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Aijun Yang,Weigao Ge 한국수학교육학회 2009 純粹 및 應用數學 Vol.16 No.2
This paper deals with the existence of positive solutions for a kind of multi-point nonlinear fractional differential boundary value problem at resonance. Our main approach is different from the ones existed and our main ingredient is the Leggett-Williams norm-type theorem for coincidences due to O'Regan and Zima. The most interesting point is the acquisition of positive solutions for fractional differential boundary value problem at resonance. And an example is constructed to show that our result here is valid.
Aijun Yang,Helin Wang 한국전산응용수학회 2012 Journal of applied mathematics & informatics Vol.30 No.1
We consider the fourth-order differential equation with one-dimensional p-Laplacian [수식] subject to the boundary conditions [수식] is a L1-Caratheodory function with [수식]. We obtain the existence of at least one nonconstant symmetric solution by applying an extension of Mawhin's continuation theorem due to Ge. Furthermore, an example is given to illustrate the results.
Interval Estimation for Discrete-time Descriptor System Based on Zonotopic Kalman Filter
Aijun Chen,Mingjian Sun,Yi Shen,Yuan Liu 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.6
This paper investigates the problem of interval estimation for discrete-time linear descriptor systems subject to unknown-but-bounded uncertainties. Based on prediction-correction mechanism, we proposed a twostep interval estimator to over-estimate the bounds of the system states. To reduce the conservatism, a novel parameterization-based approach is presented. Besides, by using a Frobenius norm-based minimization approach, optimal correction is calculated. Compared to the volume criterion, the computational efficiency is greatly enhanced. Finally, two numerical examples are presented to illustrate the efficiency and potential application of the proposed approach.
Aijun Li,Lin Chen,Yanchun Zhou 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.4
Based on the structure feature of a tree, a cylindrical Ti2AlC/graphite layered composite has been fabricated through heat treating a graphite column and six close-matched thin wall Ti2AlC cylinders bonded with the Ti2AlC powders at 1300oC and low oxygen partial pressure. SEM examination reveals that the bond interlayers between cylinders or that between cylinder and column are not fully dense without any crack formation. During the compressive test, the strain of the Ti2AlC/graphite layered composite is about twice higher than that of the monolithic Ti2AlC ceramic, and the compressive strength of the layered composite is 348 MPa. The layered composite show the noncatastrophic fracture behaviors due to the debonding and shelling off of the layers, which are different from the monolithic Ti2AlC ceramic. The mechanism of the improved deformation capacity and noncatastrophic failure modes are attributed to the presence of the central soft graphite column and cracks deflection by the bond interlayers.
Experimental study on acoustic emission characteristics of reinforced concrete components
Aijun Gu,Ying Luo,Baiqiang X 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.16 No.1
Acoustic emission analysis is an effective technique for monitoring the evolution of damage in a structure. An experimental analysis on a set of reinforced concrete beams under flexural loading was carried out. A mixed AE analysis method which used both parameter-based and signal-based techniques was presented to characterize and identify different failure mechanisms of damage, where the signal-based analysis was performed by using the Hilbert-Huang transform. The maximum instantaneous energy of typical damage events and the corresponding frequency characteristics were established, which provided a quantitative assessment of reinforced concrete beam using AE technique. In the bending tests, a \"pitch-catch\" system was mounted on a steel bar to assess bonding state of the steel bar in concrete. To better understand the AE behavior of bond-slip damage between steel bar and concrete, a special bond-slip test called pullout test was also performed. The results provided the basis of quantitative AE to identify both failure mechanisms and level of damages of civil engineering structures.
LIST EDGE AND LIST TOTAL COLORINGS OF PLANAR GRAPHS WITHOUT 6-CYCLES WITH CHORD
Aijun Dong,Guizhen Liu,Guojun Li 대한수학회 2012 대한수학회보 Vol.49 No.2
Giving a planar graph G, let $x^'_l(G)$ and $x^{''}_l(G)$ denote the list edge chromatic number and list total chromatic number of G respectively. It is proved that if a planar graph G without 6-cycles with chord, then $x^'_l(G){\leq}{\Delta}(G)+1$ and $x^{''}_l(G){\leq}{\Delta}(G)+2$ where ${\Delta}(G){\geq}6$.
Aijun Ruan,Jin Cheng 기술경영경제학회 2017 ASIAN JOURNAL OF TECHNOLOGY INNOVATION Vol.25 No.1
Accessing external knowledge is an important factor in successful innovation. Knowledgesearch is an issue of concern for Chinese firms because many firms generally have relativelyweak research and development (R&D) and innovation capabilities that cannot supportinnovative development through mere internal innovations. This study examines theinteractive effects of network centrality, structural holes, and knowledge tacitness whenformal knowledge search depth (FKSD) affects innovation performance from theperspective of formal/informal knowledge search. A survey of 161 firms in China suggeststhat FKSD positively affects innovation performance, and the effect is positively moderatedby network centrality. Given high knowledge tacitness, FKSD is more effective in fosteringinnovation performance when firms’ network centrality is higher. Furthermore, highknowledge tacitness results in rich structural holes negatively moderating the effect ofFKSD on innovation performance, whereas low tacitness generates a positive moderatingrole. This indicates that Chinese firms may consider using more formal search channels toincrease external knowledge search depth and to dynamically adjust the depth of such aformal search or the mode of network structural embeddedness according to the degree ofknowledge tacitness.
Aijun Hu,Ling Xiang 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.3
The Mathematical morphological filter (MMF) is widely applied in vibration signal processing for fault diagnosis. The Structure element (SE) and the cutoff frequency of filter have important impacts on the filtering effect, but there is no selection principle of these parameters for vibration signal processing in fault diagnosis. In this paper, the working mechanism of the MMF is studied, and a novel technique with filter characteristics and selection criterion of the MMF is proposed. The filter characteristics of morphological filter are described through frequency response analysis. The relationship between the SE length and the cutoff frequency of MMF is put forward, and the quantitative selection method of SE in engineering is proposed to effectively remove the noise and detect the impulses. The method is evaluated using both simulated signal and experimental bearing vibration signal. The results show that quantized selection method can make MMF have the better filtering effect, and can reliably extract impulsive features for bearing defect diagnosis. The study provides a theoretical basis for the application of MMF in vibration signal processing.