relative peripheral refraction.METHODS:This clinical observation study included 130 patients with myopia(-0.25 to-10.00 D)between October 2022 and January 2023 aged between 18 and 40y.The patients were divided into anisometropia(n=63;difference in binocular anisometropia≥1.00 D)and non-anisometropia(n=67;difference in binocular anisometropia<1.00 D)groups accordingly.Ocular biometric measurements were performed by optical biometrics and corneal topography to assess the steep keratometry(Ks),flap keratometry(Kf),axial length(AL),corneal astigmatism(CYL;Ks-Kf),surface regularity index(SRI),surface asymmetry index(SAI),and central corneal thickness(CCT).The RDV was measured at five retinal areas from the fovea to 53 degrees(RDV-0-10,RDV-10-20,RDV-20-30,RDV-30-40,and RDV-40-53),the total RDV(TRDV)of 53 degrees,and four regions,including RDV-superior,RDV-inferior,RDV-temporal,and RDV-nasal.An analysis of Spearman correlation was carried out to examine the correlation between RDV and the spherical equivalent(SE)and ocular biological parameters.RESULTS:Within RDV-20-53,both groups showed relative hyperopic defocus,and the increase in RDV corresponds to the increase in eccentricity.In the myopic anisometropia group,the TRDV,RDV-20-53,RDV-superior,and more myopic eyes had significantly higher RDVtemporal values than less myopic eyes.(P<0.05).In the non-anisometropia group,there was no significant difference in the RDV between the more and less myopic eyes at different eccentricities(P>0.05).There was a negative correlation between SE and TRDV(r=-0.205,P=0.001),RDV-20-53(r=-0.281,-0.183,-0.176,P<0.05),RDV-superior(r=-0.251,P<0.001),and RDV-temporal(r=-0.230,P<0.001),a negative correlation between CYL and RDV-10-30(r=-0.147,-0.180,P<0.05),and a negative correlation between SRI and RDV-0-20(r=-0.190,-0.170,P<0.05).AL had a positive correlation with RDV-20-30(r=0.164,P=0.008)and RDV-temporal(r=0.160,P=0.010).CONCLUSION:More myopic eyes in patients with myopic anisometropia show more peripheral hyperopic defocus.Diopter and corneal morphology may affect peripheral retinal defocus.展开更多
We demonstrate a method to realize unidirectional negative refraction in an acoustic parity-time(P T)-symmetric system, which is composed of a pair of metasurfaces sandwiching an air gap. The pair of metasurfaces poss...We demonstrate a method to realize unidirectional negative refraction in an acoustic parity-time(P T)-symmetric system, which is composed of a pair of metasurfaces sandwiching an air gap. The pair of metasurfaces possesses loss and gain modulations. The unidirectional negative refraction, which is strictly limited to the case of incident wave imposing on the loss end of the metasurface, is demonstrated at the exception point(EP) in this P T-symmetric system, while the incidence from the other side leads to strong reflection. Based on rigorous calculations, we explicitly show the underlying mechanism of this model to achieve unidirectional wave scatterings around the EP in the parametric space. In addition, the perfect imaging of a point source in the three-dimensional space, as a signature of negative refraction, is simulated to provide a verification of our work. We envision that this work may sharpen the understanding of P T-symmetric structures and inspire more acoustic functional devices.展开更多
AIM: To compare the results of noncycloplegic photorefraction, cycloplegic photorefraction and cycloplegic refraction in preschool and non-verbal children.METHODS: One hundred and ninety-six eyes of 98children(50 fema...AIM: To compare the results of noncycloplegic photorefraction, cycloplegic photorefraction and cycloplegic refraction in preschool and non-verbal children.METHODS: One hundred and ninety-six eyes of 98children(50 females, 48 males) were included in the study. Firstly, non-cycloplegic photorefraction was achieved with Plusoptix A09; secondly, cycloplegic photorefraction was carried out with Plusoptix A09 after10 min cyclopentolate. Finally, 30 min after instillation of twice cyclopentolate, cycloplegic refraction was obtained with autorefraction and/or standard retinoscopy. Spheric equivalent, spheric power, cylindric power and cylindrical axis measurements were statistically compared.RESULTS: The mean age was 28.8±18.5mo(range12-72mo). The differences in spherical equivalent, spheric power and cylindrical power measured by the three methods were found statistically significant(P <0.05).The spherical equivalent and spheric power measured by cycloplegic photorefraction were statistically higher than the measurements of the other methods(P <0.05). The cylindrical power measured by cycloplegic refraction was statistically lower than the measurements of the photorefraction methods(P <0.05). There was no significant difference in cylindrical axis measurements between three methods(P >0.05).CONCLUSION: For the determination of refractive errors in children, the Plusoptix A09 measurements give incorrect results after instillation of cyclopentolate.Additionally, the cylindrical power measured by Plusoptix A09 with or without cycloplegia is higher. However, the non-cycloplegic Plusoptix A09 measures spheric equivalent and spheric power similar to cycloplegic refraction measurements in preschool and non-verbal children.展开更多
BACKGROUND Myopia,as one of the common ocular diseases,often occurs in adolescence.In addition to the harm from itself,it may also lead to serious complications.Thus,prevention and control of myopia are attracting mor...BACKGROUND Myopia,as one of the common ocular diseases,often occurs in adolescence.In addition to the harm from itself,it may also lead to serious complications.Thus,prevention and control of myopia are attracting more and more attention.Previous research revealed that single-focal glasses and orthokeratology lenses(OK lenses)played an important part in slowing down myopia and preventing high myopia.AIM To compare the clinical effects of OK lenses and frame glasses against the increase of diopter in adolescent myopia and further explore the mechanism of the OK lens.METHODS Changes in diopter and axial length were collected among 70 adolescent myopia patients(124 eyes)wearing OK lenses for 1 year(group A)and 59 adolescent myopia patients(113 eyes)wearing frame glasses(group B).Refractive states of their retina were inspected through multispectral refraction topography.The obtained hyperopic defocus was analyzed for the mechanism of OK lenses on slowing down the increase of myopic diopter by delaying the increase of ocular axis length and reducing the near hyperopia defocus.RESULTS Teenagers in groups A and B were divided into low myopia(0 D--3.00 D)and moderate myopia(-3.25 D--6.00 D),without statistical differences among gender and age.After 1-year treatment,the increase of diopter and axis length and changes of retinal hyperopic defocus amount of group A were significantly less than those of group B.According to the multiple linear analysis,the retinal defocus in the upper,lower,nasal,and temporal directions had almost the same effect on the total defocus.The amount of peripheral retinal defocus(15°-53°)in group A was significantly lower than that in group B.CONCLUSION Multispectral refraction topography is progressive and instructive in clinical prevention and control of myopia.展开更多
