The purpose of this paper is to establish a direct methanol fuel cell (DMFC) prediction model by using the support vector regression (SVR) approach combined with particle swarm optimization (PSO) algorithm for its parameter selection. Two variables, cell temperature and cell current density were employed as input variables, cell voltage value of DMFC acted as output variable. Using leave-one-out cross-validation (LOOCV) test on 21 samples, the maximum absolute percentage error (APE) yields 5.66%, the mean absolute percentage error (MAPE) is only 0.93% and the correlation coefficient (R 2 ) as high as 0.995. Compared with the result of artificial neural network (ANN) approach, it is shown that the modeling ability of SVR surpasses that of ANN. These suggest that SVR prediction model can be a good predictor to estimate the cell voltage for DMFC system.
Poly(2-hydroxyethyl methacrylate) (PHEMA) in the water-swollen state is a very soft hydrogel with high water content. Therefore, it is similar to natural tissues and is widely used as a biomaterial. Unfortunately, PHEMA hydrogels have low mechanical strength and tear resistance. The incorporation of hydrophobic polycaprolactone (PCL) improves the mechanical properties of the swollen networks and preserves their biocompatibility. Three ways to combine PHEMA and PCL were investigated. Semi-interpenetrating polymer networks of PHEMA and low molecular weight PCL diol were prepared. Interpenetrating polymer networks of PHEMA and high molecular weight PCL were synthesized using two different methods depending upon the relative composition (PHEMA:PCL). Mechanical, thermal, and swelling properties were investigated.
In order to improve the stator flux observation performance of permanent magnet synchronous motor (PMSM) with DIRECT Torque Control (DTC), a stator flux sliding mode observer is proposed based on the concept of effective flux. The stator current and effective flux in the stator stationary coordinate system are taken as state variables to construct the corresponding sliding mode observer. The stator flux is calculated according to the observed effective flux. Experimental results show that the proposed observer can obtain more accurate stator flux observations than the open-loop observer. The proposed observer has strong robust suppression ability to the variation of motor inductance.
Accurate localization is a fundamental capability of autonomous driving systems, and LiDAR has been widely used for localization systems in recent years due to its high reliability and accuracy. In this paper, we propose a robust and accurate LiDAR SLAM, which innovates feature point extraction and motion constraint construction. For feature extraction, the proposed adaptive point roughness evaluation based on geometric scaling effectively improves the stability and accuracy of feature points (plane, line). Then, outliers are removed with a dynamic threshold filter, which improves the accuracy of outlier recognition. For motion constraint construction, the proposed weighted bimodal least squares is employed to optimize the relative pose between current frame and point map. The map stores both 3D coordinates and vectors (principal or normal vectors). Using vectors in current frame and point map, bimodal reprojection constraints are constructed. And all constraints are weighted according to the neighboring vector distribution in the map, which effectively reduces the negative impact of vector errors on registration. Our solution is tested in multiple datasets and achieve better performance in terms of accuracy and robustness.
Material characterization and electrochemical performance of the pulse plated Ni-W alloy coatings were assessed by varying duty cycles and pulse frequencies. Compared to DC electroplating, the pulse plating process exhibited lower cathodic current efficiency, and the obtained coatings displayed slightly lower W content. However, both the hardness and anti-corrosion properties of the coatings could be improved due to common characteristics, such as grain refinement and enhanced surface uniformity, associated with the pulse plating process. It is deduced that a synergistic effect between the adsorbed saccharin additive on electrode surface and the intermittent power supply could lead to the increase of average cathode current density, which would intensify the activation polarization effect during pulse plating. This, in turn, inhibited the reduction reaction of W ions. Simultaneously, the coating surface became smoother, and the grain refinement effect was observed. Thanks to the synergistic effect, the Ni-W alloy coating produced at a pulse frequency of 100 Hz with duty cycles of 10% and 20% exhibited the highest hardness (544 HV) and the best corrosion resistance (corrosion current density Ic: 2.81 μA·cm-2), respectively. These properties were significantly improved compared to those for the counterparts prepared by DC electroplating (hardness: 320 HV; Ic: 5.28 μA·cm-2).
Abstract This article proposes a summarization system for multiple documents. It employs not only named entities and other signatures to cluster news from different sources, but also employs punctuation marks, linking elements, and topic chains to identify the meaningful units (MUs). Using nouns and verbs to identify the similar MUs, focusing and browsing models are applied to represent the summarization results. To reduce information loss during summarization, informative words in a document are introduced. For the evaluation, a question answering system (QA system) is proposed to substitute the human assessors. In large‐scale experiments containing 140 questions to 17,877 documents, the results show that those models using informative words outperform pure heuristic voting‐only strategy by news reporters. This model can be easily further applied to summarize multilingual news from multiple sources.
Abstract There is an increasing body of evidence showing that, for a variety of copolymers, there are significant changes in the copolymer composition over the molecular weight distribution of the polymer. In this work, we have polymerized the copolymer poly(styrene‐methyl methacrylate) using ethylaluminum sesquichloride as the initiator. The copolymers produced were fractionated using a semiprep gel permeation chromatograph. The composition of the fractions was determined using infrared spectroscopy. Results show that the percent methyl methacrylate of the copolymers was higher at both the low‐ and high‐molecular‐weight regions of the polymers.
The electrical conductivity of solid oxide fuel cell (SOFC) cathode is one of the most important indices affecting the efficiency of SOFC. In order to improve the performance of fuel cell system, it is advantageous to have accurate model with which one can predict the electrical conductivity. In this paper, a model utilizing support vector regression (SVR) approach combined with particle swarm optimization (PSO) algorithm for its parameter optimization was established to modeling and predicting the electrical conductivity of Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ -x Sm 0.5 Sr 0.5 CoO 3-δ (BSCF–xSSC) composite cathode under two influence factors, including operating temperature (T) and SSC content (x) in BSCF–xSSC composite cathode. The leave-one-out cross validation (LOOCV) test result by SVR strongly supports that the generalization ability of SVR model is high enough. The absolute percentage error (APE) of 27 samples does not exceed 0.05%. The mean absolute percentage error (MAPE) of all 30 samples is only 0.09% and the correlation coefficient (R 2 ) as high as 0.999. This investigation suggests that the hybrid PSO–SVR approach may be not only a promising and practical methodology to simulate the properties of fuel cell system, but also a powerful tool to be used for optimal designing or controlling the operating process of a SOFC system.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
'/%3e%3cuse xlink:href='%23a' transform='rotate(60)'/%3e%3ccircle r='17' fill='%23000095'/%3e%3ccircle r='15' fill='%23fff'/%3e%3c/svg%3e)