Self-tuning of quantitative feedback theory for force control of an electro-hydraulic test machine

The aim of this paper is to design and fabricate an electro-hydraulic test machine (EHTM) for conducting performance and stability test of force and/or position control in the bench system and to propose a robust adaptive controller—the self-tuning quantitative feedback theory (STQFT)—in order to improve the force control performance of electro-hydraulic actuators (EHAs). By using the gradient descent method to adjust the QFT parameters, the novel STQFT controller is able to adapt to a wide range of working conditions. Experiments were carried out to evaluate the effectiveness of the proposed control method applied to the EHTM.     

Event extraction using behaviors of sentiment signals and burst structure in social media

Significant world events often cause the behavioral convergence of the expression of shared sentiment. This paper examines the use of the blogosphere as a framework to study user psychological behaviors, using their sentiment responses as a form of ‘sensor’ to infer real-world events of importance automatically. We formulate a novel temporal sentiment index function using quantitative measure of the valence value of bearing words in blog posts in which the set of affective bearing words is inspired from psychological research in emotion structure. The annual local minimum and maximum of the proposed sentiment signal function are utilized to extract significant events of the year and corresponding blog posts are further analyzed using topic modeling tools to understand their content. The paper then examines the correlation of topics discovered in relation to world news events reported by the mainstream news service provider, Cable News Network, and by using the Google search engine. Next, aiming at understanding sentiment at a finer granularity over time, we propose a stochastic burst detection model, extended from the work of Kleinberg, to work incrementally with stream data. The proposed model is then used to extract sentimental bursts occurring within a specific mood label (for example, a burst of observing ‘shocked’). The blog posts at those time indices are analyzed to extract topics, and these are compared to real-world news events. Our comprehensive set of experiments conducted on a large-scale set of 12 million posts from Livejournal shows that the proposed sentiment index function coincides well with significant world events while bursts in sentiment allow us to locate finer-grain external world events.     

Dense Platinum/Nickel Oxide Heterointerfaces with Abundant Oxygen Vacancies Enable Ampere-Level Current Density Ultrastable Hydrogen Evolution in Alkaline

Platinum (Pt) remains the benchmark electrocatalyst for alkaline hydrogen evolution reaction (HER), but its industry-scale hydrogen production is severely hampered by the lack of well-designed durable Pt-based materials that can operate at ampere-level current densities. Herein, based on the original oxide layer and parallel convex structure on the surface of nickel foam (NF), a 3D quasi-parallel architecture consisting of dense Pt nanoparticles (NPs) immobilized oxygen vacancy-rich NiO_x heterojunctions (Pt/NiO_x-O_V) as an alkaline HER catalyst is developed. A combined experimental and theoretical studies manifest that anchoring Pt NPs on NiO_x-O_V leads to electron-rich Pt species with altered density of states (DOS) distribution, which can efficiently optimize the d-band center and the adsorption of reaction intermediates as well as enhance the water dissociation ability. The as-prepared catalyst exhibits extraordinary HER performance with a low overpotential of 19.4 mV at 10 mA cm⁻², a mass activity 16.3-fold higher than that of 20% Pt/C, and a long durability of more than 100 h at 1000 mA cm⁻². Furthermore, the assembled alkaline electrolyzer combined with NiFe-layered double hydroxide requires extremely low voltage of 1.776 V to attain 1000 mA cm⁻², and can operate stably for more than 400 h, which is rarely achieved.     

THE ESTIMATION OF PARAMETERS FOR AUTOREGRESSIVE MOVING AVERAGE MODELS

Abstract. This paper provides some new and improved versions of an earlier procedure for the estimation of parameters for autoregressive moving average models suggested by the author (1979). Some numerical examples of the application of the procedure are also given.     

EXACT MAXIMUM LIKELIHOOD ESTIMATE AND LAGRANGE MULTIPLIER TEST STATISTIC FOR ARMA MODELS

Abstract. The paper provides a method for the computation of the derivatives of the exact log likelihood function of a Gaussian time series. Based on this result and using Fisher's scoring technique, an efficient method for computing the maximum likelihood estimates for an autoregressive moving average model has been obtained. Simulations suggest that the new procedure is as fast as the Box and Jenkins conditional least squares method. In a similar way, a procedure is derived to compute the Lagrange multiplier test statistics for testing the goodness of fit of the model.     

A FREQUENCY DOMAIN APPROACH TO LAGRANGE MULTIPLIER TEST FOR AUTOREGRESSIVE MOVING AVERAGE MODELS

Abstract. The paper derives a goodness of fit test for autoregressive moving average models using the frequency domain approximation to the log likelihood and the Lagrange multiplier approach. The test statistic is based on the sample autocovariances and can be quickly computed through a recursive procedure.     