A numerical model based on the mild-slope equation of water wave propagation over complicated bathymetry,taking into account the combined effects of refraction,diffraction and dissipation due to wavebreaking is presen...A numerical model based on the mild-slope equation of water wave propagation over complicated bathymetry,taking into account the combined effects of refraction,diffraction and dissipation due to wavebreaking is presented.Wave breaking is simulated by modifying the wave height probability density func-tion and the wave energy dissipation mechanism is parameterized according to that of the hydraulic jumpformulation.Solutions of the wave height,phase function,and the wave direction at every grid point areobtained by finite difference approximation of the governing equations,using Gauss-Seidel Iterative Method(GSIM)row by row.Its computational convenience allows it to be applied to large coast regions tostudy the wave transformation problem.Several case studies have been made and the results compare verywell with the experiment data and other model solutions.The capability and utility of the model forreal coast areas are illustrated by application to a shallow bay of northeast Australia.展开更多
In the case or wave interactions with structural weakness planes in rook mass the results of reflection and refraction of waves at entirely cohesive boundaries have been used all along.But,oblique incidences of compre...In the case or wave interactions with structural weakness planes in rook mass the results of reflection and refraction of waves at entirely cohesive boundaries have been used all along.But,oblique incidences of compressive stress waves at the structural weakness plane may result in relative slippage of rocks on both sides of the plane.The authors have derived the reflection and refraction coefficients for plane stress waves generated by blasting incidents on the structural weakness plane in rook mass according to its special boundary condition.The formula of energy dissipation and some computational results at the structural weakness plane are obtained.On the above basis,some problems about rook and soil engineering are discussed.展开更多
Phenomena of reflection and refraction of plane harmonic waves at a plane interface between an elastic solid and doubleporosity dual-permeability material are investigated. The elastic solid behaves non-dissipatively,...Phenomena of reflection and refraction of plane harmonic waves at a plane interface between an elastic solid and doubleporosity dual-permeability material are investigated. The elastic solid behaves non-dissipatively, while double-porosity dual-permeability materials behave dissipatively to wave propagation due to the presence of viscosity in pore fluids. All the waves(i.e., incident and reflected) in an elastic medium are considered as homogeneous(i.e., having the same directions of propagation and attenuation), while all the refracted waves in double-porosity dual-permeability materials are inhomogeneous(i.e., having different directions of propagation and attenuation). The coefficients of reflection and refraction for a given incident wave are obtained as a non-singular system of linear equations. The energy shares of reflected and refracted waves are obtained in the form of an energy matrix. A numerical example is considered to calculate the partition of incident energy among various reflected and refracted waves. The effect of incident direction on the partition of the incident energy is analyzed with a change in wave frequency, wave-induced fluid-flow, pore-fluid viscosity and double-porosity structure.It has been confirmed from numerical interpretation that during the reflection/refraction process, conservation of incident energy is obtained at each angle of incidence.展开更多
AIM: To study the change in ocular refraction in patients with pediatric cataracts(PCs) after lens extraction. METHODS: A total of 1258 patients who were undergoing cataract extraction with/without intraocular lens(IO...AIM: To study the change in ocular refraction in patients with pediatric cataracts(PCs) after lens extraction. METHODS: A total of 1258 patients who were undergoing cataract extraction with/without intraocular lens(IOL)implantation were recruited during preoperative examinations between Jan 2010 and Oct 2013. Patient ages ranged from 1.5 mo to 14y. Follow-ups were conducted at1 wk, 1, and 3 mo postoperatively and every 3 mo in the first year, then 6 mo thereafter. Ocular refraction [evaluated as spherical equivalent(SE)] and yearly myopic shift(YMS)were recorded and statistically analyzed among patients with age at surgery, baseline ocular refraction, gender,postoperative time and laterality(bilateral vs unilateral). RESULTS: By Dec 31st 2015, 1172 participants had been followed for more than 2y. The median follow-up period was 3y. The critical factors affecting the ocular refraction of PC patients were baseline ocular refraction, postoperative time for both aphakic and pseudophakic eyes. YMS grew most rapidly in young childhood and early adolescence. CONCLUSION: After lens surgeries, ocular refraction in PC patients shows an individual difference of change.Further concerns should be raising to monitor the rapid myopic shift at early adolescence of these patients.展开更多
Sinkholes and cavities can represent serious hazards to human safety and urban infrastructures,cause roadbed subsidence,and so on.It is therefore essential to evaluate various sinkholes in different depths and sizes t...Sinkholes and cavities can represent serious hazards to human safety and urban infrastructures,cause roadbed subsidence,and so on.It is therefore essential to evaluate various sinkholes in different depths and sizes to assess the risk of collapse.This paper evaluates the effect of different cavities on Rayleigh-wave propagation and body(P)wave refraction.Rayleigh(R)wave propagation is analyzed according to the classical multi-channel analysis of surface waves(MASW)method also considering the R-wave backscattering.Synthetic seismic traces are computed by means of finite element modeling(FEM)for cavity and intrusion at different depths and sizes.Furthermore,field acquisition data is used to verify the detection effect of a cavity on R-and P-waves.The results show that the presence of backscattered R-waves and the changes in the R-wave velocity spectrum can help in cavity identification.Additional possible evidence is represented by significant changes in the refraction travel times over the cavity location.It can be concluded that the field data are in good agreement with the synthetic,and it could be effective to consider the results of both R-and P-wave analysis in order to efficiently identify the cavities.展开更多
