Damage detection of nonlinear structures with analytical mode decomposition and Hilbert transform

Zuo-Cai Wang,Dong Geng,Wei-Xin Ren,Guang-Feng Zhang,Gen-Da Chen 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.1

This paper proposes an analytical mode decomposition (AMD) and Hilbert transform method for structural nonlinearity quantification and damage detection under earthquake loads. The measured structural response is first decomposed into several intrinsic mode functions (IMF) using the proposed AMD method. Each IMF is an amplitude modulated-frequency modulated signal with narrow frequency bandwidth. Then, the instantaneous frequencies of the decomposed IMF can be defined with Hilbert transform. However, for a nonlinear structure, the defined instantaneous frequencies from the decomposed IMF are not equal to the instantaneous frequencies of the structure itself. The theoretical derivation in this paper indicates that the instantaneous frequency of the decomposed measured response includes a slowly-varying part which represents the instantaneous frequency of the structure and rapidly-varying part for a nonlinear structure subjected to earthquake excitations. To eliminate the rapidly-varying part effects, the instantaneous frequency is integrated over time duration. Then the degree of nonlinearity index, which represents the damage severity of structure, is defined based on the integrated instantaneous frequency in this paper. A one-story hysteretic nonlinear structure with various earthquake excitations are simulated as numerical examples and the degree of nonlinearity index is obtained. Finally, the degree of nonlinearity index is estimated from the experimental data of a seven-story building under four earthquake excitations. The index values for the building subjected to a low intensity earthquake excitation, two medium intensity earthquake excitations, and a large intensity earthquake excitation are calculated as 12.8%, 23.0%, 23.2%, and 39.5%, respectively.

A data fusion method for bridge displacement reconstruction based on LSTM networks

Zuo-Cai Wang,Da-You Duan,Xiao-Tong Sun,Yu Xin 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.4

Bridge displacement contains vital information for bridge condition and performance. Due to the limits of direct displacement measurement methods, the indirect displacement reconstruction methods based on the strain or acceleration data are also developed in engineering applications. There are still some deficiencies of the displacement reconstruction methods based on strain or acceleration in practice. This paper proposed a novel method based on long short-term memory (LSTM) networks to reconstruct the bridge dynamic displacements with the strain and acceleration data source. The LSTM networks with three hidden layers are utilized to map the relationships between the measured responses and the bridge displacement. To achieve the data fusion, the input strain and acceleration data need to be preprocessed by normalization and then the corresponding dynamic displacement responses can be reconstructed by the LSTM networks. In the numerical simulation, the errors of the displacement reconstruction are below 9% for different load cases, and the proposed method is robust when the input strain and acceleration data contains additive noise. The hyper-parameter effect is analyzed and the displacement reconstruction accuracies of different machine learning methods are compared. For experimental verification, the errors are below 6% for the simply supported beam and continuous beam cases. Both the numerical and experimental results indicate that the proposed data fusion method can accurately reconstruct the displacement.

Laser Joining of Ti3Al-Based Alloy to Ni-Based Superalloy using a Titanium Interlayer

Xiao-Long Cai,Da-Qian Sun,Hong-Mei Li,Hong-Ling Guo,Yan Zhang,Ying-ying Che 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.8

Joining Ti3Al-based alloy to Ni-based superalloy is of great interest for applications in the aerospace fields. Direct welding of these two materials was very difficult and the joint usually fractured during laser welding which cannot form an effective welding joint. In this work, a pure titanium interlayer with a thickness of 0.4 mm was used between the base metals. The results indicated that the addition of titanium interlayer has a great effect on the joint performance. No macrocracks were found through the whole joint. The average room-temperature tensile strength of the joint with titanium was 177 MPa which still much lower than the two base metals. The weak link of the dissimilar joint was the Ti3Al/weld interface. The presence of Ti2Ni, α2-Ti3Al and AlNi2Ti brittle intermetallic compounds in the Ti3Al/weld interface deteriorated the joint properties.

Damage detection of nonlinear structures with analytical mode decomposition and Hilbert transform

Wang, Zuo-Cai,Geng, Dong,Ren, Wei-Xin,Chen, Gen-Da,Zhang, Guang-Feng Techno-Press 2015 Smart Structures and Systems, An International Jou Vol.15 No.1

