Study of High-Voltage Impulse Generation Using Piezoelectric Materials Under Elastic Wave

The simultaneous measurement/electrical actuation of piezoelectric elements has been a subject of considerable interest in previous research. Within a limited bandwidth, piezoelectric materials can be modeled electrically as a voltage source and capacitor in series and when these components are integrated into a balanced capacitive bridge, simultaneous actuation and strain sensing is possible. Unfortunately, due to the sensitivity of piezoelectric materials to changing environmental conditions (temperature) and applied voltages, an adaptive scheme is required to maintain a balanced bridge and reduce high voltage spillover into the measurement channel. Even minute changes in the piezoelectric capacitance can overwhelm the strain sensing signal with high voltage content thereby preventing accurate strain sensing. The purpose of this work is to apply the self-sensing algorithm to a flexible structure with piezoelectric sensors/actuators mounted to its surface. The flexible structure utilized in this paper is composed of a small, cantilever resonator beam with two piezoelectric patches integrated into its structure and this beam is mounted at a arbitrary location to a larger, primary cantilever beam. The first two resonances of the actuator beam were tuned to that of the primary beam. High voltage signals are applied to the patch near the root of the resonator beam and simultaneous strain-induced voltage sensing is performed. Simulations have shown that estimation performance degrades with increasing rates of piezoelectric capacitance variation and conversely, adaptation times were found to decrease with increasing adaptive gains over the limited ranges of gains applied.

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High Voltage Electron Microscopy of Ion-Milled Dental Enamel

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100050317 ◽

1974 ◽

Vol 32 ◽

pp. 60-61

Author(s):

L. D. Ackerman ◽

S. H. Y. Wei

Keyword(s):

Electron Microscopy ◽

High Voltage ◽

Third Molar ◽

Polarized Light ◽

Dental Enamel ◽

Longitudinal Section ◽

Ion Milling ◽

High Voltage Electron Microscopy ◽

Voltage Electron ◽

High Voltage Electron

Mature human dental enamel has presented investigators with several difficulties in ultramicrotomy of specimens for electron microscopy due to its high degree of mineralization. This study explores the possibility of combining ion-milling and high voltage electron microscopy as a means of circumventing the problems of ultramicrotomy.A longitudinal section of an extracted human third molar was ground to a thickness of about 30 um and polarized light micrographs were taken. The specimen was attached to a single hole grid and thinned by argon-ion bombardment at 15° incidence while rotating at 15 rpm. The beam current in each of two guns was 50 μA with an accelerating voltage of 4 kV. A 20 nm carbon coating was evaporated onto the specimen to prevent an electron charge from building up during electron microscopy.

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Three-Dimensional Visualization of the T-System of Frog Muscle Using High Voltage Electron Microscopy and a Lanthanum Stain

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100080286 ◽

1977 ◽

Vol 35 ◽

pp. 570-571 ◽

Cited By ~ 2

Author(s):

Lee D. Peachey ◽

Clara Franzini-Armstrong

Keyword(s):

Electron Microscopy ◽

High Voltage ◽

Three Dimensional ◽

Biological Tissues ◽

High Voltage Electron Microscopy ◽

Transverse Tubular System ◽

Peroxidase Reaction ◽

Voltage Electron ◽

High Voltage Electron ◽

T System

The effective study of biological tissues in thick slices of embedded material by high voltage electron microscopy (HVEM) requires highly selective staining of those structures to be visualized so that they are not hidden or obscured by other structures in the image. A tilt pair of micrographs with subsequent stereoscopic viewing can be an important aid in three-dimensional visualization of these images, once an appropriate stain has been found. The peroxidase reaction has been used for this purpose in visualizing the T-system (transverse tubular system) of frog skeletal muscle by HVEM (1). We have found infiltration with lanthanum hydroxide to be particularly useful for three-dimensional visualization of certain aspects of the structure of the T- system in skeletal muscles of the frog. Specifically, lanthanum more completely fills the lumen of the tubules and is denser than the peroxidase reaction product.

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Resolution, Contrast and Interpretation of HVEM Images of Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071582 ◽

1973 ◽

Vol 31 ◽

pp. 228-229

Author(s):

L. E. Thomas ◽

J. S. Lally ◽

R. M. Fisher

Keyword(s):

High Voltage ◽

Chromatic Aberration ◽

Crystalline Materials ◽

Resolution Parameter ◽

Instrument Resolution ◽

Imaging Conditions ◽

Beam Excitation ◽

Optimum Imaging

In addition to improved penetration at high voltage, the characteristics of HVEM images of crystalline materials are changed markedly as a result of many-beam excitation effects. This leads to changes in optimum imaging conditions for dislocations, planar faults, precipitates and other features.Resolution - Because of longer focal lengths and correspondingly larger aberrations, the usual instrument resolution parameter, CS174 λ 374 changes by only a factor of 2 from 100 kV to 1 MV. Since 90% of this change occurs below 500 kV any improvement in “classical” resolution in the MVEM is insignificant. However, as is widely recognized, an improvement in resolution for “thick” specimens (i.e. more than 1000 Å) due to reduced chromatic aberration is very large.

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Radiation-Induced Precipitation at Thin Foil Surfaces in Ni-Be Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055217 ◽

1982 ◽

Vol 40 ◽

pp. 598-599

Author(s):

T. Mukai ◽

T. E. Mitchell

Keyword(s):

Electron Microscopy ◽

High Voltage ◽

Electron Irradiation ◽

High Vacuum ◽

Thin Foil ◽

Homogeneous Precipitation ◽

High Voltage Electron Microscopy ◽

Voltage Electron ◽

High Voltage Electron ◽

Radiation Induced

Radiation-induced homogeneous precipitation in Ni-Be alloys was recently observed by high voltage electron microscopy. A coupling of interstitial flux with solute Be atoms is responsible for the precipitation. The present investigation further shows that precipitation is also induced at thin foil surfaces by electron irradiation under a high vacuum.

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The Reduction of Chromatic Aberrations Due to Instrumental Instabilities

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100064128 ◽

1971 ◽

Vol 29 ◽

pp. 14-15

Author(s):

J. S. Lally ◽

R. Evans

Keyword(s):

Electron Microscope ◽

High Voltage ◽

Focal Length ◽

Chromatic Aberration ◽

Objective Lens ◽

Usual Practice ◽

Voltage Electron ◽

Short Focal Length ◽

Chromatic Aberrations ◽

Electron Microscopes

One of the instrumental factors often limiting the resolution of the electron microscope is image defocussing due to changes in accelerating voltage or objective lens current. This factor is particularly important in high voltage electron microscopes both because of the higher voltages and lens currents required but also because of the inherently longer focal lengths, i.e. 6 mm in contrast to 1.5-2.2 mm for modern short focal length objectives.The usual practice in commercial electron microscopes is to design separately stabilized accelerating voltage and lens supplies. In this case chromatic aberration in the image is caused by the random and independent fluctuations of both the high voltage and objective lens current.

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