(1) Background: Feature selection is the biggest challenge in feature-rich sentiment analysis to select the best (relevant) feature set, offer information about the relationships between features ...(informative), and be noise-free from high-dimensional datasets to improve classifier performance. This study aims to propose a binary version of a metaheuristic optimization algorithm based on Swarm Intelligence, namely the Salp Swarm Algorithm (SSA), as feature selection in sentiment analysis. (2) Methods: Significant feature subsets were selected using the SSA. Transfer functions with various types of the form S-TF, V-TF, X-TF, U-TF, Z-TF, and the new type V-TF with a simpler mathematical formula are used as a binary version approach to enable search agents to move in the search space. The stages of the study include data pre-processing, feature selection using SSA-TF and other conventional feature selection methods, modelling using K-Nearest Neighbor (KNN), Support Vector Machine, and Naïve Bayes, and model evaluation. (3) Results: The results showed an increase of 31.55% to the best accuracy of 80.95% for the KNN model using SSA-based New V-TF. (4) Conclusions: We have found that SSA-New V3-TF is a feature selection method with the highest accuracy and less runtime compared to other algorithms in sentiment analysis.
Readily commercializable and cost‐effective next‐generation CsPbBr3 perovskite nanocrystals (PNCs) based X‐ray detectors are demonstrated. The PNCs‐based X‐ray detector exhibits higher spatial ...resolution (9.8 lp mm−1 at modulation transfer function (MTF) = 0.2 and 12.5–8.9 lp mm−1 for a linear line chart), faster response time (≈200 ns), and comparable stability (>40 Gyair s−1 of X‐ray exposure) compared with the commercialized terbium‐doped gadolinium oxysulfide (GOS)‐based detectors (spatial resolution = 6.2 lp mm−1 at MTF = 0.2 and 6.3 lp mm−1 for a linear line chart, response time = ≈1200 ns) because the PNCs‐based scintillator has ≈5.6‐fold faster average photoluminescence lifetime and stronger emission than the GOS‐based one.
A high‐performance next‐generation perovskite nanocrystal (PNC) scintillator is used for nondestructive X‐ray imaging. The high‐performance cheap CsPbBr3 PNCs scintillators are based on indirect X‐ray detectors with high‐resolution, sensitivity, and stability.
The dynamics of hydrogen-enriched partially premixed methane–air flames are investigated, focusing on the frequency response to velocity and equivalence ratio fluctuations. Large-eddy simulations ...(LES) with conjugate heat transfer are performed on the partially premixed PRECCINSTA combustor for various methane–hydrogen mixtures, maintaining a constant thermal power and global equivalence ratio of 10 kW and 0.8, respectively. To reduce the computational cost of the LES, a three-step global mechanism is calibrated for each hydrogen-enriched partially premixed flame. The accuracy of the LES is assessed against experimental data, showing a good agreement with the mean velocity field and shape of the swirl-stabilized flame. The multiple-input–single-output structure for the flame transfer function is applied to separate the individual contributions of velocity and equivalence ratio fluctuations to the overall heat release rate oscillation in the partially premixed flames. System identification with broadband forcing is used to compute the various flame transfer functions. Hydrogen enrichment significantly influences the flame response to equivalence ratio fluctuations, explained by the respective impact on the response of the heat of reaction, the flame speed, and the flame surface area to equivalence ratio fluctuations. The interaction between velocity and equivalence ratio fluctuations is further characterized by the mixing transfer function, which describes the equivalence ratio fluctuations reaching the flame. The higher mass diffusivity of hydrogen results in lower equivalence ratio fluctuations reaching the flame as the frequency increases, attenuating the pronounced effect of hydrogen on the flame sensitivity to equivalence ratio fluctuations. This study contributes to the understanding of the impact of hydrogen enrichment on the thermoacoustic response of partially premixed flames.
A virtual synchronous generator (VSG) control for converters has been proposed as a method to provide virtual inertia from power electronics connected generation and storage. Most works to date have ...analyzed VSG control under the assumption that the VSG dynamics are much slower than that the converter. This work shows that when converter and line dynamics are taken into account, the virtual inertia and damping settings are constrained by stability considerations. These conditions for stability are analyzed based on a simple transfer function approach. It is shown that for the VSG to be stable and validly approximated by a second-order system, the ratio of damping to virtual inertia is a key parameter. This letter quantifies how these VSG parameters are constrained by stability. The transfer function analysis is validated using full switching model simulations of stable and unstable cases.
In this study, an optimal fractional-order controller is proposed for a type of fractional-order model utilising the direct synthesis method. In that respect, the fractional counterpart of the ...second-order integer transfer function is selected as a closed-loop reference transfer function. The stability region of the fractional-order closed-loop reference transfer function is given via a theorem and related lemmas. Considering that a unity feedback loop is used, the parameters of the fractional-order closed-loop reference transfer function are specified based on the integral square error performance index within the specified stability region using a genetic algorithm. The time-domain characteristics of the optimal fractional-order closed-loop reference transfer function are compared with those of the optimal second-order integer closed-loop reference transfer function. The fractional- and integer-order controllers that are designed based on optimal closed-loop reference transfer functions are implemented on a real-time system. The performance of the fractional-order controller outperforms that of the integer counterpart on the integral square error criterion. Moreover, the simulation and practical results are consistent with each other.
•Low-pass filters can approximate the dynamics of heat convection in porous media.•The forced response remains linear at low reynolds numbers.•Increases in reynolds number increase the nonlinearity ...in a non-monotonic way.•Changes in porosity can alter linearity of the forced convection response.
