Intermediate Frequency Research Articles

Millimeter wave-based patient setup verification and motion tracking during radiotherapy.

Position verification and motion monitoring are critical for safe and precise radiotherapy (RT). Existing approaches to these tasks based on visible light or x-ray are suboptimal either because they cannot penetrate obstructions to the patient's skin or introduce additional radiation exposure. The low-cost mmWave radar is an ideal solution for these tasks as it can monitor patient position and motion continuously throughout the treatment delivery. To develop and validate frequency-modulated continuous wave (FMCW) mmWave radars for position verification and motion tracking during RT delivery. A 77GHz FMCW mmWave module was used in this study. Chirp Z Transform-based (CZT) algorithm was developed to process the intermediate frequency (IF) signals. Absolute distances to flat Solid Water slabs and human shape phantoms were measured. The accuracy of absolute distance and relative displacement were evaluated. Without obstruction, mmWave based on the CZT algorithm was able to detect absolute distance within 1mm for a Solid Water slab that simulated the reflectivity of the human body. Through obstructive materials, the mmWave device was able to detect absolute distance within 5mm in the worst case and within 3.5mm in most cases. The CZT algorithm significantly improved the accuracy of absolute distance measurement compared with Fast Fourier Transform (FFT) algorithm and was able to achieve submillimeter displacement accuracy with and without obstructions. The surface-to-skin distance (SSD) measurement accuracy was within 8mm in the anterior of the phantom. With the CZT signal processing algorithm, the mmWave radar is able to measure the absolute distance to a flat surface within 1mm. But the absolute distance measurement to a human shape phantom is as large as 8mm at some angles. Further improvement is necessary to improve the accuracy of SSD measurement to uneven surfaces by the mmWave radar.

A Cryogenic Wideband (2.5–14 GHz) Receiver System for the Arecibo Observatory 12 m Telescope

AbstractIn this paper we present details of the construction of a wideband, cryogenic receiver and its successful commissioning on the Arecibo Observatory 12 m telescope. The cryogenic receiver works in the 2.5–14 GHz frequency range. We upgraded the current narrow band, room temperature receivers of the telescope with the new wideband receiver. The current receiver is built around a Quadruple‐Ridged Flared Horn (QRFH) developed by Akgiray et al. (2013, https://doi.org/10.1109/tap.2012.2229953). To mitigate strong radio frequency interference (RFI) below 2.7 GHz, we installed a highpass filter before the first stage low noise amplifier (LNA). The QRFH, highpass filter, noise coupler and LNA are located inside a cryostat and are cooled to 15 K. The measured receiver temperature is 25 K (median value) over 2.5–14 GHz. The system temperature measured at zenith is about 40 K near 3.1 and 8.6 GHz and the zenith antenna gains are 0.025 and 0.018 K/Jy at the two frequencies respectively. We recommend the following improvements to the telescope system: (a) Upgrade the highpass filter to achieve better RFI rejection near 2.5 GHz; (b) Improve aperture efficiency at 8.6 GHz; (c) Upgrade the intermediate frequency system to increase the upper frequency of operation from 12 to 14 GHz.

Relatedness coefficients and their applications for triplets and quartets of genetic markers.

Relatedness coefficients which seek the identity-by-descent of genetic markers are described. The markers are in groups of two, three or four, and if four, can consist of two pairs. It is essential to use cumulants (not moments) for four-marker-gene probabilities, as the covariance of homozygosity, used in four-marker applications, can only be described with cumulants. A covariance of homozygosity between pairs of markers arises when populations follow a mixture distribution. Also, the probability of four markers all identical-by-descent equals the normalized fourth cumulant. In this article, a "genetic marker" generally represents either a gene locus or an allele at a locus. Applications of three marker coefficients mainly involve conditional regression, and applications of four marker coefficients can involve identity disequilibrium. Estimation of relatedness using genetic marker data is discussed. However, three- and four-marker estimators suffer from statistical and numerical problems, including higher statistical variance, complexity of estimation formula, and singularity at some intermediate allele frequencies.