Pierson- Moskowitz Spectrum, JONSWAP Spectrum as well as Bretschneider- Mitsuyasu Spectrum are used in this paper for analyzing the influence of wave energy directional spread on refraction of wave spectrum due to bot...Pierson- Moskowitz Spectrum, JONSWAP Spectrum as well as Bretschneider- Mitsuyasu Spectrum are used in this paper for analyzing the influence of wave energy directional spread on refraction of wave spectrum due to both current and topography of sea bed. The author’s calculation indicates that such kind influence on the characteristic value of wave height as well as the average direction of wave energy propagation can not be ignored.展开更多
AIM:To evaluate the effects of glycemic control on refraction in diabetic patients. METHODS:Twenty newly diagnosed diabetic patients were included in this study.The random blood glucose,HbA1c levels,fasting C-peptide ...AIM:To evaluate the effects of glycemic control on refraction in diabetic patients. METHODS:Twenty newly diagnosed diabetic patients were included in this study.The random blood glucose,HbA1c levels,fasting C-peptide and postprandial 2h C-peptide were measured before treatment.The patients with random blood glucose higher than 12.0mmol/L and HbA1c level higher than 10.0%were selected.Refraction,intraocular pressure,radius of the anterior corneal curvature,depth of the anterior chamber,lens thickness,vitreous length,and axial length were measured on admission and at the end of week 1,2,3 and 4 during glycemic control. RESULTS:A transient hyperopic change occurred in all the patients receiving glycemic control.The maximum hyperopic change was 1.60D(range 0.50±3.20D).Recovery of the previous refraction occurred between two and four weeks after insulin treatment.There was a positive correlation between the maximum hyperopic changes and the HbA1c levels on admission(r=0.84,P【0.05).There was a positive correlation between the maximum hyperopic changes and the daily rate of blood glucose reduction over the first 7 days of the treatment(r=0.53,P【0.05).During transient hyperopia, no significant changes were observed in the intraocular pressure, radius of the anterior corneal curvature,depth of the anterior chamber,lens thickness,vitreous length and axial length. CONCLUSION:Transient hyperopic changes occur after glycemic control in diabetic patients with severe hyperglycemia.The degrees of transient hyperopia are highly dependent on HbA1c levels before treatment and the rate of reduction of the blood glucose level.展开更多
AIM:To predict postoperative intraocular lens(IOL)position using the Sirius anterior segment analysis system and investigate the effect of lens position and IOL type on postoperative refraction.METHODS:A total of 97 p...AIM:To predict postoperative intraocular lens(IOL)position using the Sirius anterior segment analysis system and investigate the effect of lens position and IOL type on postoperative refraction.METHODS:A total of 97 patients(102 eyes)were enrolled in the final analysis.An anterior segment biometry measurement was performed preoperatively with Sirius and Lenstar.The results of predicted lens position(PLP)and IOL power were automatically calculated by the software used by the instruments.Effective lens position(ELP)was measured manually using Sirius 3 mo postoperatively.Pearson's correlation analysis and linear regression analysis were used to determine the correlation of lens position to other parameters.RESULTS:PLP and ELP were positively correlated to axial length(AL;r=0.42,P<0.0001 and r=0.49,P<0.0001,respectively).There was a weak correlation between the peLP(ELP-PLP)and the prediction error of spherical refraction(peSR;r=0.34,P<0.0001).The peLP of Softec HD IOL differed statistically from those of both the TECNIS ZCB00 and Sensor AR40E IOLs.Multiple linear regression was used to obtain the prediction formula:ELP=0.66+0.63×[aqueous depth(AQD)+0.6 LT](r=0.61,P<0.0001),and a new variable(AQD+0.6 LT)was found to have the strongest correlation with ELP.CONCLUSION:The Sirius anterior segment analysis system is helpful to predict ELP,which reduces postoperative refraction error.展开更多
AIM:To characterize peripheral refraction and its relationship with myopia development in a selected group of male teenage Chinese students.METHODS:This 2-year prospective cohort study randomly enrolled 85 non-myopic ...AIM:To characterize peripheral refraction and its relationship with myopia development in a selected group of male teenage Chinese students.METHODS:This 2-year prospective cohort study randomly enrolled 85 non-myopic boys(age,14-16 y)from the Experimental Class of Air Force in China.Cycloplegic peripheral refraction was examined at 0°,±10°,and±20°along the horizontal visual field in the right eye at the baseline and 2-year follow-up.RESULTS:The incidence of myopia at the 2-year followup was 15.29%(13/85).The baseline central refraction(CR)and peripheral refraction at±10°were significantly lower in students who developed myopia than in those who did not(P<0.05).Relative peripheral refraction(RPR)did not differ between students with and without myopia(P>0.05).At the 2-year follow-up,the RPR at±10°and 20°nasal was significantly more hyperopic in the myopic group than in the non-myopic group.Multiple linear regression analysis indicated that the change in CR was significantly correlated with the changes in RPR at 20°nasal,10°nasal,and 20°temporal.Multivariate Logistic regression analysis indicated that the baseline CR[odds ratio(OR):0.092,95%confidence interval(CI):0.012-0.688,P=0.020]and the baseline RPR at 10°nasal(OR:0.182,95%CI:0.042-0.799,P=0.024)were significantly correlated with incident myopia(Omnibus test,χ=10.20,P=0.006).CONCLUSION:CR change is significantly correlated with changes in RPR,and students who develop myopia have more relative peripheral hyperopia.More baseline CR and relative peripheral hyperopia at 10°nasal are protective of myopia onset.展开更多
