Structural system identification by measurement error-minimization observability method using multiple static loading cases

Feng-Liang Zhang,Jun Lei,Jose Antonio Lozano-Galant,Dong Xu,Jose Turmo 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.30 No.4

Evaluating the current condition of existing structures is of primary importance for economic and safety reasons. This can be addressed by Structural System Identification (SSI). A reliable static SSI depends on well-designed sensor configuration and loading cases, as well as efficient parameter estimation algorithms. Static SSI by the Measurement Error-Minimizing Observability Method (MEMOM) is a model-based deterministic static SSI method that could estimate structural parameters from static responses. In the current state of the art, this method is only applicable when structures are subjected to one loading case. This might lead to lack of information in some local regions of the structure (such as the null curvatures zones). To address this issue, the SSI by MEMOM using multiple loading cases is proposed in this work. Observability equations obtained from different loading cases are concatenated simultaneously and an optimization procedure is introduced to obtain the estimations by minimizing the discrepancy between the predicted response and the measured one. In addition, a Genetic-Algorithm (GA)-based Optimal Sensor Placement (OSP) method is proposed to tackle the OSP problem under multiple static loading cases for the very first time. In this approach, the Fisher Information Matrix (FIM)'s determinant is used as the metric of the goodness of sensor configurations. The numerical examples of a 3-span continuous bridge and a 13-story frame, are analyzed to validate the applicability of the extended SSI by MEMOM and the GA-based OSP method.

Investigation of the relationship between arc-anode attachment mode and anode temperature for nickel nanoparticle production by a DC arc discharge

Liang, Feng,Tanaka, Manabu,Choi, Sooseok,Watanabe, Takayuki Institute of Physics Publishing Ltd. 2016 Journal of Physics. D, Applied Physics Vol.49 No.12

<P>Multiple and constricted arc-anode attachment modes were observed in helium arc discharge to prepare nickel nanoparticles. The electron overheating instability resulted in the formation of multiple attachment modes. The effects of hydrogen concentration and shield gas flow rate on the characteristics of nickel nanoparticles were investigated. The evaporation rate of anode material contributed to forming different arc-anode attachments. The surface temperature of the electrode was measured during the arc discharge by two-color pyrometry combined with a high-speed camera which employs appropriate band-pass filters. The relationship between the arc-anode attachment mode and the temperature behavior of the anode surface was investigated by using two synchronized high-speed cameras. The waveform of anode jet area variation with time follows that of the highest temperature variation of anode surface with time. The fluctuation of the highest anode temperature increased when the arc anode attachment changed from multiple into constricted mode. The highest temperature fluctuation and stability of the arc contributed to nanoparticle size distribution. Nickel nanoparticles with large productivity and narrow size distribution were obtained when shield gas was employed by controlling the residence time of nanoparticle growth. The formation mechanism of different arc-anode attachment modes was explained.</P>

Mechanical behavior of recycled fine aggregate concrete after high temperature

Liang, Jiong-Feng,Wang, En,He, Chun-Feng,Hu, Peng Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.3

This paper reports mechanical behavior of recycled fine aggregate concretes after high temperatures. It is found that compressive strength of recycled fine aggregate concretes decline significantly as the temperature rises. The elastic modulus of recycled fine aggregate concretes decreases with the increase in temperature, and the decrease is much quicker than the decrease in compressive strength. The split tensile strength of recycled fine aggregate concrete decrease as the temperature rises. Through the regression analysis, the relationship of the mechanical behavior with temperature are proposed, including the compressive behavior, elastic modulus and split tensile strength, which are fitting the test data.

Joining Technology of Automotive Body using the Nano-Adhesives

Liang Feng(풍량),Dong-Ho Bae(배동호) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

In this paper, a new nano-adhesive which has been improved the conventional epoxy resin widely using in automobile industries was introduced. This nano-adhesive is organically composited with multi-walled carbon nano-tubes (MWCNT) (from 1%-4% by weight) as reinforcement. In order to optimize its quality and performance, electric and mechanical characteristics of the joints taking account the geometrical parameters of bonded layer into were assessed. The electric resistance of the nano-adhesive decreased with increase of the nano-tube weight percentage, and decrease of the thickness of the bonded layer. And in order to evaluate the overloading behaviors of the nano-adhesives and compare the results with the original epoxy resin, tensile tests were conducted on different bonded layer thickness and overlapped length of the bonded joints. From the results, the ultimate tensile strength remarkably increased at 2% weight percentage. Also surface treatment condition of the plates affected the ultimate tensile strength of the bonded joint.

