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Psychophysiological Test Methods and Procedures
Published in Samuel G. Charlton, Thomas G. O’Brien, Handbook of Human Factors Testing and Evaluation, 2019
Movement-related artifacts can be reduced by taping the electrode leads to the body or clothing so that they are prevented from moving across the skin. Providing stress-reducing loops that are taped next to the electrodes can also help. Because the biological artifacts cannot be prevented by shielding, we are left with three options: Filters can be used, artifacts can be detected and removed, or we may have to remove the contaminated sections of data from analysis. Electronic filters are useful in removing unwanted signals when their frequency does not overlap with those of the wanted signals. For example, EOG activity is fairly slow, below 10 Hz. The frequency of the EMG activity is much higher, up to several hundred hertz, but does go as low as 10 Hz. By using filters that greatly reduce activity above 10 Hz, we can effectively eliminate the effects of EMG on the EOG. Sometimes we are not so fortunate. EEG activity is commonly analyzed up to 30 Hz or higher, which includes the lower end of the EMG spectra. Using filters set to filter out activity above 10 Hz would eliminate a large part of our wanted EEG signals. In this case it may be wise to analyze the EEG only to 15 Hz or so to avoid the EMG contamination. In other cases, such as EOG contamination of EEG, it is possible to identify the contaminating EOG signals and remove them from the EEG portion of the signal. Eye blinks and eye movements have characteristics that can be used to separate them from the EEG. Several published algorithms exist to detect and remove eye contaminates from EEG signals. Commercially available EEG systems often include these routines as part of their analysis packages.
Operational Amplifiers
Published in John Okyere Attia, Circuits and Electronics, 2017
Electronic filter circuits are circuits that can be used to attenuate particular band(s) of frequency and also pass other band(s) of frequency. The following types of filters are discussed in this section: lowpass, bandpass, highpass, and band-reject. The filters have passband, stopband, and transition band. The order of the filter determines the transition from the passband to stopband.
Electricity and Transportation Markets
Published in Anco S. Blazev, Global Energy Market Trends, 2021
A surge protector or simple capacitor or varistor can also protect against most overvoltage conditions, while a lightning arrester protects against severe spikes. In many cases electronic filters are also used to remove undesirable harmonics in the power fed to sensitive devices.
Efficiency of radiofrequency-vacuum (RF/V) technology for mixed-species drying of wood disks with inherent defects
Published in Drying Technology, 2022
Asghar Tarmian, Hasan Hüseyin Ciritcioğlu, Öner Ünsal, Peyman Ahmadi, Behnam Gholampour, Reza Oladi
An industrial RF/V kiln with a capacity of 8 m3 and a maximum output power of 50 kW was used to dry the disks (Figure 1). Drying was carried out at a fixed frequency of 6.78 MHz, maximum vacuum of 0.84 bar, and electrode voltage that ranged from 4 to 10 kV. The disks were randomly solid stacked on each other between two 3-mm-thick electrode plates at a distance of about 210 mm. Regular stainless metal-sheathed PT-100 thermocouples with a diameter of 8 mm were used to monitor wood temperature. High frequency has a distorting noise effect on the PT-100 temperature sensors. An RLC (Resistor, L-Inductor-Capacitor) electronic filter unit was used to dampen high frequency signal noise produced by the RF generator in the drying system. Thus, the signal/noise ratio was balanced and the temperature measurements were taken using the PT100 thermocouple. A compression load of 70 bar was applied onto the wood disks using a hydraulic system. A mild four-step schedule was used to dry the disks (Table 3). An average power density in the range of 1-2 kW per m3 was used during drying. The temperature at the beginning of the first step was set at 27 °C, and when it reached 38 °C, the fourth step began. A maximum temperature of 45 °C was reached at the end of drying. RF power was continuously applied during the first three steps, whereas for better control, the RF generator was turned off every 60 min for 45 min during the final step. Before the drying process began, the moisture content of randomly selected samples was measured and recorded. During the drying process, the average moisture content of the disk load was monitored and calculated by measuring the initial total weight of the load and the volume of water in the collection tank. For this purpose, the weight changes were recorded using several load cells placed under the RF/V drying kiln. The tare weight of the RF/V drying system was first determined to eliminate the kiln weight; the weight of the disks loaded into the kiln was then determined by measuring the system weight a second time. The wood disks were dried to the target moisture content of 12%.
Photonic broadband signal frequency conversion and bandwidth multiplication based on a Fourier domain mode-locked optoelectronic oscillator
Published in Journal of Modern Optics, 2021
Yalan Wang, Jin Zhang, Xiang Li, Jianghai Wo, Anle Wang, Xiaoniu Peng
Finally, the single sideband (SSB) phase noise of the proposed OEO is also studied. As the instantaneous frequency of the generated signal varies periodically, its Fourier frequency is discrete with a spacing corresponding to the mode spacing of the OEO, which is 162.2 kHz when the SMF delay length is 1 km. The phase noise feature should be implemented by measuring one of the frequency lines. Due to the quasi-stationary process of the signal generation based on the FDML-OEO, the phase noise of the LFM signal would be degraded, as compared to that of the single-frequency signal generated by a stationary process [24]. Since it is difficult to filter out a single line using a conventional electronic filter, we measure the phase noise performance of the OEO by using a sinusoidal signal generated by the AWG, which can still evaluate the performance of the converted signal. During the measurement, a sinusoidal signal with a frequency of 20 GHz is applied onto the RF port of the MZM. By changing the frequency of the laser source, a converted signal with a frequency of 2.7 GHz is obtained. It needs to be noted that, unlike conventional OEO-based frequency converter in which the OEO is used only as a local oscillator (LO), the converted signal in this system is generated by the oscillation itself [25]. Thus, the phase noise of the converted signal should follow that of the OEO, as demonstrated in Figure 7. As we can see, the phase noise performance of the converted signal is slightly higher than that of the signal generated by AWG when the frequency offset is smaller than 1 kHz, which is mainly due to the instability of the OEO. However, thanks to the low noise characteristic of the OEO, the phase noise is improved by 24 dB at the frequency offset of ∼10 kHz. As a comparison, the SSB phase noise of the free-running OEO is also measured, as depicted by the blue line. Since the performance of the OEO is closely related to the delay loop, better phase noise can be expected by using a longer loop. Furthermore, to solve the mode competition problem and improve the stability of the converted signal, self-injection and phase-lock loop technology can be adopted [25].