AIM:To evaluate the effect of axial length(AL)and anterior chamber depth(ACD)on peripheral refractive profile in myopic patients compared to emmetropic participants.METHODS:This cross-sectional study was conducted in ...AIM:To evaluate the effect of axial length(AL)and anterior chamber depth(ACD)on peripheral refractive profile in myopic patients compared to emmetropic participants.METHODS:This cross-sectional study was conducted in right eyes of 58 participants of whom 38 were emmetropic and 20 were myopic.Central and peripheral refraction were measured at 10°,20°,and 30°eccentricities in nasal and temporal fields using an open-field autorefractor.The Lenstar LS900 was used to measure ACD and AL.The participants were divided into three groups of short(<22.5 mm),normal(22.5-24.5 mm),and long eye(>24.5 mm)according to AL and three groups of low ACD(<3.00 mm),normal ACD(3.00-3.60 mm),and high ACD(>3.60 mm)according to ACD.RESULTS:The mean age of the participants was 22.26±3.09 y(range 18-30 y).The peripheral mean spherical refractive error showed a hypermetropic shift in myopic and emmetropic groups although this shift was more pronounced in the myopic group.The results showed significant changes in the spherical equivalent,J0,and J45 astigmatism in all gazes with an increase in eccentricity(P<0.001).The pattern of refractive error changes was more noticeable in long and short eyes versus normal AL eyes.Moreover,the pattern of peripheral refractive changes was much more prominent in the high ACD group versus the normal ACD group and in the normal ACD group versus the low ACD group.CONCLUSION:Peripheral refraction changes are greater in participants with AL values outside the normal range and deeper ACD values compared to participants with normal AL and ACD.展开更多
The temperature field distribution directly reflects the combustion condition in a furnace.In this paper,acoustic thermometry to reconstruct temperature distribution is investigated.A method based on radial basis func...The temperature field distribution directly reflects the combustion condition in a furnace.In this paper,acoustic thermometry to reconstruct temperature distribution is investigated.A method based on radial basis function approximation with polynomial reproduction(RBF-PR)is proposed in order to improve the accuracy and stability of the method based on RBF approximation.In addition,the refraction effect of sound wave paths is considered in the process of reconstruction.The curved lines with refraction effect are numerically calculated by solving differential equations,which show that sonic waves curve towards the zones of higher temperature.The reconstructed performance is validated via numerical simulation using four temperature distribution models.Results and analysis show that the proposed method has much greater accuracy than the method based on RBF approximation,and when considering the effect of refraction,our method can reconstruct more excellent reconstruction performance than others,which do not take into account the refraction effect of sound wave paths.展开更多
The Refraction Microtremor (ReMi) method is being used around the world by the geotechnical and geophysical community to determine shear-wave velocities. This is due to its faster, less expensive and accurate determin...The Refraction Microtremor (ReMi) method is being used around the world by the geotechnical and geophysical community to determine shear-wave velocities. This is due to its faster, less expensive and accurate determination of shear wave velocities, when compared to other methods used. Unlike standard crosshole and downhole techniques, ReMi does not require any drilling. It eliminates the problem of shear-wave source and quiet site that are pre-requisites for good seismic refraction surveys. In this paper we present refraction microtremors (ReMi) measurements done at sites underlain by different soil types in Egypt. The ReMi data were collected using standard refraction equipment employing 12, 24 or 48 channels. We used deep oceanographic noise and ambient noise including energy from power generators, pile drivers and traffic. The data were processed using the SeisOpt? ReMi? (? Optim, Inc.) software to reveal one-dimensional shear-wave velocity structures beneath the arrays. To access the validity of the method for the Egyptian soils, the shear-wave profiles obtained from the ReMi measurements were compared to downhole and crosshole data for different soils. Comparisons demonstrate the robustness of the ReMi technique for obtaining shear-wave velocities for different soil types in Egypt.展开更多
The refraction groyne is a complex structure consisted with groyne and groyne’s arm. This study conducted a experiment on the flow influences around the refraction groyne due to changes in the arm angle (θ) and leng...The refraction groyne is a complex structure consisted with groyne and groyne’s arm. This study conducted a experiment on the flow influences around the refraction groyne due to changes in the arm angle (θ) and length (AL). Results of experiment were analyzed on the impacts of the refraction groyne according to the projection length (L’). Velocity increase in main channel occurred greater the upward groynes than downward groynes. The vortices occurring at recirculation area of the upward and downward refraction groynes were formed in different shapes. The thalweg height did not have great impact vis-a-vis the extended arm length ratio and refraction angle change. The length of the recirculation area showed a gradual uptrend as the arm length of the groyne increased. Such area was formed at the range of 29% - 47%. For the length of the recirculation area, it was observed to be 10.2 - 14.7 times (URG), 8.4 - 12.7 times (DRG), and 10.6 - 13.8 times (right angle groyne) the projection length (L’) incensement.展开更多
SAR interferometry with distributed satellites is a technique based on the exploitation of the interference pattern of two SAR images acquired synchronously. The interferogram contains geometric, atmospheric, topograp...SAR interferometry with distributed satellites is a technique based on the exploitation of the interference pattern of two SAR images acquired synchronously. The interferogram contains geometric, atmospheric, topographic and land defomation. This paper focuses on atmospheric effects on SAR interferometry, which shows theoretically that the relationship among ionosphere TEC and troposphere parameters such as temperature, relative humitdity and pressure with respect to slant rang changes. An atmospheric correction method is given in the end.展开更多
基金Supported by National Institute for Medical Research Development(NIMAD)affiliated with the Iranian Ministry of Health and Medical Education(No.963660).
