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1
Dong, Wei, Zi Wei Zhou, and Zheng Gan Zhou. "Application of Phase-Sensitivity Detector in Air-Coupled Ultrasonic Testing." Applied Mechanics and Materials 170-173 (May 2012): 3125–29. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.3125.
Повний текст джерелаАнотація:
The signal to noise ration of air-coupled ultrasonic testing is very poor and there is long time pulse residue, so it need adopt appropriate signal processing method to enhancing the SNR of received signal. Factors, which affect the received signal in ultrasonic testing process, is analyzed, phase sensitivity detection technology is presented to process the received signal, and ultrasonic testing information can be acquired by the calculation of phase signal. The principle of super-heterodyne receiver and phase sensitivity detector is introduced; some problem which should be pay attention in ultrasonic testing process is explained. Based on the research result, air-coupled ultrasonic testing system with phase sensitivity detector is constituted. Experiment results of image testing on carbon fiber reinforced plastic plate indicated that, phase sensitivity detection technology can improved signal to noise ratio of system and testing effect in evidence.
2
Mehmet, Moritz, and Henning Vahlbruch. "The Squeezed Light Source for the Advanced Virgo Detector in the Observation Run O3." Galaxies 8, no. 4 (November 26, 2020): 79. http://dx.doi.org/10.3390/galaxies8040079.
Повний текст джерелаАнотація:
From 1 April 2019 to 27 March 2020, the Advanced Virgo detector, together with the two Advanced LIGO detectors, conducted the third joint scientific observation run O3, aiming for further detections of gravitational wave signals from astrophysical sources. One of the upgrades to the Virgo detector for O3 was the implementation of the squeezed light technology to improve the detector sensitivity beyond its classical quantum shot noise limit. In this paper, we present a detailed description of the optical setup and performance of the employed squeezed light source. The squeezer was constructed as an independent, stand-alone sub-system operated in air. The generated squeezed states are tailored to exhibit high purity at intermediate squeezing levels in order to significantly reduce the interferometer shot noise level while keeping the correlated enhancement of quantum radiation pressure noise just below the actual remaining technical noise in the Advanced Virgo detector.
3
Schulze-Briese, Clemens. "Hybrid photon-counting detectors accelerating synchrotron and laboratory science." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C692. http://dx.doi.org/10.1107/s2053273314093073.
Повний текст джерелаАнотація:
Since their introduction in 2007, single-photon-counting PILATUS hybrid pixel detectors and MYTHEN micro-strip detectors have transformed synchrotron research by enabling new data acquisition modes and even novel experiments. At the same time data quality has improved due to the noise-free operation and the direct conversion of the X-rays, while millisecond readout time and high-frame rates allow for hitherto unknown data acquisition speed and efficiency. Instant retrigger technology, introduced in 2012 with the PILATUS3 further improves the count-rate capabilities to 107 photons/sec/pixel, allowing single photon counting at brightest synchrotron beamlines. On the other hand, the unique properties of these detectors have also been explored to improve and accelerate diffraction and scattering experiments in the laboratory. The noise-free operation is a key advantage in combination with the low-flux laboratory sources, allowing for high-throughput and optimal data quality. The modular architecture of the detectors and the vacuum-compatibility of the PILATUS detector modules are ideal prerequisites to design specific detector solutions. In-vacuum operation is ideally suited to eliminate all background arising from windows and air, resulting in optimal signal-to-noise ratio. Furthermore, the lowest accessible X-ray energy is no longer limited by windows and air absorption but rather by the beamline spectrum and the detector. The minimal X-ray energy compatible with noise-free counting for the PILATUS is below 2 keV. With EIGER, hybrid pixel detectors will enter into a new realm of spatial and temporal resolution. Continuous read-out with frame rates up to 3000 Hz and a pixel size of 75 µm are ideally suited for all scanning type of imaging experiments, time-resolved and high-throughput experiments as well as for outrunning radiation damage. A short overview of the novel aspects of the detector technology will be given. The main emphasize of the presentation will be on the science enabled by the combination of advanced source, optics and detector instrumentation.
4
Dougakiuchi, Tatsuo, and Naota Akikusa. "Application of High-Speed Quantum Cascade Detectors for Mid-Infrared, Broadband, High-Resolution Spectroscopy." Sensors 21, no. 17 (August 24, 2021): 5706. http://dx.doi.org/10.3390/s21175706.
Повний текст джерелаАнотація:
Broadband, high-resolution, heterodyne, mid-infrared absorption spectroscopy was performed with a high-speed quantum cascade (QC) detector. By strictly reducing the device capacitance and inductance via air-bridge wiring and a small mesa structure, a 3-dB frequency response over 20 GHz was obtained for the QC detector, which had a 4.6-μm peak wavelength response. In addition to the high-speed, it exhibited low noise characteristics limited only by Johnson–Nyquist noise, bias-free operation without cooling, and photoresponse linearity over a wide dynamic range. In the detector characterization, the noise-equivalent power was 7.7 × 10−11 W/Hz1/2 at 4.6 μm, and it had good photoresponse linearity up to 250 mW, with respect to the input light power. Broadband and high-accuracy molecular spectroscopy based on heterodyne detection was demonstrated by means of two distributed-feedback 4.5-μm QC lasers. Specifically, several nitrous oxide absorption lines were acquired over a wavelength range of 0.8 cm−1 with the wide-band QC detector.
5
Trozzo, Lucia, and Francesca Badaracco. "Seismic and Newtonian Noise in the GW Detectors." Galaxies 10, no. 1 (January 22, 2022): 20. http://dx.doi.org/10.3390/galaxies10010020.
Повний текст джерелаАнотація:
Gravitational wave detectors aim to measure relative length variations of the order of ΔL/L≃10−21, or less. Thus, any mechanism that is able to reproduce such a tiny variation can, in principle, threaten the sensitivity of these instruments, representing a source of noise. There are many examples of such noise, and seismic and Newtonian noise are among these and will be the subject of this review. Seismic noise is generated by the incessant ground vibration that characterizes Earth. Newtonian noise is instead produced by the tiny fluctuations of the Earth’s gravitational field. These fluctuations are generated by variations of air and soil density near the detector test masses. Soil density variations are produced by the same seismic waves comprising seismic noise. Thus, it makes sense to address these two sources of noise in the same review. An overview of seismic and Newtonian noise is presented, together with a review of the strategies adopted to mitigate them.
6
Frajuca, Carlos, Fabio da Silva Bortoli, and Nadja Simao Magalhaes. "The Analysis of a Proposed Experiment to Measure the Speed of Gravity in Short Distances." Advances in High Energy Physics 2022 (May 25, 2022): 1–8. http://dx.doi.org/10.1155/2022/1991119.
Повний текст джерелаАнотація:
In order to investigate the speed of gravitational signals travelling in air or through a different medium two experiments were designed. One of the experiments contains 2 masses rotating at very high speed and in the other experiment a sapphire bar will vibrate, in both cases they will emit a periodic tidal gravitational signal and one sapphire device that behaves as a detector, which are suspended in vacuum and cooled down to 4.2 K will act as a detector. The vibrational amplitude of the sapphire detector device is measured by an microwave signal with ultralow phase-noise that uses resonance in the whispering gallery modes inside the detector device. Sapphire has a quite high mechanical Q and electrical Q which implies a very narrow detection band thus reducing the detection sensitivity. A new detector shape for the detector device is presented in this work, yielding a detection band of about half of the device vibrational frequency. With the aid of a Finite Element Program the normal mode frequencies of the detector can be calculated with high precision. The results show a similar expected sensitivity between the two experimental setup, but the experiment with the vibration masses is more stable in frequency then it is chosen for the experimental setup to measure the speed of gravity in short distances. Then a more precise analysis is made with this experiment reaching a signal-noise ratio of 10 at a frequency of 5000 Hz.
7
Leisos, Antonios, Stavros Nonis, Apostolos Tsirigotis, George Bourlis, Kostas Papageorgiou, Ioannis Gkialas, Ioannis Manthos, and Spyros Tzamarias. "Hybrid Detection of High Energy Showers in Urban Environments." Universe 5, no. 1 (December 22, 2018): 3. http://dx.doi.org/10.3390/universe5010003.
Повний текст джерелаАнотація:
The Astroneu array comprises 9 large charged particle detectors and 3 RF antennas arranged in three autonomous stations operating at the University Campus of the Hellenic Open University in the city of Patras. Each station of the array detects extensive air showers with primary energy threshold of about 10 TeV, while double station coincidence events select showers with energies higher than 10 3 TeV. In such an environment, the radio detection of air showers is challenging. The RF signals besides being extremely weak they also suffer from strong human made electromagnetic noise. In this work, we present the analysis of double station coincidence events and we study the correlation of the RF data with the particle detectors data. We use the experimental information from the particle detectors and the antennas to select very high energy showers and we compare the timing of the RF signals with the timing of the particle detector signals as well as the strength of the RF signals with the simulation predictions.
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Fiscante, Nicomino, Pia Addabbo, Carmine Clemente, Filippo Biondi, Gaetano Giunta, and Danilo Orlando. "A Track-Before-Detect Strategy Based on Sparse Data Processing for Air Surveillance Radar Applications." Remote Sensing 13, no. 4 (February 12, 2021): 662. http://dx.doi.org/10.3390/rs13040662.
