Two-dimensional Hurwitz-Schur stability test of linear systems with interval delays

It is difficult to determine the stability of linear systems with interval delays （LID systems） because the roots of the characteristic polynomials of the systems are continuous and vary in a complex plane with the delay. To solve the problem, this paper develops a stability test of LID systems by resorting to 2-D hybrid polynomials and 2-D Hurwitz-Schur stability. Comparing with the existing test approaches for LID systems, the proposed 2-D Hurwitz-Schur stability test is easy to apply, and can obtain closed form constraint conditions for system parameters. This paper proposes some theorems as sufficient conditions for the stability of LID systems, and also reveals that recent results about the stability test of linear systems with any delays （LAD systems） are not suitable for LID systems because they are very conservative for the stability of LID systems.

A new nonparametric stability test with an application to major Chinese macroeconomic time series

In this paper, we propose a new test for testing the stability in macroeconomic time series, based on the LASSO variable selection approach and nonparametric estimation of a time-varying model. The wild bootstrap is employed to obtain its data-dependent critical values. We apply the new method to test the stability of bivariate relations among 92 major Chinese macroeconomic time series. We find that more than 70% bivariate relations are significantly unstable.

Predicting stability of integrated circuit test equipment using upper side boundary values of normal distribution

In response to the growing complexity and performance of integrated circuit(IC),there is an urgent need to enhance the testing and stability of IC test equipment.A method was proposed to predict equipment stability using the upper side boundary value of normal distribution.Initially,the K-means clustering algorithm classifies and analyzes sample data.The accuracy of this boundary value is compared under two common confidence levels to select the optimal threshold.A range is then defined to categorize unqualified test data.Through experimental verification,the method achieves the purpose of measuring the stability of qualitative IC equipment through a deterministic threshold value and judging the stability of the equipment by comparing the number of unqualified data with the threshold value,which realizes the goal of long-term operation monitoring and stability analysis of IC test equipment.

Methane dehydroaromatization with periodic CH_4-H_2 switch:A promising process for aromatics and hydrogen

Long-term stability test of Mo/HZSM-5-N catalysts（HZSM-5-N stands for nano-sized HZSM-5） in methane dehydroaromatization（MDA）reaction has been performed with periodic CH4-H2 switch at 1033-1073 K for more than 1000 h.During this test,methane conversion ranges from 13% to 16%,and mean yield to aromatics（i.e.benzene and naphthalene） exceeds 10%.N2-physisorption,XRD,NMR and TPO measurements were performed for the used Mo/HZSM-5 catalysts and coke deposition,and the results revealed that the periodic hydrogenation can effectively suppress coke deposition by removing the inert aromatic-type coke,thus ensuring Mo/HZSM-5 partly maintained its activity even in the presence of large amount of coke deposition.The effect of zeolite particle size on the catalytic activity was also explored,and the results showed that the nano-sized zeolite with low diffusion resistance performed better.It is recognized that the size effect was enhanced by reaction time,and it became more remarkable in a long-term MDA reaction even at a low space velocity.

Technological Valorization of Algerian Dates Downgraded from <i>Deglet Nour</i>Variety to Semi-Candied Dates in Dates Syrup

The objective of this study is the valorization of downgraded dates from a high Algerian date variety Deglet Nour, locally called “h’chef”. The work starts with the implementation of a food formulation of semi-candied dates in syrup extracted from dates. This formulation was based on dehydration-impregnation by immersion (D.I.I.). The downgraded dates were cleaned, cut, blanched, and then immersed in date syrups with increasing differential concentrations in Brix degrees: 65°, 70° and 75°. The chosen date/syrup immersion ratio is 1:2 (w/w). The obtained semi-candied dates were the subject of physicochemical and sensory analyses. The characterization of the downgraded dates before immersion showed high sugar content with a rate 52.67 g% g of dry matter and low water content (14%) which favors their use in semi-candied products. The physico-chemical analyses results of the three semi-candied dates products show an increase in their final sugar content, i.e. from 53.55% to 60.78% and in ashes between 1.76 p.cent and 1.94 p.cent. On the other hand, sensory analysis results confirm that the semi-candied dates with a syrup of 75° Brix present the most appreciated and preferable organoleptic characteristics than the other variables. Finally, following appertisation, the stability test reveals good microbiological quality (100°C for 20 minutes) of the three (3) semi-candied formulations of dates. Thus, the valorization of the “h’chef” as sorting gap Deglet Nour date allowed its transformation into semi-candied dates, stable, appreciable on the organoleptic side. This new formulation could constitute a value-added product if eventually manufactured on an industrial scale, mainly in southern Algeria.

