P型 α-多孔 SiC. 的光致發光光潽硏究

이기환,김영유,두영뢰,우배매 公州大學校 基礎科學硏究所 1998 自然科學硏究 Vol.7 No.-

The photoluminescence (PL) spectra from p-type a-porous silicon carbides prepared under UV photo-assisted process and under dark-current condition are investigated in detail. Emission bands with peak energies of 2.35, 2.50, 2.70, and 3.43 are resolved. The PL stability in tune and the PL difference arising from different tuning excitation energies are studied. It is found that the PL spectra of the a-porous silicon carbide depend strongly on the preparation conditions for electrochemical etching. The PL spectrum of the sample prepared under photo-assisted process has an enhancement on the lower-energy side of the emission; on the contray, another one under dark-current condition has an enhancement at the higher energy side, and the former stability is better than the latter one, and the latter PL intensity decreases with the increase of the time in the air. The reasons about these differences are discussed.

Detection and parametric identification of structural nonlinear restoring forces from partial measurements of structural responses

Lei, Ying,Hua, Wei,Luo, Sujuan,He, Mingyu Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.2

Compared with the identification of linear structures, it is more challenging to conduct identification of nonlinear structure systems, especially when the locations of structural nonlinearities are not clear in structural systems. Moreover, it is highly desirable to develop methods of parametric identification using partial measurements of structural responses for practical application. To cope with these issues, an identification method is proposed in this paper for the detection and parametric identification of structural nonlinear restoring forces using only partial measurements of structural responses. First, an equivalent linear structural system is proposed for a nonlinear structure and the locations of structural nonlinearities are detected. Then, the parameters of structural nonlinear restoring forces at the locations of identified structural nonlinearities together with the linear part structural parameters are identified by the extended Kalman filter. The proposed method simplifies the identification of nonlinear structures. Numerical examples of the identification of two nonlinear multi-story shear frames and a planar nonlinear truss with different nonlinear models and locations are used to validate the proposed method.

Mechanical Performance of Prefabricated External Wall Panel under Horizontal Displacement

Ying Xu,Shuai-Ying Wang,Lei Chai,Cong-Cong Luo 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.11

In this paper, experiment and Finite Element Method (FEM) approaches are employed to study the mechanical performance of prefabricated external wall panel under lateral displacement. Tensile bond strength test and Z-shaped specimen direct shear test of the bonding interface of mortar to ceramsite concrete are performed, the normal and shear mechanical property of the interface is studied respectively. Scaled model test of prefabricated external wall panel under lateral displacement is then performed to obtain loaddisplacement curve, and mechanical behavior of prefabricated external wall panel in different stages is studied. Moreover, ABAQUS finite element analysis model for scaled model test panel is established based on previous study about bond interface and the results from experiment and FEM analysis are relatively consistent with each other. It is found that with the gradual increase in tangential contact stiffness of joint interfaces, the overall lateral stiffness of wall panels will approach complete joint consolidation conditions before the peak load. However, when the tangential contact stiffness of joint interfaces increases to a certain extent, there will be little change in initial lateral stiffness.

Data fusion based improved Kalman filter with unknown inputs and without collocated acceleration measurements

Ying Lei,Sujuan Luo,Ying Su 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.3

The classical Kalman filter (KF) can provide effective state estimation for structural identification and vibration control, but it is applicable only when external inputs are measured. So far, some studies of Kalman filter with unknown inputs (KF-UI) have been proposed. However, previous KF-UI approaches based solely on acceleration measurements are inherently unstable which leads to poor tracking and fictitious drifts in the identified structural displacements and unknown inputs in the presence of measurement noises. Moreover, it is necessary to have the measurements of acceleration responses at the locations where unknown inputs applied, i.e., with collocated acceleration measurements in these approaches. In this paper, it aims to extend the classical KF approach to circumvent the above limitations for general real time estimation of structural state and unknown inputs without using collocated acceleration measurements. Based on the scheme of the classical KF, an improved Kalman filter with unknown excitations (KF-UI) and without collocated acceleration measurements is derived. Then, data fusion of acceleration and displacement or strain measurements is used to prevent the drifts in the identified structural state and unknown inputs in real time. Such algorithm is not available in the literature. Some numerical examples are used to demonstrate the effectiveness of the proposed approach.

Probabilistic structural damage detection approaches based on structural dynamic response moments

Lei, Ying,Yang, Ning,Xia, Dandan Techno-Press 2017 Smart Structures and Systems, An International Jou Vol.20 No.2

Because of the inevitable uncertainties such as structural parameters, external excitations and measurement noises, the effects of uncertainties should be taken into consideration in structural damage detection. In this paper, two probabilistic structural damage detection approaches are proposed to account for the underlying uncertainties in structural parameters and external excitation. The first approach adopts the statistical moment-based structural damage detection (SMBDD) algorithm together with the sensitivity analysis of the damage vector to the uncertain parameters. The approach takes the advantage of the strength SMBDD, so it is robust to measurement noise. However, it requests the number of measured responses is not less than that of unknown structural parameters. To reduce the number of measurements requested by the SMBDD algorithm, another probabilistic structural damage detection approach is proposed. It is based on the integration of structural damage detection using temporal moments in each time segment of measured response time history with the sensitivity analysis of the damage vector to the uncertain parameters. In both approaches, probability distribution of damage vector is estimated from those of uncertain parameters based on stochastic finite element model updating and probabilistic propagation. By comparing the two probability distribution characteristics for the undamaged and damaged models, probability of damage existence and damage extent at structural element level can be detected. Some numerical examples are used to demonstrate the performances of the two proposed approaches, respectively.

