China
Africa
Explore chapters and articles related to this topic
Beta and Alpha Particle Autoradiography
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Anders Örbom, Brian W. Miller, Tom Bäck
A key benefit of single-particle digital autoradiography with alphas is the ability to quantify the activity directly. Beta emitters have a continuous energy spectrum ranging from low to high energies. Accordingly, most detectors employ an energy threshold for detection above noise levels. Also, there will be an energy dependent efficiency associated with the scintillator. These factors and beta spectra differences among isotopes require the use of isotope-specific calibration standards for quantification. Alpha particles, however, have discrete energies and a short range (e.g., 20–80 μm) in the scintillator detector. This makes them easy to detect at nearly 100 percent efficiency in single-particle detectors, without the need for relative activity calibration standards. Miller showed with the iQID approximately 100 per cent detection efficiency (within the uncertainty of certified electroplated alpha sources) for alphas [47]. Imaging and activity quantification is illustrated in Figure 30.14 with 211At (7.2h half-life) and estimating the activity using spatio-temporal information for each event.
Spectroscopic Methods
Published in Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus, Environmental Chemical Analysis, 2018
Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus
All spectrometers, although they use very different spectral regions and produce different types of information, use certain common components. These fall into the categories of light sources, monochromators, and radiation detectors. In absorbance spectroscopy a source of radiation must be provided in order to measure the amount absorbed. In fluorescence spectroscopy, a source is needed to excite the fluorescence that will be measured. After light is transmitted through or emitted by the sample, it is necessary to measure its intensity at one or more wavelengths. A detector is a device to convert the energy of the radiation into current or voltage in the measuring circuitry. Often the electrical signal is very small and requires amplification before it can be analyzed. The type of detector needed to determine the intensity of emitted or transmitted light depends on the wavelength. For all detectors, the desired properties are linearity, sensitivity, stability, and a wide linear dynamic range. Of course, all these properties are not always available, but the quality and usefulness of a detector can be measured by comparing these qualities among different choices. Finally, it is often necessary to select a band of wavelengths for use in the measurement. This is done by filtering out unwanted wavelengths or by dispersing the radiation from the sample or from the source into its component wavelengths, thus separating them in space.
Temperature and heat flux measurements
Published in Stefano Discetti, Andrea Ianiro, Experimental Aerodynamics, 2017
The ability of an IR detector to measure thermal radiation with an acceptable S/N ratio is quantified by means of the detectivity. The noise level can be characterized with a noise equivalent power, which is the total radiative power (in watts) needed to produce an output equal to the detector noise. According to Jones’s definition [65,66], the detectivity increases with the size of the detector (of surface A, in cm2) and the equivalent noise bandwidth Δf (in Hz), while it is inversely proportional to the NEP. Hence, the normalized detectivity is defined as [65,66] D*=AΔfNEP An overview of normalized detectivity for different detector materials is shown in Figure 6.18, from the comprehensive review of Rogalski [67].
Investigation and Analysis of Thermoelectrically Cooled CZT Performance
Published in Nuclear Technology, 2023
Amanda D. E. Foley, Swomitra K. Mohanty, Glenn E. Sjoden
An adjoint calculation was performed for our 5 × 5 × 5-mm3 detector; the CZT crystal efficiency was modeled using the three-dimensional (3-D) SN code PENTRAN using the adjoint mode with S32/P2 quadrature and angular anisotropy, respectively, with 12 energy groups spanning [0, 1] MeV (Ref. 12). The solution angular/energy/spatial cell matrix resulted in ~108 equations. As an exemplar of the results, a plot of the scalar CZT crystal detector efficiency (adjoint) for 275-keV gamma rays and 650-keV gamma rays is in Fig. 4. The figure shows that the CZT detector efficiency is an order of magnitude higher for the 275-keV gamma rays than for the 650-keV gamma rays. The efficiency for the 250- and 650-keV gamma rays drops by five and four orders of magnitude, respectively, when the source is moved from 0 to 2 cm from the detector.
A Non-Linear Improved CNN Equalizer with Batch Gradient Decent In 5G Wireless Optical Communication
Published in IETE Journal of Research, 2023
Asish B. Mathews, Arun B. Mathews, C. Agees Kumar
Scientists are looking at novel waveforms to meet the demanding criteria set, which are already taking place in numerous aspects of the world. In low-access optical communication networks with higher bandwidth access and low operating costs, numerous applications that use big data and cloud computing play an active role. In Amplitude Modulation Direct Detection systems, nonlinear components such as the Electro Optical (EO) modulator, square law detector, and fiber propagation cause nonlinear distortion. The device’s performance is decreased as a result of these characteristics. The coordination mechanism has become increasingly important for a variety of machine learning techniques [1,2]. Optical fiber communication tasks that are performed from a machine learning perspective include performance observation, fiber nonlinearity reduction, carrier recovery, and recognizing modulation format [3,4]. Fiber dispersion and nonlinear effects restrict the data rate in current optical transmission networks [5].
Single Chip Realizable High Performance Full-Wave Rectifier
Published in International Journal of Electronics, 2022
Atul Kumar, Bhartendu Chaturvedi, Jitendra Mohan, Sudhanshu Maheshwari
A rectifier is an essential block in various applications such as DC power supplies, amplitude modulation (AM) detector, voltage multiplier, AC voltmeters, AC ammeters, clipper circuits, signal polarity detector, sample and hold circuits and peak value detectors. At a low frequency range, the rectifier may find applications in biomedical systems. Radio frequency identification and radio frequency energy harvesting are the very high frequency applications of rectifier circuits (Fischer et al., 2016; Muhammad et al., 2020). Therefore, in current scenario, novel rectification blocks are always popular and always on demand. Consequently, proposed novel blocks are also well tested at low frequencies as low as 10 Hz, at medium frequencies in the range of 10 kHz–100 kHz and at high frequencies as high as 1 MHz.