On the optimization of Tuned Mass Damper Inerter (TMDI) systems for buildings subjected to real ground motions using slime mould algorithm

This paper proposes a novel optimization framework for the optimal design of Tuned Mass Damper Inerter (TMDI) devices to mitigate the excess vibration of multi degree of freedom (MDOF) buildings under earthquake ground motions. Minimizing the H∞- norm of the top floor displacement transfer functions is considered as the objective function for the optimization process. A Tuned Mass Damper Inerter (TMDI) is employed in which a TMD is placed at the top floor of a building connected via inerter. The top floor displacement of the building under eighteen (18) real earthquake ground motions classified in terms of low, intermediate and high frequency contents, is minimized using three optimization algorithms, particle swarm optimization (PSO), slime mould algorithm (SMA) and Harris Hawks optimization (HHO). The effectiveness of different algorithms is assessed using the RMS (root mean square) based values and the reduction ratio. The optimised parameters of the TMDI (mass ratio, frequency ratio, damping ratio and inertance ratio) obtained using the slime mould algorithm (SMA) are found to be better than the other optimization algorithms for the numerical example carried out in this paper. The results show that, the optimised TMDI has significant effect on the suppression of top floor displacement, acceleration with a lightweight TMD. The optimal parameters of TMDI shows a remarkable potential in suppressing maximum displacement reduction ratios of 0.83, 0.85 and 0.86 in response to low, intermediate and high frequency content earthquake ground motion, respectively. Based on the numerical results, the passive TMDI unveils a promising vibration calming system for damped elastic structure.

Experimental and numerical study on atmospheric‐pressure air dielectric barrier discharge via 50 Hz/5000 Hz dual‐frequency excitation

AbstractA dual‐frequency (DF) dielectric barrier discharge, excited by the superposition of a 50 Hz low frequency (LF) and a 5000 Hz intermediate frequency (IF), is proposed to enhance discharge. The effect of the LF voltage component on the breakdown behaviour of the DF discharge during different periods has been studied both experimentally and numerically. The number of high‐current pulses rises as the LF voltage increases. The statistical analysis shows that the number of the current pulse amplitude above 80 mA in the DF discharge reaches nearly 6 times that in the IF discharge. Additionally, the total discharge energy in the DF discharge is significantly higher than that in the IF discharge. The simulation reproduces the temporal variation of the breakdown behaviours in the DF discharge. The simulated results reveal that the maximal electric field strength of the breakdown process is greater in the DF discharge compared to the IF discharge during a half‐period of DF. Finally, the comparison between the IF and DF discharges exhibits that the LF voltage regulates the accumulation of residual charged species on the dielectric surface after the breakdown by modulating the residual voltage between the air gap.

Associations of Indoor Ventilation Frequency with Depression and Anxiety in Chinese Older Adults

Depression and anxiety carry an important public health burden. Indoor air pollution is associated with depression and anxiety. Ventilation can reduce the concentration of indoor air pollution and improve indoor air quality. This study explored the relationship between indoor ventilation frequency and depression and anxiety in older adults using the data from the 2018 Chinese Longitudinal Healthy Longevity Survey. Compared with older people with low indoor ventilation frequency, those with high indoor ventilation frequency had 51% lower odds of depression (OR=0.49, 95% CI: 0.43 to 0.57) and 37% lower odds of anxiety (OR=0.63, 95% CI: 0.43 to 0.91), and those with intermediate indoor ventilation frequency had 35% lower odds of depression (OR=0.65, 95% CI: 0.56 to 0.75) and 45% lower odds of anxiety (OR=0.55, 95% CI: 0.37 to 0.82). The results were similar across the seasons. However, there were sex, age, lifestyle, and cooking fuel use-specific differences in these associations. The findings emphasize that high ventilation frequency may be conducive to improving mental health in older adults, especially women, the old elder, nonsmokers, nondrinkers, and those who do not exercise and cooked at home.

Expresión de receptores de andrógeno en pacientes con carcinoma de mama del subtipo triple negativo.

