Integrated vehicle dynamics management for distributed‐drive electric vehicles with active front steering using adaptive neural approaches against unknown nonlinearity

This paper proposes a new integrated vehicle dynamics management for enhancing the yaw stability and wheel slip regulation of the distributed‐drive electric vehicle with active front steering. To cope with the unknown nonlinear tire dynamics with uncertain disturbances in integrated control problem of vehicle dynamics, a neuro‐adaptive predictive control is therefore proposed for multiobjective coordination of constrained systems with unknown nonlinearity. Unknown nonlinearity with unmodeled dynamics is modeled using a random projection neural network via adaptive machine learning, where a new adaptation law is designed in premise of Lyapunov stability. Given the computational efficiency, a neurodynamic method is extended to solve the constrained programming problem with unknown nonlinearity. To test the performance of the proposed control method, simulations were conducted using a validated vehicle model. Simulation results show that the proposed neuro‐adaptive predictive controller outperforms the classical model predictive controller in tracking nominal wheel slip ratio, desired vehicle yaw rate and sideslip angle, showing its significance in vehicle yaw stability enhancement and wheels slip regulation.     

AdaBoost Models for Corporate Bankruptcy Prediction with Missing Data

Very little existing research in corporate bankruptcy prediction discusses modeling where there are missing values. This paper investigates AdaBoost models for corporate bankruptcy prediction with missing data. Three AdaBoost models integrated with different imputation methods are tested on two data sets with very different sample sizes. The experimental results show that the AdaBoost algorithm combined with imputation methods has strong predictive accuracy in both data sets and it is a useful alternative for bankruptcy prediction with missing data.     

Assessing the effectiveness of a voluntary online discussion forum on improving students’ course performance

The purpose of this study was to evaluate the effectiveness of voluntary discussion forums in a higher education setting. Specifically, we examined intrinsic forum participation and investigated its relation to course performance across two experiments. In Experiment 1 (N = 1284) an online discussion forum was implemented at the beginning of an undergraduate introductory psychology course, and measures of course performance (i.e., writing assignment grades, exam grades, and extra-credits obtained) were compared with measures of forum participation. In Experiment 2 (N = 1334) an online discussion forum was implemented halfway through a second undergraduate introductory psychology course, after an initial measure of course performance was obtained, to control for the potential confound of student engagement (e.g., students who perform better in the course use the forum more). Overall, the results showed that students who participated in the forum tended to have better performance in the course, and furthermore that participating in the discussion forum, particularly reading posts on the forum, slightly improved exam performance. This study provides empirical support for the theoretical proposition that there is a facilitation effect of discussion forum participation on course performance. The results also suggest that implementation of an online discussion forum is beneficial even if a teacher only invests minimal time on the forum.     

Tracking 3-D motion from straight lines with trifocal tensors

We present a novel approach to track the position and orientation of a stereo camera using line features in the images. The method combines the strengths of trifocal tensors and Bayesian filtering. The trifocal tensor provides a geometric constraint to lock line features among every three frames. It eliminates the explicit reconstruction of the scene even if the 3-D scene structure is not known. Such a trifocal constraint thus makes the algorithm fast and robust. The twist motion model is applied to further improve its computation efficiency. Another major contribution is that our approach can obtain the 3-D camera motion using as little as 2 line correspondences instead of 13 in the traditional approaches. This makes the approach attractive for realistic applications. The performance of the proposed method has been evaluated using both synthetic and real data with encouraging results. Our algorithm is able to estimate 3-D camera motion in real scenarios accurately having little drifting from an image sequence longer than a 1,000 frames.     

