Concept design for a low-frequency array

2000 ◽  
Author(s):  
Jaap D. Bregman
Keyword(s):  
Low Frequency ◽  
Concept Design

scholarly journals INVESTIGATING 3D RECONSTRUCTION OF NON-COLLABORATIVE SURFACES THROUGH PHOTOGRAMMETRY AND PHOTOMETRIC STEREO

2021 ◽  
Vol XLIII-B2-2021 ◽  
pp. 519-526
Author(s):  
A. Karami ◽  
F. Menna ◽  
F. Remondino
Keyword(s):  
Surface Topography ◽  
Surface Deformation ◽  
Low Frequency ◽  
Experimental Tests ◽  
Photometric Stereo ◽  
Light Sources ◽  
Concept Design ◽  
Textured Surfaces ◽  
Main Concept ◽  
3D Information

Abstract. 3D digital reconstruction techniques are extensively used for quality control purposes. Among them, photogrammetry and photometric stereo methods have been for a long time used with success in several application fields. However, generating highly-detailed and reliable micro-measurements of non-collaborative surfaces is still an open issue. In these cases, photogrammetry can provide accurate low-frequency 3D information, whereas it struggles to extract reliable high-frequency details. Conversely, photometric stereo can recover a very detailed surface topography, although global surface deformation is often present. In this paper, we present the preliminary results of an ongoing project aiming to combine photogrammetry and photometric stereo in a synergetic fusion of the two techniques. Particularly, hereafter, we introduce the main concept design behind an image acquisition system we developed to capture images from different positions and under different lighting conditions as required by photogrammetry and photometric stereo techniques. We show the benefit of such a combination through some experimental tests. The experiments showed that the proposed method recovers the surface topography at the same high-resolution achievable with photometric stereo while preserving the photogrammetric accuracy. Furthermore, we exploit light directionality and multiple light sources to improve the quality of dense image matching in poorly textured surfaces.

A Concept Design and Hydrodynamic Behavior of a Spar Platform

2003 ◽  
Author(s):  
Marcio de Abreu Grove ◽  
Carlos Antonio Levi da Conceic¸a˜o ◽  
Richard David Schachter
Keyword(s):  
Design Method ◽  
Low Frequency ◽  
Vertical Motion ◽  
Concept Design ◽  
Hydrodynamic Behavior ◽  
Spar Platform ◽  
The North ◽  
Campos Basin ◽  
The North Sea ◽  
And Storage

This paper presents a study of a Production and Storage Spar Platform concept design for operations in deep water, under the environmental conditions of the Campos Basin, Brazil. This study is the result of a research sponsored by Ageˆncia Nacional do Petro´leo – ANP. The theme was chosen due the good results obtained by this kind of platform in the North Sea and the Gulf of Mexico. Since the exploration of hydrocarbonets is moving to deeper waters, where the Spar concept seems to be one of the best options for the task, due to its simplicity in construction and operation. Although it looks simple, this work had required perceptive studies, and the best way chosen to carry it out, was dividing it in two directions: one dealing with the design method and naval architecture aspects and other with its hydrodynamic behavior. The first line took into consideration the hull generation, compartmentation, weight distribution and stability. A design methodology is presented and the interaction of these factors are showed, taking into account the hydrodynamic results. The second line has favored the evaluation and the control of the vertical motion, excited by dominant waves from the spectra of energy of the sea, and the horizontal motions due the low frequency excitations, and its interaction with the mooring system.

scholarly journals Towards a Concept Design for a LOFAR

2002 ◽  
Vol 199 ◽  
pp. 484-485 ◽  
Author(s):  
Jaap D. Bregman
Keyword(s):  
Data Processing ◽  
High Performance ◽  
Phased Array ◽  
Low Frequency ◽  
Software Radio ◽  
Concept Design ◽  
Digital Beamforming ◽  
Sky Survey ◽  
Array Technology ◽  
The Cost

The LOw Frequency ARray is a Digital Software Radio Telescope under study by the NFRA and the NRL. A scaleable architecture is proposed for the antenna stations of an aperture synthesis array operating in the 10 — 160 MHz frequency band. The use of advanced phased array technology with digital beamforming results in a multi-beam capability of up to 64 beams, which cover together about a steradian on the sky, and can be placed such that all relevant science objects are covered simultaneously. Based on the fast expansion of high performance processing technology, it is just after 2003 that signal and data processing will no longer dominate the cost of LOFAR in producing a confusion limited sky survey at the mJy level.