Pharmacokinetics, Tissue Distribution and Excretion of Coumarin Components from Psoralea corylifolia L. in Rats

Liang Feng,Ling Wang,Xuehua Jiang 대한약학회 2010 Archives of Pharmacal Research Vol.33 No.2

Coumarin components from Psoralea corylifolia L. are novel drugs in which psoralen and isopsoralen are the active components. The pharmacokinetics, tissue distribution and excretion of the two compounds were studied by liquid chromatography-tandem mass spectrometry after intravenous administration to Wistar rats. The elimination half-lives of psoralen and isopsoralen were 4.88 and 5.35 h. After dosing, the area under the curves of the tissues decreased in the following order: liver > lung > heart > kidney > spleen > brain for psoralen; and kidney > lung > liver > heart > spleen > brain for isopsoralen. After dosing, 51.27% of psoralen and 56.25% of isopsoralen were excreted as prototype, and urine was the major excretion route. In addition, the pharmacokinetics of psoralen and isopsoralen after oral administration to Wistar rats were also studied. The elimination half-lives of psoralen and isopsoralen were 4.13 and 5.56 h, and their relative bioavailabilities were 61.45% and 70.35%. Overall, the results show that coumarin components from P. corylifolia L. have high oral bioavailability, they are rapidly and widely distributed into tissues after intravenous administration, but they are slowly cleared and excreted.

Development of Nano-adhesives and Joining Technology

Liang Feng,Dong-Ho Bae 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11

In this paper, a new nano-adhesive which has been improved the conventional epoxy resin widely using in automobile industries was introduced. Multi-walled carbon nano-tubes (MWCNT) (from 1%-4% by weight) were mixed in epoxy resin through a high speed mechanical agitator. The trapped air and reaction volatiles were removed from the mixture using a high vacuum. In order to optimize its quality and performance, electric and mechanical characteristics of the joints taking account the geometrical parameters of bonded layer into were assessed. The electric resistance of the nano-adhesive decreased with increase of the nano-tube weight percentage, and decrease of the thickness of the bonded layer. And in order to evaluate the overloading behaviors of the nano-adhesives and compare the results with the original epoxy resin, tensile tests were conducted on different bonded layer thickness and overlapped length of the bonded joints. From the results, the ultimate tensile strength remarkably increased at 2% weight percentage. Also surface treatment condition of the plates also affected the ultimate tensile strength of the bonded joint.

Operational modal analysis of Canton Tower by a fast frequency domain Bayesian method

Feng-Liang Zhang,Yan-Chun Ni,Yan-Chun Ni,You-Wu Wang 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.17 No.2

The Canton Tower is a high-rise slender structure with a height of 610 m. A structural health monitoring system has been instrumented on the structure, by which data is continuously monitored. This paper presents an investigation on the identified modal properties of the Canton Tower using ambient vibration data collected during a whole day (24 hours). A recently developed Fast Bayesian FFT method is utilized for operational modal analysis on the basis of the measured acceleration data. The approach views modal identification as an inference problem where probability is used as a measure for the relative plausibility of outcomes given a model of the structure and measured data. Focusing on the first several modes, the modal properties of this supertall slender structure are identified on non-overlapping time windows during the whole day under normal wind speed. With the identified modal parameters and the associated posterior uncertainty, the distribution of the modal parameters in the future is predicted and assessed. By defining the modal root-mean-square value in terms of the power spectral density of modal force identified, the identified natural frequencies and damping ratios versus the vibration amplitude are investigated with the associated posterior uncertainty considered. Meanwhile, the correlations between modal parameters and temperature, modal parameters and wind speed are studied. For comparison purpose, the frequency domain decomposition (FDD) method is also utilized to identify the modal parameters. The identified results obtained by the Bayesian method, the FDD method and a finite element model are compared and discussed.

