The study on the frequency estimation of a real sinusoid has been addressed in this article. Discrete‐Fourier‐transform (DFT)‐based frequency estimation always uses the maximum bin of DFT as a coarse ...estimation followed by a fine estimation algorithm, which computes a correction term to compensate for the initial frequency offset caused by the coarse estimation. To enhance the frequency estimation accuracy, a fine estimation algorithm based on DFT samples and fuzzy logic (FL) is proposed in this study. Firstly, a modified phase‐based algorithm is presented to estimate the sign of the correction term. Then, a main‐lobe coefficient and a side‐lobe coefficient are constructed using the amplitude of three spectral lines to calculate the correction term. A FL controller is utilised to generate a weighted factor to adjust the weight of the main‐lobe coefficient and the side‐lobe coefficient in the formula of the correction term. Compared with other existing fine algorithms, the proposed algorithm improves the correct probability of sign estimation by 10%–20%, and improves the estimation accuracy by 5%–8% at lower carrier‐to‐noise ratios (CNRs). In addition, the performance of the proposed algorithm is less affected by the initial frequency offset than other algorithms.
To further enhance the positioning accuracy and stability of the INS/GNSS integrated navigation system, we present a new fuzzy strong tracking cubature Kalman filter (FSTCKF) algorithm for data ...fusion. A fuzzy logic controller is designed for the strong tracking cubature Kalman filter (STCKF), which aims at strengthening the filter’s ability to identify and respond to the dynamics. Chi-square tests are separately conducted on the innovation vector in order to reveal the dynamic properties inside the velocity and position states. Thereafter, parallel fuzzy inferences are conducted to generate a time-varying smoothing factor matrix, which helps the STCKF obtain the multiple fading factors distributed to each state variable. Numerical simulations and real data testing results demonstrate the superiority and robustness of the proposed FSTCKF algorithm. Not only can the proposed algorithm maintain the accuracy and stability in steady conditions, but further increase the dynamic tracking ability as well. Finally, the positioning performances of the INS/GNSS can be improved.
Smoothing process can effectively improve the accuracy of the Global Navigation Satellite System (GNSS) position estimation algorithm. In this study, a Doppler‐aided GNSS position estimation ...algorithm with a B‐spline smoothing strategy is proposed. B‐spline signal processing is used to smoothen the code measurements with Doppler measurements, which were selected because they are more robust and immune to cycle slips than carrier phase measurements. Next, the mathematical expressions of the smoothing process and position estimation are derived. The smoothing process is based on the structure of a digital filter, which is especially suitable for real‐time applications. The Cramer–Rao lower bound of the proposed algorithm is derived. Moreover, a complete implementation structure of the proposed algorithm is presented. The validity of the proposed algorithm is verified through scenario simulation in terms of static, kinematic, and adverse environments. The advantages of the proposed algorithm are demonstrated by comparison with existing algorithms.
In numerous animals, one essential chemosensory organ that detects chemical signals is the vomeronasal organ (VNO), which is involved in species-specific behaviors, including social and sexual ...behaviors. The purpose of this study is to investigate the mechanism underlying the processing of chemosensory cues in semi-aquatic mammals using muskrats as the animal model. Muskrat (
) has a sensitive VNO system that activates seasonal breeding behaviors through receiving specific substances, including pheromones and hormones. Vomeronasal organ receptor type 1 (V1R) and type 2 (V2R) and estrogen receptor α and β (ERα and ERβ) were found in sensory epithelial cells, non-sensory epithelial cells and lamina propria cells of the female muskrats' VNO. V2R and ERα mRNA levels in the VNO during the breeding period declined sharply, in comparison to those during the non-breeding period, while V1R and ERβ mRNA levels were detected reversely. Additionally, transcriptomic study in the VNO identified that differently expressed genes might be related to estrogen signal and metabolic pathways. These findings suggested that the seasonal structural and functional changes in the VNO of female muskrats with different reproductive status and estrogen was regulated through binding to ERα and ERβ in the female muskrats' VNO.
Sidelobe raising, caused by multipath and multiple-access interference (MAI), hinders the signal detection and time-delay estimation of multicarrier code-division multiple-access (MC-CDMA) signals, ...which are crucial for localization and tracking applications as well as the sampling-instant configuration of demodulators. Therefore, we propose a method based on reiterative minimum mean-square error (RMMSE) filters to mitigate the MAI and multipath influence. The RMMSE filter is modified to adapt to the multicarrier modulation and symbol involvement characteristics of MC-CDMA signals. The superiority of the proposed method in terms of sidelobes suppression, compared with existing matched filter, least square estimator, least mean square, and single-carrier RMMSE methods, is verified through simulations in the presence of MAIs and short-time-delay multipath. The results show the advantages of the proposed method in terms of high temporal resolution and robustness to MAI influence. This study could contribute toward multipath detection and aid multipath mitigation techniques in strong MAI scenarios.
