scholarly journals Improvement of Detection Sensitivity of Microbubbles as Sensors to Detect Ambient Pressure

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4083 ◽  
Author(s):  
Fei Li ◽  
Deyu Li ◽  
Fei Yan
Keyword(s):  
Scattering Amplitude ◽  
Ambient Pressure ◽  
Pressure Variation ◽  
Detection Sensitivity ◽  
Mechanical Index ◽  
Pressure Sensitivity ◽  
Acoustic Parameters ◽  
Promising Tool ◽  
Noninvasive Estimation ◽  
The Media

Microbubbles are considered a promising tool for noninvasive estimation of local blood pressure. It is reported that the subharmonic scattering amplitude of microbubbles decreases by 9 to 12 dB when immersed in the media under an ambient pressure variation from 0 to 180 mmHg. However, the pressure sensitivity still needs to be improved to satisfy clinical diagnostic requirements. Here, we investigated the effects of acoustic parameters on the pressure sensitivity of microbubbles through measuring the acoustic attenuation and scattering properties of commercially available SonoVue microbubbles. Our results showed that the first harmonic, subharmonic, and ultraharmonic amplitudes of microbubbles were reduced by 6.6 dB, 10.9 dB, and 9.3 dB at 0.225 mechanical index (MI), 4.6 dB, 19.8 dB, and 12.3 dB at 0.25 MI, and 18.5 dB, 17.6 dB, and 12.6 dB at 0.3 MI, respectively, when the ambient pressure increased from 0 to 180 mmHg. Our finding revealed that a moderate MI (0.25–0.4) exciting microbubbles could significantly improve their sensitivities to detect ambient pressure.

scholarly journals IMPACT PRESSURES PRODUCED BY BREAKING WAVES

1974 ◽  
Vol 1 (14) ◽  
pp. 104 ◽  
Author(s):  
Norbert L. Ackerman ◽  
Ping-Ho Chen
Keyword(s):  
Water Surface ◽  
Ambient Pressure ◽  
Pressure Rise ◽  
Breaking Waves ◽  
Absolute Pressure ◽  
Maximum Pressure ◽  
Sound Waves ◽  
The Media ◽  
Entrapped Air ◽  
Entrained Air

Experiments were conducted in a vacuum tank in order to investigate the effect which entrained air has on impact loads which are produced when waves break upon a structure. In these experiments a flat plate was dropped onto a still water surface in an environment where the ambient pressure of the surrounding air could be controlled. Rings of varying height were fixed to the surface of the falling plate in order to trap different volumes of air between the falling plate and the water, Experimentally determined values were obtained of the maximum pressure pmax when the plate struck the water surface for various ring heights 6 and ambient pressures p0 in the vacuum tank. Experimental results indicate that the pressure rise or shock pressure Ps ~ (Pmax~Po) decreased with reductions in the ambient pressure and volume of entrapped air. Even when air was removed such that the absolute pressure in the tank was equal to the vapor pressure of the water, water hammer conditions, where the peak pressures depend upon the celerity of sound waves in the media, were never found to occur.

scholarly journals Observation of Pressure Variation in the Cavitation Region of Submerged Journal Bearings

1982 ◽  
Vol 104 (2) ◽  
pp. 157-163 ◽  
Author(s):  
I. Etsion ◽  
L. P. Ludwig
Keyword(s):  
Journal Bearing ◽  
Reverse Flow ◽  
Ambient Pressure ◽  
Journal Bearings ◽  
Pressure Variation ◽  
Pressure Measurements ◽  
Pressure Profiles ◽  
Cavitation Region ◽  
Cavitation Pressure ◽  
Visual Observations

Visual observations and pressure measurements in the cavitation zone of a submerged journal bearing are described. Tests were performed at various shaft speeds and ambient pressure levels. Some photographs of the cavitation region are presented showing strong reverse flow at the downstream end of the region. Pressure profiles are presented showing significant pressure variations inside the cavitation zone, contrary to common assumptions of constant cavitation pressure.

Measurement Technique for Unsteady Low-Speed Flow Fields Using Poly(TMSP)-Based Pressure Sensitive Paint

2015 ◽  
Author(s):  
Hideo Mori ◽  
Kyohei Maeda ◽  
Masato Furukawa ◽  
Masao Akiyoshi
Keyword(s):  
Flow Field ◽  
Pressure Variation ◽  
Aerodynamic Noise ◽  
Pressure Sensitivity ◽  
Pressure Sensitive Paint ◽  
Oxygen Quenching ◽  
Low Speed ◽  
Pressure Sensitive ◽  
Speed Flow ◽  
Polymer Type

Nonstationary analysis of flow field is required to detect the source of aerodynamic noise, in order to accomplish the reduction of aerodynamic noise in life environment, including low-frequency noise, which may be harmful for human health. Pressure sensitive paint (PSP) is a quantitative pressure visualization technique on solid surfaces based on oxygen quenching of luminescent molecule. Polymer-type PSP composed of PtTFPP, a luminescent molecule with high oxygen quenching probability, and poly(TMSP), a glassy polymer with high oxygen permeability, has high pressure sensitivity for low-speed flow field. However, the pressure sensitivity of the polymer-type PSP for nonstationary pressure change has not been examined enough. In this study, we investigate the time response of the poly(TMSP)-based PSP, to evaluate the feasibility of the polymer-type PSP as a measurement tool for nonstationary low-speed flows, when the frequency of pressure fluctuation is relatively low. Because response time of polymer-type PSP is proportional to the square of the thickness of the PSP layer, we prepare thinner-layer PSP to increase the response speed by reducing the amount of polymer. The polymer-type PSP is applied to measurement of nonstationary pressure distribution around a circular cylinder in low-speed flow, and compare the amplitude spectra of PSP and that of pressure probe, which are obtained by FFT analysis. As a result it is clarified that the sensitivity of the PSP for pressure variation lower than 100Hz is as high as that for stationary pressure. For pressure variation higher than 100Hz the sensitivity decreases as the frequency of pressure variation increases, but pressure variation with the amplitude of about 300Pa can be detected by the poly(TMSP)-based PSP even if the frequency is as high as 850Hz. Furthermore we have visualized the distribution of the integrated intensity of the PSP amplitude spectrum around the peak, to visualize the area with large pressure variation on the cylinder surface.

