scholarly journals Air-Coupled Ultrasonic Probe Integrity Test Using a Focused Transducer with Similar Frequency and Limited Aperture for Contrast Enhancement

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7196
Author(s):  
Linas Svilainis ◽  
Andrius Chaziachmetovas ◽  
Darius Kybartas ◽  
Tomas Gomez Alvarez-Arenas
Keyword(s):  
Focal Point ◽  
Center Frequency ◽  
Transduction Efficiency ◽  
Special Design ◽  
Integrity Test ◽  
Ultrasonic Probe ◽  
Similar Frequency ◽  
Convenient Means ◽  
Proposed Modification ◽  
Transducer Probe

Air-coupled ultrasonic probes require a special design approach and handling due to the significant mismatch to the air. Outer matching layers have to be soft so can be easily damaged and excitation voltages might cause the degradation of electrodes or bonding between the layers. Integrity inspection is desired during design, manufacturing, and exploitation. Spatial distribution of a transduction efficiency over piezoelement surface is proposed as a convenient means for the air-coupled probe integrity inspection. Focused transducer of similar center frequency is used to scan the surface of the inspected probe. However, such approach creates a challenge, i.e., area of the scanning beam is much smaller than the total receiving area of the inspected probe, therefore, contrast and imaging resolution are significantly degraded. Masking aperture made from cardboard and felt, placed at the focal point was proposed as solution. Far-range sidelobes were suppressed down to the noise floor (−50 dB) and the near-range sidelobes were reduced down to −17 dB. The proposed modification allows to use a similar frequency focused transducer. Probe integrity inspection can be carried out at significantly enhanced contrast and lateral resolution. Natural and artificial defects can be detected by the use of the proposed method.

DESIGN AND FABRICATION OF A 20 MHz ANNULAR ARRAY FOR MEDICAL ULTRASOUND

2012 ◽  
Vol 05 (01) ◽  
pp. 1150010
Author(s):  
ZHENHUA HU ◽  
JUE PENG
Keyword(s):  
Focal Point ◽  
Impedance Matching ◽  
Center Frequency ◽  
Depth Of Field ◽  
Single Element ◽  
Medical Ultrasound ◽  
Annular Array ◽  
Array Transducer ◽  
Small Depth

Most high frequency (> 15 MHz) medical ultrasound systems are based on single element transducers mechanically scanned. These systems can provide images with excellent resolution. However, single element transducers are often limited by the fixed focal point and small depth of field. Annular arrays consisting of concentric rings of elements are focused electronically. These arrays are desirable to avoid the fixed focal point of the single element transducers and improve the depth of field. This paper reports the design, fabrication, and characterization of a 5-element equal-area annular array transducer. After electrical impedance matching, the average center frequency was 20 MHz and -6 dB bandwidths ranged from 34 to 42%. The ILs for the matched annuli ranged from 6.1 to 26.5 dB.

scholarly journals Design, Fabrication, and Evaluation of Multifocal Point Transducer for High-Frequency Ultrasound Applications

Sensors ◽  
2019 ◽  
Vol 19 (3) ◽  
pp. 609 ◽  
Author(s):  
Thanh Nguyen ◽  
Nguyen Truong ◽  
Nhat Bui ◽  
Van Nguyen ◽  
Giang Hoang ◽  
...  
Keyword(s):  
High Frequency ◽  
Polyvinylidene Fluoride ◽  
Focal Point ◽  
Cnc Machining ◽  
Numerical Control ◽  
Center Frequency ◽  
Pvdf Film ◽  
High Frequency Ultrasound ◽  
Linear Pattern ◽  
Frequency Ultrasound

The present study illustrates the design, fabrication, and evaluation of a novel multifocal point (MFP) transducer based on polyvinylidene fluoride (PVDF) film for high-frequency ultrasound application. The fabricated MFP surface was press-focused using a computer numerical control (CNC) machining tool-customized multi-spherical pattern object. The multi-spherical pattern has five spherical surfaces with equal area and connected continuously to have the same energy level at focal points. Center points of these spheres are distributed in a linear pattern with 1 mm distance between each two points. The radius of these spheres increases steadily from 10 mm to 13.86 mm. The designed MFP transducer had a center frequency of 50 MHz and a −6 dB bandwidth of 68%. The wire phantom test was conducted to study and demonstrate the advantages of this novel design. The obtained results for MFP transducer revealed a significant increase (4.3 mm) of total focal zone in the near-field and far-field area compared with 0.48 mm obtained using the conventional single focal point transducer. Hence, the proposed method is promising to fabricate MFP transducers for deeper imaging depth applications.

scholarly journals Fuzzy Support System for Total Hip Arthroplasty Stem by Ultrasonic Intraoperative Measurement

2012 ◽  
Vol 2012 ◽  
pp. 1-8
Author(s):  
Naomi Yagi ◽  
Yutaka Hata ◽  
Nao Shibanuma
Keyword(s):  
Total Hip Arthroplasty ◽  
Support System ◽  
Hip Arthroplasty ◽  
Fuzzy System ◽  
Fuzzy Inference ◽  
Center Frequency ◽  
Ultrasonic Probe ◽  
Stem Size ◽  
Total Hip ◽  
Difference Time

