scholarly journals Electro-acustic influence of the measuring system on the photoacoustic signal amplitude and phase in frequency domain

2016 ◽  
Vol 14 (1) ◽  
pp. 9-20 ◽  
Author(s):  
Sanja Aleksic ◽  
Dragana Markushev ◽  
Dragan Pantic ◽  
Mihajlo Rabasovic ◽  
Dragan Markushev ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Flicker Noise ◽  
Modulation Frequency ◽  
Signal Amplitude ◽  
Photoacoustic Signal ◽  
Measuring System ◽  
Coherent Noise ◽  
Characteristic Frequencies ◽  
Signal Distortions ◽  
Set Up

The paper discusses the most common impacts of the measuring system on the amplitude and phase of the photoacoustic signals in the frequency domain using the open-cell experimental set-up. The highest signal distortions are detected at the ends of the observed modulation frequency range from 20 Hz to 20 kHz. The attenuation of the signal is observed at lower frequencies, caused by the electronic filtering of the microphone and sound card, with characteristic frequencies of 15 Hz and 25 Hz. At higher frequencies, the dominant signal distortions are caused by the microphone acoustic filtering, having characteristic frequencies around 9 kHz and 15 kHz. It has been found that the microphone incoherent noise, the so called flicker noise, is negligibly small in comparison to the signal and does not affect the signal shape. However, a coherent noise originating from the power modulation system of the light source significantly affects the shape of the signal in the range greater than 10 kHz. The effects of the coherent noise and measuring system influence are eliminated completely using the relevant signal correction procedure targeting the photoacoustic signal generated by the sample.

scholarly journals In-Line Analysis of Diffusion Processes in Micro Channels by Long Distance Raman Photometric Measurement Technology—A Proof of Concept Study

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 116
Author(s):  
Julian Deuerling ◽  
Shaun Keck ◽  
Inasya Moelyadi ◽  
Jens-Uwe Repke ◽  
Matthias Rädle
Keyword(s):  
Numerical Aperture ◽  
Spot Size ◽  
Measuring System ◽  
Optical Systems ◽  
Measurement Technology ◽  
Long Distance ◽  
Measuring Point ◽  
Acetone Concentration ◽  
Micro Channels ◽  
Set Up

This work presents a novel method for the non-invasive, in-line monitoring of mixing processes in microchannels using the Raman photometric technique. The measuring set-up distinguishes itself from other works in this field by utilizing recent state-of-the-art customized photon multiplier (CPM) detectors, bypassing the use of a spectrometer. This addresses the limiting factor of integration times by achieving measuring rates of 10 ms. The method was validated using the ternary system of toluene–water–acetone. The optical measuring system consists of two functional units: the coaxial Raman probe optimized for excitation at a laser wavelength of 532 nm and the photometric detector centered around the CPMs. The spot size of the focused laser is a defining factor of the spatial resolution of the set-up. The depth of focus is measured at approx. 85 µm with a spot size of approx. 45 µm, while still maintaining a relatively high numerical aperture of 0.42, the latter of which is also critical for coaxial detection of inelastically scattered photons. The working distance in this set-up is 20 mm. The microchannel is a T-junction mixer with a square cross section of 500 by 500 µm, a hydraulic diameter of 500 µm and 70 mm channel length. The extraction of acetone from toluene into water is tracked at an initial concentration of 25% as a function of flow rate and accordingly residence time. The investigated flow rates ranged from 0.1 mL/min to 0.006 mL/min. The residence times from the T-junction to the measuring point varies from 1.5 to 25 s. At 0.006 mL/min a constant acetone concentration of approx. 12.6% was measured, indicating that the mixing process reached the equilibrium of the system at approx. 12.5%. For prototype benchmarking, comparative measurements were carried out with a commercially available Raman spectrometer (RXN1, Kaiser Optical Systems, Ann Arbor, MI, USA). Count rates of the spectrophotometer surpassed those of the spectrometer by at least one order of magnitude at identical target concentrations and optical power output. The experimental data demonstrate the suitability and potential of the new measuring system to detect locally and time-resolved concentration profiles in moving fluids while avoiding external influence.

scholarly journals Contactless Monitoring of Breathing Patterns and Respiratory Rate at the Pit of the Neck: A Single Camera Approach

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Carlo Massaroni ◽  
Daniel Simões Lopes ◽  
Daniela Lo Presti ◽  
Emiliano Schena ◽  
Sergio Silvestri
Keyword(s):  
Respiratory Rate ◽  
Frequency Domain ◽  
Time Domain ◽  
Breathing Pattern ◽  
Vital Signs ◽  
Image Resolution ◽  
Measuring System ◽  
Respiratory Pattern ◽  
Breathing Patterns ◽  
Vital Signs Monitoring