Breast carcinoma of the triple-negative subtype (TNBC) does not express estrogen, progesterone or human epidermal growth factor recep-tor 2 (HER2) receptors. A subclassification of TNBC has been proposed into four subgroups, one of which is the luminal androgen receptor. The objective of this work was to determine the expression of the androgen receptor (AR) in women with TNBC, diagnosed by immunohistochemistry, at the Hospital Metropolitano del Norte, Valencia, Venezuela. The sample consisted of 191 pa-tients who met the inclusion criteria. The mean age of the patients at the time of diagnosis was 54.91 years. Histologically, the majority of the tumors were moderately differentiated or undifferentiated. The percentage of AR expres-sion was 22% (42 of 191). In the association between AR expression and the Ki-67 proliferative index, a greater number of AR positive cases was observed in tumors with Ki-67 expression of less than 40%. The AR positivity found in this study represents an intermediate frequency in relation to other investigations. No statistically significant differences were found with the age of the patients and histological grade of the tumors, while the Ki-67 proliferative index was lower for AR+ tumors, compared to TNBC in general.

Exposure Time Control Method for Higher Intermediate Frequency in Optical Heterodyne Imaging and Its Application to Electric-Field Imaging Based on Electro-Optic Effect.

We propose and demonstrate a method for equivalent time sampling using image sensors to selectively detect only the target frequency. Shortening the exposure time of the image sensor and using equivalent time sampling allows for the detection of frequency components that are higher than the frame rate. However, the imaging system in our previous work was also sensitive to the frequency component at 1/4 of the frame rate. In this study, we control the phase relationship between the exposure time and observed signal by inserting an additional interval once every four frames to detect the target frequency selectively. With this technique, we conducted electric field imaging based on the electro-optic effect under high noise conditions in the low-frequency band to which the conventional method is sensitive. The results demonstrated that the proposed method improved the signal-to-noise ratio.

Frequency-dependent electron power absorption mode transitions in capacitively coupled argon-oxygen plasmas

Phase Resolved Optical Emission Spectroscopy (PROES) measurements combined with 1d3v Particle-in-Cell/Monte Carlo Collisions simulations are performed to investigate the excitation dynamics in low-pressure capacitively coupled plasmas (CCPs) in argon-oxygen mixtures. The system used for this study is a geometrically symmetric CCP reactor operated in a 70% Ar-30% O2 mixture at 120 Pa, applying a peak-to-peak voltage of 350 V, with a wide range of driving RF frequencies (2 MHz  ⩽f⩽ 15 MHz). The measured and calculated spatio-temporal distributions of the electron impact excitation rates from the Ar ground state to the Ar 2p1 level show good qualitative agreement. The distributions show significant frequency dependence, which is generally considered to be predictive of transitions in the dominant discharge operating mode. Three frequency ranges can be distinguished, showing distinctly different excitation characteristics: (i) in the low frequency range ( f⩽ 3 MHz), excitation is strong at the sheaths and weak in the bulk region; (ii) at intermediate frequencies (3.5 MHz ⩽f⩽ 5 MHz), the excitation rate in the bulk region is enhanced and shows striation formation; (iii) above 6 MHz, excitation in the bulk gradually decreases with increasing frequency. Boltzmann term analysis was performed to quantify the frequency-dependent contributions of the Ohmic and ambipolar terms to the electron power absorption.

A Full-Duplex 60 GHz Transceiver with Digital Self-Interference Cancellation

This paper presents the design and measurement of an IEEE 802.11ad standard compatible RF transceiver for 60 GHz wireless communication systems. In addition to the traditional half-duplex (HD) mode, this work supports full-duplex (FD) operations to deliver better channel utilization and faster response times for the system. The isolation between the transmitter and receiver from the architecture design to system integration for FD operations has been fully considered. A digital self-interference cancellation (DSIC) is implemented in MATLAB to verify the FD performance. The super-heterodyne architecture with an intermediate frequency (IF) of 12 GHz is designed to suppress the image frequencies without using extra filters. A flexible phase-locked loop (PLL) synthesizer provides a local oscillator (LO) frequency with a 2 kHz resolution. Other than the time division duplex (TDD) mode used in the conventional 60 GHz system, a wide-bandwidth baseband digital variable-gain amplifier (DVGA) with a 3 dB bandwidth of more than 4 GHz also supports frequency division duplex (FDD) operations. The transceiver chip is fabricated using the Tower Jazz 0.18 µm SiGe BiCMOS process. With an on-board antenna, the transceiver covers all four channels in the 802.11ad standard, with MCS-12 (7.04 Gbps under 1.76 GSym/s and 16-QAM) under 1.5 m. In the proposed system design, the RF frontend-based self-interference (SI) suppression from the local transmitter to receiver LNA is around 54 dB. To achieve a practical FD application, the SI is further suppressed with the help of a digital SI compensation. The measured power consumption for the transmitter and receiver configurations are 194 mW and 231 mW, respectively, in HD mode and 398 mW for the FDD or FD operation mode.