This paper describes a fuzzy system of stem implantation on total hip arthroplasty by an ultrasonic device. The system can perform automatic and accurate assessment in the surgery. In this system, we employ a single ultrasonic probe whose center frequency is 1,000 Hz. We detect the acoustic signals when knocking the inserted stem with a hammer. We then have a correlation between the degree of tightening and the attenuation time of acoustic signal. That is, the higher tightened degree implies shorter attenuation period. The support system selects the most suitable stem size by fuzzy inference with respect to the attenuation time and its difference time from correct stem to one larger size stem which dynamically adapts to each patient. As a result, we successfully determined the suitable stem in comparison to the results of the practical surgery.

Integrating perspectives: How the development of second-personal competence lays the foundation for a second-personal morality

2020 ◽  
Vol 43 ◽  
Author(s):  
John Corbit ◽  
Chris Moore
Keyword(s):  
Empirical Evidence ◽  
Developmental Process ◽  
Focal Point ◽  
Personal Information ◽  
Personal Competence ◽  
Triadic Interactions ◽  
Personal Morality ◽  
Integrative Process

Abstract The integration of first-, second-, and third-personal information within joint intentional collaboration provides the foundation for broad-based second-personal morality. We offer two additions to this framework: a description of the developmental process through which second-personal competence emerges from early triadic interactions, and empirical evidence that collaboration with a concrete goal may provide an essential focal point for this integrative process.

CBED Shadow Images and Cs:Aberration Measurement

1982 ◽  
Vol 40 ◽  
pp. 696-697
Author(s):  
R. W. Carpenter ◽  
I.Y.T. Chan ◽  
J. M. Cowley
Keyword(s):  
Focal Point ◽  
Spherical Aberration ◽  
Optic Axis ◽  
Wide Angle ◽  
Caustic Surface ◽  
Convergent Beam

Wide-angle convergent beam shadow images(CBSI) exhibit several characteristic distortions resulting from spherical aberration. The most prominent is a circle of infinite magnification resulting from rays having equal values of a forming a cross-over on the optic axis at some distance before reaching the paraxial focal point. This distortion is called the tangential circle of infinite magnification; it can be used to align and stigmate a STEM and to determine Cs for the probe forming lens. A second distortion, the radial circle of infinite magnification, results from a cross-over on the lens caustic surface of rays with differing values of ∝a, also before the paraxial focal point of the lens.

Microtomy of spherical Al2O3 powders

1983 ◽  
Vol 41 ◽  
pp. 74-75
Author(s):  
E.J. Jenkins ◽  
D.S. Tucker ◽  
J.J. Hren
Keyword(s):  
Thin Film ◽  
Size Range ◽  
Particle Aggregation ◽  
Ion Milling ◽  
Thin Sections ◽  
Α Phase ◽  
Convenient Means ◽  
Van Der Waals Attraction ◽  
Negative Feature ◽  
Film Substrate

The size range of mineral and ceramic particles of one to a few microns is awkward to prepare for examination by TEM. Electrons can be transmitted through smaller particles directly and larger particles can be thinned by crushing and dispersion onto a substrate or by embedding in a film followed by ion milling. Attempts at dispersion onto a thin film substrate often result in particle aggregation by van der Waals attraction. In the present work we studied 1-10 μm diameter Al2O3 spheres which were transformed from the amprphous state to the stable α phase.After the appropriate heat treatment, the spherical powders were embedded in as high a density as practicable in a hard EPON, and then microtomed into thin sections. There are several advantages to this method. Obviously, this is a rapid and convenient means to study the microstructure of serial slices. EDS, ELS, and diffraction studies are also considerably more informative. Furthermore, confidence in sampling reliability is considerably enhanced. The major negative feature is some distortion of the microstructure inherent to the microtoming operation; however, this appears to have been surprisingly small. The details of the method and some typical results follow.

Electrostatic optics and aberration correction in the 1940s and today

1992 ◽  
Vol 50 (1) ◽  
pp. 6-7
Author(s):  
Gertrude F. Rempfer
Keyword(s):  
Electron Microscope ◽  
Focal Point ◽  
Focal Length ◽  
High Vacuum ◽  
Electron Optics ◽  
Applied Physics ◽  
Electrostatic Lenses ◽  
Commercial Instrument ◽  
The University ◽  
Theory And Experiment