文摘AIM:To compare the subjective refraction data with non-cycloplegic auto-refraction findings in the geriatric population above 60 years of age according to the different crystalline lens conditions.METHODS:This report is a part of the Tehran Geriatric Eye Study(TGES)that was conducted from January 2019 to January 2020 on elderly population 60 years of age and above in Tehran.The samples were selected by multistage stratified random cluster sampling.Of 3791 individual invitees,3310(response rate:87.3%)participated in this study.All study participants underwent non-cycloplegic autorefraction(auto-refractometer/keratometer Nidek ARK-510)and subjective refraction.RESULTS:Regarding the sphere,eyes with mixed cataract had the worst limits of agreement(LoA:-1.24 to 0.87)and the best agreement was related to the pseudophakic eyes(LoA:-0.83 to 0.54).The highest(0.27±0.31 D)and lowest(0.21±0.27 D)differences between the two methods regarding the cylinder power were observed in eyes with cortical cataract and normal eyes,respectively.The worst LoA between the two methods in measuring the cylinder power was related to the eyes with mixed cataract(LoA:-0.44 to 0.96).Regarding the J0(horizontal/vertical components of astigmatism),the mean values of J0 obtained by auto-refraction were tended more toward against the rule direction in all crystalline lens conditions,and the two methods had the greatest difference in cortical cataract cases(0.05±0.17 D).Regarding the J45(oblique components of astigmatism),the lowest(0±0.11 D)and highest(-0.01±0.12 D)differences were observed in normal eyes and eyes with cortical cataract,respectively.CONCLUSION:The auto-refractometer/keratometer Nidek ARK-510 results in the elderly with different phakic and pseudophakic conditions do not correspond well with subjective refraction findings.This discrepancy in spherical findings is more pronounced in individuals with mixed cataract than in other cases.
基金Project supported by the National Natural Science Foundation of China(Grant No.61671279)financial support from Xi’an Key Laboratory of Optical Information Manipulation and Augmentation(OMA)。
文摘We investigate the electromagnetic properties of a four-level dense atomic gas medium with Doppler effect.It is shown that the relative permittivity and relative permeability of the medium can be negative simultaneously with low absorption in the same detuning interval on account of electromagnetically induced transparency.Furthermore,with the suitable parameters,the nonreciprocal negative refraction can be obtained due to the Doppler effect,and the nonreciprocity frequency band can be regulated by adjusting the temperature,the intensity of the control field and the atomic density in this hot atomic medium.
文摘AIM:To investigate the differences in retinal refraction difference values(RDVs)of adult patients with myopic anisometropia compared with those without myopic anisometropia,and to investigate the relationship between ocular biometric measurements and relative peripheral refraction.METHODS:This clinical observation study included 130 patients with myopia(-0.25 to-10.00 D)between October 2022 and January 2023 aged between 18 and 40y.The patients were divided into anisometropia(n=63;difference in binocular anisometropia≥1.00 D)and non-anisometropia(n=67;difference in binocular anisometropia<1.00 D)groups accordingly.Ocular biometric measurements were performed by optical biometrics and corneal topography to assess the steep keratometry(Ks),flap keratometry(Kf),axial length(AL),corneal astigmatism(CYL;Ks-Kf),surface regularity index(SRI),surface asymmetry index(SAI),and central corneal thickness(CCT).The RDV was measured at five retinal areas from the fovea to 53 degrees(RDV-0-10,RDV-10-20,RDV-20-30,RDV-30-40,and RDV-40-53),the total RDV(TRDV)of 53 degrees,and four regions,including RDV-superior,RDV-inferior,RDV-temporal,and RDV-nasal.An analysis of Spearman correlation was carried out to examine the correlation between RDV and the spherical equivalent(SE)and ocular biological parameters.RESULTS:Within RDV-20-53,both groups showed relative hyperopic defocus,and the increase in RDV corresponds to the increase in eccentricity.In the myopic anisometropia group,the TRDV,RDV-20-53,RDV-superior,and more myopic eyes had significantly higher RDVtemporal values than less myopic eyes.(P<0.05).In the non-anisometropia group,there was no significant difference in the RDV between the more and less myopic eyes at different eccentricities(P>0.05).There was a negative correlation between SE and TRDV(r=-0.205,P=0.001),RDV-20-53(r=-0.281,-0.183,-0.176,P<0.05),RDV-superior(r=-0.251,P<0.001),and RDV-temporal(r=-0.230,P<0.001),a negative correlation between CYL and RDV-10-30(r=-0.147,-0.180,P<0.05),and a negative correlation between SRI and RDV-0-20(r=-0.190,-0.170,P<0.05).AL had a positive correlation with RDV-20-30(r=0.164,P=0.008)and RDV-temporal(r=0.160,P=0.010).CONCLUSION:More myopic eyes in patients with myopic anisometropia show more peripheral hyperopic defocus.Diopter and corneal morphology may affect peripheral retinal defocus.
基金supported by the National Key R&D Program of China (Grant Nos. 2022YFA1404400 and 2022YFA1404403)the National Natural Science Foundation of China (Grant No. 92263208)+3 种基金the Natural Science Foundation of Jiangsu Province (Grant No. BK20210541)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No. 21KJB140003)the Fundamental Research Funds for the Central Universitiesthe Open Fund of State Key Laboratory of Acoustics (Grant No. SKLA202313)。
文摘We demonstrate a method to realize unidirectional negative refraction in an acoustic parity-time(P T)-symmetric system, which is composed of a pair of metasurfaces sandwiching an air gap. The pair of metasurfaces possesses loss and gain modulations. The unidirectional negative refraction, which is strictly limited to the case of incident wave imposing on the loss end of the metasurface, is demonstrated at the exception point(EP) in this P T-symmetric system, while the incidence from the other side leads to strong reflection. Based on rigorous calculations, we explicitly show the underlying mechanism of this model to achieve unidirectional wave scatterings around the EP in the parametric space. In addition, the perfect imaging of a point source in the three-dimensional space, as a signature of negative refraction, is simulated to provide a verification of our work. We envision that this work may sharpen the understanding of P T-symmetric structures and inspire more acoustic functional devices.
