Identification of factors that accelerate hydrogen production by Clostridium butyricum RAK25832 using casamino acids as a nitrogen source

The ability of Clostridium butyricum RAK25832 to use casamino acids as a nitrogen source was investigated. Strain RAK25832 showed the capacity to utilize different types of carbon sources. With glucose as a carbon source (10 g/L), the preferred final concentration of casamino acids was 26.67 g/L, with a cumulative hydrogen production, production rate, and yield of 2505 mL H₂/L, 160 mL/h, and 1.81 mol H₂/mol glucose, respectively. Eighteen metal elements were screened to identify the most important metals for biohydrogen production, and four elements were optimized. The optimal medium composition was MgCl₂·6H₂O (0.1 g/L), K₂HPO₄·3H₂O (6.67 g/L), NaHCO₃ (2.6 g/L), and FeCl₂·4H₂O (0.002 g/L). Vitamin supplementation of the medium showed no significant effect on hydrogen production. Under the optimized conditions, cumulative hydrogen production reached 3074 mL H₂/L. This is the first study to demonstrate the use of casamino acids as a nitrogen source by C. butyricum.     

基于翻领松量结构模型的翻折领结构设计方法

为解决翻领松量计算精准性及翻折领通用结构设计方法的问题,提出了一种基于翻领松量结构模型的翻折领结构设计方法。通过构建翻领松量结构模型确定了翻领松量计算系数,对6种不同状态下的翻领间隙量变化进行数据统计分析,依据翻领间隙回归系数模型确定了翻领松量计算给定常数,运用SPSS统计软件对实验数据进行了相关性分析、回归分析、配对样本T检验,并推导出翻领松量计算公式。实验结果表明:使用该公式计算的翻领松量提高了翻折领结构造型的准确性,基于翻领松量结构模型的翻折领结构设计方法可以满足不同翻折领领型结构设计要求。     

Interval functional observers for time-delay systems with additive disturbances

This article considers the design of interval functional observers to estimate a linear function of the state vector of time-delay systems subject to both input and output additive disturbances. Two novel functional observers are proposed and designed such that they bound the set of all admissible values of a linear function of the state vector at each instant of time. By contrast to interval observers currently available in the literature, both observers proposed in this article utilize multiple delayed output measurement and have a more general structure. This trade-off feature overcomes some drawbacks in previous work and enables interval functional observers to be designed for a wider class of time-delay systems. Conditions for the existence of interval functional observers are derived and an effective design algorithm for computing unknown observer matrices is provided. Two illustrative examples are given to show the advantages and effectiveness of our design method.     

High energy storage density and discharging efficiency in La3+/Nb5+-co-substituted (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics

In this work, [(Bi_1-xLa_x)_0.5Na_0.5]_0.94Ba_0.06(Ti_1-5y/4Nb_y)O₃ ceramics have been developed by the dual-substitution of La³⁺ for Bi³⁺ and Nb⁵⁺ for Ti⁴⁺ and prepared by an ordinary sintering technique. All ceramics can be well-sintered at 1200 °C. The addition of La³⁺ and Nb⁵⁺ reduces the grain size and improve the dielectric breakdown strength of the ceramics; moreover, after the introduction of La³⁺ and Nb⁵⁺, the remanent polarization of the ceramics is significantly reduced, while the maximum polarization remains the same large value as that of the ceramic without the doping of La³⁺ and Nb⁵⁺. As a result, high energy storage density and discharge efficiency are achieved at x/y = 0.07/0.02, giving the large storage density of 1.83 J/cm³ and high discharging efficiency of 70%. The present work presents a feasible strategy to develop energy storage materials based on perovskite ferroelectrics by the partial substitutions in the A and B sites.     

Double polarization hysteresis and dramatic influence of small compositional variations on the electrical properties in Bi4Ti3O12 ceramics

This work reports the existence of double polarization hysteresis (P–E) loop in Aurivillius-phase ferroelectric Bi₄Ti₃O₁₂ (BiT) and reveals dramatic influence of small compositional variations on the electrical properties of it. The double polarization hysteresis is a characteristic of the interaction of defects with domain walls. This characteristic becomes more pronounced in Bi-deficient and Mg-doped BiT due to an increase in oxygen vacancy concentration at the lattices. Normal and saturated P–E loop is recalled by Nb donor doping, and associated composition Bi₄Ti_2.97Nb_0.03O_12.015 (BiT-0.03Nb) shows high remnant polarization (P_r = 12.5 μC/cm²) and large field-induced strain (S₃₃ = 5.6 × 10^?4). In addition, this doping results in bulk conductivity (σ_b) of BiT decreasing dramatically and associated activity energy (E_a) increasing significantly. In contrast, high oxide ion conductivity is induced with Mg²⁺ acceptor doping, and at 600 °C the optimum composition has ionic conductivity of ?0.65 × 10^?2 S cm^?1 in the bulk.     