scholarly journals Pre-deliquescent water uptake in deposited nanoparticles observed with in situ ambient pressure X-ray photoelectron spectroscopy

2021 ◽  
Vol 21 (6) ◽  
pp. 4709-4727
Author(s):  
Jack J. Lin ◽  
Kamal Raj R ◽  
Stella Wang ◽  
Esko Kokkonen ◽  
Mikko-Heikki Mikkelä ◽  
...  
Keyword(s):  
Sodium Chloride ◽  
Water Uptake ◽  
Malonic Acid ◽  
Atmospheric Chemistry ◽  
Photoelectron Spectroscopy ◽  
Ambient Pressure ◽  
Aerosol Particles ◽  
Particle Surface ◽  
Detection Sensitivity ◽  
X Ray

Abstract. We study the adsorption of water onto deposited inorganic sodium chloride and organic malonic acid and sucrose nanoparticles at ambient water pressures corresponding to relative humidities (RH) from 0 % to 16 %. To obtain information about water adsorption at conditions which are not accessible with typical aerosol instrumentation, we use surface-sensitive ambient pressure X-ray photoelectron spectroscopy (APXPS), which has a detection sensitivity starting at parts per thousand. Our results show that water is already adsorbed on sodium chloride particles at RH well below deliquescence and that the chemical environment on the particle surface is changing with increasing humidity. While the sucrose particles exhibit only very modest changes on the surface at these relative humidities, the chemical composition and environment of malonic acid particle surfaces is clearly affected. Our observations indicate that water uptake by inorganic and organic aerosol particles could already have an impact on atmospheric chemistry at low relative humidities. We also establish the APXPS technique as a viable tool for studying chemical changes on the surfaces of atmospherically relevant aerosol particles which are not detected with typical online mass- and volume-based methods.

Comparative Study on Sensing Characteristics of Optical Surface Plasmon Resonance Sensors Using A Single LHM-Dielectric Interface: A Theoretical Study

2021 ◽  
Author(s):  
benamar bouhafs ◽  
Abdellatif CHERIFI
Keyword(s):  
Surface Plasmon Resonance ◽  
Surface Plasmon ◽  
Plasmon Resonance ◽  
Detection Sensitivity ◽  
Planar Surface ◽  
Surface Sensitivity ◽  
Left Handed ◽  
The Media ◽  
The Impact ◽  
Sensing Characteristics

Abstract This work addresses a theoretical analysis on optical planar surface plasmon resonance (SPR) sensors. The proposed plasmonic system consists of an active left-handed material (LHM) stacked between a glass-prism and a sensing environment. To evaluate the limits of the surface sensitivity related to SPR excitation, two arrangements between previous media are separately investigated for comparison. Employing the transfer matrix method (TMM), angular TM-reflectance calculations and intrinsic sensing characteristics of previous arrangements, have been investigated with the impact of thicknesses and refractive index (RI) of the media involved. We found the suitable prism material RI, and the preferential arrangement between LHM and sensing environment allowing, thus the increase of the detection sensitivity of SPR excitation. The results of TM-reflectance obtained by varying the sensing environment RI, indicate the ability of the configuration to support an surface plasmon (SP) mode, with a tunable Q-factor from 72 to 748. In addition, distinct optical functionalities achieved with the proposed mono-layer LHM system exhibiting a single SPR mode, and multiple resonant oscillations, are highlighted on both the effects of RI and structure ‘thicknesses. Finally, the relationships between characteristics of TM-reflectance spectra versus the performance parameters are analytically derived.

Disk Protrusion Measurement in a Back-Heating Study for Heat Assisted Magnetic Recording

2020 ◽  
Author(s):  
Shaomin Xiong ◽  
Robert Smith ◽  
Erhard Schreck
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Local Heating ◽  
Hard Disk Drives ◽  
Detection Sensitivity ◽  
Experimental Setup ◽  
Heat Assisted Magnetic Recording ◽  
Management Scheme ◽  
The Media ◽  
Disk Spacing

Abstract Heat assisted magnetic recording (HAMR) is a promising technology for the next generation hard disk drives (HDDs). Understanding the heat transfer at nanoscales and implementing a proper thermal management scheme become very critical as a few heat sources and energy delivery components are compactly integrated in a HAMR drive. Recently, a back-heating experimental setup is used to study heat transfer behavior. It is found that the detection of head disk contact and head disk spacing control become more complicated in this experimental setup because the local heating generates a protrusion on the media surface. In this paper, we demonstrate a method to enhance the contact detection sensitivity significantly by modulating the head disk spacing. It shows that a light contact between the head TFC protrusion and media protrusion can be effectively detected. Thereafter, the media protrusion can be measured and the head disk spacing can be well set.

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