An enhanced tunable rotational energy harvester with variable stiffness system for low-frequency vibration

2015 ◽  
Vol 230 (5) ◽  
pp. 732-736 ◽  
Author(s):  
Seon-Jun Jang ◽  
In-Ho Kim ◽  
Kyoungwoo Park ◽  
Hyung-Jo Jung
Keyword(s):  
Numerical Simulation ◽  
Energy Harvester ◽  
Proof Mass ◽  
Low Frequency ◽  
Variable Stiffness ◽  
Rotational Energy ◽  
Concept Design ◽  
Design And Implementation ◽  
Low Frequency Vibration ◽  
Serial Connection

An enhanced tunable rotational energy harvester for low-frequency vibration is proposed. It consists of a rotational vibrating system and a translating proof mass suspended by wire. The active tuning of the resonant frequency is implemented using the serial connection control of spiral springs, which is named here as a variable stiffness system. The concept, design, and implementation for the proposed device are presented. The numerical simulation and the vertical shaker test are performed, respectively, and the results showed that the proposed energy harvester could effectively generate the electricity under the low-frequency vibration and readily change its natural frequency as well.

A Study on the Fine Structure of the Lateral Line Organ of the Sea Eel

1973 ◽  
Vol 31 ◽  
pp. 648-649
Author(s):  
K. Hama
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Lateral Line ◽  
Low Frequency ◽  
Sensory Cells ◽  
Apical Surface ◽  
Voltage Electron ◽  
Sensory Epithelia ◽  
Low Frequency Vibration ◽  
Transmission Electron

The lateral line organs of the sea eel consist of canal and pit organs which are different in function. The former is a low frequency vibration detector whereas the latter functions as an ion receptor as well as a mechano receptor.The fine structure of the sensory epithelia of both organs were studied by means of ordinary transmission electron microscope, high voltage electron microscope and of surface scanning electron microscope.The sensory cells of the canal organ are polarized in front-caudal direction and those of the pit organ are polarized in dorso-ventral direction. The sensory epithelia of both organs have thinner surface coats compared to the surrounding ordinary epithelial cells, which have very thick fuzzy coatings on the apical surface.

Lectin Binding to Human Breast Tumor Cells

1976 ◽  
Vol 34 ◽  
pp. 34-35
Author(s):  
Robert E. Nordquist ◽  
J. Hill Anglin ◽  
Michael P. Lerner
Keyword(s):  
Carcinoma Cell ◽  
Ricinus Communis ◽  
Lectin Binding ◽  
Low Frequency ◽  
Breast Carcinoma Cell Line ◽  
Human Breast ◽  
Human Breast Tumor ◽  
Duct Carcinoma ◽  
Specific Antigens ◽  
Ricin Agglutinin

A human breast carcinoma cell line (BOT-2) was derived from an infiltrating duct carcinoma (1). These cells were shown to have antigens that selectively bound antibodies from breast cancer patient sera (2). Furthermore, these tumor specific antigens could be removed from the living cells by low frequency sonication and have been partially characterized (3). These proteins have been shown to be around 100,000 MW and contain approximately 6% hexose and hexosamines. However, only the hexosamines appear to be available for lectin binding. This study was designed to use Concanavalin A (Con A) and Ricinus Communis (Ricin) agglutinin for the topagraphical localization of D-mannopyranosyl or glucopyranosyl and D-galactopyranosyl or DN- acetyl glactopyranosyl configurations on BOT-2 cell surfaces.

Practical High Resolution Microscopy

1968 ◽  
Vol 26 ◽  
pp. 302-303
Author(s):  
P. A. Marsh ◽  
T. Mullens ◽  
D. Price
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Low Frequency ◽  
Resolving Power ◽  
Careful Attention ◽  
Electron Microscopes ◽  
The Relationship ◽  
High Resolution Microscopy ◽  
New Facilities

It is possible to exceed the guaranteed resolution on most electron microscopes by careful attention to microscope parameters essential for high resolution work. While our experience is related to a Philips EM-200, we hope that some of these comments will apply to all electron microscopes.The first considerations are vibration and magnetic fields. These are usually measured at the pre-installation survey and must be within specifications. It has been our experience, however, that these factors can be greatly influenced by the new facilities and therefore must be rechecked after the installation is completed. The relationship between the resolving power of an EM-200 and the maximum tolerable low frequency interference fields in milli-Oerstedt is 10 Å - 1.9, 8 Å - 1.4, 6 Å - 0.8.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

SEM image sharpness analysis

1996 ◽  
Vol 54 ◽  
pp. 142-143
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Quantitative Information ◽  
Primary Electron ◽  
Image Sharpness ◽  
Critical Dimensions ◽  
Sem Image ◽  
Frequency Changes ◽  
Electron Microscopes ◽  
Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

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