frequency bandwidth
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This paper presents the design results of a 100-channel integrated circuit dedicated to various biomedical experiments requiring both electrical stimulation and recording ability. The main design motivation was to develop an architecture that would comprise not only the recording and stimulation, but would also block allowing to meet different experimental requirements. Therefore, both the controllability and programmability were prime concerns, as well as the main chip parameters uniformity. The recording stage allows one to set their parameters independently from channel to channel, i.e., the frequency bandwidth can be controlled in the (0.3 Hz–1 kHz)–(20 Hz–3 kHz) (slow signal path) or (0.3 Hz–1 kHz)–4.7 kHz (fast signal path) range, while the voltage gain can be set individually either to 43.5 dB or 52 dB. Importantly, thanks to in-pixel circuitry, main system parameters may be controlled individually allowing to mitigate the circuitry components spread, i.e., lower corner frequency can be tuned in the 54 dB range with approximately 5% precision, and the upper corner frequency spread is only 4.2%, while the voltage gain spread is only 0.62%. The current stimulator may also be controlled in the broad range (69 dB) with its current setting precision being no worse than 2.6%. The recording channels’ input-referred noise is equal to 8.5 µVRMS in the 10 Hz–4.7 kHz bandwidth. The single-pixel occupies 0.16 mm2 and consumes 12 µW (recording part) and 22 µW (stimulation blocks).

The exploration of marine resources has become an essential part of the development of marine strategies of various countries. MEMS vector hydrophone has great application value in the exploration of marine resources. However, existing MEMS vector hydrophones have a narrow frequency bandwidth and are based on rigid substrates, which are not easy to be bent in the array of underwater robots. This paper introduces a new type of flexible buckling crossbeam–cilium flexible MEMS vector hydrophone, arranged on a curved surface by a flexible substrate. A hydrophone model in the fluid domain was established by COMSOL Multiphysics software. A flexible hydrophone with a bandwidth of 20~4992 Hz, a sensitivity of −193.7 dB, excellent “8” character directivity, and a depth of concave point of 41.5 dB was obtained through structured data optimization. This study plays a guiding role in the manufacture and application of flexible hydrophones and sheds light on a new way of marine exploration.

Abstract Objectives The current study aims to assess different high-frequency (HF) band power calculations based on different frequency bandwidth values, and compare them with the time domain the root mean square of successive RR differences (RMSSD) value in preterm infants. Methods At week 32, electrocardiogram (ECG) and breathing rate (BR) were recorded for 24 h on 30 preterm infants born between 28 and 32 weeks. The recording held in the neonatal intensive care unit without any interruption of routine. Results The median 24 h BR was 40–78 breaths per minute. The RMSSD was highly and positively correlated with frequency bands that were based on each preterms BR range, or on a constant frequency with band limits of 0.4–2 Hz. Conclusions At week 32, HF band Hz limits should be calculated based on each child’s breathing rate, generally between 0.4 and 2 Hz.

Abstract Wide range frequency bandwidth on seismic data is a necessity due to its close relation to resolution and depth of target. High-frequency seismic waves provide high-resolution imaging that defines thin bed layers in shallow sediment, while low-frequency seismic waves can penetrate into deeper target depth. As a result of broadband seismic technology, its wide range of frequency bandwidth is a suitable geophysical exploration method in the oil and gas industry. A major obstacle that is frequently found in marine seismic data acquisition is the existence of multiples. Short period multiple and reverberation are commonly attenuated by the predictive deconvolution method on prestack data. Advanced methods are needed to suppress long period multiple in marine seismic data. The 2D broadband marine seismic data from deep Morowali Waters, Sulawesi, contains both short and long period multiples. The predictive deconvolution, which is applied to the processing sequences, successfully eliminates short period multiple on prestack data. The combination of F-k filter and Surface Related Multiple Elimination (SRME) methods are successful in attenuating long period multiple of the 2D broadband marine seismic data. The Prestack Time Migration section shows fine resolution of seismic images.

Abstract Magnetoelectric seismometers can measure earthquake information and play an important role in earthquake monitoring. Aiming at the wider effective frequency bandwidth of magnetoelectric seismometers, a novel seismometer based on topology optimization structural pendulum is reported. The topology optimization of leaf spring structure in magnetoelectric seismometer is designed, the natural frequency and spurious frequency characteristics of the novel seismometer are analyzed. Based on variable density theory, the Solid Isotropic Material with Penalization (SIMP) model of the seismometer is established, and the Method of Moving Asymmetric (MMA) is adopted to obtain the optimal topology structure. The finite element analysis using ANSYS shows that novel seismometer after topology optimization structure is characteristic with lower natural frequency and higher spurious frequency than that of before optimization seismometer. The real vibration experimental results indicate that after topology optimization, the effective frequency bandwidth of seismometer is increased by 55.50%, improving from [1s, 51Hz] to [4s, 78Hz].

This paper presents the design, manufacturing, and testing of a Ku-band magnified active Tx/Rx multibeam antenna based on a discrete constrained lens. Multibeam antennas based on constrained lenses generate a significant number of beams on a large operative frequency bandwidth. The main novelty and challenge in this development are associated with the combined transmitting and receiving functionality of this active array. An innovative RF building blockchain working in dual-polarization and covering both the transmitting and receiving bandwidth is successfully implemented. In order to improve the accommodation constraints and the thermal control, the active lens is magnified by two confocal paraboloidal reflectors. To validate the design procedure, experimental results are compared with numerical ones.

Abstract Methods and algorithms for calculating the frequency of self-oscillations in swirling coolant flows of nuclear power plants with VVER reactors have been developed. The frequency of self-oscillations occurring in the acoustic sections of the primary circuit and their connections in the starting modes of the power unit and when operating at the rated power level is predicted. It is established that the self-oscillation frequencies can fall into the frequency bandwidth of mechanical vibrations and vibrations of the reactor plant’s internal devices. It is shown that in order to prevent the resonance of self-oscillations of the coolant with the vibration frequencies of internal devices, it is necessary and sufficient to take the frequency of self-oscillations outside the bandwidth of the vibration frequency of structures. The results of verification of the results of forecasting the frequency of self-oscillations in swirling coolant flows at a nuclear power plant unit with VVER are presented. The application of the developed technique shows that the pendulum oscillations of the VVER - 1200 body are caused by an increase in the parameters of the coolant and the geometric dimensions of the VVER - 1200 reactor compared to VVER-1000.

Abstract In this work, the reverse dispersion entropy (RDE) is used to process the squared envelope signal in order to detect nonstationarites. Based on the idea of spectral kurtosis (SK) and kurtogram, the squared envelope signal is first extracted by applying STFT to vibration signal. Then, as an alternative to negative Shannon entropy, the RDE is used to process the squared envelope to detect the range of frequencies at which the transients occur. The RDEgram color-coded map is used to represent the RDE values as a function of frequency and frequency resolution from which the ideal filter parameters can be inferred. Once, the best frequency and frequency bandwidth pair are found, an optimum FIR filter can be designed to filter the original vibration signal. The proposed method is tested against simulated and actual vibration signals and proved to be superior to existing methods.