文摘AIM: To compare the results of noncycloplegic photorefraction, cycloplegic photorefraction and cycloplegic refraction in preschool and non-verbal children.METHODS: One hundred and ninety-six eyes of 98children(50 females, 48 males) were included in the study. Firstly, non-cycloplegic photorefraction was achieved with Plusoptix A09; secondly, cycloplegic photorefraction was carried out with Plusoptix A09 after10 min cyclopentolate. Finally, 30 min after instillation of twice cyclopentolate, cycloplegic refraction was obtained with autorefraction and/or standard retinoscopy. Spheric equivalent, spheric power, cylindric power and cylindrical axis measurements were statistically compared.RESULTS: The mean age was 28.8±18.5mo(range12-72mo). The differences in spherical equivalent, spheric power and cylindrical power measured by the three methods were found statistically significant(P <0.05).The spherical equivalent and spheric power measured by cycloplegic photorefraction were statistically higher than the measurements of the other methods(P <0.05). The cylindrical power measured by cycloplegic refraction was statistically lower than the measurements of the photorefraction methods(P <0.05). There was no significant difference in cylindrical axis measurements between three methods(P >0.05).CONCLUSION: For the determination of refractive errors in children, the Plusoptix A09 measurements give incorrect results after instillation of cyclopentolate.Additionally, the cylindrical power measured by Plusoptix A09 with or without cycloplegia is higher. However, the non-cycloplegic Plusoptix A09 measures spheric equivalent and spheric power similar to cycloplegic refraction measurements in preschool and non-verbal children.
文摘BACKGROUND Myopia,as one of the common ocular diseases,often occurs in adolescence.In addition to the harm from itself,it may also lead to serious complications.Thus,prevention and control of myopia are attracting more and more attention.Previous research revealed that single-focal glasses and orthokeratology lenses(OK lenses)played an important part in slowing down myopia and preventing high myopia.AIM To compare the clinical effects of OK lenses and frame glasses against the increase of diopter in adolescent myopia and further explore the mechanism of the OK lens.METHODS Changes in diopter and axial length were collected among 70 adolescent myopia patients(124 eyes)wearing OK lenses for 1 year(group A)and 59 adolescent myopia patients(113 eyes)wearing frame glasses(group B).Refractive states of their retina were inspected through multispectral refraction topography.The obtained hyperopic defocus was analyzed for the mechanism of OK lenses on slowing down the increase of myopic diopter by delaying the increase of ocular axis length and reducing the near hyperopia defocus.RESULTS Teenagers in groups A and B were divided into low myopia(0 D--3.00 D)and moderate myopia(-3.25 D--6.00 D),without statistical differences among gender and age.After 1-year treatment,the increase of diopter and axis length and changes of retinal hyperopic defocus amount of group A were significantly less than those of group B.According to the multiple linear analysis,the retinal defocus in the upper,lower,nasal,and temporal directions had almost the same effect on the total defocus.The amount of peripheral retinal defocus(15°-53°)in group A was significantly lower than that in group B.CONCLUSION Multispectral refraction topography is progressive and instructive in clinical prevention and control of myopia.
文摘A numerical model based on the mild-slope equation of water wave propagation over complicated bathymetry,taking into account the combined effects of refraction,diffraction and dissipation due to wavebreaking is presented.Wave breaking is simulated by modifying the wave height probability density func-tion and the wave energy dissipation mechanism is parameterized according to that of the hydraulic jumpformulation.Solutions of the wave height,phase function,and the wave direction at every grid point areobtained by finite difference approximation of the governing equations,using Gauss-Seidel Iterative Method(GSIM)row by row.Its computational convenience allows it to be applied to large coast regions tostudy the wave transformation problem.Several case studies have been made and the results compare verywell with the experiment data and other model solutions.The capability and utility of the model forreal coast areas are illustrated by application to a shallow bay of northeast Australia.
基金sponsored by the National Natural Science Foundation under Grant No.58974150。
文摘In the case or wave interactions with structural weakness planes in rook mass the results of reflection and refraction of waves at entirely cohesive boundaries have been used all along.But,oblique incidences of compressive stress waves at the structural weakness plane may result in relative slippage of rocks on both sides of the plane.The authors have derived the reflection and refraction coefficients for plane stress waves generated by blasting incidents on the structural weakness plane in rook mass according to its special boundary condition.The formula of energy dissipation and some computational results at the structural weakness plane are obtained.On the above basis,some problems about rook and soil engineering are discussed.
文摘Phenomena of reflection and refraction of plane harmonic waves at a plane interface between an elastic solid and doubleporosity dual-permeability material are investigated. The elastic solid behaves non-dissipatively, while double-porosity dual-permeability materials behave dissipatively to wave propagation due to the presence of viscosity in pore fluids. All the waves(i.e., incident and reflected) in an elastic medium are considered as homogeneous(i.e., having the same directions of propagation and attenuation), while all the refracted waves in double-porosity dual-permeability materials are inhomogeneous(i.e., having different directions of propagation and attenuation). The coefficients of reflection and refraction for a given incident wave are obtained as a non-singular system of linear equations. The energy shares of reflected and refracted waves are obtained in the form of an energy matrix. A numerical example is considered to calculate the partition of incident energy among various reflected and refracted waves. The effect of incident direction on the partition of the incident energy is analyzed with a change in wave frequency, wave-induced fluid-flow, pore-fluid viscosity and double-porosity structure.It has been confirmed from numerical interpretation that during the reflection/refraction process, conservation of incident energy is obtained at each angle of incidence.