An increasing number of technologies require prediction of unsteady forced convection in porous media when the inlet flow is unsteady. To gain further insight into this problem, the unsteady equations of continuity, Navier Stokes and energy are solved within the pores formed by several cylindrical flow obstacles. The system is modulated by sine waves superimposed on the inlet flow velocity, and the spatio-temporal responses of the flow and temperature fields are calculated. The results are then utilised to assess the linearity of the thermal response represented by the Nusselt number on the obstacles. It is shown that for linear cases, a transfer function can be devised for predicting the dynamic response of the Nusselt number. It is further argued that such a transfer function can be approximated by a classic low-pass filter which resembles the average response of the individual obstacles. This indicates that there exists a frequency threshold above which the thermal system is essentially insensitive to flow modulations. The results also show that changes in Reynolds number and porosity of the medium can push the dynamic response of the system towards non-linearity. Yet, there appears to be no monotonic change in the linearity of the response with respect to the Reynolds number and porosity. In general, it is found that for low Reynolds numbers, the dynamics of heat convection can be predicted decently by taking a transfer function approach. The findings of this study can enable further understanding of unsteady forced convection in porous media subject to time-varying inlet flows.
•Land snail Δ47-derived temperature correlates well with growing season temperature.•Clumped temperatures of Cathaica are about 3 °C higher than those of Bradybaena.•A species-specific Δ47 transfer ...function is needed to reconstruct paleotemperature.•Body water δ18O of Bradybaena shows a robust correlation with rainfall δ18O in northern China.
Land snail fossils are abundantly distributed in geological deposits and their isotopic compositions provide a means to determine paleoclimatic changes. With the development of the clumped isotopes (Δ47) geothermometer, many efforts have been made in recent years to study clumped isotopes in land snail shell carbonate. Although there have been several recent attempts, there is, as yet, no empirical calibration function to convert land snail Δ47 to environmental temperature. Here, we systematically analyzed clumped isotopes (Δ47) of two common land snail species (Bradybaena and Cathaica) from China. Results showed that temperatures calculated using the Δ47 (T47) of both species did not correlate with the mean annual temperatures (MAT) at the study sites. However, the T47-MAT offset is negatively correlated to MAT, suggesting that land snails tend to add shell during the warmer months at colder sites or modulate their body temperature differently in colder regions. Meanwhile, clumped temperatures of Cathaica are 3.4 ± 1.5 °C higher than those of Bradybaena at 18 sites, indicating that a species-specific transfer function is needed to reconstruct paleotemperature using land snail clumped isotopes. After determining the proper duration of the growing season for land snails at different locations, we developed a Δ47-growth season temperature (GST) transfer function for the two species. The calibration function for Bradybaena land snails is expressed by a linear regression between 1/T2 and absolute Δ47 (R2 = 0.94): Δ47 = (0.0513 ± 0.0036) × 106/T2 + (0.0930 ± 0.0413), where Δ47 is expressed in ‰ and T in K. The calibration function for Cathaica is as follows (R2 = 0.80): Δ47 = (0.055 ± 0.011) × 106/T2 + (0.035 ± 0.129). The function for Cathaica was successfully applied to reconstruct mean summer (June-July-August) temperatures during the Last Glacial Maximum and modern times on the central Chinese Loess Plateau, based on Δ47 data of Cathaica sp. provided by Eagle et al (2013a). This testifies to the validity of the aforementioned constructed transfer function. In addition, the calculated δ18O of body water (δ18OBW) for Bradybaena showed a robust correlation with the δ18O of rainfall (δ18Op), particularly in northern China, which points to the potential to trace hydrological changes in the region. In contrast, Cathaica δ18OBW did not show a straightforward relation to δ18Op. This inter-species complexity warrants further study.
In this paper, a fractional order PID controller cascaded with a fractional filter is proposed for higher order processes. In this analytical design methodology, one or two reduced fractional orders ...plus time delay models are used to represent higher order system transfer functions. The controller parameters are determined so as to meet certain frequency domain specifications. A unity feedback reference model is employed where Bode’s ideal loop transfer function plus time delay of the fractional order model is placed in the forward path. The addition of this time delay provides the exact determination of frequency domain specifications if the system either intrinsically owns a time delay or a time delay is injected by its reduced order model. The proposed methodology is compared with two other related methodologies and it has been observed that the proposed controller performs much better than the others. Moreover, some empirical formulas for time domain characteristics of the reference model are numerically derived in terms of certain frequency domain specifications and time delay of the fractional reduced order model. The accuracy of these formulas is tested by simulations. The iso-damping, noise attenuation and load disturbance suppression performances of the proposed controller are also considered and compared with those of other related controllers.
•A fractional PID controller with a fractional filter is proposed for higher order processes.•The reduced fractional order plus time delay models are used to represent higher order processes.•The controller parameters are determined to meet certain frequency domain specifications.•Bode’s ideal loop transfer function plus time delay in the forward path is employed as a reference model•Some empirical formulas for time domain characteristics of the reference model are derived.
Inductive power transfer (IPT) is an emerging technology that may create new possibilities for wireless power charging and transfer applications. However, the rather complex control method and low ...efficiency remain the key obstructing factors for general deployment. In a regularly compensated IPT circuit, high efficiency and controllability of the voltage transfer function are always conflicting requirements under varying load conditions. In this paper, the relationships among compensation parameters, circuit efficiency, voltage transfer function, and conduction angle of the input current relative to the input voltage are studied. A design and optimization method is proposed to achieve a better overall efficiency as well as good output voltage controllability. An IPT system design procedure is illustrated with design curves to achieve a desirable voltage transfer ratio, optimizing between efficiency enhancement and current rating of the switches. The analysis is supported with experimental results.
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