A comparative study of data-driven battery capacity estimation based on partial charging curves

With its generality and practicality, the combination of partial charging curves and machine learning(ML) for battery capacity estimation has attracted widespread attention. However, a clear classification,fair comparison, and performance rationalization of these methods are lacking, due to the scattered existing studies. To address these issues, we develop 20 capacity estimation methods from three perspectives:charging sequence construction, input forms, and ML models. 22,582 charging curves are generated from 44 cells with different battery chemistry and operating conditions to validate the performance. Through comprehensive and unbiased comparison, the long short-term memory(LSTM) based neural network exhibits the best accuracy and robustness. Across all 6503 tested samples, the mean absolute percentage error(MAPE) for capacity estimation using LSTM is 0.61%, with a maximum error of only 3.94%. Even with the addition of 3 m V voltage noise or the extension of sampling intervals to 60 s, the average MAPE remains below 2%. Furthermore, the charging sequences are provided with physical explanations related to battery degradation to enhance confidence in their application. Recommendations for using other competitive methods are also presented. This work provides valuable insights and guidance for estimating battery capacity based on partial charging curves.

AN APPLICATION OF EVOLUTIONARY PROGRAMMING IN FIR FILTER DESIGN WITH FREQUENCY SAMPLING METHOD

Frequency sampling is one of the popular methods in FIR digital filter design. In the frequency sampling method the value of transition band samples, which are usually obtained by consulting a table, must be determined in order to make the attenuation within the stopband maximal. However, the value obtained by searching for table can not be ensured to be optimal. Evolutionary programming (EP), a multi agent stochastic optimization technique, can lead to global optimal solutions for complex problems. In this paper a new application of EP to frequency sampling method is introduced. Two examples of lowpass and bandpass FIR filters are presented, and the steps of EP realization and experimental results are given. Experimental results show that the value of transition band samples obtained by EP can be ensured to be optimal and the performance of the filter is improved.

Range resolution and sampling frequency trade-off for GPS passive radar

In a global positioning system(GPS)passive radar,a high resolution requires a high sampling frequency,which increases the computational load.Balancing the computational load and the range resolution is challenging.This paper presents a method to trade off the range resolution and the computational load by experimentally determining the optimal sampling frequency through an analysis of multiple sets of GPS satellite data at different sampling frequencies.The test data are used to construct a range resolution-sampling frequency trade-off model using least-squares estimation.The theoretical analysis shows that the experimental data are the best fit using smoothing and nthorder derivative splines.Using field GPS C/A code signal-based GPS radar,the trade-off between the optimal sampling frequency is determined to be in the 20461.25–24553.5 kHz range,which supports a resolution of 43–48 m.Compared with the conventional method,the CPU time is reduced by approximately 50%.

Silicon PIN photodiode applied to acquire high-frequency sampling XAFS spectra

Experimental techniques based on SR facilities have emerged with the development of synchrotron radiation(SR)sources.Accordingly,detector miniaturization has become significant for the development of SR experimental techniques.In this study,the miniaturization of a detector was achieved by coupling a commercial silicon PIN photodiode(SPPD)into a beamstop,aiming for it not only to acquire X-ray absorption fine structure(XAFS)spectra,but also to protect the subsequent two-dimensional detector from high-brilliance X-ray radiation damage in certain combination techniques.This mini SPPD detector coupled to a beamstop was used as the rear detector in both the conventional sampling scheme and novel high-frequency(HF)sampling scheme to collect the transmission XAFS spectra.Traditional ion chambers were also used to collect the transmission XAFS spectra,which were used as the reference.These XAFS spectra were quantitatively analyzed and compared;the results demonstrated that the XAFS spectra collected by this SPPD in both the conventional sampling scheme and HF sampling scheme are feasible.This study provides a new detector-selection scheme for the acquisition of the quick-scanning XAFS(QXAFS)and HF sampling XAFS spectra.The SPPD detector presented in this study can partially meet the requirements of detector miniaturization.