Повний текст джерелаАнотація:
In this paper we consider the tracking problem of a moving target competing against noise and clutter in a surveillance radar scenario. For a single array-antenna multiple-target tracking system and according to the Track-Before-Detect paradigm, we present a novel approach based on a three-stage processing chain that involves the Sparse Learning via Iterative Minimization algorithm, the k-means clustering method and the ad hoc detector by exploiting the sparse nature of the operating scenario. Under the latter assumption, the detection strategy declares the presence of targets subsequently to the retrieval of their corresponding tracks performed by jointly processing the received echoes of multiple consecutive radar scans. Simulation results show that the proposed approach is able to provide good tracking and detection capabilities for different multiple target trajectories with low Signal-to-Interference-plus-Noise ratio and results in providing advantages when compared to a number of other reference Track-Before-Detect strategies based on sparse data processing techniques.
9
SUGAI, H., K. FUJIKI, K. ISHII, S. MATSUYAMA, A. TERAKAWA, Y. KIKUCHI, M. FUJIWARA, et al. "IMPROVEMENT OF THE DETECTION EFFICIENCY OF THE IN-AIR SUBMILLI-PIXE CAMERA FOR BIOLOGICAL APPLICATIONS." International Journal of PIXE 22, no. 01n02 (January 2012): 37–43. http://dx.doi.org/10.1142/s0129083512400050.
Повний текст джерелаАнотація:
The detection efficiency of the submilli-PIXE camera was improved by installing a new X-ray detector with a smaller distance from specimens. The distortion of elemental images caused by position dependent detection efficiency was corrected by estimating the detection efficiency based on the geometrical configuration of the detection system. The detection efficiency of characteristic X-rays from heavy elements such as iron and bromine became from 11 to 23 times higher than the previous system. The signal to noise ratios was improved from 1.8 to 2.5 times higher and detection limit was also decreased from 1/8 to 1/6 compared to the previous system. The in-air submilli-PIXE camera with improved detection system can be useful to biological applications.
10
Bastian-Querner, Benjamin, Lucas S. Binn, Sebastian Böser, Jannes Brostean-Kaiser, Dustin Hebecker, Klaus Helbing, Timo Karg, et al. "The Wavelength-Shifting Optical Module." Sensors 22, no. 4 (February 11, 2022): 1385. http://dx.doi.org/10.3390/s22041385.
Повний текст джерелаАнотація:
The Wavelength-shifting Optical Module (WOM) is a novel photosensor concept for the instrumentation of large detector volumes with single-photon sensitivity. The key objective is to improve the signal-to-noise ratio, which is achieved by decoupling the photosensitive area of a sensor from the cathode area of its photomultiplier tube (PMT). The WOM consists of a transparent tube with two PMTs attached to its ends. The tube is coated with wavelength-shifting paint that absorbs ultraviolet photons with nearly 100% efficiency. Depending on the environment, e.g., air (ice), up to 73% (41%) of the subsequently emitted optical photons can be captured by total internal reflection and propagate towards the PMTs, where they are recorded. The optical properties of the paint, the geometry of the tube, and the coupling of the tube to the PMTs have been optimized for maximal sensitivity based on theoretical derivations and experimental evaluations. Prototypes were built to demonstrate the technique and to develop a reproducible construction process. Important measurable characteristics of the WOM are the wavelength-dependent effective area, the transit time spread of detected photons, and the signal-to-noise ratio. The WOM outperforms bare PMTs, especially with respect to the low signal-to-noise ratio with an increase of a factor up to 8.9 in air (5.2 in ice). Since the gain in sensitivity is mostly in the UV regime, the WOM is an ideal sensor for Cherenkov and scintillation detectors.
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Kabakchiev, Hristo, Vera Behar, Ivan Garvanov, Dorina Kabakchieva, Avgust Kabakchiev, and Hermann Rohling. "FSR Systems for Detection of Air Objects Using Cosmic Radio Emissions." Sensors 21, no. 2 (January 11, 2021): 465. http://dx.doi.org/10.3390/s21020465.
Повний текст джерелаАнотація:
The paper analyses the possibility of Forward Scatter Radar (FSR) systems to detect airplanes using cosmic emission from pulsars and planets (pulsar, Sun, Moon). A suboptimal multichannel algorithm for joint detection and evaluation of the parameters of the forward scattering signal created by an airplane (duration and velocity) is proposed, with preliminary compensation of the powerful direct signal emitted by cosmic sources (pulsar, Sun and Moon). The expressions for calculation of the Signal-to-Noise Ratio (SNR) at the input of the detector and the compensator are obtained. The detection characteristics are also obtained, and the requirements for the suppression coefficient of the compensator are evaluated. A methodology for calculating the maximum distance for detecting an aircraft using a described algorithm is proposed. The obtained results show that due to the Forward Scatter (FS) effect, there is the theoretical possibility to detect airplanes at close ranges by FSRs, which use very weak signals from cosmic sources.
12
Kabakchiev, Hristo, Vera Behar, Ivan Garvanov, Dorina Kabakchieva, Avgust Kabakchiev, and Hermann Rohling. "FSR Systems for Detection of Air Objects Using Cosmic Radio Emissions." Sensors 21, no. 2 (January 11, 2021): 465. http://dx.doi.org/10.3390/s21020465.
Повний текст джерелаАнотація:
The paper analyses the possibility of Forward Scatter Radar (FSR) systems to detect airplanes using cosmic emission from pulsars and planets (pulsar, Sun, Moon). A suboptimal multichannel algorithm for joint detection and evaluation of the parameters of the forward scattering signal created by an airplane (duration and velocity) is proposed, with preliminary compensation of the powerful direct signal emitted by cosmic sources (pulsar, Sun and Moon). The expressions for calculation of the Signal-to-Noise Ratio (SNR) at the input of the detector and the compensator are obtained. The detection characteristics are also obtained, and the requirements for the suppression coefficient of the compensator are evaluated. A methodology for calculating the maximum distance for detecting an aircraft using a described algorithm is proposed. The obtained results show that due to the Forward Scatter (FS) effect, there is the theoretical possibility to detect airplanes at close ranges by FSRs, which use very weak signals from cosmic sources.
13
Cox, Stephen E., Sidney R. Hemming, and Damian Tootell. "The Isotopx NGX and ATONA Faraday amplifiers." Geochronology 2, no. 2 (September 3, 2020): 231–43. http://dx.doi.org/10.5194/gchron-2-231-2020.
Повний текст джерелаАнотація:
Abstract. We installed the new Isotopx ATONA Faraday cup detector amplifiers on an Isotopx NGX mass spectrometer at Lamont-Doherty Earth Observatory in early 2018. The ATONA is a capacitive transimpedance amplifier, which differs from the traditional resistive transimpedance amplifier used on most Faraday detectors for mass spectrometry. Instead of a high-gain resistor, a capacitor is used to accumulate and measure charge. The advantages of this architecture are a very low noise floor, rapid response time, stable baselines, and very high dynamic range. We show baseline noise measurements and measurements of argon from air and cocktail gas standards to demonstrate the capabilities of these amplifiers. The ATONA exhibits a noise floor better than a traditional 1013 Ω amplifier in normal noble gas mass spectrometer usage, superior gain and baseline stability, and an unrivaled dynamic range that makes it practical to measure beams ranging in size from below 10−16 to above 10−9 A using a single amplifier.
14
Zheng, Huadan, Haoyang Lin, Lei Dong, Zhao Huang, Xiaohang Gu, Jieyuan Tang, Linpeng Dong, Wenguo Zhu, Jianhui Yu, and Zhe Chen. "Quartz-Enhanced Photothermal-Acoustic Spectroscopy for Trace Gas Analysis." Applied Sciences 9, no. 19 (September 26, 2019): 4021. http://dx.doi.org/10.3390/app9194021.
Повний текст джерелаАнотація:
A crystal quartz tuning fork (QTF) was used as a detector to collect and amplify laser-induced photoacoustic and photothermal waves simultaneously for trace chemical analysis. A wavelength modulation technique was applied to the proposed quartz-enhanced photothermal-acoustic spectroscopy (QEPTAS) to improve the detection signal-to-noise ratio. The QTF detector was exposed to the illumination of a near-infrared distributed feedback laser at distances of 1 m and 2 m to evaluate the QEPTAS sensor performance. The QEPTAS sensor performance was determined by detecting water vapor in ambient air using a near-infrared distributed feedback laser with a power of ~10 mW and a wavelength of 1.39 μm. With an optimized modulation depth of 0.47 cm−1, the normalized noise equivalent absorption (NNEA) coefficients of 8.4 × 10−7 W·cm−1·Hz−1/2 and 3.7 × 10−6 W·cm−1·Hz−1/2 were achieved for a distance of 1 m and 2 m, respectively. The developed QEPTAS technique reduces the requirements for laser beam quality, resulting in a simple but robust sensor structure and demonstrates the ability of remote sensing of gas concentrations.
15
Donath, Tilman, Benjamin Lüthi, and Clemens Schulze-Briese. "Latest Hybrid Pixel Detectors for increased q/t-resolution in SAXS." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C882. http://dx.doi.org/10.1107/s2053273314091177.