Velocity plus displacement equivalent force control for real-time substructure testing

This paper employs a velocity plus displacement（V＋D）-based equivalent force control（EFC） method to solve the velocity/displacement difference equation in a real-time substructure test. This method uses type 2 feedback control loops to replace mathematical iteration to solve the nonlinear dynamic equation. A spectral radius analysis of the amplification matrix shows that the type 2 EFC-explicit, Newmark-β method has beneficial numerical characteristics for this method. Its stability limit of Ω = 2 remains unchanged regardless of the system damping because the velocity is achieved with very high accuracy during simulation. In contrast, the stability limits of the central difference method using direct velocity prediction and the EFC-average acceleration method with linear interpolation are shown to decrease with an increase in system damping. In fact, the EFC-average acceleration method is shown to change from unconditionally stable to conditionally stable. We also show that if an over-damped system with a damping ratio of 1.05 is considered, the stability limit is reduced to Ω =1.45. Finally, the results from an experiment with a single-degree-of-freedom structure installed with a magneto-rheological（MR） damper are presented. The results demonstrate that the proposed method is able to follow both displacement and velocity commands with moderate accuracy, resulting in improved test performance and accuracy for structures that are sensitive to both velocity and displacement inputs. Although the findings of the study are promising, additional test data and several further improvements will be required to draw general conclusions.

Recent Advances in Stability Improvement Strategies of M-N_(x)/C Catalysts Towards Oxygen Reduction Reaction

Although fuel cells possess advantages of high energy conversion efficiency and zero-carbon emission,their large-scale commercialization is restricted by expensive and scarce platinum(Pt)catalysts.Metal-nitrogen-carbon(M-Nx/C)catalysts are hailed as the most promising candidates to replace Pt due to their considerable oxygen reduction reaction(ORR)activity and low cost.Despite tremendous progress in terms of active site identification and activity improvement being achieved in the past few decades,the M-Nx/C catalysts still suffer from insufficient durability,which drastically limits their practical application.In this regard,understanding degradation mechanisms and customizing stabilization strategies are of significant importance yet challengeable.In this review,we summarize the recent advances in the stability improvement of M-Nx/C catalysts.The stability test protocols of the M-Nx/C are firstly introduced.Subsequently,with the combination of advanced ex situ and in situ characterization techniques and density functional theory calculation,we present a comprehensive overview of the main degradation mechanisms during ORR process.Aiming at these deactivation issues,a variety of novel improvement strategies are developed to enhance the stability of M-Nx/C.Finally,the current challenges and prospects to design highly stable M-Nx/C catalysts are also proposed.

Improved 2-D Stability Margin Test for 2-D Discrete Systems

An improved 2 D stability margin test and its algorithm for 2 D discrete systems are proposed.The stability margin test procedure can be slmplified by using the inner term polynomials of B(z 1,z 2) to construct a margin test table.Different from other well known 2 D stability margin test algorithms,the new approach can directly obtain the stability margin.

Hydrothermal synthesis and characterization of Dy-doped CeVO_(4) nanorods used for photodegradation of methylene blue and rhodamine B

Pure CeVO_(4) and Dy-doped CeVO_(4) nanorods containing different weight contents of Dy dopant were synthesized by hydrothermal method.Effect of Dy dopant on photodegradation of methylene blue(MB)and rhodamine B(RhB) was evaluated under UV light irradiation within 80 min.Pure CeVO_(4) and Dydoped CeVO_(4) nanorods were characterized by X-ray diffraction(XRD),Raman spectroscopy,transmission electron microscopy(TEM) and UV-visible spectroscopy.In this research,CeVO_(4) nanorods are tetragonal phase with the detection of main peak shift after being doped with Dy.The length of nanorods is deceased from 50 to 200 nm for pure CeVO_(4) to 50-100 nm for 3% Dy-doped CeVO_(4).Photodegradation of MB and RhB by CeVO_(4) nanorods under UV light irradiation is improved by Dy-dopant that plays the role in accepting electrons and reducing electron-hole recombination.MB and RhB solutions degraded by 3% Dy-doped CeVO_(4) nanorods was 94% and 93% within 80 min,respectively.