Designing novel sodium bismuth titanate lead-free incipient perovskite for piezoactuator applications

Bismuth-based lead-free incipient piezoceramics have potential in piezoactuators owing to their large strain response. However, a substantial strain hysteresis and poor temperature/frequency stability heavily restrict their practical applications. Herein, we designed a compositional inhomogeneity and constructed quenched random fields to enhance the relaxor dynamics by introducing a classical relaxor material, Ba(Zr_0.2Ti_0.8)O₃, into a nonergodic material, (Na_0.5Bi_0.5)TiO₃–0.15SrTiO₃. Intriguingly, we obtained a large piezoelectric coefficient of 602 pm/V and a narrow hysteresis of 32% at the x = 0.04 (BZT4) composition. The strain properties present a robust frequency (~2%, 1-20 Hz) and temperature stability (~13%, 25-150°C). The excellent actuating properties of BZT4 were due to a field-induced reversible ergodic relaxor-ferroelectric transformation, and the narrow hysteresis can be attributed to quick switching of the dynamic relaxor phase to external stimuli. The origin of the structural transition and salient strain performance was systematically investigated. This study provides a novel route for designing lead-free incipient perovskite with a large strain, narrow hysteresis and high stability for eco-friendly actuators.     

Complex structural contribution of the morphotropic phase boundary in Na0.5Bi0.5TiO3 - CaTiO3 system

The correlation between structure and dielectric properties of lead-free (1-x)Na_0.5Bi_0.5TiO₃ - xCaTiO₃ ((1-x)NBT - xCT) polycrystalline ceramics was investigated systematically by X-ray diffraction, combined with impedance spectroscopy for dielectric characterizations. The system shows high miscibility in the entire composition range. A morphotropic phase boundary (MPB), at 0.09?≤?x?<?0.15 was identified where rhombohedral and orthorhombic symmetries coexist at room temperature. The fraction of orthorhombic phase increases gradually with x in the MPB region. Dielectric measurements reveal that the relative permittivity increase with addition of Ca²⁺. This behavior is unusual with this kind of doping. A thermal hysteresis occurred only in the MPB composition which varies in a non-monotonically manner with x, detected by dielectric properties. This phenomenon is related to the crystalline microstructure by a linear relationship between the fraction of each phase and dielectric properties, and, more precisely, to the strong interaction between rhombohedral and orthorhombic phases.     

Memory-based dynamic event-triggered control for networked interval type-2 fuzzy systems subject to DoS attacks

In this article, the memory-based dynamic event-triggered controller design issue is investigated for networked interval type-2 (IT2) fuzzy systems under non-periodic denial-of-service (DoS) attacks. For saving limited network bandwidth, a novel memory-based dynamic event-triggered mechanism (DETM) is proposed to schedule data communication. Unlike existing event-triggered generators, the developed memory-based DETM can utilize a series of newly released signals and further save network resources by introducing interval dynamic variables. Moreover, to improve design flexibility, an IT2 fuzzy controller with freely selectable fuzzy rule number and premise membership functions (MFs) is synthesized. Then, a new switched time-delay system with imperfectly matched MFs is established under the consideration of memory-based DETM and DoS attacks simultaneously. Besides, based on the property of MFs, the boundary information of membership grades and slack matrices are introduced in the stability analysis. Furthermore, by using a piecewise Lyapunov–Krasovskii method, membership-functions-dependent criteria are deduced to ensure the asymptotic stability of built fuzzy switched systems. Finally, the effectiveness of proposed control strategies is demonstrated by simulation examples.     

Distinguishability of interval type-2 fuzzy sets data by analyzing upper and lower membership functions

In this paper, we deal with the problem of classification of interval type-2 fuzzy sets through evaluating their distinguishability. To this end, we exploit a general matching algorithm to compute their similarity measure. The algorithm is based on the aggregation of two core similarity measures applied independently on the upper and lower membership functions of the given pair of interval type-2 fuzzy sets that are to be compared. Based on the proposed matching procedure, we develop an experimental methodology for evaluating the distinguishability of collections of interval type-2 fuzzy sets. Experimental results on evaluating the proposed methodology are carried out in the context of classification by considering interval type-2 fuzzy sets as patterns of suitable classification problem instances. We show that considering only the upper and lower membership functions of interval type-2 fuzzy sets is sufficient to (i) accurately discriminate between them and (ii) judge and quantify their distinguishability.     

区间集上的一元格蕴涵代数方程

把格蕴涵代数中滤子、素滤子、LI-理想、对偶原子和凸子格等概念拓展到区间集进行了重新定义,研究了三种基本的区间集上的一元格蕴涵代数方程,并给出了方程的可解性判断条件以及方程解集的若干性质.