Experimental and theoretical investigation of perturbation set up in a plasma with beam by a charged filament

1974 ◽  
Vol 17 (8) ◽  
pp. 839-843
Author(s):  
Yu. Ya. Brodskii ◽  
V. A. Mironov ◽  
V. N. Us
Keyword(s):  
Theoretical Investigation ◽  
Charged Filament ◽  
Set Up

Computer utterances: Sequence and event in digital architecture

2017 ◽  
Vol 15 (4) ◽  
pp. 268-284
Author(s):  
Pablo Miranda
Keyword(s):  
World War Ii ◽  
Theoretical Investigation ◽  
Theoretical Formulation ◽  
Design Work ◽  
Von Neumann ◽  
Digital Architecture ◽  
Technical Report ◽  
Geometric Representations ◽  
Set Up ◽  
First Time

Barely a month before the end of World War II, a technical report begun circulating among allied scientists: the ‘First Draft of a Report on the EDVAC’, attributed to John von Neumann, described for the first time the design and implementation of the earliest stored-program computer. The ‘First Draft’ became the template followed by subsequent British and American computers, establishing the standard characteristics of most computing machines to date. This article looks at how the material and design choices described in this report influenced architecture, as it set up the technological matrix onto which a discipline relying on a tradition of drawn geometry would be eventually completely remediated. It consists of two parts: first, a theoretical section, analysing the repercussions for architecture of the type of computer laid out in the ‘First Draft’. Second, a description of a design experiment, a sort of information furniture, that tests and exemplifies some of the observations from the first section. This experiment examines the possibilities of an architecture that, moving beyond geometric representations, uses instead the programming of events as its rationale. The structure of this article reflects a methodology in which theoretical formulation and design experiments proceed in parallel. The theoretical investigation proposes concepts that can be tested and refined through design and conversely design work determines and encourages technical, critical and historical research. This relation is dialogical: theoretical investigation is not simply a rationalisation and explanation of earlier design work; inversely, the role of design is not just to illustrate previously formulated concepts. Both design and theorisation are interdependent but autonomous in their parallel development.

scholarly journals Oscillations in a bridge caused by the passage of a locomotive

1928 ◽  
Vol 118 (779) ◽  
pp. 60-96 ◽  
Keyword(s):  
Experimental Data ◽  
Theoretical Investigation ◽  
Mathematical Analysis ◽  
The State ◽  
Experimental Results ◽  
Present Stage ◽  
Practical Experiment ◽  
Underlying Theory ◽  
Reasonable Degree ◽  
Set Up

For purposes of bridge design it is all important to be able to predict with a reasonable degree of accuracy the state of oscillation which will be set up when a given locomotive crosses a bridge at any specified speed. A large amount of experimental data relating to impact effects on bridges has been accumulated, but in default of an underlying theory sufficiently comprehensive in character to account for the phenomena observed, the conclusions emerging from experimental results have been somewhat disappointing and vague. The problem is one which most essentially calls for the closest possible cooperation between mathematical analysis and practical experiment. At the present stage experiment has outrun theory, and it was with the object of redressing, in some measure, this lack of balance that the following theoretical investigation was undertaken.

The Effects of Drying Techniques on Clay-Rich Soil Texture

1974 ◽  
Vol 32 ◽  
pp. 466-467
Author(s):  
T. G. Naymik
Keyword(s):  
Critical Point ◽  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Drying Methods ◽  
Air Drying ◽  
Freeze Dried ◽  
Critical Point Drying ◽  
Set Up ◽  
The Relationship ◽  
Quartz Grains