Disturbance-diversity relationships of microbial communities change based on growth substrate.

Disturbance events can impact ecological community dynamics. Understanding how communities respond to disturbances and how those responses can vary is a challenge in microbial ecology. In this study, we grew a previously enriched specialized microbial community on either cellulose or glucose as a sole carbon source and subjected them to one of five different disturbance regimes of varying frequencies ranging from low to high. Using 16S rRNA gene amplicon sequencing, we show that the community structure is largely driven by substrate, but disturbance frequency affects community composition and successional dynamics. When grown on cellulose, bacteria in the genera Cellvibrio, Lacunisphaera, and Asticcacaulis are the most abundant microbes. However, Lacunisphaera is only abundant in the lower disturbance frequency treatments, while Asticcacaulis is more abundant in the highest disturbance frequency treatment. When grown on glucose, the most abundant microbes are two Pseudomonas sequence variants and a Cohnella sequence variant that is only abundant in the highest disturbance frequency treatment. Communities grown on cellulose exhibited a greater range of diversity (1.95-7.33 Hill 1 diversity) that peaks at the intermediate disturbance frequency treatment or one disturbance every 3 days. Communities grown on glucose, however, ranged from 1.63 to 5.19 Hill 1 diversity with peak diversity at the greatest disturbance frequency treatment. These results demonstrate that the dynamics of a microbial community can vary depending on substrate and the disturbance frequency and may potentially explain the variety of diversity-disturbance relationships observed in microbial systems.IMPORTANCEA generalizable diversity-disturbance relationship (DDR) of microbial communities remains a contentious topic. Various microbial systems have different DDRs. Rather than finding support or refuting specific DDRs, we investigated the underlying factors that lead to different DDRs. In this study, we measured a cellulose-enriched microbial community's response to a range of disturbance frequencies from high to low, across two different substrates: cellulose and glucose. We demonstrate that the community displays a unimodal DDR when grown on cellulose and a monotonically increasing DDR when grown on glucose. Our findings suggest that the same community can display different DDRs. These results suggest that the range of DDRs we observe across different microbial systems may be due to the nutritional resources microbial communities can access and the interactions between bacteria and their environment.

The impact of the frequency content of far-field earthquakes on the optimum parameters and performance of tuned mass damper inerter

Tuned mass damper inerter is a passive control device that is proven to be effective in mitigating structural responses under earthquake excitations, however, its efficiency highly depends on its design parameters. This paper aims to investigate how the optimum parameters of TMDI change with the frequency content of far-field earthquakes to minimize the need for repeatedly optimizing these parameters for varying far-field earthquakes and structural characteristics. To achieve this objective, the ratio of the earthquake's frequency to the structure's frequency is defined as an index to simultaneously represent the structure and the earthquake. Case studies of 5, 10, 15, and 20-story building structures are analyzed under twenty-three far-field earthquakes which are categorized into three main groups based on their frequency (PGA/PGV) including “Low”, “Intermediate”, and “High”. Particle Swarm Optimization (PSO) is employed to obtain the optimum parameters of TMDI including the damping and the frequency ratio to minimize two distinct objective functions: (1) the peak displacement and (2) the peak acceleration of the top story in a time domain analysis. To validate the applicability of the proposed method in determining the optimal parameters of TMDI regardless of the earthquake and structure frequency, a 10-story benchmark building is employed. Moreover, this study demonstrates the effectiveness of TMDI in minimizing the objective functions concerning the frequency content of the earthquake. It also illustrates the trend of the PSO optimization process. The results show that the index provides a discernible pattern for the variation of the optimum parameters of TMDI. Furthermore, it is demonstrated that the difference in the structural response between tuning the TMDI with the PSO algorithm and the suggested method is less than 3 % when the index is greater than 1. As the ratio of earthquake frequency to the frequency of structure increases, the objective functions will correspondingly increase. The results also indicate that, an increment in the inertance ratio leads to an increase in the value of optimum parameters of TMDI. Furthermore, among all structures analyzed, those subjected to intermediate frequency earthquakes exhibit the most significant reduction in both objective functions.

