Measurement of low-absorption coefficients using the beat frequency shift between transverse modes of a laser

1970 ◽  
Vol 6 (7) ◽  
pp. 475-477 ◽  
Author(s):  
Y. Kohanzadeh ◽  
D. Auston
Keyword(s):  
Frequency Shift ◽  
Beat Frequency ◽  
Absorption Coefficients ◽  
Transverse Modes

On Quantifying Detectable Fatigue Crack Size in Aluminum Beams Using Vibration and Impedance-Based Methods

2009 ◽  
Author(s):  
Mana Afshari ◽  
Brad A. Butrym ◽  
Daniel J. Inman
Keyword(s):  
Fatigue Crack ◽  
Frequency Shift ◽  
Electrical Impedance ◽  
Fatigue Cracks ◽  
Beat Frequency ◽  
Crack Size ◽  
Beam Model ◽  
Bernoulli Beam ◽  
Frequency Method ◽  
Euler Bernoulli Beam

This paper looks at the impedance-based and vibration methods used for the structural health monitoring (SHM) of aluminum beams and attempts to quantify the smallest fatigue crack size that is detectable by these two methods. The vibration-based method presented in this paper, uses the recent model of Aydin [1] which is based on a simple Euler-Bernoulli beam model. This method treats cracks as localized reduction in the beam’s stiffness and models them as massless rotational springs at the locations of the cracks. The beam is then considered to be of multiple sections connected by these springs. The beam studied in the present work is assumed to be an aluminum, uniform, Euler-Bernoulli beam having a single fatigue crack and being axially loaded. It is further assumed that frequencies can only be measured to within half a Hertz. This results in formulas that can be used to predict specific detectable sizes of fatigue cracks given specific geometry of the beam. For example for a beam of dimension 240×19.1×4.8 mm, it is found that the fatigue crack must be approximately 12.5% of the beam width in order to induce a frequency shift of 0.5 Hz. In the second part of this paper, different sets of experiments are conducted on aluminum beams. First, saw-cuts are made in the beams and the resultant shift in the beams’ natural frequency is examined to find the minimum detectable cut length. In order to improve this minimum detectable damage size, the beat frequency method is applied, which enhances the minimum detectable frequency shift. These results are then compared to those of the electrical impedance measurements through the HP 4194A Impedance analyzer. At the end, the aluminum beams are being fatigued and by measuring their electrical impedance at different numbers of fatigue cycling, their detectable fatigue crack size is investigated.

scholarly journals Investigation on the Formation of Laser Transverse Pattern Possessing Optical Lattices

2022 ◽  
Vol 9 ◽  
Author(s):  
Xin Wang ◽  
Zilong Zhang ◽  
Yuan Gao ◽  
Suyi Zhao ◽  
Yuchen Jie ◽  
...  
Keyword(s):  
Optical Lattices ◽  
Beat Frequency ◽  
Transverse Mode ◽  
Mode Locking ◽  
Vortex Lattices ◽  
Transverse Modes ◽  
Fixed Phase ◽  
Phase Singularities ◽  
Complex Symmetric ◽  
Transverse Pattern

Optical lattices (OLs) with diverse transverse patterns and optical vortex lattices (OVLs) with special phase singularities have played important roles in the fields of atomic cooling, particle manipulation, quantum entanglement, and optical communication. As a matter of consensus until now, the OL patterns are generated by coherently superimposing multiple transverse modes with a fixed phase difference through the transverse mode locking (TML) effect. There are phase singularities in the dark area of this kind of OL pattern, so it is also called OVL pattern. However, in our research, it is found that some high-order complex symmetric OL patterns can hardly be analyzed by TML model. Instead, the analysis method of incoherent superposition of mode intensity could be applied. The OL pattern obtained by this method can be regarded as in non-TML state. Therefore, in this article, we mainly study the distinct characteristics and properties of OL patterns in TML and non-TML states. Through intensity comparison, interferometry, and beat frequency spectrum, we can effectively distinguish OL pattern in TML and non-TML states, which is of significance to explore the formation of laser transverse pattern possessing OL.