This paper proposes an analytical mode decomposition (AMD) and Hilbert transform method for structural nonlinearity quantification and damage detection under earthquake loads. The measured structural response is first decomposed into several intrinsic mode functions (IMF) using the proposed AMD method. Each IMF is an amplitude modulated-frequency modulated signal with narrow frequency bandwidth. Then, the instantaneous frequencies of the decomposed IMF can be defined with Hilbert transform. However, for a nonlinear structure, the defined instantaneous frequencies from the decomposed IMF are not equal to the instantaneous frequencies of the structure itself. The theoretical derivation in this paper indicates that the instantaneous frequency of the decomposed measured response includes a slowly-varying part which represents the instantaneous frequency of the structure and rapidly-varying part for a nonlinear structure subjected to earthquake excitations. To eliminate the rapidly-varying part effects, the instantaneous frequency is integrated over time duration. Then the degree of nonlinearity index, which represents the damage severity of structure, is defined based on the integrated instantaneous frequency in this paper. A one-story hysteretic nonlinear structure with various earthquake excitations are simulated as numerical examples and the degree of nonlinearity index is obtained. Finally, the degree of nonlinearity index is estimated from the experimental data of a seven-story building under four earthquake excitations. The index values for the building subjected to a low intensity earthquake excitation, two medium intensity earthquake excitations, and a large intensity earthquake excitation are calculated as 12.8%, 23.0%, 23.2%, and 39.5%, respectively.

Molecular diversity and relationships among diverse sources of maize inbreds

Lee Suk-Ha,Zheng Da-Hao,Van Kyu-Jung,Kim Moon-Young,Cai Chunmei,Jun Tae-Hun 한국작물학회 2007 한국작물학회 학술발표대회 논문집 Vol.2007 No.-

Sagittal Pelvic Radius in Low-Grade Isthmic Lumbar Spondylolisthesis of Chinese Population

Zhao, Yang,Shen, Cai-Liang,Zhang, Ren-Jie,Cheng, Da-Wei,Dong, Fu-Long,Wang, Jun The Korean Neurosurgical Society 2016 Journal of Korean neurosurgical society Vol.59 No.3

Objective : To investigate the variation of pelvic radius and related parameters in low-grade isthmic lumbar spondylolisthesis. Methods : Seventy-four patients with isthmic lumbar spondylolisthesis and 47 controls were included in this study. There were 17 males and 57 females between 30 and 66 years of age, including 30 with grade I slippages and 44 grade II slippages; diseased levels included 34 cases on L4 and 40 cases on L5. Thoracic kyphosis (TK), the pelvic radius (PR), the pelvic angle (PA), pelvic morphology (PR-S1), and total lumbopelvic lordosis (PR-T12) were assessed from radiographs. Results : Statistically significant differences were found for the PA, PR-T12, and PR-S1 ($24.5{\pm}6.6^{\circ}$, $83.7{\pm}9.8^{\circ}$, and $25.4{\pm}11.2^{\circ}$, respectively) of the patients with spondylolisthesis and the healthy volunteers ($13.7{\pm}7.8^{\circ}$, $92.9{\pm}9.2^{\circ}$, and $40.7{\pm}8.9^{\circ}$, respectively). The TK/PR-T12 ratios were between 0.15 and 0.75. However, there were no differences in all the parameters between the L4 and L5 spondylolysis subgroups (p>0.05). The TK and PR-S1 of grade II were less than grade I, but the PA was greater. The PR-T12 of female patients were less than male patients, but the PA was greater (p<0.05). Conclusion : Pelvic morphology differed in patients with low-grade isthmic lumbar spondylolisthesis compared to controls. Gender and the grade of slippage impacted the sagittal configuration of the pelvis, but the segment of the vertebral slip did not. Overall, the spine of those with spondylolisthesis remains able to maintain sagittal balance despite abnormal pelvic morphology.

Prognostic Significance of Overexpression of EZH2 and H3k27me3 Proteins in Gastric Cancer

He, Long-Jun,Cai, Mu-Yan,Xu, Guo-Liang,Li, Jian-Jun,Weng, Zi-Jin,Xu, Da-Zhi,Luo, Guang-Yu,Zhu, Sen-Lin,Xie, Dan Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.7

The enhancer of zeste homolog 2 (EZH2) methyl transferase and histone 3 lysine 27 (H3K27me3) protein can repress gene transcription, and their aberrant expression has been observed in various human cancers. This study determined their expression levels in gastric cancer tissues with reference to clinicopathological features and patient survival. We collected 117 gastric cancer and corresponding normal tissues for immunohistochemistry analysis. In gastric cancers, 82/117 (70.1%) were positive for EZH2 and 66/117 (56.4%) for H3K27me3 proteins in contrast to only 5.41% and 7.25% of normal gastric mucosa specimens, respectively. Kaplan-Meier survival data showed the average overall and disease-free survival of EZH2 high expression patients was 25.2 and 20.2 months, respectively, shorter than that with EZH2 low expression (40.5 and 35.9 months). The average overall survival and disease-free survival of high H3K27me3 expression patients was 23.4 and 17.4 months, shorter than without H3K27me3 expression (37.6 and 34.5 months). The average overall survival and disease-free survival of patients with both EZH2 and H3K27me3 expression was 18.8 and 12.9 months, respectively, shorter than that with either alone (34.7 and 31.2 months) or with low levels of both (43.9 and 39.9 months). Multivariate Cox regression analysis showed that H3K27me3 and EZH2 expression, tumor size differentiation and clinical stage were all independent prognostic factors for predicting patient survival. This study demonstrated that detection of both EZH2 and H3K27me3 proteins can predict poor survival of gastric cancer patients, superior to single protein detection. In addition, H3K27me3 and EZH2 protein expression could predict lymph node metastasis.