An 18–28 GHz dual-mode down-converter IC for 5G applications

Emerging spectrum trends require a higher integration of 5G New Radio Frequency Range 1 (FR1) and Frequency Range 2 (FR2) bands to enhance the availability of spectrum and spectrum-sharing opportunities. To enable the reception of both FR1 and FR2 bands in a seamless hardware entity, we propose combining homodyne and heterodyne architectures. This necessitates the incorporation of a down-converter module that transfers the incoming signals from FR2 bands down to FR1, ensuring compatibility with an FR1 direct-conversion receiver (DCR) for the final signal reception. The primary focus of this paper is the design and implementation of the required integrated down-converter. The module includes an integrated balun, a low-noise amplifier (LNA) with a bypass mode, a dual-mode mixer, and an intermediate frequency (IF) amplifier. The introduced bypass mode helps to further elevate the linearity performance compared to the nominal mode. The bypass mode is designed for joint communication and sensing operation to avoid the compression of the receiver. This work also incorporates a local oscillator (LO) signal distribution network with phase tuning elements using a mixed-signal approach. The circuit is implemented in a 22-nm CMOS process, and the active die area is 0.6 mm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {mm}^\ ext {2}$$\\end{document}. The measurements demonstrate that the implemented chip can efficiently perform the required frequency conversion over a wide frequency range of 18–28 GHz. Conversion gain of 4.5–7.5 dB, noise figure of 15–19.7 dB, 1 dB compression point (IP1dB) of − 16 to − 10 dBm, and input third-order intercept point (IIP3) of − 5 to 0 dBm are achieved. The measured IP1 dB and IIP3 for the bypass mode are +0.5 to +4.5 dBm and +8.5 to +10 dBm, respectively.

A Science Friction Story: Molecular Interactions in Semiflexible Polymer Networks

AbstractEstablished model theories, developed to capture the mechanical behavior of soft, complex materials composed of semiflexible polymers, assume that entropic interactions between filaments are primarily responsible for determining the mechanical response. In recent studies, the generally accepted tube model has been challenged in terms of this basic assumption about filament–filament interactions, but also because of its predictions regarding the frequency dependence of the elastic modulus in the intermediate frequency regime. A central question is how molecular interactions and friction between network constituents influence the rheological response of isotropic entangled networks of semiflexible polymers. It has been previously shown that friction forces between aligned pairs of actin filaments are not negligible. Here, the influence of friction forces and attractive interactions on network rheology is systematically investigated by means of targeted surface modification. It is shown that these forces have a qualitative and quantitative influence on the viscoelastic properties of semiflexible polymer networks and contribute to their response to nonlinear deformations. By comparing two polymer model systems with respect to their surface compositions, a possible explanation is given about the origin of acting forces on a molecular level.

Terahertz Replica Generation of Ultra-High Data Rate Transmission in an Electro-Optical Semiconductor Optical Amplifier Mach–Zehnder Interferometer System