On-line integration of structural identification/damage detection and structural reliability evaluation of stochastic building structures

Ying Lei,Longfei Wang,Lanxin Lu,Dan-dan Xia 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.6

Recently, some integrated structural identification/damage detection and reliability evaluation of structures with uncertainties have been proposed. However, these techniques are applicable for off-line synthesis of structural identification and reliability evaluation. In this paper, based on the recursive formulation of the extended Kalman filter, an on-line integration of structural identification/damage detection and reliability evaluation of stochastic building structures is investigated. Structural limit state is expanded by the Taylor series in terms of uncertain variables to obtain the probability density function (PDF). Both structural component reliability with only one limit state function and system reliability with multi-limit state functions are studied. Then, it is extended to adopt the recent extended Kalman filter with unknown input (EKF-UI) proposed by the authors for on-line integration of structural identification/damage detection and structural reliability evaluation of stochastic building structures subject to unknown excitations. Numerical examples are used to demonstrate the proposed method. The evaluated results of structural component reliability and structural system reliability are compared with those by the Monte Carlo simulation to validate the performances of the proposed method

C-Type Natriuretic Peptide/Natriuretic Peptide Receptor 2 Is Involved in Cell Proliferation and Testosterone Production in Mouse Leydig Cells

Lei Yang,Lanjie Lei,Qihan Zhao,Ying Gong,Gaopeng Guan,Shaoxin Huang 대한남성과학회 2019 The World Journal of Men's Health Vol.37 No.2

Purpose: This study investigated the role of natriuretic peptide receptor 2 (NPR2) on cell proliferation and testosterone secre-tion in mouse Leydig cells.Materials and Methods: Mouse testis of different postnatal stages was isolated to detect the expression C-type natriuretic peptide (CNP) and its receptor NPR2 by quantitative reverse transcription polymerase chain reaction (RT-qPCR). Leydig cells isolated from mouse testis were cultured and treated with shNPR2 lentiviruses or CNP. And then the cyclic guanosine mono-phosphate production, testosterone secretion, cell proliferation, cell cycle and cell apoptosis in mouse Leydig cells were ana-lyzed by ELISA, RT-qPCR, Cell Counting Kit-8, and flow cytometry. Moreover, the expression of NPR2, cell cycle, apoptosis proliferation and cell cycle related gene were detected by RT-qPCR and Western blot. Results: Knockdown of NPR2 by RNAi resulted in S phase cell cycle arrest, cell apoptosis, and decreased testosterone secre-tion in mouse Leydig cells.Conclusions: Our study provides more evidences to better understand the function of CNP/NPR2 pathway in male reproduc-tion, which may help us to treat male infertility.

A two-stage and two-step algorithm for the identification of structural damage and unknown excitations: numerical and experimental studies

Ying Lei,Feng Chen,Huan Zhou 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.1

Extended Kalman Filter (EKF) has been widely used for structural identification and damage detection. However, conventional EKF approaches require that external excitations are measured. Also, in the conventional EKF, unknown structural parameters are included as an augmented vector in forming the extended state vector. Hence the sizes of extended state vector and state equation are quite large, which suffers from not only large computational effort but also convergence problem for the identification of a large number of unknown parameters. Moreover, such approaches are not suitable for intelligent structural damage detection due to the limited computational power and storage capacities of smart sensors. In this paper, a two-stage and two-step algorithm is proposed for the identification of structural damage as well as unknown external excitations. In stage-one, structural state vector and unknown structural parameters are recursively estimated in a two-step Kalman estimator approach. Then, the unknown external excitations are estimated sequentially by least-squares estimation in stage-two. Therefore, the number of unknown variables to be estimated in each step is reduced and the identification of structural system and unknown excitation are conducted sequentially, which simplify the identification problem and reduces computational efforts significantly. Both numerical simulation examples and lab experimental tests are used to validate the proposed algorithm for the identification of structural damage as well as unknown excitations for structural health monitoring.

Identification of structural systems and excitations using vision-based displacement measurements and substructure approach

Ying Lei,Chengkai Qi 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.30 No.3

In recent years, vision-based monitoring has received great attention. However, structural identification using vision-based displacement measurements is far less established. Especially, simultaneous identification of structural systems and unknown excitation using vision-based displacement measurements is still a challenging task since the unknown excitations do not appear directly in the observation equations. Moreover, measurement accuracy deteriorates over a wider field of view by vision-based monitoring, so, only a portion of the structure is measured instead of targeting a whole structure when using monocular vision. In this paper, the identification of structural system and excitations using vision-based displacement measurements is investigated. It is based on substructure identification approach to treat of problem of limited field of view of vision-based monitoring. For the identification of a target substructure, substructure interaction forces are treated as unknown inputs. A smoothing extended Kalman filter with unknown inputs without direct feedthrough is proposed for the simultaneous identification of substructure and unknown inputs using vision-based displacement measurements. The smoothing makes the identification robust to measurement noises. The proposed algorithm is first validated by the identification of a three-span continuous beam bridge under an impact load. Then, it is investigated by the more difficult identification of a frame and unknown wind excitation. Both examples validate the good performances of the proposed method.

Kinetic modeling of C2–C7 olefins interconversion over ZSM-5 catalyst

Lei Ying,Jiajia Zhu,Youwei Cheng,Lijun Wang,Xi Li 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.33 No.-

The kinetics of C2–C7 olefins interconversion were studied by feeding individual olefin into industrialZSM-5 catalyst at temperatures of 400–490 8C, space time of 0.0046–0.34 h and partial pressure of13.1 kPa. A kinetic model involving oligomerization, cracking and aromatization of olefins wasestablished. The results showed that the calculated apparent activation energy was negative foroligomerization reactions and positive for cracking reactions. The proposed kinetic model was able topredict the product concentrations in the C2–C7 olefins interconversion over ZSM-5 catalyst, with R2values ranged from 0.969 to 0.996 for the major species.