Metabolic Adaptation in Obesity and Type II Diabetes: Myokines, Adipokines and Hepatokines

Oh, Kyoung-Jin,Lee, Da Som,Kim, Won Kon,Han, Baek Soo,Lee, Sang Chul,Bae, Kwang-Hee,Cai, Lu MDPI 2017 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.18 No.1

<P>Obesity and type II diabetes are characterized by insulin resistance in peripheral tissues. A high caloric intake combined with a sedentary lifestyle is the leading cause of these conditions. Whole-body insulin resistance and its improvement are the result of the combined actions of each insulin-sensitive organ. Among the fundamental molecular mechanisms by which each organ is able to communicate and engage in cross-talk are cytokines or peptides which stem from secretory organs. Recently, it was reported that several cytokines or peptides are secreted from muscle (myokines), adipose tissue (adipokines) and liver (hepatokines) in response to certain nutrition and/or physical activity conditions. Cytokines exert autocrine, paracrine or endocrine effects for the maintenance of energy homeostasis. The present review is focused on the relationship and cross-talk amongst muscle, adipose tissue and the liver as secretory organs in metabolic diseases.</P>

Gut Microbiota Community and Its Assembly Associated with Age and Diet in Chinese Centenarians

( Fang Wang ),( Ting Yu ),( Guo Hong Huang ),( Da Cai ),( Xiaolin Liang ),( Hai Yan Su ),( Zhenjun Zhu ),( Danlei Li ),( Yang Yang ),( Pei Hong Shen ),( Rui Feng Mao ),( Lian Yu ),( Mou Ming Zhao ),( 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.8

Increasing evidence suggests that gut microbiota underpin the development of health and longevity. However, our understanding of what influences the composition of this community of the longevous has not been adequately described. Therefore, illumina sequencing analysis was performed on the gut microbiota of centenarians (aged 100-108 years; RC) and younger elderlies (aged 85-99 years; RE) living in Bama County, Guangxi, China and the elderlies (aged 80-92 years; CE) living in Nanning City, Guangxi, China. In addition, their diet was monitored using a semiquantitative dietary questionary (FFQ 23). The results revealed the abundance of Roseburia and Escherichia was significantly greater, whereas that of Lactobacillus, Faecalibacterium, Parabacteroides, Butyricimonas, Coprococcus, Megamonas, Mitsuokella, Sutterella, and Akkermansia was significantly less in centenarians at the genus level. Both clustering analysis and UniFraq distance analysis showed structural segregation with age and diet among the three populations. Using partial least square discriminate analysis and redundancy analysis, we identified 33 and 34 operational taxonomic units (OTUs) as key OTUs that were significantly associated with age and diet, respectively. Age-related OTUs were characterized as Ruminococcaceae, Clostridiaceae, and Lachnospiraceae, and the former two were increased in the centenarians; diet-related OTUs were classified as Bacteroidales, Lachnospiraceae, and Ruminococcaceae. The former two were deceased, whereas the later one was increased, in the high-fiber diet. The age and high-fiber diet were concomitant with changes in the gut microbiota of centenarians, suggesting that age and high-fiber diet can establish a new structurally balanced architecture of gut microbiota that may benefit the health of centenarians.

Expression and characterization of RNA-dependent RNA polymerase of Ectropis obliqua virus

( Mei Juan Lin ),( Shan Ye ),( Yi Xiong ),( Da Wei Cai ),( Jia Min Zhang ),( Yuan Yang Hu ) 한국생화학분자생물학회 (구 한국생화학회) 2010 BMB Reports Vol.43 No.4

Replication of positive-strand RNA virus is mediated by a virus- encoded RNA-dependent RNA polymerase (RdRp). To study the replication of Ectropis obliqua virus (EoV), a newly identified insect virus belonging to the family Iflaviradae, we expressed the RNA polymerase domain in Escherichia coli and purified it on a Ni-chelating HisTrap affinity column. It is demonstrated that EoV RdRp initiated RNA synthesis in a primer- and poly (A)-dependent manner in vitro. Furthermore, the effect of primer concentration, temperature, metal ions (Mg2+, Mn2+, and K+) on enzymatic activity were determined. Our study represented a first step towards understanding the mechanism of EoV replication. [BMB reports 2010; 43(4): 284-290]