Integrally and spectrally direct normal incidence radiation measurements and their bearing on atmospheric transmission on Baghdad

Radiation measurements are being carried out at Pune since 1957. The radiation data for the period 1986-90 are studied here with reference to general sky condition and rainfall distribution. Global irradiances show a decrease of about 5 per cent over the last four decades, The diffuse irradiation contributes about 23 per cent to the global irradiance during winter months, Its proportion increases to more than 70 per cent during the monsoon period. The specific rainfall distribution affects both global and diffuse irradiances but in opposite directions, The diffuse irradiance shows increases as the atmospheric transmission decreases, However, the changes found have not become statistically highly significant as yet.

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Analysis of Contrast Reversal in SEM Images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009525x ◽

1972 ◽

Vol 30 ◽

pp. 398-399

Author(s):

M. D. Coutts ◽

E. R. Levin

Keyword(s):

Incident Beam ◽

Normal Incidence ◽

Beam Current ◽

Secondary Emission ◽

Image Contrast ◽

Sem Images ◽

Secondary Electrons ◽

Image Position

On tilting samples in an SEM, the image contrast between two elements, x and y often decreases to zero at θε, which we call the no-contrast angle. At angles above θε the contrast is reversed, θ being the angle between the specimen normal and the incident beam. The available contrast between two elements, x and y, in the SEM can be defined as,(1)where ix and iy are the total number of reflected and secondary electrons, leaving x and y respectively. It can easily be shown that for the element x,(2)where ib is the beam current, isp the specimen absorbed current, δo the secondary emission at normal incidence, k is a constant, and m the reflected electron coefficient.

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Characterization of Rh/Si multilayer structure by HREM and HAADF

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121016 ◽

1992 ◽

Vol 50 (1) ◽

pp. 122-123

Author(s):

Y. Cheng ◽

J. Liu ◽

M.B. Stearns ◽

D.G. Steams

Keyword(s):

Normal Incidence ◽

High Resolution Electron Microscopy ◽

X Rays ◽

Beam Direction ◽

Cross Sectional ◽

Optical Elements ◽

Resolution Electron ◽

Point To Point ◽

Better Than

The Rh/Si multilayer (ML) thin films are promising optical elements for soft x-rays since they have a calculated normal incidence reflectivity of ∼60% at a x-ray wavelength of ∼13 nm. However, a reflectivity of only 28% has been attained to date for ML fabricated by dc magnetron sputtering. In order to determine the cause of this degraded reflectivity the microstructure of this ML was examined on cross-sectional specimens with two high-resolution electron microscopy (HREM and HAADF) techniques.Cross-sectional specimens were made from an as-prepared ML sample and from the same ML annealed at 298 °C for 1 and 100 hours. The specimens were imaged using a JEM-4000EX TEM operating at 400 kV with a point-to-point resolution of better than 0.17 nm. The specimens were viewed along Si [110] projection of the substrate, with the (001) Si surface plane parallel to the beam direction.

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On resolving fine periodic microstructures in the optical microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153798 ◽

1989 ◽

Vol 47 ◽

pp. 364-365

Author(s):

W.S. Putnam ◽

C. Viney

Keyword(s):

Liquid Crystalline ◽

Numerical Aperture ◽

Polarized Light ◽

Normal Incidence ◽

Optical Microscope ◽

Angle Of Incidence ◽

Resolution Limit ◽

Crystalline Materials ◽

Periodic Microstructures ◽

Liquid Crystalline Materials

Many sheared liquid crystalline materials (fibers, films and moldings) exhibit a fine banded microstructure when observed in the polarized light microscope. In some cases, for example Kevlar® fiber, the periodicity is close to the resolution limit of even the highest numerical aperture objectives. The periodic microstructure reflects a non-uniform alignment of the constituent molecules, and consequently is an indication that the mechanical properties will be less than optimal. Thus it is necessary to obtain quality micrographs for characterization, which in turn requires that fine detail should contribute significantly to image formation.It is textbook knowledge that the resolution achievable with a given microscope objective (numerical aperture NA) and a given wavelength of light (λ) increases as the angle of incidence of light at the specimen surface is increased. Stated in terms of the Abbe resolution criterion, resolution improves from λ/NA to λ/2NA with increasing departure from normal incidence.

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Microspectroscopy Using a Solid Immersion Lens

Microscopy and Microanalysis ◽

10.1017/s1431927600026817 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 148-149

Author(s):

C.D. Poweleit ◽

J Menéndez

Keyword(s):

Spatial Resolution ◽

Focal Plane ◽

Numerical Aperture ◽

Normal Incidence ◽

Spot Size ◽

Index Of Refraction ◽

Objective Lens ◽

Improvement Factor ◽

Oil Immersion ◽

Long Time

Oil immersion lenses have been used in optical microscopy for a long time. The light’s wavelength is decreased by the oil’s index of refraction n and this reduces the minimum spot size. Additionally, the oil medium allows a larger collection angle, thereby increasing the numerical aperture. The SIL is based on the same principle, but offers more flexibility because the higher index material is solid. in particular, SILs can be deployed in cryogenic environments. Using a hemispherical glass the spatial resolution is improved by a factor n with respect to the resolution obtained with the microscope’s objective lens alone. The improvement factor is equal to n2 for truncated spheres.As shown in Fig. 1, the hemisphere SIL is in contact with the sample and does not affect the position of the focal plane. The focused rays from the objective strike the lens at normal incidence, so that no refraction takes place.

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