Повний текст джерелаАнотація:
The PILATUS was the first Hybrid Pixel Detector available for SAXS. It has transformed data collection by its photon-counting technology, which enables noise-free X-ray detection with high dynamic range and excellent stability at high frame rates. These properties are essential for superior data quality in all scattering experiments, especially for optimal background correction when studying low-concentration samples. Besides optimal data quality at each sampling point, highest resolution is desired in most SAXS experiments both in q-range and in time. The newly developed EIGER pixel detector more than doubles the q-resolution that can be achieved when compared with PILATUS3 for the same sample-to-detector distance. EIGER features a pixel size of only 75 µm (in comparison: PILATUS3 has 172 µm). To characterize the spatial resolution of these detectors, point-spread functions were measured at the PTB laboratory at BESSY II, which show that the resolution is directly proportional to the pixel size with minimal cross talk between neighboring pixels. The EIGER 1M detector allows data acquisition at up to 3'000 frames per second. This enables unprecedented temporal resolution in time-resolved SAXS measurements and increases the speed of novel imaging techniques such as scanning SAXS/WAXS and coherent diffractive imaging applications, allowing images to be recorded faster or with higher spatial resolution. The design of the EIGER detector makes it vacuum compatible. Operation at low X-ray energies and correspondingly large scattering angles is another way of increasing q-resolution and also gives access to the lowest q data near the beam stop. In-vacuum detectors enable measurements with ultra-soft x-rays and thus high q-resolution. Moreover they optimize the data quality in scattering experiments by removing absorption and scatter caused from air and windows. An in-vacuum PILATUS 1M detector has been installed at the BESSY-2 FCM beamline and is applied for SAXS/GI-SAXS measurements at energies from 1.75 to 10 keV. For simultaneous SAXS/WAXS applications covering an even wider q-range, in-vacuum detectors with L-shaped detection surface are under development. These will detect the WAXS signal, while a clearance in the detector permits the direct beam to pass on to a SAXS detector placed at larger distance. These latest detector developments will be presented along with corresponding experimental results.
16
Busch, Kenneth W., Marianna A. Busch, Renaud Mercier Ythier, and Arvie J. Kuehn. "Design Parameters for an Optimized Flame/Furnace Infrared Emission (FIRE) Radiometer." Applied Spectroscopy 47, no. 12 (December 1993): 2072–80. http://dx.doi.org/10.1366/0003702934066433.
Повний текст джерелаАнотація:
Several design aspects of an optimized flame/furnace infrared emission (FIRE) radiometer are discussed. For a source in thermal equilibrium, the optimum excitation temperature for CO2 is predicted to be 2500 K, based on the stability of the molecule and the population of excited states as functions of temperature. The influence of spectral bandpass on the magnitude of flame background was studied for several wavelengths within the profile of the 4.4-µm emission band of CO2. For the dispersive FIRE radiometer used in this study, the system was found to be detectornoise limited over the range of spectral bandwidths accessible by the instrument (0.01–0.08 µm). When a hydrogen/air flame was used as the excitation source, the maximum signal-to-background ratio was obtained at 4.40 µm with a spectral bandpass of 0.08 µm. For this same experimental arrangement, a mathematical model was used to predict that the maximum signal-to-noise ratio would occur at 4.40 µm with a spectral bandpass of about 0.25 µm. The influence of chopping frequency on detector noise was determined for two different types of wavelength isolation. When a room-temperature bandpass filter was employed, a modulation frequency of 600–1000 Hz was satisfactory for avoiding 1/ f noise from the PbSe detector. However, when a monochromator was employed, chopping frequencies beyond 1000 Hz produced some additional reduction in 1/ f noise. The specific detectivity for the PbSe detector (6.2 × 108 cm Hz0.5 W−1), calculated from the measured noise at a modulation frequency of 600 Hz, is in good agreement with values reported in the literature for 4.40 µm under the same experimental conditions.
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Pamurti, Andarina Aji. "KAJIAN PARTICULATE MATTER DAN KEBISINGAN PADA PERMUKIMAN DI SEKITAR JALAN TOL KEDUNGMUNDU SEMARANG." Indonesian Journal of Spatial Planning 2, no. 1 (April 28, 2021): 54. http://dx.doi.org/10.26623/ijsp.v2i1.3325.
Повний текст джерелаАнотація:
<div><table cellspacing="0" cellpadding="0"><tbody><tr><td align="left" valign="top"><p><em>The construction of toll roads has a positive impact to facilitate the mobility rate of the community. But the construction of toll roads also has a negative impact on the residential area around the toll road, namely air pollution due to the burning of vehicle fuel. PM2.5 and PM10 air particles are particles that damage the working system of the lungs. The health of the environment where settled is an important support that affects health, especially in the era of pandemic covid. Air particle measurement using portable PM2.5 and PM10 Air Quality Tester Detector. The daily average level of PM2.5 particles in residential areas around Semarang's Kedungmundu toll road is 65.44 μg/Nm³, while the PM10 particle content is 95.2 μg/Nm³. PM2.5 levels exceed the standards of the National Ambient Air Quality Standard (BMUA), The WHO Air Quality Guidline and Ambient Air Quality Standards (USEPA). For PM10 exceeds WHO standard. In addition to air pollution, another impact is that these residential areas have noise. The daily average noise value when measuring the sampling time is 62.23 dB, this value is exceeding the standard threshold of the Regulation of the Minister of Environment for residential areas. So the residential area around Kedungmundu Semarang toll road is less feasible for health when viewed from the value of PM 2.5 and PM10 as well as noise. This study aims to determine the level of PM2.5 and PM10 particles as well as noise in residential areas around the Kedungmundu Semarang toll road. Once the measurement results are obtained, it will be used as a reference for planners to provide solutions for settlements that have an impact due to toll road construction activities with dense vehicle intensity.</em></p></td></tr></tbody></table></div>
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Manning, Christopher J., and Peter R. Griffiths. "Noise Sources in Step-Scan FT-IR Spectrometry." Applied Spectroscopy 51, no. 8 (August 1997): 1092–101. http://dx.doi.org/10.1366/0003702971941755.
Повний текст джерелаАнотація:
Step-scan Fourier transform infrared (FT-IR) spectrometry has been accepted as a useful tool for obtaining vibrational spectra of a variety of time-dependent systems. Unfortunately, a significant signal-to-noise ratio (SNR) disadvantage has been associated with the step-scan mode of data collection relative to the same data collection time with conventional rapid-scan FT-IR spectrometry. The key difference between the two methods is the average mirror velocity, which alters the dynamic range of the detector signal, as well as the frequencies of its components. The SNR disadvantage is shown to be related to low-frequency multiplicative fluctuations, caused in part by temperature variations, which convolve noise with measured spectra. Refractive index variations of air or purge gas in the paths of the infrared- and reference-laser radiation can be a particularly serious temperature-induced problem. The various noise sources are described, and experiments confirming that some are related to temperature variations are reported.
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Laroche, Gaétan, Jean Giroux, Alain Bordeleau, and Jean-Marc Garneau. "Investigation of Electrical and Optical Subtractions Using Two Input-Port and Two Output-Port FT-IR Spectrometers." Applied Spectroscopy 48, no. 3 (March 1994): 356–62. http://dx.doi.org/10.1366/0003702944028362.
Повний текст джерелаАнотація:
Two FT-IR spectrometers, each using two input ports and two output ports, have been used to minimize the effect of background noise and source fluctuation noise in infrared emission spectra of various sources. Blackbody sources, propane/air flames, and infrared flares have been studied, and spectra were recorded in the spectral region ranging from 1.7 to 5 μm. With the use of the two input-port and one output-port configurations, it was found that real-time optical subtraction could generate 80% background-noise-free spectra. When the spectrometers were operated in the one input-port and two output-port configurations, spectra that were free of source fluctuation noise were obtained with the use of real-time electrical subtraction of signals measured at both detectors. New signal processing techniques have thus been developed. An increase in the signal-to-fluctuation-noise ratio by a factor of seven has been observed in the interferograms, which in turn leads to a 2 × increase of the signal-to-noise ratio in the corresponding spectra. During this signal processing sequence requiring the use of two analog-to-digital converters (ADC) (one for each detector channel), intensity information was then lost, so that no calibrated spectra could be measured. However, with the use of a single-channel ADC, it was shown that, by a process of simply subtracting signals recorded from both detectors operated under similar amplifier gain, fluctuation noise could be partly removed and intensity information could also be retained. In conjunction with the high scanning velocity of the interferometer (60 scans/s at a 16-cm−1 resolution), this technique has proven to be very useful in measuring emission spectra of highly fluctuating infrared sources, such as flares.
20
Phillips, Walter C., Martin Stanton, Alexander Stewart, Hua Qian, Charles Ingersoll, and Robert M. Sweet. "Multiple CCD detector for macromolecular X-ray crystallography." Journal of Applied Crystallography 33, no. 2 (April 1, 2000): 243–51. http://dx.doi.org/10.1107/s0021889899015666.
Повний текст джерелаАнотація:
A charge-coupled device (CCD)-based detector designed for macromolecular crystallography is described. The detector has an area of 200 × 200 mm, a readout time of 1.6 s, and total noise equivalent to approximately three 12 keV X-ray photons per pixel. The detector is constructed from a 2 × 2 array of four identical units, each unit consisting of a 4.1:1 demagnifying fiber-optic taper bonded to a 1 k × 1 k, 24 µm pixel, CCD sensor. Each CCD is read out in parallel though four channels and digitized to 16 bits. A Gd2O2S phosphor X-ray-to-light converter bonded to an aluminized-plastic film is held in contact with the input surfaces of the fiber-optic tapers with an air pillow. The full width at half-maximum (FWHM) of the point response function is 120 µm, the response is linear to better than 1% over the entire range of intensity from background to nearly full well, the gain is 3.4 e per 8 keV incident X-ray photon, the noise is 12.6 e per pixel for a 10 s integration time, the modulation transfer function (MTF) is 0.35 at 5 line pairs (lp) mm−1(the Nyquest frequency), and the measured detective quantum efficiency (DQE) is 0.74 for relatively strong Bragg peaks. Data collected from crystallographic studies with synchrotron radiation are presented. In an anomalous difference Patterson map for a data set collected in 40 min on a monoclinic myoglobin crystal, the magnitude of the Fe–Fe peaks is 18 times the standard uncertainty of the map.