基金Supported by National Natural Science Foundation of China (No.81873675 No.81770967)+2 种基金National Key R&D Program of China (No.2018YFC0116500 No.2017YFC1104600)Fundamental Research Funds for the Central Universities (No.16ykjc28)
文摘AIM: To study the change in ocular refraction in patients with pediatric cataracts(PCs) after lens extraction. METHODS: A total of 1258 patients who were undergoing cataract extraction with/without intraocular lens(IOL)implantation were recruited during preoperative examinations between Jan 2010 and Oct 2013. Patient ages ranged from 1.5 mo to 14y. Follow-ups were conducted at1 wk, 1, and 3 mo postoperatively and every 3 mo in the first year, then 6 mo thereafter. Ocular refraction [evaluated as spherical equivalent(SE)] and yearly myopic shift(YMS)were recorded and statistically analyzed among patients with age at surgery, baseline ocular refraction, gender,postoperative time and laterality(bilateral vs unilateral). RESULTS: By Dec 31st 2015, 1172 participants had been followed for more than 2y. The median follow-up period was 3y. The critical factors affecting the ocular refraction of PC patients were baseline ocular refraction, postoperative time for both aphakic and pseudophakic eyes. YMS grew most rapidly in young childhood and early adolescence. CONCLUSION: After lens surgeries, ocular refraction in PC patients shows an individual difference of change.Further concerns should be raising to monitor the rapid myopic shift at early adolescence of these patients.
文摘Sinkholes and cavities can represent serious hazards to human safety and urban infrastructures,cause roadbed subsidence,and so on.It is therefore essential to evaluate various sinkholes in different depths and sizes to assess the risk of collapse.This paper evaluates the effect of different cavities on Rayleigh-wave propagation and body(P)wave refraction.Rayleigh(R)wave propagation is analyzed according to the classical multi-channel analysis of surface waves(MASW)method also considering the R-wave backscattering.Synthetic seismic traces are computed by means of finite element modeling(FEM)for cavity and intrusion at different depths and sizes.Furthermore,field acquisition data is used to verify the detection effect of a cavity on R-and P-waves.The results show that the presence of backscattered R-waves and the changes in the R-wave velocity spectrum can help in cavity identification.Additional possible evidence is represented by significant changes in the refraction travel times over the cavity location.It can be concluded that the field data are in good agreement with the synthetic,and it could be effective to consider the results of both R-and P-wave analysis in order to efficiently identify the cavities.
文摘Pierson- Moskowitz Spectrum, JONSWAP Spectrum as well as Bretschneider- Mitsuyasu Spectrum are used in this paper for analyzing the influence of wave energy directional spread on refraction of wave spectrum due to both current and topography of sea bed. The author’s calculation indicates that such kind influence on the characteristic value of wave height as well as the average direction of wave energy propagation can not be ignored.
文摘AIM:To evaluate the effects of glycemic control on refraction in diabetic patients. METHODS:Twenty newly diagnosed diabetic patients were included in this study.The random blood glucose,HbA1c levels,fasting C-peptide and postprandial 2h C-peptide were measured before treatment.The patients with random blood glucose higher than 12.0mmol/L and HbA1c level higher than 10.0%were selected.Refraction,intraocular pressure,radius of the anterior corneal curvature,depth of the anterior chamber,lens thickness,vitreous length,and axial length were measured on admission and at the end of week 1,2,3 and 4 during glycemic control. RESULTS:A transient hyperopic change occurred in all the patients receiving glycemic control.The maximum hyperopic change was 1.60D(range 0.50±3.20D).Recovery of the previous refraction occurred between two and four weeks after insulin treatment.There was a positive correlation between the maximum hyperopic changes and the HbA1c levels on admission(r=0.84,P【0.05).There was a positive correlation between the maximum hyperopic changes and the daily rate of blood glucose reduction over the first 7 days of the treatment(r=0.53,P【0.05).During transient hyperopia, no significant changes were observed in the intraocular pressure, radius of the anterior corneal curvature,depth of the anterior chamber,lens thickness,vitreous length and axial length. CONCLUSION:Transient hyperopic changes occur after glycemic control in diabetic patients with severe hyperglycemia.The degrees of transient hyperopia are highly dependent on HbA1c levels before treatment and the rate of reduction of the blood glucose level.
基金Supported by Jiangsu Provincial Medical Innovation Team(No.CXTDA2017039)the Soochow Scholar Project of Soochow University(No.R5122001)。
文摘AIM:To predict postoperative intraocular lens(IOL)position using the Sirius anterior segment analysis system and investigate the effect of lens position and IOL type on postoperative refraction.METHODS:A total of 97 patients(102 eyes)were enrolled in the final analysis.An anterior segment biometry measurement was performed preoperatively with Sirius and Lenstar.The results of predicted lens position(PLP)and IOL power were automatically calculated by the software used by the instruments.Effective lens position(ELP)was measured manually using Sirius 3 mo postoperatively.Pearson's correlation analysis and linear regression analysis were used to determine the correlation of lens position to other parameters.RESULTS:PLP and ELP were positively correlated to axial length(AL;r=0.42,P<0.0001 and r=0.49,P<0.0001,respectively).There was a weak correlation between the peLP(ELP-PLP)and the prediction error of spherical refraction(peSR;r=0.34,P<0.0001).The peLP of Softec HD IOL differed statistically from those of both the TECNIS ZCB00 and Sensor AR40E IOLs.Multiple linear regression was used to obtain the prediction formula:ELP=0.66+0.63×[aqueous depth(AQD)+0.6 LT](r=0.61,P<0.0001),and a new variable(AQD+0.6 LT)was found to have the strongest correlation with ELP.CONCLUSION:The Sirius anterior segment analysis system is helpful to predict ELP,which reduces postoperative refraction error.