Ciliary coordination in newt lung cells requires microtubule-based linkages between basal bodies: A correlative light and EM study

1992 ◽  
Vol 50 (1) ◽  
pp. 570-571
Author(s):  
Robert Hard ◽  
Gerald Rupp ◽  
Matthew L. Withiam-Leitch ◽  
Lisa Cardamone
Keyword(s):  
Basal Body ◽  
Untreated Control ◽  
Beat Frequency ◽  
Primary Cultures ◽  
Living Cells ◽  
Power Stroke ◽  
Ultrastructural Changes ◽  
Lung Cells ◽  
Basal Bodies ◽  
Ciliated Cells

In a coordinated field of beating cilia, the direction of the power stroke is correlated with the orientation of basal body appendages, called basal feet. In newt lung ciliated cells, adjacent basal feet are interconnected by cold-stable microtubules (basal MTs). In the present study, we investigate the hypothesis that these basal MTs stabilize ciliary distribution and alignment. To accomplish this, newt lung primary cultures were treated with the microtubule disrupting agent, Colcemid. In newt lung cultures, cilia normally disperse in a characteristic fashion as the mucociliary epithelium migrates from the tissue explant. Four arbitrary, but progressive stages of dispersion were defined and used to monitor this redistribution process. Ciliaiy beat frequency, coordination, and dispersion were assessed for 91 hrs in untreated (control) and treated cultures. When compared to controls, cilia dispersed more rapidly and ciliary coordination decreased markedly in cultures treated with Colcemid (2 mM). Correlative LM/EM was used to assess whether these effects of Colcemid were coupled to ultrastructural changes. Living cells were defined as having coordinated or uncoordinated cilia and then were processed for transmission EM.

Interfacial properties of GaSb/InAs superlattices

1993 ◽  
Vol 51 ◽  
pp. 826-827
Author(s):  
M. E. Twigg ◽  
B. R. Bennett ◽  
J. R. Waterman ◽  
J. L. Davis ◽  
B. V. Shanabrook ◽  
...  
Keyword(s):  
Gaas Substrate ◽  
Molecular Beam ◽  
Infrared Detector ◽  
Interfacial Properties ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
Absorption Coefficients ◽  
X Ray ◽  
Short Period ◽  
High Optical Absorption

Recently, the GaSb/InAs superlattice system has received renewed attention. The interest stems from a model demonstrating that short period Ga1-xInxSb/InAs superlattices will have both a band gap less than 100 meV and high optical absorption coefficients, principal requirements for infrared detector applications. Because this superlattice system contains two species of cations and anions, it is possible to prepare either InSb-like or GaAs-like interfaces. As such, the system presents a unique opportunity to examine interfacial properties.We used molecular beam epitaxy (MBE) to prepare an extensive set of GaSb/InAs superlattices grown on an GaSb buffer, which, in turn had been grown on a (100) GaAs substrate. Through appropriate shutter sequences, the interfaces were directed to assume either an InSb-like or GaAs-like character. These superlattices were then studied with a variety of ex-situ probes such as x-ray diffraction and Raman spectroscopy. These probes confirmed that, indeed, predominantly InSb-like and GaAs-like interfaces had been achieved.

Role of the Cilia Membrane in Control of Microtubule Sliding

1980 ◽  
Vol 38 ◽  
pp. 612-615
Author(s):  
Edna S. Kaneshiro
Keyword(s):  
Control Mechanism ◽  
Beat Frequency ◽  
Surface Membrane ◽  
Ciliary Membrane ◽  
Ciliary Beating ◽  
Ciliary Reversal ◽  
Voltage Dependent ◽  
Reversal Mechanism ◽  
And Function

It is currently believed that ciliary beating results from microtubule sliding which is restricted in regions to cause bending. Cilia beat can be modified to bring about changes in beat frequency, cessation of beat and reversal in beat direction. In ciliated protozoans these modifications which determine swimming behavior have been shown to be related to intracellular (intraciliary) Ca2+ concentrations. The Ca2+ levels are in turn governed by the surface ciliary membrane which exhibits increased Ca2+ conductance (permeability) in response to depolarization. Mutants with altered behaviors have been isolated. Pawn mutants fail to exhibit reversal of the effective stroke of ciliary beat and therefore cannot swim backward. They lack the increased inward Ca2+ current in response to depolarizing stimuli. Both normal and pawn Paramecium made leaky to Ca2+ by Triton extrac¬tion of the surface membrane exhibit backward swimming only in reactivating solutions containing greater than IO-6 M Ca2+ Thus in pawns the ciliary reversal mechanism itself is left operational and only the control mechanism at the membrane is affected. The topographic location of voltage-dependent Ca2+ channels has been identified as a component of the ciliary mem¬brane since the inward Ca2+ conductance response is eliminated by deciliation and the return of the response occurs during cilia regeneration. Since the ciliary membrane has been impli¬cated in the control of Ca2+ levels in the cilium and therefore is the site of at least one kind of control of microtubule sliding, we have focused our attention on understanding the structure and function of the membrane.

On a new method in spectroscopy : laser-induced frequency shift of self-excited ion oscillations

1992 ◽  
Vol 2 (7) ◽  
pp. 1367-1372
Author(s):  
R. C. Bobulescu ◽  
M. A. Brǎtescu ◽  
C. Stǎnciulescu ◽  
G. Musa
Keyword(s):  
Frequency Shift ◽  
New Method ◽  
Spectroscopy Laser
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