This article presents an analysis of an electro-optical up-converter relying on a semiconductor optical amplifier Mach–Zehnder interferometer (SOA-MZI). The pulsed control signal is generated by an optical pulse clock (OPC) with a repetition rate of fs= 19.5 GHz. The intermediate frequency (IF) signal, which carries the modulation format known as quadratic phase shift keying (QPSK) at a frequency fIF, is shifted at the output of the SOA-MZI to high outlet mixing frequencies nfs±fIF, where n represents the harmonic order of the OPC. To examine the characteristics of the sampled QPSK signals, we employ the Virtual Photonics Inc. (VPI) emulator and evaluate them using significate metrics like error vector magnitudes (EVMs), conversion gains, and bit error rates (BERs). The up-mixing process is mainly achieved through the cross-phase modulation (XPM) effect in the SOA-MZI, which operates within a 195.5 GHz ultrahigh frequency (UHF). The electro-optical SOA-MZI up-converter demonstrates consistent uplifting conversion gains across the scope of the output mixing frequencies. The simulated conversion gain deteriorates from 38 dB at 20 GHz to 13 dB at 195.5 GHz. The operational efficiency of the electro-optical SOA-MZI design, employing the standard modulation approach, is also evaluated by measuring the EVM values. The EVM attains a 24% performance level at a data rate of 5 Gbit/s in conjunction with the UHF of 195.5 GHz. To corroborate our results, we compare them with real-world experiments conducted with the UHF of 59 GHz. The maximum frequency range of 1 THz is attained by increasing the OPC repetition rate. Ultimately, through elevating the control frequency to 100 GHz, the generation of terahertz replicas of the 4096-QAM (quadrature amplitude modulation) compound signal becomes achievable at heightened UHF, extending 1 THz, while maintaining a data transmission rate of 120 Gbit/s and upholding exceptional performance characteristics.

Photovoltaic limitations of FAPbI3 nanocrystal solar cells associated with ligand washing processes

The processing of perovskite nanocrystals (PNCs) solar cells (SCs) usually incorporates ligand washing (LW) procedures. We show that a LW step of FAI in EtAc assists in the removal of the oleic acid/oleylamine ligands and improves the JSC and FF values of FAPbI3 based SCs. Although by increasing the exposure time of EtAc the removal of oleic acid/oleylamine ligands is more effective, sintering/necking of the FAPbI3 results to NC agglomerations and formation of defects/traps are observed within the active layer by the reported photoluminescence studies. Despite identifying the balanced in LW procedure exposure time, limitations on the performance of FAPbI3 PNCs SCs are reported. To identify the photovoltaic limitations impedance spectroscopy studies are presented and show that in the case of FAPbI3 PNC SCs an intermediate frequency response manifests. The observed impedance spectroscopy intermediate frequency response correlates with a parasitic resistance effect, indicating charge transport limitations and charge recombination losses even after the applied LW processing procedure.

Disease Activity and Tendency to Relapse in ANCA-Associated Vasculitis Are Reflected in Neutrophil and Intermediate Monocyte Frequencies.

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of autoimmune diseases with inflammation affecting small blood vessels and includes granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). In this study, we investigated granulocyte and monocyte subsets in a large cohort of AAV patients with emphasis on disease activity and tendency to relapse. A cohort of 105 patients with GPA or MPA and 126 healthy controls (HCs) were included. Clinical and laboratory data were collected for all patients, including disease activity, tendency to relapse, and pharmacological treatment. Using flow cytometry, circulating eosinophils, basophils, neutrophils, and monocytes were assessed. The monocytes were subdivided into classical (CD14++CD16-), intermediate (CD14++CD16+), and nonclassical (CD14-CD16+) monocytes. Mature (CD16high) or newly released (CD16dim) neutrophils were defined, as well as the frequency of CD177+ neutrophils. AAV patients displayed increased frequencies of intermediate monocytes, mature and newly released neutrophils, and an expanded population of CD177+ neutrophils compared to HC. MPA patients differed from GPA patients in terms of lower frequency of classical monocytes. No differences in cell frequencies regarding ANCA phenotype were observed. Paired data from 23 patients demonstrated that active disease was associated with an increased frequency of mature neutrophils and a decreased frequency of monocytes, in particular intermediate monocytes. Moreover, GPA patients with a tendency to relapse displayed an increased frequency of mature neutrophils with increased expression of CD177+. Relapsing MPA patients, on the other hand, showed decreased frequency of intermediate monocytes. Finally, rituximab treatment was associated with increased frequencies of classical and intermediate monocytes. In conclusion, AAV patients exhibit a skewing of different neutrophil and monocyte subpopulations that are associated with disease subtypes, disease activity, rituximab treatment, and propensity to relapse. These changes may contribute to the inflammatory process and could potentially be used as biomarkers for relapse prediction.