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Sood, Pramit, Jens Zosel, Michael Mertig, Wolfram Oelßner, Olaf Herrmann, and Michael Woratz. "Development and test of a highly sensitive and selective hydrogen sensor system." Journal of Sensors and Sensor Systems 9, no. 2 (October 5, 2020): 309–17. http://dx.doi.org/10.5194/jsss-9-309-2020.
Повний текст джерелаАнотація:
Abstract. A miniaturized field-applicable sensor system was developed for the measurement of hydrogen (H2) in air in the concentration range 0.2–200 ppmv. The sensor system is based on the application of an yttria-stabilized zirconia (YSZ) solid electrolyte cell (SEC) as a coulometric detector with gas chromatographic (GC) pre-separation. The main system components for injection, chromatographic separation, and the oxygen pumping cell were significantly miniaturized and tested separately to characterize important measurement properties like selectivity, lower limit of detection, repeatability, and signal-to-noise ratio. Measurements were conducted under varying GC parameters and detector operating conditions. While changing the detector temperature influences the hydrogen peak significantly due to diffusion processes at the electrode–electrolyte interface; different oxygen-partial pressures at the measuring electrode have no visible effect. The combination of two packed columns with 1 m length, one filled with a molecular sieve (13X) and the other one with silica gel, enabled highly reproducible and selective H2 measurements with more than 90 % analyte turnover compared to Faraday's law. The resulting insights were used to define appropriate system parameters, construction guidelines, and material properties for the final test prototype.
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Busch, Marianna A., and Kenneth W. Busch. "Signal-to-Noise Comparison of Flame/Furnace Infrared Emission (FIRE) Spectrometry with Room-Temperature, Nondispersive Infrared Absorption Spectrophotometry." Applied Spectroscopy 47, no. 7 (July 1993): 912–21. http://dx.doi.org/10.1366/0003702934415138.
Повний текст джерелаАнотація:
A theoretical model has been developed for the comparison of the performance of a detector-noise-limited, flame infrared emission (FIRE) spectrometer with that of a room-temperature, nondispersive, infrared absorption (NDIR) spectrophotometer. The ratio of the signal-to-noise ratio (SNR) in emission to that in absorption is found to depend on the product of five terms: (1) the ratio of the noise in absorption to that in emission; (2) the ratio of the solid angles in emission and absorption; (3) the ratio of the pathlengths in emission and absorption; (4) the ratio of the number densities in emission and absorption; and (5) the ratio of the Boltzmann factor for the flame to the Bose-Einstein factor for the blackbody source. Implications for gas chromatographic detection are considered. Under conditions in which chemical conversion of the sample into an infrared-active species is not required and both measurements employ an uncooled PbSe detector, a sample cell volume of 30 μL, and a filter bandwidth of 0.30 μm at a wavelength 4.35 μm (the antisymmetric stretching vibration of CO2), the major factor which determines the ratio of the two SNRs will be the ratio of the solid angle × pathlength product, which has a constant value of 100, regardless of the sample cell path-length chosen. If a hydrogen/air flame is used in emission (2272 K) and a Nernst glower is used in absorption (1800 K), the FIRE spectrometer is predicted to produce an SNR that is at least 19 times better than that produced by the corresponding NDIR absorption photometer, regardless of the pathlength of the absorption cell.
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Barker, J. G., and D. F. R. Mildner. "Survey of background scattering from materials found in small-angle neutron scattering." Journal of Applied Crystallography 48, no. 4 (June 27, 2015): 1055–71. http://dx.doi.org/10.1107/s1600576715010729.
Повний текст джерелаАнотація:
Measurements and calculations of beam attenuation and background scattering for common materials placed in a neutron beam are presented over the temperature range of 300–700 K. Time-of-flight (TOF) measurements have also been made, to determine the fraction of the background that is either inelastic or quasi-elastic scattering as measured with a3He detector. Other background sources considered include double Bragg diffraction from windows or samples, scattering from gases, and phonon scattering from solids. Background from the residual air in detector vacuum vessels and scattering from the3He detector dome are presented. The thickness dependence of the multiple scattering correction for forward scattering from water is calculated. Inelastic phonon background scattering at small angles for crystalline solids is both modeled and compared with measurements. Methods of maximizing the signal-to-noise ratio by material selection, choice of sample thickness and wavelength, removal of inelastic background by TOF or Be filters, and removal of spin-flip scattering with polarized beam analysis are discussed.
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Hursin, Mathieu, Oskari Pakari, Gregory Perret, Pavel Frajtag, Vincent Lamirand, Imre Pázsit, Victor Dykin, Gabor Por, Henrik Nylén, and Andreas Pautz. "VALIDATION OF AXIAL VOID PROFILE MEASURED BY NEUTRON NOISE TECHNIQUES IN CROCUS." EPJ Web of Conferences 247 (2021): 08004. http://dx.doi.org/10.1051/epjconf/202124708004.
Повний текст джерелаАнотація:
Recently a joint project has been carried out between the Paul Scherrer Institut, the Ecole Polytechnique Federale de Lausanne and swissnuclear, an industrial partner, in order to determine the axial void distribution in a channel installed in the reflector of the zero power research reactor CROCUS, using neutron noise techniques. The main objective of the present paper is to report on the validation of the results against an alternative measurement technique using gamma-ray attenuation and simulations with the TRACE code. For the gamma-ray attenuation experiments, the channel used in CROCUS is installed out of the core in a Plexiglass water tank. The source and detector are fixed and the channel is moved axially to keep the geometry of the source/detector arrangement untouched. This is key to measure the void effect by gamma attenuation due to the low contrast of this technique. The paper compares the experimental results obtained with both techniques, with the outcomes of simulations carried out with the TRACE code. Even though the quantitative void fraction estimations are not consistent, the trends obtained with the simulation and experimental techniques are the same. The discrepancies between the various experimental techniques and the simulation outcomes are related to the heterogeneous distribution of the water-air mixture in the radial sections of the channel.
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Adams, Cameron, Christabel Brand, Michael Dentith, Marco Fiorentini, Stefano Caruso, and Manasvi Mehta. "The use of pXRF for light element geochemical analysis: a review of hardware design limitations and an empirical investigation of air, vacuum, helium flush and detector window technologies." Geochemistry: Exploration, Environment, Analysis 20, no. 3 (January 27, 2020): 366–80. http://dx.doi.org/10.1144/geochem2019-076.
Повний текст джерелаАнотація:
Light element data are required for robust and accurate lithogeochemical interpretations and are important components in the study of hydrothermal alteration and mineralization processes. In this contribution we review the latest available portable energy dispersive X-Ray Fluorescence (pXRF) technologies exclusively in the context of light element analysis, with focus on the acquisition of data for Na, Mg, Al and Si. We discuss pXRF hardware design limitations, quantify variables that attenuate X-ray energies through numerical modelling, including common pXRF configurations, and empirically investigate modern pXRF technologies used to mitigate X-ray attenuation and improve light element analysis.The void between the sample and detector is a key issue regarding the success of pXRF light element analysis. Dry-air (normal conditions), vacuum purge and helium flush systems are evaluated. Modelled data that use a nominal sample-detector void of 10 mm show that using helium in lieu of air improves X-ray transmission effectiveness from ≈2% to ≈99% for Na and ≈10% to ≈100% for Mg. Modelled detector window data show that using a graphene detector window in lieu of a traditional beryllium detector window improves X-ray transmission effectiveness for Na from ≈38% to ≈64% and ≈57% to ≈77% for Mg. Progressive X-ray transmission effectiveness equates to ≈63% Na and ≈76% Mg when using a helium-graphene pXRF configuration v. ≈1% for Na and ≈6% Mg when using a traditional in-air beryllium pXRF arrangement (i.e. without sample or X-ray entrance window media).Empirically determined improvements of the resolved signal are more modest than those of modelled X-ray transmission effectiveness data. Instrument noise, spectral overlaps and random counting errors are unavoidable and inherent with the limitations of modern detector technologies. However, the employment of helium with graphene detector window technology allows very precise data to be obtained at significantly shorter scan times (i.e. 20 s, instead of the traditional 60–180 s, i.e. 3–9 times faster): a scan time of 20 s can achieve a precision of ≈18% @ ≈0.4% Na and ≈8% @ ≈0.3% Mg for elemental interference-free samples. Precision will improve with increasing analyte concentration.
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Neji, Bilel, Ndricim Ferko, Raymond Ghandour, Abdullah S. Karar, and Houssam Arbess. "Micro-Fabricated RTD Based Sensor for Breathing Analysis and Monitoring." Sensors 21, no. 1 (January 5, 2021): 318. http://dx.doi.org/10.3390/s21010318.
Повний текст джерелаАнотація:
The design, micro-fabrication, and characterization of a resistance temperature detector (RTD) based micro sensor for minimally invasive breathing analysis and monitoring is presented. Experimental results demonstrate that the change in air temperature while inhaling and exhaling can be transduced into a time varying electrical signal, which is subsequently used to determine the breathing frequency (respiratory rate). The RTD is placed into a Wheatstone bridge to simultaneously reduce the sensor’s output noise and improve overall system accuracy. The proposed design could potentially aid health care providers in the determination of respiratory rates, which is of critical importance during the current COVID-19 pandemic.