Loss of Nckx3 Exacerbates Experimental DSS-Induced Colitis in Mice through p53/NF-κB Pathway

Inflammatory bowel diseases (IBDs) comprises a range of chronic inflammatory conditions of the intestinal tract. The incidence and prevalence of IBDs are increasing worldwide, but the precise etiology of these diseases is not completely understood. Calcium signaling plays a regulatory role in cellular proliferation. Nckx3, a potassium-dependent Na⁺/Ca²⁺ exchanger, is not only expressed in the brain but also in the aortic, uterine, and intestinal tissues, which contain abundant smooth muscle cells. This study investigated the role of Nckx3 in intestinal inflammation. Microarray analyses revealed the upregulation of the innate immune response-associated genes in the duodenum of Nckx3 knockout (KO) mice. The Nckx3 KO mice also showed an increase in IBD- and tumorigenesis-related genes. Using dextran sodium sulfate (DSS)-induced experimental colitis mice models, the Nckx3 KO mice showed severe colitis. Furthermore, the pathways involving p53 and NF-κB signaling were significantly upregulated by the absence of Nckx3. Overall, Nckx3 plays a critical role in the innate immune and immune response and may be central to the pathogenesis of IBD.     

Phase transition behavior and electrical properties of lead-free (1-x)KNLNS-xBNKZ piezoelectric ceramics

Lead-free (1-x)(K_0,48Na_0,48Li_0,04)(Nb_0,95Sb_0,05)O₃-xBi_0.5(Na_0.82K_0.18)_0.5ZrO₃ (KNLNS-xBNKZ) piezoelectric ceramics (x?=?0, 0.02, 0.04, 0.06, 0.08, and 0.1) were successfully prepared by the two-step sintering method. The effects of different BNKZ contents on the crystal structure, ferroelectric phase transition, and electrical properties of the as-prepared ceramics were systematically researched. The ceramics with a perovskite structure possessed an orthorhombic phase (space group?=?Amm2) at x?=?0, a mixed orthorhombic-tetragonal phase (Amm2?+?P4/mbm) at x?=?0.02, a mixed rhombohedral-tetragonal (R-T) phase (R3m?+?P4/mbm) at x?=?0.04–0.06, and a rhombohedral phase (R3m) at x>0.06. At x?=?0.04 (rhombohedral and tetragonal (R-T) phases coexisted), the ceramics manifested the best electrical properties with d₃₃?=?224 pC/N, k_p = 0.44, k_t = 0.47, T_C = 218^oC, and remanent polarization (P_r)?=?11.5µC/cm². The improvement of the electrical properties of KNLNS-BNKZ ceramics was achieved by controlling their phase compositions and microstructures.

     

Preparation of polyaniline–titanium dioxide hybrid materials in supercritical CO2

Polyaniline–titanium dioxide (PANI–TiO₂) hybrid materials were synthesized in supercritical CO₂ using two different methods. In the first method, separately synthesized TiO₂ particles were mixed with aniline to perform polymerization in supercritical CO₂. The second method included the preparation of aniline–TiO₂ hybrids through a sol–gel reaction of titanium isopropoxide in the presence of aniline. Further polymerization of aniline–TiO₂ hybrids in supercritical CO₂ produced PANI–TiO₂ hybrid particles. The final products showed the intrusion of PANI into the internal structure of TiO₂. The PANI–TiO₂ hybrid materials were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), electrical conductivity (EC), Fourier-transform infrared (FT-IR) and X-ray diffraction (XRD) measurements. PANI–TiO₂ nano-composites synthesized with the first method showed a relatively low electrical conductivity of 3.78 × 10⁻² S/cm at 20 °C. TGA suggested that the particles contained 40.6% TiO₂ by mass and showed a strong interaction at the interface of TiO₂ and PANI. The electrical conductivity of the hybrid particles produced using the second method increased to 7.75 × 10⁻² S/cm and the TGA results showed 34.4% TiO₂ by mass. Through SEM and TEM analyses it was confirmed that the PANI has been interpenetrated into the three-dimensional network of the TiO₂ when the second method was used.     

The effect of thermal radiation on the solidification dynamics of metal oxide melt droplets

Cooling and solidification of metal oxide droplets in water are considered, using a single-particle model which takes into account heat conduction and thermal radiation transfer within the particle. It is shown that, for millimeter-size particles, near-infrared absorption of the particle's substance determines the solidification pattern and dynamics. For semi-transparent aluminum oxide particles, the rate of surface solidification is controlled by convective heat transfer. For opaque corium particles, thermal radiation from the particle surface leads to fast surface solidification. The impact of so-formed crust layer on subsequent particle fragmentation is discussed with respect to its influence on steam explosion.