I became involved in electron optics in early 1945, when my husband Robert and I were hired by the Farrand Optical Company. My husband had a mathematics Ph.D.; my degree was in physics. My main responsibilities were connected with the development of an electrostatic electron microscope. Fortunately, my thesis research on thermionic and field emission, in the late 1930s under the direction of Professor Joseph E. Henderson at the University of Washington, provided a foundation for dealing with electron beams, high vacuum, and high voltage.At the Farrand Company my co-workers and I used an electron-optical bench to carry out an extensive series of tests on three-electrode electrostatic lenses, as a function of geometrical and voltage parameters. Our studies enabled us to select optimum designs for the lenses in the electron microscope. We early on discovered that, in general, electron lenses are not “thin” lenses, and that aberrations of focal point and aberrations of focal length are not the same. I found electron optics to be an intriguing blend of theory and experiment. A laboratory version of the electron microscope was built and tested, and a report was given at the December 1947 EMSA meeting. The micrograph in fig. 1 is one of several which were presented at the meeting. This micrograph also appeared on the cover of the January 1949 issue of Journal of Applied Physics. These were exciting times in electron microscopy; it seemed that almost everything that happened was new. Our opportunities to publish were limited to patents because Mr. Farrand envisaged a commercial instrument. Regrettably, a commercial version of our laboratory microscope was not produced.

A confocal laser scanning microscope for fluorescence and reflection at video rates

1989 ◽  
Vol 47 ◽  
pp. 134-135
Author(s):  
P.M. Houpt ◽  
A. Draaijer
Keyword(s):  
Light Source ◽  
Laser Scanning ◽  
Focal Point ◽  
Confocal Laser Scanning Microscope ◽  
Confocal Laser ◽  
Point Light Source ◽  
Volume Of Interest ◽  
Ion Laser ◽  
Point Light ◽  
Point Detector

In confocal microscopy, the object is scanned by the coinciding focal points (confocal) of a point light source and a point detector both focused on a certain plane in the object. Only light coming from the focal point is detected and, even more important, out-of-focus light is rejected.This makes it possible to slice up optically the ‘volume of interest’ in the object by moving it axially while scanning the focused point light source (X-Y) laterally. The successive confocal sections can be stored in a computer and used to reconstruct the object in a 3D image display.The instrument described is able to scan the object laterally with an Ar ion laser (488 nm) at video rates. The image of one confocal section of an object can be displayed within 40 milliseconds (1000 х 1000 pixels). The time to record the total information within the ‘volume of interest’ normally depends on the number of slices needed to cover it, but rarely exceeds a few seconds.

Do Work Characteristics Mediate the Negative Effect of Transformational Leadership on Impaired Well-Being?

2017 ◽  
Vol 61 (4) ◽  
pp. 167-180 ◽  
Author(s):  
Sylvie Vincent-Höper ◽  
Sabine Gregersen ◽  
Albert Nienhaus
Keyword(s):  
Transformational Leadership ◽  
Focal Point ◽  
Leadership Behavior ◽  
Workplace Health Promotion ◽  
Well Being ◽  
Mediating Effect ◽  
Equation Modeling ◽  
Related Factor ◽  
Work Characteristics ◽  
Role Clarity

Abstract: In recent years, transformational leadership as a health-related factor has become a focal point of interest in research and practice. However, the pathways and mechanisms underlying this association are not yet well understood. In order to gain knowledge on how or why transformational leadership and employee well-being are associated, we investigated the mediating effect of the work characteristics role clarity and predictability. The study was carried out on 618 employees working in the health-care sector in Germany. We tested the mediator effect using structural equation modeling. The results indicate that role clarity and predictability fully mediate the relation between transformational leadership and negative indicators of well-being. These results give credit to the notion that work characteristics play an important role in identifying health-relevant aspects of leadership behavior. Our findings advance the understanding of how to enhance employee well-being and have implications for the design of leadership-related interventions of workplace health promotion.

Tests und Tools

2007 ◽  
Vol 6 (2) ◽  
pp. 85-90 ◽  
Author(s):  
Rüdiger Hossiep ◽  
Sabine Bräutigam
Keyword(s):  
Integrity Test ◽  
Integrity Tests

Zusammenfassung. Vorgestellt wird das IBES (Inventar berufsbezogener Einstellungen und Selbsteinschätzungen), das erste publizierte deutschsprachige Verfahren der Gattung “Integrity Test”. Ziel des Instrumentes ist die Vorhersage kontraproduktiven Verhaltens in Unternehmen (z. B. Absentismus, Diebstahl, Aggression). Die Konstruktion erfolgte in enger Anlehnung an Inhalte prominenter amerikanischer Integrity Tests. Das IBES besteht aus einem einstellungsorientierten Teil mit 60 Items, die den vier Skalen “Vertrauen”, “Geringe Verbreitung unerwünschten Verhaltens”, “Nicht-Rationalisierung” und “Verhaltensabsichten” zugeordnet sind sowie einem eigenschaftsorientierten Teil mit 55 Items, unterteilt in die fünf Skalen “Gelassenheit/Selbstwertgefühl”, “Zuverlässigkeit/Voraussicht”, “Vorsicht”, “Zurückhaltung” und “Konfliktmeidung”. Die Anwendbarkeit des Verfahrens in der Praxis wird insbesondere vor dem Hintergrund der Datenbasis und des Itemmaterials kritisch diskutiert.

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