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Houtz, Derek, Reza Naderpour, and Mike Schwank. "Portable L-Band Radiometer (PoLRa): Design and Characterization." Remote Sensing 12, no. 17 (August 27, 2020): 2780. http://dx.doi.org/10.3390/rs12172780.
Повний текст джерелаАнотація:
A low-mass and low-volume dual-polarization L-band radiometer is introduced that has applications for ground-based remote sensing or unmanned aerial vehicle (UAV)-based mapping. With prominent use aboard the ESA Soil Moisture and Ocean Salinity (SMOS) and NASA Soil Moisture Active Passive (SMAP) satellites, L-band radiometry can be used to retrieve environmental parameters, including soil moisture, sea surface salinity, snow liquid water content, snow density, vegetation optical depth, etc. The design and testing of the air-gapped patch array antenna is introduced and is shown to provide a 3-dB full power beamwidth of 37°. We present the radio-frequency (RF) front end design, which uses direct detection architecture and a square-law power detector. Calibration is performed using two internal references, including a matched resistive source (RS) at ambient temperature and an active cold source (ACS). The radio-frequency (RF) front end does not require temperature stabilization, due to characterization of the ACS noise temperature by sky measurements. The ACS characterization procedure is presented. The noise equivalent delta (Δ) temperature (NEΔT) of the radiometer is ~0.14 K at 1 s integration time. The total antenna temperature uncertainty ranges from 0.6 to 1.5 K.
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Koyuncu, Hakan, Ashish Bagwari, and Geetam Singh Tomar. "Simulation of a Smart Sensor Detection Scheme for Wireless Communication Based on Modeling." Electronics 9, no. 9 (September 14, 2020): 1506. http://dx.doi.org/10.3390/electronics9091506.
Повний текст джерелаАнотація:
The principle of sensing and sending information applies to all kinds of communications in different media like air, water, etc. During data transmission through sensors, the most important issue is sensing failure problems. In communication systems, sensing failure problems generally occur and affect sensor system performance. In this study, sensing failure issues are discussed, and a smart sensor is introduced that detects the communication signals. The characteristics of these sensors are identified with signal-to-noise ratio (SNR) readings. The proposed sensor system has high performance and it is better than many systems in the literature. Graphical findings show that the suggested scheme increases device efficiency and has more performance than the energy detector (ED) and ED-ADT-2013 by 33.5%, adaptive spectrum sensing (ASS)-2012 by 41.5%, energy detecting technique for adaptive spectrum sensing (EDT-ASS)-2015 by 28.2%, energy detector, and cyclo-2010 by 57.0%, and energy-SNR adaptive threshold (ADT) detector-2016 by 52.8% at −12 dB SNR, respectively. The proposed sensor detection scheme performs well compared to other existing sensors regarding sensing time. It was found that cooperative spectrum sensing (CSS) with the proposed method outperforms HwQ-2012 and CSS-EDT-ASS-2015 by 22.70% and 16.10% in terms of probability at −12 dB SNR, respectively, and detects the signal at −19.70 dB SNR.
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Boublik, M., S. J. Tumminia, W. Hellmann, Q. Zhang, J. F. Hainfeld, and J. S. Wall. "Structural analysis of biological macromolecular assemblies by scanning transmission electron microscopy." Proceedings, annual meeting, Electron Microscopy Society of America 49 (August 1991): 262–63. http://dx.doi.org/10.1017/s0424820100085617.
Повний текст джерелаАнотація:
Separation of the resolution and contrast affecting components and the optimized placement of detectors for the collection of elastic (contrast-forming) electrons on Brookhaven dedicated STEM make it possible to quantitatively detect greater than 90% of the available elastically scattered electrons. The high contrast and superior signal-to-noise ratio associated with the STEM annular detector allow for the imaging of unstained freeze-dried biological macromolecular complexes (chromatin, viruses, nucleic acids) at radiation doses as low as 1 e/Å. Specimens prepared in this way are free of the main resolution-limiting conditions of conventional TEM i.e. staining , air drying and radiation damage. The image intensity of unstained specimens can be related to their local projected mass and used for calculation of the total mass and mass distribution within any selected particle. Elimination of staining makes it possible to use heavy metals as high-resolution markers for topographical mapping of components and/or functional sites on a particular macromolecular complex.
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Jongaramrungruang, Siraput, Georgios Matheou, Andrew K. Thorpe, Zhao-Cheng Zeng, and Christian Frankenberg. "Remote sensing of methane plumes: instrument tradeoff analysis for detecting and quantifying local sources at global scale." Atmospheric Measurement Techniques 14, no. 12 (December 22, 2021): 7999–8017. http://dx.doi.org/10.5194/amt-14-7999-2021.
Повний текст джерелаАнотація:
Abstract. Methane (CH4) is the second most important anthropogenic greenhouse gas with a significant impact on radiative forcing, tropospheric air quality, and stratospheric water vapor. Remote sensing observations enable the detection and quantification of local methane emissions across large geographical areas, which is a critical step for understanding local flux distributions and subsequently prioritizing mitigation strategies. Obtaining methane column concentration measurements with low noise and minimal surface interference has direct consequences for accurately determining the location and emission rates of methane sources. The quality of retrieved column enhancements depends on the choices of the instrument and retrieval parameters. Here, we studied the changes in precision error and bias as a result of different spectral resolutions, instrument optical performance, and detector exposure times by using a realistic instrument noise model. In addition, we formally analyzed the impact of spectrally complex surface albedo features on retrievals using the iterative maximum a posteriori differential optical absorption spectroscopy (IMAP-DOAS) algorithm. We built an end-to-end modeling framework that can simulate observed radiances from reflected solar irradiance through a simulated CH4 plume over several natural and artificial surfaces. Our analysis shows that complex surface features can alias into retrieved methane abundances, explaining the existence of retrieval biases in current airborne methane observations. The impact can be mitigated with higher spectral resolution and a larger polynomial degree to approximate surface albedo variations. Using a spectral resolution of 1.5 nm, an exposure time of 20 ms, and a polynomial degree of 25, a retrieval precision error below 0.007 mole m−2 or 1.0 % of total atmospheric CH4 column can be achieved for high albedo cases, while minimizing the bias due to surface interference such that the noise is uncorrelated among various surfaces. At coarser spectral resolutions, it becomes increasingly harder to separate complex surface albedo features from atmospheric absorption features. Our modeling framework provides the basis for assessing tradeoffs for future remote sensing instruments and algorithmic designs. For instance, we find that improving the spectral resolution beyond 0.2 nm would actually decrease the retrieval precision, as detector readout noise will play an increasing role. Our work contributes towards building an enhanced monitoring system that can measure CH4 concentration fields to determine methane sources accurately and efficiently at scale.
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Bremnes, Alexander, Lise Kristin Kubosch, and Borgny Ween. "Optimization of Codman® Hakim® adjustable valve radiography." Radiography Open 3, no. 1 (March 31, 2017): 14. http://dx.doi.org/10.7577/radopen.1998.
Повний текст джерелаАнотація:
Purpose Cerebrospinal fluid shunt valves is an important tool in hydrocephalus treatment. Adjustable valves, sensitive to MRI, are onerous. They need be controlled; in case of re-settings. The vendor give advices for the radiographic procedure; however, hospitals use variations. The purpose was to investigate the different variations. Method Eight images consisting combinations of protocol features, were subjectively and anonymous rated for image quality. The panel consisted of 60 professionals; 50 radiographers and 10 radiologists, from two hospitals doing neurosurgery services. Signal-to-noise ratio compared the level of desired signal to the level of background noise. Results 348 scores were distributed onto all eight images, revealing the image quality difference was within acceptance. Options as valve on the head side near to the detector versus far to; differing geometry, use of head bowl versus not use, air-gap versus grids, were favored by both professional groups and at both hospitals in a clear priority image, given 2.5 times scores over average (108/43). Noise, revealed being the strongest indicator for priority of the best image for shunt evaluation. ConclusionsIt is a potential to improve image optimization in shunt radiography.
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Linardatos, Dionysios, Vaia Koukou, Niki Martini, Anastasios Konstantinidis, Athanasios Bakas, George Fountos, Ioannis Valais, and Christos Michail. "On the Response of a Micro Non-Destructive Testing X-ray Detector." Materials 14, no. 4 (February 13, 2021): 888. http://dx.doi.org/10.3390/ma14040888.
Повний текст джерелаАнотація:
Certain imaging performance metrics are examined for a state-of-the-art 20 μm pixel pitch CMOS sensor (RadEye HR), coupled to a Gd2O2S:Tb scintillator screen. The signal transfer property (STP), the modulation transfer function (MTF), the normalized noise power spectrum (NNPS) and the detective quantum efficiency (DQE) were estimated according to the IEC 62220-1-1:2015 standard. The detector exhibits excellent linearity (coefficient of determination of the STP linear regression fit, R2 was 0.9978), while its DQE peaks at 33% and reaches 10% at a spatial frequency of 3 cycles/mm, for the measured with a Piranha RTI dosimeter (coefficient of variation CV = 0.03%) exposure value of 28.1 μGy DAK (detector Air Kerma). The resolution capabilities of the X-ray detector under investigation were compared to other commercial CMOS sensors, and were found in every case higher, except from the previous RadEye HR model (CMOS—Gd2O2S:Tb screen pair with 22.5 μm pixel pitch) version which had slightly better MTF. The present digital imager is designed for industrial inspection applications, nonetheless its applicability to medical imaging, as well as dual-energy is considered and certain approaches are discussed in this respect.