Vital signs monitoring is pivotal not only in clinical settings but also in home environments. Remote monitoring devices, systems, and services are emerging as tracking vital signs must be performed on a daily basis. Different types of sensors can be used to monitor breathing patterns and respiratory rate. However, the latter remains the least measured vital sign in several scenarios due to the intrusiveness of most adopted sensors. In this paper, we propose an inexpensive, off-the-shelf, and contactless measuring system for respiration signals taking as region of interest the pit of the neck. The system analyses video recorded by a single RGB camera and extracts the respiratory pattern from intensity variations of reflected light at the level of the collar bones and above the sternum. Breath-by-breath respiratory rate is then estimated from the processed breathing pattern. In addition, the effect of image resolution on monitoring breathing patterns and respiratory rate has been investigated. The proposed system was tested on twelve healthy volunteers (males and females) during quiet breathing at different sensor resolution (i.e., HD 720, PAL, WVGA, VGA, SVGA, and NTSC). Signals collected with the proposed system have been compared against a reference signal in both the frequency domain and time domain. By using the HD 720 resolution, frequency domain analysis showed perfect agreement between average breathing frequency values gathered by the proposed measuring system and reference instrument. An average mean absolute error (MAE) of 0.55 breaths/min was assessed in breath-by-breath monitoring in the time domain, while Bland-Altman showed a bias of −0.03 ± 1.78 breaths/min. Even in the case of lower camera resolution setting (i.e., NTSC), the system demonstrated good performances (MAE of 1.53 breaths/min, bias of −0.06 ± 2.08 breaths/min) for contactless monitoring of both breathing pattern and breath-by-breath respiratory rate over time.

Surface Displacement Measurement of Soil Mass by White Light Digital Image Analysis in Frequency Domain

2014 ◽  
Vol 915-916 ◽  
pp. 1234-1237
Author(s):  
Jun Jun Li ◽  
Xin Wei Yang ◽  
Wen Guang Shi
Keyword(s):  
Image Analysis ◽  
Frequency Domain ◽  
Digital Image ◽  
White Light ◽  
Digital Image Analysis ◽  
Surface Displacement ◽  
Soil Mass ◽  
Measuring System ◽  
Surface Displacements ◽  
Simple Measuring

The surface displacement of soil mass is an important standard for safety in civil engineering. In this paper, white light digital image analysis in frequency domain is introduced tomeasure surface displacement of soil mass. This method has the characteristics of whole-field, non-contact measurement and the simple measuring system and can obtain displacements by frequency domination correlation arithmetic. Surface displacements of soil mass are obtained by white light digital image analysis in frequency domain. Comparing the experimental results and the theoretical values, the little error exists and the usefulness of this method is certified.

scholarly journals Photon Phase Shift Imaging Research on Frequency Domain Diffuse Optic Tomography

2021 ◽  
Author(s):  
huseyin ozgur kazanci
Keyword(s):  
Phase Shift ◽  
Frequency Domain ◽  
Laser Intensity ◽  
Model Problem ◽  
Modulation Frequency ◽  
Forward Model ◽  
Problem Solution ◽  
Inverse Problem Solution ◽  
Phase Data ◽  
Cartesian Coordinate

Abstract Diffuse optic imaging is an important biomedical optic research tool. Diffuse optic tomography (DOT) modality needs progressive philosophical approaches for scientific contribution. Technological developments and philosophical approaches should both go forward. Phase-shift based frequency domain (FD) diffuse optical tomography (FDDOT) method was well established in the literature. The instruments were tested for brain neurofunctional imaging. A mixture of AC laser intensity and phase data were used at these works. According to those works; deep volume resolution was improved by only using phase data. Because phase data is only related to the photon mean free path in imaging tissue media. Besides this advantage, laser intensity data is also affected by noisy background light and electrical artifacts. Another most important advantage of only using phase data can be explained as time-resolved temporal change can be directly related to phase shift of modulated frequency source. At this work, the frequency domain (FD) DOT imaging method which uses phase shift data were used for simulation phantom. Laser source-driven forward model problem weight matrix simulation data was given to the simple pseudo-inverse-based inverse problem solution algorithm for one inclusion example. The inclusion image was reconstructed and demonstrated successfully. Forward model problem weight functions inside the tissue simulation media were calculated and used based on the phase shifts at the same core modulation frequency. 100 MHz modulation frequency was selected due to its FDDOT standard. 13 sources and 13 detectors were placed on the back-reflected imaging surface. 40 x, y, z cartesian coordinate grid elements were used in the image reconstruction algorithm. Photon absorption coefficient: ma = 0.1 cm-1, and scattering coefficient: ms = 100 cm-1 values were set for background simulation phantom. One inclusion object was embedded inside the imaging tissue simulation phantom background. x, y, z cartesian coordinate grid sizes were selected for 100 mm for each direction. Photon phase shift fluencies were added to the forward model problem. The forward model problem was built according to the frequency domain photon migration diffusion approximation. Forward model problem photon fluencies were calculated according to the diffusion equation approximation. The simple pseudoinverse mathematical inverse problem solution algorithm was applied to test the results. The embedded inclusion object was reconstructed successfully with the high-resolution image quality. In general, DOT techniques suffer for the low image quality, but in this work, the high-quality image was reconstructed and demonstrated. The philosophical approach has future promising DOT imaging capability. The phase shift version of the FDDOT modality has an important advantage for future purpose.

scholarly journals Gamma spectrometry technique for the determination of residence time in Submarine Groundwater Discharges

