نتایج جستجو برای: refraction
تعداد نتایج: 8286 فیلتر نتایج به سال:
PURPOSE To test the hypothesis that relative peripheral hyperopia predicts development and progression of myopia. METHODS Refraction along the horizontal visual field was measured under cycloplegia at visual field angles of 0°, ±15°, and ±30° at baseline, 1 and 2 years in over 1700 initially 7-year-old Chinese children, and at baseline and 1 year in over 1000 initially 14-year olds. One refra...
We review the intensively discussed ideas about wave propagation and refraction in media where both electric permittivity and magnetic permeability are negative. The criticism against negative refraction as violating the causality principle is considered. Starting from the initial wave equations, refraction of beams at the boundary of a left-handed medium is analyzed. The physics of a perfect l...
In this work, we realize a low loss negative refraction using indefinite metamaterial of a close arrangement of split-ring resonator (SRR) arrays. A beam shift experiment has been performed to verify the negative refraction and demonstrate the low loss property. The enhanced magnetic resonance between two neighbouring SRRs broadens the resonance range and produces a frequency range with low los...
We review the intensively discussed ideas about wave propagation and refraction in media where both electric permittivity and magnetic permeability are negative. The criticism against negative refraction as violating the causality principle is considered. Starting from the initial wave equations, refraction of beams at the boundary of a left-handed medium is analyzed. The physics of a perfect l...
The study of conical refraction for media other than biaxial non-magnetic crystals has never been considered in the literature – as far as the authors are aware. Hence, in this paper, we investigate how conical refraction can arise for broader classes of biaxial metamaterials using a new classification scheme previously developed by the authors. Namely, conical refraction is shown to occur for ...
PURPOSE To determine the precision (repeatability) of several methods of calculating refraction from higher-order wavefront aberration data and to compare these wavefront refractions with lower-order (LO) wavefront refraction, subjective refraction, and autorefraction. METHODS Four clinicians refracted 16 normal participants aged 23.6 +/- 1.2 years, 69% female with an average spherical equiva...
Although Love waves are widely analyzed in earthquake seismology, there is much less attention on utilizing Love waves than Rayleigh waves by the near-surface community. Unlike incident P and Sv waves, a plane SH wave for a series of horizontal layers refracts and reflects only SH waves, which makes the shallow SH-wave refraction method more popular to define shear (S)-wave velocity in nearsurf...
In this paper, a two-dimensional phononic crystal comprising of steel rod in water is investigated. Three cross- sections for this rod are considered using finite element method (EFM). We plot the equifrequency surface of the first band, because of equifrequency surface convex around the edge of the first Brillouin Zone, we guess the negative effective phononic mass and so negative refraction. ...
PURPOSE To compare the patterns of relative peripheral astigmatic refraction (tangential and sagittal power errors) and eccentric eye length between progressing and stable young-adult myopes. METHODS Sixty-two right eyes of 62 white patients participated in the study, of which 30 were nonprogressing myopes (NP group) for the last 2 years and 32 were progressing myopes (P group). Groups were m...
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