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Noda, Y., S. Koizumi, and D. Yamaguchi. "Multi-tube area detector developed for reactor small-angle neutron scattering spectrometer SANS-J-II." Journal of Applied Crystallography 49, no. 1 (February 1, 2016): 128–38. http://dx.doi.org/10.1107/s1600576715022797.
Повний текст джерелаАнотація:
A newly developed multi-tube area detector for a small-angle neutron scattering (SANS) spectrometer (SANS-J-II) at the research reactor JRR-3 in Tokai, Japan, has been implementedviathe use of one-dimensional position-sensitive3He detectors (tubes). Ninety-six active tubes of 8 mm in diameter and 650 and 580 mm in length were filled with 15 atm (1.52 MPa) of3He and aligned vertically parallel in order to cover a sufficiently large area for small-angle scattering measurement. These tubes are enclosed in an air chamber together with neutron encode and GATENET modules (VME boards), which compose a standard data acquisition system for the spallation neutron source of the Japan Proton Accelerator Research Complex. This system facilitates the acquisition of time-of-flight neutron event data. The multi-tube detector is mounted on a truck moving in a vacuum chamber of the SANS spectrometer. After discriminating noise originating from γ-rays, and calibrating the positions and sensitivities of individual tubes, the resolution was determined (i.e.channel widths along parallel and vertical directions along a tube). The counting rate of one tube was determined to be 1.4 × 103counts per second with a counting loss of 1%. This implies that the new detector, composed of 96 tubes, can detect more than 105neutrons per second with a counting loss of 1%. To demonstrate its use, small-angle scattering originating from a diblock copolymer film with a highly oriented lamellar microdomain was observed. The data acquisition in event mode has a great advantage in time-resolved measurements that are synchronized with external stimuli imposed on a sample.
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Vivas Saltos, Holanda Teresa, Laura Gema Mendoza Cedeño, Julio Abel Loureiro Salabarría, María Isabel Delgado Moreira, María Fernanda Pincay Cantos, and Verónica Monserrate Vera Villamil. "Contaminación atmosférica y aerobiología del casco urbano de Calceta-Manabí." Revista de Investigaciones en Energía, Medio Ambiente y Tecnología: RIEMAT ISSN: 2588-0721 4, no. 1 (July 19, 2019): 47. http://dx.doi.org/10.33936/riemat.v4i1.1945.
Повний текст джерелаАнотація:
air pollution and noise generation represent environmental risk factors for public health in Calceta. Due to the lack of information on air pollutants, the objective of this work was to estimate the concentration of carbon monoxide (CO), sedimentary particulate matter (SPM), sound pressure level (SPL) and aerobic bacteria in the urban area of the Calceta. 18 data collection points were established covering an area of 6.9 km2; the concentration of CO was measured with a portable detector; the MPS collection was carried out during 30 days continuously by passive method; for the NPS measurements, the 15-second method (Leq-15s) was applied; Aerobiology was performed in Petri dishes with nutrient medium. The concentration of CO in a sector of the urban area of Calceta has an arithmetic mean of 5804,26 μg/m3 and according to the EPA this level is capable of affecting the population in general. The levels of SPM and SPL reflect the breach of the limits established in the national regulations for both pollutants. Bacterial concentrations were lower than 500 CFU/m3. The present study is a baseline in air quality that will allow in perspective the implementation of measures for the benefit of public health.
Index Terms— Environmental monitoring, lung diseases, air
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Davies, T. P., and P. L. Dyson. "An improved signal-to-noise ratio of a cool imaging photon detector for Fabry - Perot interferometer measurements of low-intensity air glow." Measurement Science and Technology 8, no. 4 (April 1, 1997): 456–58. http://dx.doi.org/10.1088/0957-0233/8/4/016.
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Teymurazyan, A., J. A. Rowlands, and G. Pang. "Monte Carlo simulation of a quantum noise limited Čerenkov detector based on air-spaced light guiding taper for megavoltage x-ray imaging." Medical Physics 41, no. 4 (March 14, 2014): 041907. http://dx.doi.org/10.1118/1.4867867.
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Cerqueira, Joaci Dos Santos, Helder Neves de Albuquerque, Mário Luiz Farias Cavalcanti, and Francisco De Assis Salviano de Sousa. "Use of portable environmental sensors in the monitoring of the thermoelectric power plants operation." Revista Ibero-Americana de Ciências Ambientais 11, no. 6 (July 6, 2020): 178–201. http://dx.doi.org/10.6008/cbpc2179-6858.2020.006.0016.
Повний текст джерелаАнотація:
Thermoelectric power plants can directly cause environmental impacts with respect to emissions of atmospheric gases caused by combustion for operation, being the main agents: unburned hydrocarbons, carbon oxides, sulfur oxides, nitrogen oxides, volatile organic compounds and material particulate. Thus, this research aimed to measure and compare the instantaneous levels of the chemical compounds CO2, CO, SO2, noise, air temperature, relative humidity, dew point temperature, wind speed and luminescence in two peri-urban areas of the surrounding a thermoelectric power plant in the interior of Paraíba, Brazil. To this end, data were collected using environmental sensors (a Garmin Gpsmap 62sc GPS camera 5mp; a Canon powershot SX60HS 16.1MP LCD 3.0 semi-professional digital camera, 65x optical zoom; an ITMCO2-600 meter for measuring CO2 and CO; one ITMP-600 multifunctional meter for AVG/MAX/MIN/DIF measurement, temperature measurement, humidity measurement, sound level measurement, luminescence measurement and wind speed measurement; and a GasAlert Extreme SO2 Gas detector to measure concentrations of sulfur in the environment), from October 2015 to March 2017, during daytime, between 7:00am to 9:00am, with weekly frequency, with instantaneous sampling measurements being collected at the collection points, near the thermoelectric power plant (Area 1) and close to the BR/104 highway (Area 2). The results showed that the records through the environmental sensors were not significant among the areas surveyed regarding the values of CO, CO2, SO2, air temperature, relative humidity, dew point temperature and luminescence. Regarding the wind speed, the two areas showed little variation. The noise levels in Area 1, on the other hand, during the operation of the thermoelectric power plant in its fullness, there was an increase above the permitted level, according to current Brazilian regulations, causing damage to the health of the inhabitants of its surroundings, in addition to harming the fauna of the surrounding area. around, mainly, the birds that are driven away by the noise, and, consequently, reducing the diversity of the avifauna surrounding the Thermoelectric. Thus, the use of environmental sensors to monitor the air quality of this area is very important, thus serving as a comparative support for future studies, as well as establishing the genesis for an environmental database in this metropolitan region of Campina Grande/PB, Brazil.
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Muslim, Buldan, Charisma Juni Kumalasari, Novie Chiuman, and Muhammad Ichsan Fadhil Arafah. "KAJIAN APLIKASI PANTULAN SINYAL GNSS UNTUK PEMANTAUAN KETINGGIAN PERMUKAAN AIR LAUT." Komunikasi Fisika Indonesia 16, no. 2 (October 31, 2019): 138. http://dx.doi.org/10.31258/jkfi.16.2.138-142.
Повний текст джерелаАнотація:
Design and experiment of ocean current power generation system have been carried out using the Bach In Indonesia, the tsunami early warning system only applies the earthquake and hydrosphere relationship model to predict tsunamis. To date, no tsunami detector has used radar or GNSS technology. GNSS technology can be applied as an early warning system for tsunamis, provided that tsunamis are caused by earthquakes greater than 7 magnitudes, occur 70 kilometers below sea level, and are caused by normal faults. This could be an alternative to Bouy GNSS which is expensive to install and maintain, especially for countries with vast oceans such as Indonesia. In this paper, a review of the application of GNSS signal reflection was carried out using one International GNSS Service (IGS) station, JOG2, and one Continuously Operating Reference Station (CORS), CLSA, each located in Java and Sumatra to investigate the availability of sea level monitoring in Indonesia. Determination of sea level is obtained from two methods, the GNSS signal phase data analysis method and the GNSS Signal-to-Noise Ratio (SNR) data analysis method. Both methods use reflected GNSS signals or multipath effects to obtain sea level. The results of the study show that the number of satellites that pass through Indonesia every 15 minutes is enough to get sea-level data every 15 minutes to one hour. This shows that it is possible to apply the multipath effect to obtain sea level information in Indonesia to detect tides and tsunamis as part of the tsunami early warning system in Indonesia.
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Obersteiner, F., H. Bönisch, and A. Engel. "An automated gas chromatography time-of-flight mass spectrometry instrument for the quantitative analysis of halocarbons in air." Atmospheric Measurement Techniques 9, no. 1 (January 25, 2016): 179–94. http://dx.doi.org/10.5194/amt-9-179-2016.