Assessment of the crack growth characteristics at the low corrosion fatigue limit of an A106 Gr b steel pipe weld

In the area of heavy construction, welding processes are vital in the production and maintenance of pipelines and power plants. The fusion welding process generates formidable welding residual stresses and metallurgical change, which increase the crack driving force and reduce the resistance of brittle fracture as well as environmental fracture. This is a serious problem with many alloys as well as A106 Gr B steel pipe. This pipe, used in petrochemical and heavy chemical plants, either degrades due to corrosive environments, e.g., chlorides and sulfides, and/or becomes damaged during service due to the various corrosion damage mechanisms. Thus, in this study, the sulfide corrosion fatigue strength of multi-pass welded A106 Gr B steel pipe was evaluated in a 5.0 wt.% NaCl solution that was saturated with H2S gas at room temperature on the basis of NACE TM 0177-90. The crack growth characteristics of the welded pipe were then assessed at the low limit of sulfide corrosion fatigue strength, which was previously obtained from the sulfide corrosion fatigue (SCF) tests. From the results, in terms of the SCF, all the specimens failed at the heat-affected zone, where a high welding residual stress distributes. It was found that the fatigue crack grew at the low corrosion fatigue limit (σ _{SCFun-notched}), which was 32 % (160MPa) of the ultimate tensile strength (502MPa) of the welded specimens.     

K0.5Na0.5NbO3‐Based Lead‐Free Transparent Electro‐Optic Ceramics Prepared by Pressureless Sintering

Transparent lead‐free electro‐optic (EO) ceramics (K_0.5Na_0.5) _0.9Li_0.1Nb_0.9Bi_0.1O₃ have been fabricated by pressureless sintering. The ceramics have a fine‐grained structure and cubic‐like symmetry. The comodification with Li and Bi induces a diffuse phase transition, causing the ceramics become relaxor‐like and contain polar nanoregions. Our results reveal that excess Bi₂O₃ can further enhance the changes in the crystal structure and dielectric behavior of the ceramics, causing them become more cubic‐like and more relaxor‐like, respectively. These can reduce the light scattering arisen from birefringence and domain walls, and thus improving the optical properties. For the ceramics added with 4 and 6 mol% excess Bi₂O₃, the optical transmittance reaches a high value of 60%–70% in the near‐infrared region. The ceramics also exhibits a good linear EO response, giving an effective EO coefficient of 30–40 pm/V.     

Synthesis and photovoltaic properties of novel alternating phenylenevinylene or fluorenevinylene copolymers containing perylene bisimide

Two novel alternating phenylenevinylene copolymers P6 and P12 as well as one fluorenevinylene copolymer F connected at the 1,7 bay positions with perylene bisimide were synthesized by Heck coupling. They were characterized by GPC, FT-IR, ¹H NMR, TGA, TMA, UV–vis, cyclic voltammetry and photoluminescence (PL) emission spectra. The copolymers were soluble in common organic solvents and thermally stable up to ～300 °C. Their glass transition temperatures were 48–60 °C. The long wavelength absorption maximum was located at 510–542 nm with optical band gaps of ～2.0 eV. The PL emission maximum of P6 and P12 was red-shifted relative to F. The photovoltaic performance of P6, P12 and F was also investigated.     

Phase Transitions and Electrical Properties of (Na1−xKx)(Nb1−ySby)O3 Lead-Free Piezoelectric Ceramics With a MnO2 Sintering Aid

Lead-free piezoelectric ceramics (Na_{1− x} K _x )(Nb_{1− y} Sb _y )O₃+ z mol% MnO₂ have been prepared by a conventional solid-state sintering technique. Our results reveal that Sb⁵⁺ diffuses into the K_0.5Na_0.5NbO₃ lattices to form a solid solution with a single-phase orthorhombic perovskite structure. The partial substitution of Sb⁵⁺ for B-site ion Nb⁵⁺ decreases the paraelectric cubic-ferroelectric tetragonal phase transition ( T _c) and the ferroelectric tetragonal-ferroelectric orthorhombic phase transition ( T _O–F), and retains strong ferroelectricity. A small amount of MnO₂ is enough to improve the densification of the ceramics. The co-effects of MnO₂ doping and Sb substitution lead to significant improvements in ferroelectric and piezoelectric properties. The ceramics with x =0.45–0.525, y =0.06–0.08, and z =0.5–1 exhibit excellent ferroelectric and piezoelectric properties: d ₃₃=163–204 pC/N, k _P=0.47–0.51, k _t=0.46–0.52, ɛ=640–1053, tan δ=1.3–3.0%, P _r=18.1–22.6 μC/cm², E _c=0.72–0.98 kV/mm, and T _C=269°–314°C.