基金Supported by National Natural Science Foundation of China(No.81800854)Joint Innovation Project of National Defense Technology Innovation Zone(No.20-163-15-ZT-001-001-10)Efficiency Improvement Project of Air Force Medical University(No.2021HKYX24)。
文摘AIM:To characterize peripheral refraction and its relationship with myopia development in a selected group of male teenage Chinese students.METHODS:This 2-year prospective cohort study randomly enrolled 85 non-myopic boys(age,14-16 y)from the Experimental Class of Air Force in China.Cycloplegic peripheral refraction was examined at 0°,±10°,and±20°along the horizontal visual field in the right eye at the baseline and 2-year follow-up.RESULTS:The incidence of myopia at the 2-year followup was 15.29%(13/85).The baseline central refraction(CR)and peripheral refraction at±10°were significantly lower in students who developed myopia than in those who did not(P<0.05).Relative peripheral refraction(RPR)did not differ between students with and without myopia(P>0.05).At the 2-year follow-up,the RPR at±10°and 20°nasal was significantly more hyperopic in the myopic group than in the non-myopic group.Multiple linear regression analysis indicated that the change in CR was significantly correlated with the changes in RPR at 20°nasal,10°nasal,and 20°temporal.Multivariate Logistic regression analysis indicated that the baseline CR[odds ratio(OR):0.092,95%confidence interval(CI):0.012-0.688,P=0.020]and the baseline RPR at 10°nasal(OR:0.182,95%CI:0.042-0.799,P=0.024)were significantly correlated with incident myopia(Omnibus test,χ=10.20,P=0.006).CONCLUSION:CR change is significantly correlated with changes in RPR,and students who develop myopia have more relative peripheral hyperopia.More baseline CR and relative peripheral hyperopia at 10°nasal are protective of myopia onset.
文摘AIM:To evaluate the effect of axial length(AL)and anterior chamber depth(ACD)on peripheral refractive profile in myopic patients compared to emmetropic participants.METHODS:This cross-sectional study was conducted in right eyes of 58 participants of whom 38 were emmetropic and 20 were myopic.Central and peripheral refraction were measured at 10°,20°,and 30°eccentricities in nasal and temporal fields using an open-field autorefractor.The Lenstar LS900 was used to measure ACD and AL.The participants were divided into three groups of short(<22.5 mm),normal(22.5-24.5 mm),and long eye(>24.5 mm)according to AL and three groups of low ACD(<3.00 mm),normal ACD(3.00-3.60 mm),and high ACD(>3.60 mm)according to ACD.RESULTS:The mean age of the participants was 22.26±3.09 y(range 18-30 y).The peripheral mean spherical refractive error showed a hypermetropic shift in myopic and emmetropic groups although this shift was more pronounced in the myopic group.The results showed significant changes in the spherical equivalent,J0,and J45 astigmatism in all gazes with an increase in eccentricity(P<0.001).The pattern of refractive error changes was more noticeable in long and short eyes versus normal AL eyes.Moreover,the pattern of peripheral refractive changes was much more prominent in the high ACD group versus the normal ACD group and in the normal ACD group versus the low ACD group.CONCLUSION:Peripheral refraction changes are greater in participants with AL values outside the normal range and deeper ACD values compared to participants with normal AL and ACD.
基金This research is supported by the National Science Foundation of China(No.11674093 and No.11474091)the Fundamental Research Funds for the Central Universities of China(No.2018 MS131)the State Key Laboratory of Acoustics,Institute of Acoustics,Chinese Academy of Science,China(SKLA201808).
文摘The temperature field distribution directly reflects the combustion condition in a furnace.In this paper,acoustic thermometry to reconstruct temperature distribution is investigated.A method based on radial basis function approximation with polynomial reproduction(RBF-PR)is proposed in order to improve the accuracy and stability of the method based on RBF approximation.In addition,the refraction effect of sound wave paths is considered in the process of reconstruction.The curved lines with refraction effect are numerically calculated by solving differential equations,which show that sonic waves curve towards the zones of higher temperature.The reconstructed performance is validated via numerical simulation using four temperature distribution models.Results and analysis show that the proposed method has much greater accuracy than the method based on RBF approximation,and when considering the effect of refraction,our method can reconstruct more excellent reconstruction performance than others,which do not take into account the refraction effect of sound wave paths.
文摘The Refraction Microtremor (ReMi) method is being used around the world by the geotechnical and geophysical community to determine shear-wave velocities. This is due to its faster, less expensive and accurate determination of shear wave velocities, when compared to other methods used. Unlike standard crosshole and downhole techniques, ReMi does not require any drilling. It eliminates the problem of shear-wave source and quiet site that are pre-requisites for good seismic refraction surveys. In this paper we present refraction microtremors (ReMi) measurements done at sites underlain by different soil types in Egypt. The ReMi data were collected using standard refraction equipment employing 12, 24 or 48 channels. We used deep oceanographic noise and ambient noise including energy from power generators, pile drivers and traffic. The data were processed using the SeisOpt? ReMi? (? Optim, Inc.) software to reveal one-dimensional shear-wave velocity structures beneath the arrays. To access the validity of the method for the Egyptian soils, the shear-wave profiles obtained from the ReMi measurements were compared to downhole and crosshole data for different soils. Comparisons demonstrate the robustness of the ReMi technique for obtaining shear-wave velocities for different soil types in Egypt.
文摘The refraction groyne is a complex structure consisted with groyne and groyne’s arm. This study conducted a experiment on the flow influences around the refraction groyne due to changes in the arm angle (θ) and length (AL). Results of experiment were analyzed on the impacts of the refraction groyne according to the projection length (L’). Velocity increase in main channel occurred greater the upward groynes than downward groynes. The vortices occurring at recirculation area of the upward and downward refraction groynes were formed in different shapes. The thalweg height did not have great impact vis-a-vis the extended arm length ratio and refraction angle change. The length of the recirculation area showed a gradual uptrend as the arm length of the groyne increased. Such area was formed at the range of 29% - 47%. For the length of the recirculation area, it was observed to be 10.2 - 14.7 times (URG), 8.4 - 12.7 times (DRG), and 10.6 - 13.8 times (right angle groyne) the projection length (L’) incensement.
文摘SAR interferometry with distributed satellites is a technique based on the exploitation of the interference pattern of two SAR images acquired synchronously. The interferogram contains geometric, atmospheric, topographic and land defomation. This paper focuses on atmospheric effects on SAR interferometry, which shows theoretically that the relationship among ionosphere TEC and troposphere parameters such as temperature, relative humitdity and pressure with respect to slant rang changes. An atmospheric correction method is given in the end.