Three techniques were incorporated for drying clay-rich specimens: air-drying, freeze-drying and critical point drying. In air-drying, the specimens were set out for several days to dry or were placed in an oven (80°F) for several hours. The freeze-dried specimens were frozen by immersion in liquid nitrogen or in isopentane at near liquid nitrogen temperature and then were immediately placed in the freeze-dry vacuum chamber. The critical point specimens were molded in agar immediately after sampling. When the agar had set up the dehydration series, water-alcohol-amyl acetate-CO2 was carried out. The objectives were to compare the fabric plasmas (clays and precipitates), fabricskeletons (quartz grains) and the relationship between them for each drying technique. The three drying methods are not only applicable to the study of treated soils, but can be incorporated into all SEM clay soil studies.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

Eels Under Standing Wave Conditions

1982 ◽  
Vol 40 ◽  
pp. 492-495
Author(s):  
O.L. Krivanek ◽  
J. TaftØ
Keyword(s):  
Standing Wave ◽  
Wave Conditions ◽  
Set Up ◽  
A Site ◽  
Complex Crystal

It is well known that a standing electron wavefield can be set up in a crystal such that its intensity peaks at the atomic sites or between the sites or in the case of more complex crystal, at one or another type of a site. The effect is usually referred to as channelling but this term is not entirely appropriate; by analogy with the more established particle channelling, electrons would have to be described as channelling either through the channels or through the channel walls, depending on the diffraction conditions.

Low-Loss Images in a Stem/Tem Microscope

1976 ◽  
Vol 34 ◽  
pp. 496-497 ◽  
Author(s):  
David C. Joy ◽  
Dennis M. Maher
Keyword(s):  
High Resolution ◽  
Surface Topography ◽  
Beam Direction ◽  
Low Loss ◽  
Specimen Holder ◽  
Glancing Angle ◽  
High Resolution Images ◽  
Set Up ◽  
Conventional Manner ◽  
Objective Type

High-resolution images of the surface topography of solid specimens can be obtained using the low-loss technique of Wells. If the specimen is placed inside a lens of the condenser/objective type, then it has been shown that the lens itself can be used to collect and filter the low-loss electrons. Since the probeforming lenses in TEM instruments fitted with scanning attachments are of this type, low-loss imaging should be possible.High-resolution, low-loss images have been obtained in a JEOL JEM 100B fitted with a scanning attachment and a thermal, fieldemission gun. No modifications were made to the instrument, but a wedge-shaped, specimen holder was made to fit the side-entry, goniometer stage. Thus the specimen is oriented initially at a glancing angle of about 30° to the beam direction. The instrument is set up in the conventional manner for STEM operation with all the lenses, including the projector, excited.

UHV-TEM studies of laser-induced damage

1991 ◽  
Vol 49 ◽  
pp. 632-633
Author(s):  
T.S. Savage ◽  
R. Ai ◽  
D. Dunn ◽  
L.D. Marks
Keyword(s):  
Surface Science ◽  
Rapid Heating ◽  
Local Heating ◽  
Routine Practice ◽  
Transmission Electron ◽  
Northwestern University ◽  
Laser Induced Damage ◽  
Set Up ◽  
Focusing Lens ◽  
Diffusion Of Impurities

The use of lasers for surface annealing, heating and/or damage has become a routine practice in the study of materials. Lasers have been closely looked at as an annealing technique for silicon and other semiconductors. They allow for local heating from a beam which can be focused and tuned to different wavelengths for specific tasks. Pulsed dye lasers allow for short, quick bursts which can allow the sample to be rapidly heated and quenched. This short, rapid heating period may be important for cases where diffusion of impurities or dopants may not be desirable.At Northwestern University, a Candela SLL - 250 pulsed dye laser, with a maximum power of 1 Joule/pulse over 350 - 400 nanoseconds, has been set up in conjunction with a Hitachi UHV-H9000 transmission electron microscope. The laser beam is introduced into the surface science chamber through a series of mirrors, a focusing lens and a six inch quartz window.