Повний текст джерелаАнотація:
Abstract. We present the characterization and application of a new gas chromatography time-of-flight mass spectrometry instrument (GC-TOFMS) for the quantitative analysis of halocarbons in air samples. The setup comprises three fundamental enhancements compared to our earlier work (Hoker et al., 2015): (1) full automation, (2) a mass resolving power R = m/Δm of the TOFMS (Tofwerk AG, Switzerland) increased up to 4000 and (3) a fully accessible data format of the mass spectrometric data. Automation in combination with the accessible data allowed an in-depth characterization of the instrument. Mass accuracy was found to be approximately 5 ppm in mean after automatic recalibration of the mass axis in each measurement. A TOFMS configuration giving R = 3500 was chosen to provide an R-to-sensitivity ratio suitable for our purpose. Calculated detection limits are as low as a few femtograms by means of the accurate mass information. The precision for substance quantification was 0.15 % at the best for an individual measurement and in general mainly determined by the signal-to-noise ratio of the chromatographic peak. Detector non-linearity was found to be insignificant up to a mixing ratio of roughly 150 ppt at 0.5 L sampled volume. At higher concentrations, non-linearities of a few percent were observed (precision level: 0.2 %) but could be attributed to a potential source within the detection system. A straightforward correction for those non-linearities was applied in data processing, again by exploiting the accurate mass information. Based on the overall characterization results, the GC-TOFMS instrument was found to be very well suited for the task of quantitative halocarbon trace gas observation and a big step forward compared to scanning, quadrupole MS with low mass resolving power and a TOFMS technique reported to be non-linear and restricted by a small dynamical range.
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Freisz, Severine, Juergen Graf, Matthew Benning, and Vernon Smith. "Low Multiplicity Sulfur SAD Phasing in the Home lab." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C607. http://dx.doi.org/10.1107/s2053273314093929.
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Advances in crystallographic hardware and software are enabling structural biologists to investigate more challenging projects. Recent developments in hardware and software are greatly increasing the capabilities of in-house diffraction systems making it more routine to obtain de novo structural information in the home lab. Single-wavelength anomalous diffraction (SAD) techniques with Cu Ka or Ga Ka radiation are now widely used for structure solution even in cases involving weak anomalous scatterers, like sulfur. We have now introduced the D8 Venture solution for structural biology with the PHOTON 100 detector featuring the first CMOS active pixel sensor for X-ray crystallography. Our new microfocus source, the METALJET delivers beam intensity exceeding those of typical bending-magnet beamlines. The very high intensity, the small beam focus and the lower air scatter produced by Gallium Kα radiation help to greatly reduce the background scatter. This provides greater signal to noise essential to identify weak anomalous signal. Due to the very weak anomalous scattering of S, data multiplicities in the order of 40 are typically necessary to obtain phases by S-SAD. Collecting high-multiplicity data minimizes systematic experimental errors to measure with very high accuracy the minute intensity difference between Friedel Pairs (1.0 – 1.5 %) [1]. This requires software which optimizes the collection strategy, for example with respect to overall data collection time to minimize radiation damage. The combination of a brighter, more stable X-ray source with a high sensitivity low noise detector have greatly improved the quality of data collected in-house. The high quality allows successful SAD measurements far away from the absorption edge. Here we present a low multiplicity sulfur-SAD phasing experiment on a small Thaumatin crystal showing the high quality of the data collected on the D8 VENTURE with the METALJET.
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Pan, Jin Feng, and Yan Zhang. "The Denoising Method for Transient Speed Signal of Diesel Engine." Advanced Materials Research 291-294 (July 2011): 2081–84. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.2081.
Повний текст джерелаАнотація:
A new denoising method for the diesel engine transient speed signal was proposed, especially for the signal seriously corrupted by impulsive noises. This method takes two steps. The first step is to do impulsive noise removing. An improved differential rank impulse detector was used to do impulsive noise detection in this paper. After the impulsive noise was detected, it was replaced by the median value of the window it was in. Then the second step low pass filtering is taking on. Experiments show that the proposed method could remove the noise of the acquired diesel transient speed signals effectively, the denoised signal could reflect the real working conditions of the diesel engine.
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Raymond, Jason L., Ronald A. Roy, and James Kwan. "A multi-frequency sonochemical reactor utilizing a cylindrically focused acoustic wavefield for improved sonochemical efficiency." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A61. http://dx.doi.org/10.1121/10.0010657.
Повний текст джерелаАнотація:
Sonochemistry involves several steps. First, an acoustic wave must be generated with sufficient energy to nucleate cavitation. This cavitation event must then be energetic enough to produce radicals through the sonolysis of the gas or vapor molecules in the bubble. Finally, these radical species must survive long enough to react with other chemical species to yield the desired product. The sonochemical efficiency (SE) is thus defined as the ratio of the product yield to the input acoustic power. Here, we put forward a novel approach to enhancing the SE by designing a multi-frequency (0.25 to 1MHz) sonochemical reactor that reflects a cylindrically spreading acoustic wave 180°. The reflected wave converges to cylindrically shaped high-intensity “hot zone” positioned along the axis of the reaction vessel. At modest power input, we detected noise with a passive cavitation detector in air-saturated water, suggesting the direct nucleation of cavitation. Using the Weissler reaction to determine the production of hydroxyl radicals, we determined the SE of our sonochemical reactor at various operation conditions. We also compared these values to conventional bath, horn, and plate sonochemical reactors. The comparison suggested that our reactor design had a better sonochemical efficiency for the Weissler reaction.
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Lipka, V. M., V. V. Ryukhtin, and Yu G. Dobrovolsky. "Photodetector resistant to background light noise with extended dynamic range of input signals." Технология и конструирование в электронной аппаратуре, no. 3-4 (2021): 3–8. http://dx.doi.org/10.15222/tkea2021.3-4.03.
Повний текст джерелаАнотація:
Measurement of periodic optical information signals in the background light noise with a photodetector with extended dynamic range is an urgent task of modern electronics and thus has become the aim of this study. To increase the dynamic range of the photodetector, a new version of the automatic gain control (AGC) circuit has been developed, which consists of an AGC controller, an output photodetector amplifier and an AGC detector. The authors measured the dynamic range of the photodetector when receiving optical radiation with a wavelength of 1064 nm in the power range from 2.10–8 to 2.10–5 W at a modulation frequency of 20 kHz with the AGC on. Under these conditions, the dynamic range of the photodetector was found to be up to 67 dB. If the AGC was off, the dynamic range did not exceed 30 dB. Thus, the study made it possible to create a photodetector with an extended dynamic range up to 67 dB based on a new version of the AGC circuit. The design of the photodetector allowed choosing a useful signal of a particular modulation frequency in the frequency range from 3 to 45 kHz and effectively suppresses the frequencies caused by optical interference in the low frequency range from the frequency of the input signal of constant amplitude up to 3 kHz inclusive. This compensates the current up to 15 mA, which is equivalent to the power of light interference of about 15 mW. Further research should address the issues of reliability of the proposed photodetector design and optimization of its optical system. The photodetector can be used in geodesy and ambient air quality monitoring.
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Xu, X., L. L. P. van Stee, J. Williams, J. Beens, M. Adahchour, R. J. J. Vreuls, U. A. T. Brinkman, and J. Lelieveld. "Comprehensive two-dimensional gas chromatography (GC×GC) measurements of volatile organic compounds in the atmosphere." Atmospheric Chemistry and Physics Discussions 3, no. 1 (February 27, 2003): 1139–81. http://dx.doi.org/10.5194/acpd-3-1139-2003.
Повний текст джерелаАнотація:
Abstract. During the MINOS campaign in August 2001 comprehensive two-dimensional gas chromatography (GC×GC) was applied to the in situ measurements of atmospheric volatile organic compounds (VOCs) at the Finokalia ground station, Crete. The measurement system employs a thermal desorption unit for on-line sampling and injection, and a GCxGC separation system equipped with a flame ionization detector (FID) for detection. The system was optimized to resolve C7−C14 organic components. Two-dimensional chromatograms from measurements of Finokalia air samples show several hundred well-separated peaks. To facilitate peak identification, cartridge samples collected at Finokalia were analyzed using the same GC×GC system coupled with a time-of-flight mass spectrometer (TOF-MS). The resulting mass spectra were deconvoluted and compared to spectra from a database for tentative peak identification. About 650 peaks have been identified in the two-dimensional plane, with significant signal/noise ratios (>100) and high spectra similarities (>800). By comparing observed retention indices with those found in the literature, 235 of the identifications have been confirmed. 150 of the confirmed compounds show up in the C7−C14 range of the chromatogram from the in situ measurement. However, at least as many peaks remain unidentified. For quantification of the GCxGC measurements, peak volumes of measured compounds have been integrated and externally calibrated using a standard gas mixture.
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Xu, X., L. L. P. Stee, J. Williams, J. Beens, M. Adahchour, R. J. J. Vreuls, U. A. Brinkman, and J. Lelieveld. "Comprehensive two-dimensional gas chromatography (GC × GC) measurements of volatile organic compounds in the atmosphere." Atmospheric Chemistry and Physics 3, no. 3 (June 10, 2003): 665–82. http://dx.doi.org/10.5194/acp-3-665-2003.
Повний текст джерелаАнотація:
Abstract. During the MINOS campaign in August 2001 comprehensive two-dimensional gas chromatography (GC x GC) was applied to the in situ measurements of atmospheric volatile organic compounds (VOCs) at the Finokalia ground station, Crete. The measurement system employs a thermal desorption unit for on-line sampling and injection, and a GC x GC separation system equipped with a flame ionization detector (FID) for detection. The system was optimized to resolve C7-C14 organic components. Two-dimensional chromatograms from measurements of Finokalia air samples show several hundred well-separated peaks. To facilitate peak identification, cartridge samples collected at Finokalia were analyzed using the same GC x GC system coupled with a time-of-flight mass spectrometer (TOF-MS). The resulting mass spectra were deconvoluted and compared to spectra from a database for tentative peak identification. About 650 peaks have been identified in the two-dimensional plane, with significant signal/noise ratios (>100) and high spectra similarities (>800). By comparing observed retention indices with those found in the literature, 235 of the identifications have been confirmed. 150 of the confirmed compounds show up in the C7-C14 range of the chromatogram from the in situ measurement. However, at least as many peaks remain unidentified. For quantification of the GC x GC measurements, peak volumes of measured compounds have been integrated and externally calibrated using a standard gas mixture.
