Geometric Derivation of the Half-Angle Formulas for an Acute Angle

The scanning transmission electron microscope (STEM) constructed by the authors employs a field emission gun and a 1.15 mm focal length magnetic lens to produce a probe on the specimen. The aperture size is chosen to allow one wavelength of spherical aberration at the edge of the objective aperture. Under these conditions the profile of the focused spot is expected to be similar to an Airy intensity distribution with the first zero at the same point but with a peak intensity 80 per cent of that which would be obtained If the lens had no aberration. This condition is attained when the half angle that the incident beam subtends at the specimen, 𝛂 = (4𝛌/Cs)¼

Download Full-text

Low-workfunction field-emission source for high-resolution EELS

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125592 ◽

1987 ◽

Vol 45 ◽

pp. 132-133

Author(s):

P. E. Batson

Keyword(s):

High Resolution ◽

Energy Loss ◽

Electron Probe ◽

Collection Efficiency ◽

Electron Sources ◽

Wien Filter ◽

Half Angle ◽

Thermal Emitter ◽

Electron Energy Loss ◽

Intrinsic Energy

In recent years,instrumentation for electron energy loss spectroscopy (EELS) has been steadily improved to increase energy resolution and collection efficiency. At present 0.40eV at 10mR collection half angle is available with commercial magnetic sectors (e.g. Gatan, Inc. and VG Microscopes, Ltd.), and 70meV at 10mR has been demonstrated by use of a Wien filter within a large deceleration field. When these high resolution spectrometers are coupled to the modern small electron probe instrument, we obtain a tool which promises to reveal local changes in bandstructure and bonding near defects and interfaces in heterogeneous materials.Unfortunately, typical electron sources have intrinsic energy widths which limit attainable spectroscopic resolution in the absence of some monochromation system. For instance, the W thermal emitter has a half width of about 1eV.

Download Full-text

Crack divergence phenomena in tempered glass

Strength Fracture and Complexity ◽

10.3233/sfc-204002 ◽

2020 ◽

Vol 13 (3) ◽

pp. 115-129

Author(s):

Shin’ichi Aratani

Keyword(s):

Optimal Design ◽

High Speed ◽

Glass Plate ◽

Acute Angle ◽

Divergence Angle ◽

High Speed Photography ◽

Tempered Glass ◽

Thick Glass

High speed photography using the Cranz-Schardin camera was performed to study the crack divergence and divergence angle in thermally tempered glass. A tempered 3.5 mm thick glass plate was used as a specimen. It was shown that two types of bifurcation and branching existed as the crack divergence. The divergence angle was smaller than the value calculated from the principle of optimal design and showed an acute angle.

Download Full-text

Effect of postural changes on intraocular pressure in patients with acute angle-closure glaucoma in Indian population

Latin American Journal of Ophthalmology ◽

10.25259/lajo_18_2019 ◽

2020 ◽

Vol 3 ◽

pp. 2

Author(s):

Sanjay Mishra ◽

Ashok Kumar

Keyword(s):

Intraocular Pressure ◽

Acute Angle ◽

Angle Closure Glaucoma ◽

Angle Closure ◽

Sitting Position ◽

Rebound Tonometer ◽

Antiglaucoma Medication ◽

Primary Angle Closure Glaucoma ◽

Postural Changes ◽

Healthy Control

Objective: The objective of the study was to compare the posture-induced intraocular pressure (IOP) changes in primary angle-closure glaucoma (PACG) with or without glaucoma medications, and healthy control eyes with normal IOPs in Indian subjects. Materials and Methods: The IOP was measured in the sitting position and the supine position after 10, 20, and 30 min with a rebound tonometer. Results: Twenty-five patients with PACG and 30 controls with normal IOPs were studied. The IOP in the sitting position measured with the rebound tonometer was 13.8 + 3.2 mm Hg in eyes with PAC, and 12.9 + 2.9 mm Hg in eyes with normal IOPs. The IOP increased to 14.4 mm Hg, 16.8 mm Hg, and 18.9 mm Hg at 10 min, 20 min, and 30 min in PACG subjects. In normal age-matched controls, the IOP increased to 13.4 mm Hg, 14.9 mm Hg, and 17.8 mm Hg at 10 min, 20 min, and 30 min, respectively, but none of these differences were significant (P = 0.09; P = 0.08, P = 0.08). The mean postural IOP change from baseline was also not significant between the two groups. Only three patients were on single antiglaucoma medication with well-controlled IOP in the PACG group. Conclusions: Postural IOP changes are comparable among eyes with PACG with and without glaucoma medications, and control eyes.