Pressure fluctuation and its influencing factors in circulating water pump

In order to investigate the effect of sampling frequency and time on pressure fluctuations, the three-dimensional unsteady numerical simulations were conducted in a circulating water pump. Through comparison of turbulence models with hydraulic performance experiment, SST k-co model was confirmed to study the rational determination of sampling frequency and time better. The Fast Fourier Transform （FFT） technology was then adopted to process those fluctuating pressure signals obtained. On these bases, the characteristics of pressure fluctuations acting on the tongue were discussed. It is found that aliasing errors decrease at higher sampling frequency of 17 640 Hz, but not at a lower sampling frequency of 1 764 Hz. Correspondingly, an output frequency range ten-times wider is obtained at 17 640 Hz. Compared with 8R, when the sampling time is shorter, the amplitudes may be overvalued, and the frequencies and amplitudes of low-frequency fluctuations can not be well predicted. The frequencies at the tongue are in good agreement with the values calculated by formula and the frequency compositions less than the blade passing frequency are accurately predicted.

Sample indexed spatial orthogonal frequency division multiplexing

Optical spatial modulation （OSM） is a multiple-transmitter technique that can provide higher data rates with low system complexity as compared with single-input single-output systems. Orthogonal frequency division multiplexing （OFDM） is widely implemented to achieve better spectral efficiency in wireless channels. Asymmetrically clipped optical OFDM （O-OFDM） and DC-biased O-OFDM are two well-known O-OFDM techniques suitable for intensity-modulation direct-detection optical systems. In this work, sample indexed spatial OFDM （SIS-OFDM） is proposed to combine OSM and O-OFDM in a novel way and achieve significant per- formance gain. By assigning time-domain samples of the O-OFDM transmit symbol to different transmitters, SIS-OFDM achieves much better spectral efficiency and reduces computational complexity at the transmitter as compared with previous work that combines OSM with O-OFDM in the frequency domain. We also consider the impact of optical source biasing on overall performance, and the relative performance of imaging receiver （ImR） versus non-imaging receiver （NImR） design for our proposed SIS-OFDM technique. Results indicate that for an Ntx x Nrx multiple-input multiple-output configuration where Nix = N = 4, SIS-OFDM using ImR can achieve up to 135 dB of signal-to-noise ratio gain over comparable system using a NImR. Also, using Nc number of O-OFDM subcarriers provides up to Nsc × log2（Ntx） additional bits per symbol of spectral efficiency over technioues that combine OSM and O-OFDM in the freollencv domain.

A Novel Spectrum Handoff-Based Sensing-Throughput Tradeoff Scheme in Cognitive Radio

In cognitive radio(CR), there is a tradeoff between spectrum sensing time and throughput of secondary user(SU). In the conventional sensing-throughput tradeoff scheme, when the presence of the primary user(PU) is detected, the SU will stop forwarding data and wait to redetect the PU in the following frame, yielding great throughput loss. In order to improve the SU's throughput, a novel sensing-throughput tradeoff scheme is proposed, which allows the SU to search for a new idle channel through spectrum searching and transfer to this channel to continue communication, when the presence of the PU is detected. An optimization problem is proposed to maximize the SU's throughput in the proposed scheme through jointly optimizing the sensing time, the searching time and the number of available channels, providing that the detection probability to the PU is guaranteed. By fixing the number of channels, based on alternating direction optimization, the joint optimization algorithm of sensing time and searching time is proposed, and then the optimal number of channels is obtained through enumerative searching. The simulation results show that there exist the optimal solutions to the proposed scheme, and the proposed scheme outperforms the conventional scheme notably, with different detection probabilities and sampling frequencies.

SAMPLING FORMULAE OF HIGHER ORDER

Shannon sampling theorem is the basic theorem in signal reconstruction based ondiscrete sampling values in communication theory. The convergence rate of thisformula, however, is very slow. Professor Pen Rui-reng. after some slight compromiseon sampling rate, has come to the 3rd order, the 4th order and the 5th order samplingformulae. The calculation of the third order formula on the computer proves that itconverges much faster than the Shannon formula. This paper gives a general methodto comstruct a higher order sampling formula.