A simple way for producing holographic filters suitable for image improvement

1978 ◽  
Vol 36 (1) ◽  
pp. 226-227
Author(s):  
K.-H. Herrmann ◽  
E. Reuber ◽  
P. Schiske
Keyword(s):  
Transfer Functions ◽  
Diffraction Order ◽  
Lateral Position ◽  
Simple Method ◽  
Spatial Frequencies ◽  
Resolution Electron ◽  
Wiener Filters ◽  
Image Improvement ◽  
Optical Reconstruction ◽  
Set Up

Aposteriori deblurring of high resolution electron micrographs of weak phase objects can be performed by holographic filters [1,2] which are arranged in the Fourier domain of a light-optical reconstruction set-up. According to the diffraction efficiency and the lateral position of the grating structure, the filters permit adjustment of the amplitudes and phases of the spatial frequencies in the image which is obtained in the first diffraction order.In the case of bright field imaging with axial illumination, the Contrast Transfer Functions (CTF) are oscillating, but real. For different imageforming conditions and several signal-to-noise ratios an extensive set of Wiener-filters should be available. A simple method of producing such filters by only photographic and mechanical means will be described here.A transparent master grating with 6.25 lines/mm and 160 mm diameter was produced by a high precision computer plotter. It is photographed through a rotating mask, plotted by a standard plotter.

3-D optical transfer in excitation field synthesis microscopes

1995 ◽  
Vol 53 ◽  
pp. 64-65
Author(s):  
Vijay Krishnamurthi ◽  
Brent Bailey ◽  
Frederick Lanni
Keyword(s):  
Standing Wave ◽  
Spatial Information ◽  
3D Structure ◽  
Complete Recovery ◽  
Weighting Factor ◽  
Optical Transfer Function ◽  
Excitation Field ◽  
Optical Transfer ◽  
Set Up ◽  
Focus Plane

Excitation field synthesis (EFS) refers to the use of an interference optical system in a direct-imaging microscope to improve 3D resolution by axially-selective excitation of fluorescence within a specimen. The excitation field can be thought of as a weighting factor for the point-spread function (PSF) of the microscope, so that the optical transfer function (OTF) gets expanded by convolution with the Fourier transform of the field intensity. The simplest EFS system is the standing-wave fluorescence microscope, in which an axially-periodic excitation field is set up through the specimen by interference of a pair of collimated, coherent, s-polarized beams that enter the specimen from opposite sides at matching angles. In this case, spatial information about the object is recovered in the central OTF passband, plus two symmetric, axially-shifted sidebands. Gaps between these bands represent "lost" information about the 3D structure of the object. Because the sideband shift is equal to the spatial frequency of the standing-wave (SW) field, more complete recovery of information is possible by superposition of fields having different periods. When all of the fields have an antinode at a common plane (set to be coincident with the in-focus plane), the "synthesized" field is peaked in a narrow infocus zone.

Convergent Beam Electron Diffraction Zone Axis Pattern Map of Zirconium

1990 ◽  
Vol 48 (2) ◽  
pp. 496-497
Author(s):  
E. Silva ◽  
R. Scozia
Keyword(s):  
Electron Diffraction ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
Pole Piece ◽  
Small Particles ◽  
Present Communication ◽  
Beam Electron ◽  
Zero Layer ◽  
Set Up ◽  
Convergent Beam

The purpose in obtaining zone axis pattern map (zap map) from a given material is to provide a quick and reliable tool to identify cristaline phases, and crystallographic directions, even in small particles. Bend contours patterns and Kossel lines patterns maps from Zr single crystal in the [0001] direction have been presented previously. In the present communication convergent beam electron diffraction (CBED) zap map of Zr will be shown. CBED patterns were obtained using a Philips microscope model EM300, which was set up to carry out this technique. Convergent objective upper pole piece for STEM and some electronic modifications in the lens circuits were required, furthermore the microscope was carefully cleaned and it was operated at a vacuum eminently good.CBED patterns in the Zr zap map consist of zero layer disks, showing fine details within them which correspond to intersecting set of higher order Laue zone (HOLZ) deficiency lines.

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