Download Full-text

Glaucoma at a tertiary referral eye hospital in Nepal

Nepalese Journal of Ophthalmology ◽

10.3126/nepjoph.v3i2.5263 ◽

1970 ◽

Vol 3 (2) ◽

pp. 123-127

Author(s):

I Paudyal ◽

SS Thapa ◽

G Paudyal ◽

R Gurung ◽

S Ruit

Keyword(s):

Primary Open Angle Glaucoma ◽

Open Angle Glaucoma ◽

Applanation Tonometry ◽

Acute Angle ◽

Secondary Glaucoma ◽

Angle Closure Glaucoma ◽

Field Analysis ◽

Angle Closure ◽

Open Angle ◽

Tertiary Referral

Background: Glaucoma is an important cause of blindness. Objective: To report the distribution of various types of glaucoma among patients presenting to a tertiary eye hospital in Nepal. Materials and methods: All new patients visiting the hospital between March 2007 and February 2008 underwent a comprehensive eye examination. Whenever glaucoma was suspected, patients were referred to fellowship-trained glaucoma specialists. Patients received a comprehensive glaucoma workup including applanation tonometry, stereoscopic examination of the optic nerve head performed by the glaucoma specialists, and a Humphrey visual field analysis (SITA 24 - 2). Results: 447 patients were newly diagnosed with glaucoma. 171 (38.2 %) patients had primary open-angle glaucoma (POAG), while 143 (32 %) had primary angle-closure glaucoma (PACG). The average age of presentation of patients with POAG was 65.78 ± 9.1 years, while the average age for PACG patients was 54.6 ±12.8 years. 30 (21 %) patients with PACG had acute angle-closure on presentation, while 113 (79 %) had chronic angle closure glaucoma. 107 (75 %) of these patients with PACG had visual acuity of less than 3/60 (20/ 400) in the worse eye at presentation. The most common form of secondary glaucoma was lens-induced (5.3 %), followed by neovascular (3.2 %) and uveitic glaucoma (3.2 %). Conclusion: The most common glaucoma seen in a tertiary referral eye hospital of Nepal is primary open-angle glaucoma. Among the angle-closure glaucoma, chronic angle-closure is the most common. Lens-induced glaucoma is still the commonest cause of secondary glaucoma. Keywords: glaucoma, open-angle, angle-closure, lens-induced DOI: http://dx.doi.org/10.3126/nepjoph.v3i2.5263 Nepal J Ophthalmol 2011; 3(2): 123-127

Download Full-text

ACUTE ANGLE‐CLOSURE GLAUCOMA PRECIPITATED BY MIOTICS PLUS ADRENALINE EYE‐DROPS

The Medical Journal of Australia ◽

10.5694/j.1326-5377.1966.tb91971.x ◽

1966 ◽

Vol 2 (26) ◽

pp. 1252-1252

Keyword(s):

Acute Angle ◽

Angle Closure Glaucoma ◽

Angle Closure ◽

Eye Drops ◽

Acute Angle Closure ◽

Acute Angle Closure Glaucoma

Download Full-text

A New Approach for Design Optimization and Parametric Analysis of Symmetric Compound Parabolic Concentrator for Photovoltaic Applications

Sustainability ◽

10.3390/su13094606 ◽

2021 ◽

Vol 13 (9) ◽

pp. 4606

Author(s):

Faisal Masood ◽

Perumal Nallagownden ◽

Irraivan Elamvazuthi ◽

Javed Akhter ◽

Mohammad Azad Alam

Keyword(s):

Parametric Analysis ◽

Concentration Ratio ◽

Synergistic Effects ◽

Geometric Optimization ◽

Design Parameters ◽

Imaging Device ◽

Compound Parabolic Concentrator ◽

Photovoltaic Applications ◽

Half Angle ◽

The Impact

A compound parabolic concentrator (CPC) is a non-imaging device generally used in PV, thermal, or PV/thermal hybrid systems for the concentration of solar radiation on the target surface. This paper presents the geometric design, statistical modeling, parametric analysis, and geometric optimization of a two-dimensional low concentration symmetric compound parabolic concentrator for potential use in building-integrated and rooftop photovoltaic applications. The CPC was initially designed for a concentration ratio of “2×” and an acceptance half-angle of 30°. A MATLAB code was developed in house to provoke the CPC reflector’s profile. The height, aperture width, and concentration ratios were computed for different acceptance half-angles and receiver widths. The interdependence of optical concentration ratio and acceptance half-angle was demonstrated for a wide span of acceptance half-angles. The impact of the truncation ratio on the geometric parameters was investigated to identify the optimum truncation position. The profile of truncated CPC for different truncation positions was compared with full CPC. A detailed statistical analysis was performed to analyze the synergistic effects of independent design parameters on the responses using the response surface modeling approach. A set of optimized design parameters was obtained by establishing specified optimization criteria. A 50% truncated CPC with an acceptance half-angle of 21.58° and receiver width of 193.98 mm resulted in optimum geometric dimensions.

Download Full-text