Tracking, telemetry, and command (TT&C) channel simulators need to accurately simulate the satellite motion parameters and dynamic transmission delays in TT&C channels. In this letter, a generalized ...high-precision simulation method using B-spline interpolation and differentiation is proposed. It regenerates the motion parameters with a high sampling rate using only the available distance data with a low sampling rate, and delays the arbitrary band-limited TT&C signals by the transmission delay resulting from the obtained distance. A modified recursive filter structure is constructed to implement simultaneous B-spline interpolation and differentiation with low implementation complexity. Compared with conventional methods, the proposed approach simulates the motion parameters with higher precision and preserves their continuity.
Coherent integration of direct-sequence spread-spectrum (DSSS) signals is a commonly used technique to improve receiver performance. However, this approach is susceptible to the code phase migration ...(CPM) and Doppler frequency migration (DFM) effects resulting from the relative motion between transmitter and receiver. In this paper, the CPM and DFM effects are explored and characterized. To evaluate the CPM effect, a simple analytic expression for the coherent integration results under motions of arbitrary orders is developed. In addition, the theoretically derived integration loss and time synchronization error caused by CPM are quantitatively examined. The DFM effect is evaluated under the motions of arbitrary orders by Fresnel integration and numerical fitting. The obtained closed-form expressions are verified by simulation and are shown to be useful for the performance analysis and the DSSS receiver design. The theoretical and the numerical results show that when the amount of CPM is larger than about one code chip duration, the signal-to-noise ratio gain obtained by coherent integration no longer increases because of the integration loss caused by CPM. In addition, the integration loss (in decibel units) caused by DFM is approximately inversely proportional to the square of the time-bandwidth product when the time-bandwidth product is small, and it is inversely proportional to the logarithm of the time-bandwidth product when this product is large.
Multiple-access interference mitigation is important in code-division multiple-access (CDMA) systems for both information recovery and signal acquisition. Therefore, in this letter, we propose an ...open-loop adaptive filter based on the reiterative minimum mean-square error for the acquisition of CDMA signals. The method is based on the existing multistatic adaptive pulse compression method, appropriately adapted to the characteristics of CDMA continuous-wave signals. The efficacy of the proposed method in such systems is verified by simulation, and its superiority when compared with the existing least-mean-square method in terms of the number of reiterations is established.
Background
Uncovering molecular pathogenesis and mechanisms of small cell lung cancer (SCLC) will contribute to SCLC therapy. Multiple studies demonstrated that
miR-451a
acts as an anti-tumor miRNA ...in non-small cell lung cancer. However, the mechanism of
miR-451a
in SCLC was ambiguous.
Objective
We aimed to explore the function of
miR-451a
in SCLC and decipher the underlying mechanisms.
Methods
TargetScan and dual-luciferase reporter assays were used to analyze the target genes of
miR-451a
. Cell counting kit-8 and colony formation assays were performed to assess the roles of
miR-451a
on cell growth. Gene set enrichment analysis (GSEA) was utilized to enrich biological pathways. Western blot was used to measure protein expression.
Results
MiR-451a
expression was reduced dramatically in SCLC tissues and cell lines (NCI-H1688 and NCI-H446). Helicase, Lymphoid Specific (
HELLS
) was proved to be a target gene of
miR-451a
. In addition, cell proliferation assays in SCLC cells transfected with
miR-451a
mimic and/or
HELLS
revealed that
miR-451a
inhibited cell proliferation via targeting
HELLS
. Moreover, the roles of
miR-451a
/
HELLS
in expression of key proteins in mTOR and apoptosis signaling pathways suggested that
miR-451a
inactivated mTOR and activated apoptosis signaling pathway via directly silencing
HELLS
.
Conclusions
Our study indicated that
miR-451a
hinders SCLC cell proliferation in vitro through regulating mTOR and apoptosis signaling pathways via silencing
HELLS
, suggesting that
miR-451a
could be a promising tumor suppressor in SCLC. And there is a potential for
miR-451a
to be a drug target and biomarker for SCLC.
The volume of telemetry data is gradually increasing, both because of the increasingly larger number of parameters involved and the use of higher sampling frequencies. Efficient data compression ...schemes are therefore needed in space telemetry systems to improve transmission efficiency and reduce the burden of required spacecraft resources, in particular of their transmitter power. In this paper, a differentialclustering (D-CLU) compression algorithm for lossless compression of real-time aerospace telemetry data is proposed. Because of the temporal-spatial correlation characteristics of telemetry data, the use of a differential compression strategy can efficiently improve compression performance. However, differential compression faces two non-negligible problems, reliability and compression ratio, both of which may be solved by clustering. This is the approach pursued in the proposed D-CLU compression algorithm. The algorithm involves both clustering and coding. In the clustering stage, a one-pass clustering method based on a similarity metric is used to group the original data into clusters. In the coding stage, two traditional encoding algorithms, Lempel-Ziv-Welch and run-length encoding, are used to encode the data, based on the clustering results. Compared with the direct use of differential compression, the clustering-based differential compression algorithm can reduce the error propagation range, thus increasing reliability. The experimental results demonstrate that the proposed D-CLU algorithm can also achieve better compression performance than the other existing algorithms.
PDF