CO2/Cr-tolerance and oxygen reduction reaction of novel high-entropy perovskite cathode for intermediate temperature solid oxide fuel cell

The development and exploration of cathode oxides with outstanding electrocatalytic activity are critical processes aimed at achieving a decrease in the operation temperature of solid oxide fuel cells (SOFC). Herein, a novel high-entropy oxide, La0.2Pr0.2Nd0.2Sm0.2Gd0.2BaCoFeO5+δ (HEP), which incorporates five lanthanide species (La, Pr, Nd, Sm, and Gd) in the A-site of perovskite, has been specifically developed and assessed as selected cathode for intermediate-temperature SOFC. Investigations of phase structure, chemical compatibility, oxygen transport characteristics, oxygen reaction kinetic, thermal expansion, surface chemical state, conductivity, as well as CO2/Cr-durability are thoroughly performed to assess the basic physicochemical properties of the HEP cathodes. The HEP cathode possesses good operational stability, moderate thermal expansion behavior, fast oxygen transport dynamics, and superior chemical compatibility with the electrolyte. At 700 °C, the polarization resistance low to 0.072 Ω cm2 and output power density high to 332.2 mW cm−2 were obtained for the symmetrical and electrolyte-supported single cells. Furthermore, a stable current density is obtained for the single cell operating at 600 °C and 0.5 V for 100 h. Analysis of electrochemical impedance spectra (EIS) and distribution of relaxation time (DRT) data at different oxygen partial pressures reveal that the charge-transfer and oxygen ions ionization processes at intermediate frequencies present a significant limiting step in the rate of the oxygen reduction reaction. However, under realistic utilization conditions, cathodes of cells often endure irreversible performance degradation owing to the Cr deposition from interconnects or CO2 poisoning in air. Hence, the behavior of Cr and CO2 poisoning is also systematically investigated in symmetrical cell measurements; the results confirm that the HEP cathode displays good resistance to Cr and CO2 poisoning. Overall, our findings indicate that the HEP material is regarded as a favored ceramic cathode for SOFC.

Autonomic nervous system responses in the intermediate band to cranial cutaneous stimulation.

Cardiovascular rhythms representing functional states of the autonomic nervous system (ANS) are insufficiently reflected by the current physiological model based on low and high frequency bands (LF, HF, resp.). An intermediate (IM) frequency band generated by a brainstem pacemaker was included in systemic physiological ANS analyses of forehead skin perfusion (SP), ECG, and respiration. Data of 38 healthy participants at T0 and T1 (+1 week) before, during, and following osteopathic cranial vault hold (CVH) stimulation were analyzed including momentary frequencies of highest amplitude, amplitudes in low (0.05-0.12 Hz), IM (0.12-0.18 Hz), and high (0.18-0.4 Hz) frequency bands, and established heart rate variability (HRV) metrics. During CVH, LF interval durations increased, whereas IM/HF band durations decreased significantly. Amplitudes increased significantly in all frequency bands. A cluster analysis found one response pattern dominated by IM activity (47% of participants) with highly stable0.08 Hz oscillation to CVH, and one dominated by LF activity (0.10 Hz) at T0, increasing to IM activity at T1. Showing frequency ratios at ≈3:1, respiration was not responsible for oscillations in PPG during CVH. HRV revealed no significant responses. Rhythmic patterns in SP and respiration matched previous findings on a reticular "0.15 Hz rhythm". Involvement of baroreflex pathways is discussed as alternative explanation.

An improved error cancellation method for high speed FMCW radar based on FPGA platform

AbstractTarget detection of frequency‐modulated continuous wave radar has the problems of high noise and low detection accuracy. The reason is due to the influence of internal hardware and external environment. In response to this issue, this article uses the field programmable gate array platform to perform frequency modulation on the radar module, time‐frequency conversion, autoregression moving average model, inverse proportion function compensation, and frequency domain selection processing on the intermediate frequency in‐phase signals collected by the oscilloscope. The algorithm proposed in this article could effectively reduce noise and system errors. Compared with traditional methods before filtering and variational mode decomposition Hilbert–Huang Transform algorithm, the effective target detection rate of this method is improved by 50%.