2019 ◽  
Vol 18 ◽  
pp. 155
Author(s):  
G. Eleftheriou ◽  
C. Tsabaris ◽  
D. L. Patiris ◽  
E. Androulakaki ◽  
M. Kokkoris ◽  
...  
Keyword(s):  
Residence Time ◽  
Water Samples ◽  
Gamma Ray ◽  
Measuring System ◽  
Gamma Ray Spectrometry ◽  
Reference Source ◽  
Radium Isotopes ◽  
Time Period ◽  
Submarine Groundwater ◽  
Set Up

The evaluation of time period that meteoric water remains in the ground (residence time) before exiting in the open sea can be a valuable information for the submarine groundwater discharges (SGD) in the costal zones. Coastal waters contain elevated dissolved activities of radium isotopes compared to the open ocean, where excess activities are zero. Lately it has been shown by Moore et al., that residence time can be estimated by a model based on radium radioisotopes ratio reduction throughout the coast. However the standard methods for the estimation of radium isotopes concentration in the water are sophisticated, time consuming or require big amount of sample. Hereby, a method based on the direct gamma ray spectrometry of untreated water samples from coastal areas is applied to determine the residence time of the SGD. Efficiency calibration of the spectrometry set up has been performed for two different volumetric sample geometries, using 152Eu/154Eu solution as reference source. In order to ensure the reliability of the method, the background courting rate magnitude and variance through time have been defined for the radioisotopes of interest. Additionally, the minimum detectible activity (MDA) of the measuring system was determined, in Becquerel per cubic meter, as a function of energy in water samples. The developed method was applied and validated for water samples from the submarine spring in Stoupa Bay, southwestern Peloponnesus. The defined residence time varies from 3 to 6 days, being in good agreement with the results of the standard geological pigment-tracer method.

A procedure for optimally removing localized coherent noise

Geophysics ◽  
1995 ◽  
Vol 60 (1) ◽  
pp. 191-203 ◽  
Author(s):  
A. Frank Linville ◽  
Robert A. Meek
Keyword(s):  
Seismic Data ◽  
Seismic Profile ◽  
Noise Attenuation ◽  
Signal Distortion ◽  
Coherent Noise ◽  
Vertical Seismic Profile ◽  
Seismic Records ◽  
Signal Distortions ◽  
Notch Filtering ◽  
Phase Differences

Primary reflections in seismic records are often obscured by coherent noise making processing and interpretation difficult. Trapped water modes, surface waves, scattered waves, air waves, and tube waves to name a few, must be removed early in the processing sequence to optimize subsequent processing and imaging. We have developed a noise canceling algorithm that effectively removes many of the commonly encountered noise trains in seismic data. All currently available techniques for coherent noise attenuation suffer from limitations that introduce unacceptable signal distortions and artifacts. Also, most of those techniques impose the dual stringent requirements of equal and fine spatial sampling in the field acquisition of seismic data. Our technique takes advantage of characteristics usually found in coherent noise such as being localized in time, highly aliased, nondispersive (or only mildly so), and exhibit a variety of moveout patterns across the seismic records. When coherent noise is localized in time, a window much like a surgical mute is drawn around the noise. The algorithm derives an estimate of the noise in the window, automatically correcting for amplitude and phase differences, and adaptively subtracts this noise from the window of data. This signal estimate is then placed back in the record. In a model and a land data example, the algorithm removes noise more effectively with less signal distortion than does f-k filtering or velocity notch filtering. Downgoing energy in a vertical seismic profile (VSP) with irregular receiver spacing is also removed.

ENHANCEMENT OF GREEN ALGAE HYDROGEN PRODUCTION BY LASER IRRADIATION

2016 ◽  
Vol 78 (3) ◽  
Author(s):  
Mohamad Aizat Abu Bakar ◽  
Noriah Bidin
Keyword(s):  
Diode Laser ◽  
Green Algae ◽  
Capillary Tube ◽  
Red Light ◽  
Wild Strain ◽  
Gas Production ◽  
Hydrogen Gas ◽  
Measuring System ◽  
Red Light Laser ◽  
Set Up

Biohydrogen is an alternative to support the increasing hydrogen demand in the future. Biohydrogen is hydrogen gas produced by green algae and bacteria in certain quantity. The aim of this research is to enhance hydrogen gas production by green algae (Closterium sp.) using laser light. The laser used in this experiment was a diode laser operating in continuous mode with wavelength of 655 nm. Green algae are placed in a sulphur deprived medium so it will produce hydrogen gas. This algae is irradiated with diode laser for 30 minutes then stop before continue for the next 30 minutes. This process is repeated until the total irradiation is 120 minutes. Both strains of green algae are set up into measuring system under exposure of sunlight in a constant room temperature. The volume and rate of hydrogen gas produced is examined by measuring the dye position in capillary tube of 0.5 mm radius. The results showed that there is a 9.0% increase of hydrogen gas production in radiated strain of green algae compared to the wild strain. The rate of hydrogen gas production of radiated algae is faster than the wild strain. This showed that, red light laser has absorbed cell green algae and mutated its behaviour for producing more hydrogen gas. This result is in good agreement with other researcher.  

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