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Vangi, D., M. Bruzzi, J. N. Caron, and M. S. Gulino. "Compact Probe for Non-Contact Ultrasonic Inspection with the Gas-Coupled Laser Acoustic Detection (GCLAD) Technique." Experimental Mechanics 62, no. 3 (October 21, 2021): 403–15. http://dx.doi.org/10.1007/s11340-021-00786-7.
Повний текст джерелаАнотація:
Abstract Background Gas-Coupled Laser Acoustic Detection (GCLAD) is a non-contact ultrasonic detection technique whose functioning relies on the deviation that a probe laser beam sustains when intersected by an acoustic wavefront propagating in a fluid. The maximum sensitivity of the technique is typically obtained when the ultrasound insists on an ample portion of the probe laser beam extension, but such a condition can be unfeasible in several non-destructive testing applications (as in case of limited accessibility to the component). Objective In the present work, a solution is provided enabling transformation of the GCLAD device in a point detector. This is based on the use of two mirrors for confining the laser beam in an area with limited width and depth, where reflections however maximize the portion of the probe laser beam subjected to ultrasonic oscillation. Methods The characteristics of the obtained GCLAD probe are thoroughly analysed by applying the device to the detection of surface acoustic waves, propagating on a metal bar and refracting into the air. Two different inspection configurations are considered, whose difference lies in the mutual orientation between laser beam and solid surface. The effect on the received signal amplitude of the number of beam reflections, the dimensions of the resulting device, and the bar axisimmetry is investigated in both configurations. Results The optimization of all the analysed standpoints enables obtaining a compact GCLAD probe that features the same signal amplitude of the non-compact alternative. To obtain maximum responsivity of the system, the number of reflections must be maximized, while the distance between the mirrors must be carefully set based on the employed inspection configuration and the eventual axisimmetry of the specimen. The devised GCLAD compact probe is capable of expanding the application range of the technique also to those cases in which the use of point detectors is desirable, without compromising the signal-to-noise ratio of the resulting acquisitions compared to the non-compact alternative.
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Zara, Marina, K. Folkert Boersma, Isabelle De Smedt, Andreas Richter, Enno Peters, Jos H. G. M. van Geffen, Steffen Beirle, et al. "Improved slant column density retrieval of nitrogen dioxide and formaldehyde for OMI and GOME-2A from QA4ECV: intercomparison, uncertainty characterisation, and trends." Atmospheric Measurement Techniques 11, no. 7 (July 11, 2018): 4033–58. http://dx.doi.org/10.5194/amt-11-4033-2018.
Повний текст джерелаАнотація:
Abstract. Nitrogen dioxide (NO2) and formaldehyde (HCHO) column data from satellite instruments are used for air quality and climate studies. Both NO2 and HCHO have been identified as precursors to the ozone (O3) and aerosol essential climate variables, and it is essential to quantify and characterise their uncertainties. Here we present an intercomparison of NO2 and HCHO slant column density (SCD) retrievals from four different research groups (BIRA-IASB, IUP Bremen, and KNMI as part of the Quality Assurance for Essential Climate Variables (QA4ECV) project consortium, and NASA) and from the OMI and GOME-2A instruments. Our evaluation is motivated by recent improvements in differential optical absorption spectroscopy (DOAS) fitting techniques and by the desire to provide a fully traceable uncertainty budget for the climate data record generated within QA4ECV. The improved NO2 and HCHO SCD values are in close agreement but with substantial differences in the reported uncertainties between groups and instruments. To check the DOAS uncertainties, we use an independent estimate based on the spatial variability of the SCDs within a remote region. For NO2, we find the smallest uncertainties from the new QA4ECV retrieval (0.8 × 1015 molec. cm−2 for both instruments over their mission lifetimes). Relative to earlier approaches, the QA4ECV NO2 retrieval shows better agreement between DOAS and statistical uncertainty estimates, suggesting that the improved QA4ECV NO2 retrieval has reduced but not altogether eliminated systematic errors in the fitting approach. For HCHO, we reach similar conclusions (QA4ECV uncertainties of 8–12 × 1015 molec. cm−2), but the closeness between the DOAS and statistical uncertainty estimates suggests that HCHO uncertainties are indeed dominated by random noise from the satellite's level 1 data. We find that SCD uncertainties are smallest for high top-of-atmosphere reflectance levels with high measurement signal-to-noise ratios. From 2005 to 2015, OMI NO2 SCD uncertainties increase by 1–2 % year−1, which is related to detector degradation and stripes, but OMI HCHO SCD uncertainties are remarkably stable (increase < 1 % year−1) and this is related to the use of Earth radiance reference spectra which reduces stripes. For GOME-2A, NO2 and HCHO SCD uncertainties increased by 7–9 and 11–15 % year−1 respectively up until September 2009, when heating of the instrument markedly reduced further throughput loss, stabilising the degradation of SCD uncertainty to < 3 % year−1 for 2009–2015. Our work suggests that the NO2 SCD uncertainty largely consists of a random component ( ∼ 65 % of the total uncertainty) as a result of the propagation of measurement noise but also of a substantial systematic component ( ∼ 35 % of the total uncertainty) mainly from stripe effects. Averaging over multiple pixels in space and/or time can significantly reduce the SCD uncertainties. This suggests that trend detection in OMI, GOME-2 NO2, and HCHO time series is not limited by the spectral fitting but rather by the adequacy of assumptions on the atmospheric state in the later air mass factor (AMF) calculation step.
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Zaraska, Krzysztof, Janina Gaudyn, Adam Bieńkowski, Marek Dohnalik, Andrzej Czerwiński, Mariusz Płuska, and Monika Machnik. "X-Ray Inspection of LTCC Devices." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2011, CICMT (September 1, 2011): 000215–23. http://dx.doi.org/10.4071/cicmt-2011-wp13.
Повний текст джерелаАнотація:
The appeal of LTCC (Low Temperature Cofired Ceramic) process lies in the possibility of creating multilayer (3D) structures, integrating conductor paths, passive elements, such as inductors and resistors and resonance cavities. Unfortunately, the very nature of cofired device makes post-firing optical inspection of buried elements impossible, as the ceramic material is opaque to visible light. This limitation, however, does not exist at X-ray wavelengths. The aim of this paper is to provide a practical overview of application of high resolution X-ray imaging for non-destructive inspection and fault detection in multilayer LTCC structures. First, we present a simplified mathematical description of X-ray absorption inside an LTCC structure and demonstrate that due to physical properties of substrate (glass/Al2O3 ceramic), conductor material (silver) and cavity fill (air), a high contrast image of the investigated structure can be obtained. Next, we show application of a commercial off-the shelf industrial X-ray system for imaging various faults in LTCC structures, such as: via voids (caused by inadequate filling of a via hole with conductor material), microcracks, paste creep (during lamination, excess via conductor leaks out of the via hole and in between the tape layers, shorting the via to an adjacent circuit), interruptions in conductor paths and alignment errors. We also demonstrate application of computed tomography for verifying 3D geometry of buried resonance cavities and detecting tape delaminations. Finally, we discuss limitations of the method, related to structure thickness (number of layers), material composition, imaging geometry and equipment characteristics, such as detector resolution and spatial noise.
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Chen, Guang Hua, Wen Zhou, Feng Jiao Wang, Bin Jie Xiao, and Sun Fang Dai. "Lane Detection Based on Improved Canny Detector and Least Square Fitting." Advanced Materials Research 765-767 (September 2013): 2383–87. http://dx.doi.org/10.4028/www.scientific.net/amr.765-767.2383.
Повний текст джерелаАнотація:
The video images of road monitoring system contain noise, which blurs the difference between the lane and the background. The lane detection algorithm based on traditional Canny edge detector hardly detects the single-pixel lane accurately and it produces pseudo lane. The paper proposes an effective lane detection method based on improved Canny edge detector and least square fitting. The proposed method improves the dual-threshold selection of traditional Canny detector by using the histogram concavity analysis, which sets the optimal threshold automatically. The least square method is used to fit the feature points of detected edges to accurate and single-pixel wide lane. Experimental results show that the proposed method detects the lane of video images accurately in the noise environment.
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Qu, Fu Yong, and Xiang Wei Meng. "Detection Performance of Several Nonparametric Detectors under K-Distributed Clutter." Advanced Materials Research 433-440 (January 2012): 6417–21. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.6417.
Повний текст джерелаАнотація:
Because of nonparametric detectors’ ability of ensuring constant false alarm rate (CFAR) for a wide class of input noise distributions and engineering implementation simply, much efforts have been directed towards the study of nonparametric methods of signal detection. This paper deals with a comparative analysis of nonparametric detectors-GS, MW, Savage detector under K-distributed clutter in homogeneous and nonhomogeneous background caused by multiple targets and clutter edge. Some results of detection probability versus signal-to-clutter ratio (SCR) are presented in curves for different detector parameter values in homogeneous and multiple targets background. And the ability to control the false alarm probability for the three nonparametric detectors is presented in table. The simulation results show that S detector performs robustly in homogeneous background and clutter edge background, and can tolerate more interfering targets through increasing the number of reference cells and pulse sweeps. Therefore as a compromise solution, S detector with moderate parameters can be used in actual radar system.