Instantaneous frequency analysis of broadband LFM signals by photonics-assisted equivalent frequency sampling

We propose a photonics-assisted equivalent frequency sampling(EFS)method to analyze the instantaneous frequency of broadband linearly frequency modulated(LFM)microwave signals.The proposed EFS method is implemented by a photonic scanning receiver,which is operated with a frequency scanning rate slightly different from the repetition rate of the LFM signals.Compared with the broadband LFM signal analysis based on temporal sampling,the proposed method avoids the use of high-speed analog to digital converters,and the instantaneous frequency acquisition realized by frequency-to-time mapping is also simplified since real-time Fourier transformation is not required.Feasibility of the proposed method is verified through an experiment,in which frequency analysis of Kα-band LFM signals with a bandwidth up to 3 GHz is demonstrated with a moderate sampling rate of 100 MSa/s.The proposed method is highly demanded for analyzing the instantaneous frequency of broadband LFM signals used in radar and electronic warfare systems.

Optimization of sampling frequency for routine river water quality monitoring

Sampling frequency is an important factor to be considered during the design of a water monitoring network,and the cost-effective selection of possible ways and means for the optimization of sampling frequency is still needed.This paper introduces water pollution index deviation ratio comparison(WPI DRC),a procedure for the optimization of sampling frequency for a routine river water quality monitoring system.Sampling frequency optimized using WPI DRC at monitoring station X5 in the mainstream of Xiangjiang River is compared with that established using the traditional Statistical Algorithm method.The result of comparison indicates that WPI DRC is more feasible than the traditional one.And then,the sampling frequencies for other 16 monitoring stations also have been optimized,and the results show the sampling frequencies of all the stations except that X4 are reduced,and there is no unacceptable difference between water quality evaluation results at 17 stations before and after the optimization.Therefore,it is concluded that WPI DRC is an effective optimization process with operable results,which can be used to fulfill the requirement of practical monitoring work.

A software sampling frequency adaptive algorithm for reducing spectral leakage

Spectral leakage caused by synchronous error in a nonsynchronous sampling system is an important cause that reduces the accuracy of spectral analysis and harmonic measurement.This paper presents a software sampling fre-quency adaptive algorithm that can obtain the actual signal frequency more accurately,and then adjusts sampling in-terval base on the frequency calculated by software algo-rithm and modifies sampling frequency adaptively.It can reduce synchronous error and impact of spectral leakage;thereby improving the accuracy of spectral analysis and harmonic measurement for power system signal where fre-quency changes slowly.This algorithm has high precision just like the simulations show,and it can be a practical method in power system harmonic analysis since it can be implemented easily.

Influence of sampling frequency on detectability of fish community and fish species in a fishery-independent survey

Understanding the dynamics and regulation of a particular ecological process requires monitoring of the process at appropriate spatial and temporal scales.Information collected at an inappropriate spatiotemporal scale may be insufficient for capturing spatio-temporal dynamics of fish populations and community.In this study,a Monte Carlo method was developed to evaluate the detectability performances of different sampling frequencies,sampling timings and sampling intensities on fish community indices and fish species.Species richness indices tended to decrease with an increased sampling frequency,while species diversity indices had small changes in response to changes in sampling frequency.The diversity index was more likely to be influenced by the choice of sampling timing compared to the richness index.The total number of species,especially seasonal and rare species present in the simulated sampling,increased with sampling frequency.Although sampling frequency is more important than sampling intensity,sampling intensity is also important for the detectability of fish species.This study showed that sampling frequency and intensity could greatly influence the estimation of fish community.Choices of sampling timing,sampling frequency and intensity may result in different estimates of fish species compositions and community structure.It is very necessary to consider the importance of sufficient sampling frequency and intensity in a survey program.