Mode identifiability of a cable-stayed bridge based on a Bayesian method

Feng-Liang Zhang,Yi-Qing Ni,Yan-Chun Ni 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.17 No.3

Modal identification based on ambient vibration data has attracted extensive attention in the past few decades. Since the excitation for ambient vibration tests is mainly from the environmental effects such as wind and traffic loading and no artificial excitation is applied, the signal to noise (s/n) ratio of the data acquired plays an important role in mode identifiability. Under ambient vibration conditions, certain modes may not be identifiable due to a low s/n ratio. This paper presents a study on the mode identifiability of an instrumented cable-stayed bridge with the use of acceleration response data measured by a long-term structural health monitoring system. A recently developed fast Bayesian FFT method is utilized to perform output-only modal identification. In addition to identifying the most probable values (MPVs) of modal parameters, the associated posterior uncertainties can be obtained by this method. Likewise, the power spectral density of modal force can be identified, and thus it is possible to obtain the modal s/n ratio. This provides an efficient way to investigate the mode identifiability. Three groups of data are utilized in this study: the first one is 10 data sets including six collected under normal wind conditions and four collected during typhoons; the second one is three data sets with wind speeds of about 7.5 m/s; and the third one is some blind data. The first two groups of data are used to perform ambient modal identification and help to estimate a critical value of the s/n ratio above which the deficient mode is identifiable, while the third group of data is used to perform verification. A couple of fundamental modes are identified, including the ones in the vertical and transverse directions respectively and coupled in both directions. The uncertainty and s/n ratio of the deficient mode are investigated and discussed. A critical value of the modal s/n ratio is suggested to evaluate the mode identifiability of the deficient mode. The work presented in this paper could provide a base for the vibration-based condition assessment in future.

Selective Radiotherapy after Distant Metastasis of Nasopharyngeal Carcinoma Treated with Dose-Dense Cisplatin plus Fluorouracil

Liang, Yong,Bu, Jun-Guo,Cheng, Jin-ling,Gao, Wei-Wei,Xu, Yao-Can,Feng, Jian,Chen, Bo-Yu,Liang, Wei-Chao,Chen, Ke-Quan Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.14

Purpose: To investigate the efficacy and safety of selective radiotherapy after distant metastasis of nasopharyngeal carcinoma (NPC) treated with dose-dense cisplatin plus fluorouracil. Materials and Methods: Eligible patients were randomly assigned to a study group treated with dose-dense cisplatin plus fluorouracil following selective radiotherapy and a control group receiving traditional cisplatin plus fluorouracil following selective radiotherapy according to a 1:1 distribution using a digital random table method. The primary endpoint was overall survival (OS). Secondary endpoints were progression-free survival (PFS), objective response rate, relapse or progression rate in the radiation field and treatment toxicity. Results: Of 52 patients in the study group, 20 cases underwent radiotherapy., while in the control group of 51 patients, 16 underwent radiotherapy. The median PFS, median OS, survival rates in 1, 2 and 3 years in study and control group were 20.9 vs 12.7months, 28.3 vs 18.8months, 85.2%vs 65.9%, 62.2% vs 18.3%, and 36.6%vs 5.2% (p values of 0.00, 0.00, 0.04, 0.00 and 0.00, respectively). Subgroup analysis showed that the median OS and survival rates of 1, 2, 3 years for patients undergoing radiotherapy in the study group better than that in control group( 43.2vs24.1 months, 94.1% vs 86.7%, 82.4% vs 43.3%, 64.7% vs 17.3%, (p=0.00, 0.57, 0.04 and 0.01, respectively). The complete response rate, objective response rate after chemotherapy and three months after radiotherapy, relapse or progression rate in radiation field in study group and in control group were 19.2% vs 3.9%, 86.5% vs 56.9%, 85% vs 50%, 95% vs 81.3% and 41.3% vs 66.7% (p =0.03, 0.00, 0.03,0.30, 0.01 respectively). The grade 3-4 acute adverse reactions in the study group were significantly higher than in the control group (53.8% vs 9.8%, p=0.00). Conclusions: The survival of patients benefits from selective radiotherapy after distant metastasis of NPC treated with dose-dense cisplatin plus fluorouracil.

Pharmacokinetics, Tissue Distribution, Metabolism, and Excretion of Ginsenoside Rg1 in Rats

Liang Feng,Ling Wang,Changjiang Hu,Xuehua Jiang 대한약학회 2010 Archives of Pharmacal Research Vol.33 No.12

The pharmacokinetics, tissue distribution, metabolism, and excretion of ginsenosides Rg1 were studied in Wistar rats, by measuring the concentrations of Rg1 and its metabolites in the blood, tissues, bile, urine, and feces after dosing. After intravenous (i.v.) administration, the elimination half-lives of Rg1 and its metabolites were 1.82, 5.87, and 6.87 h, and the area under the curves were 1595.7, 597.5, and 805.6 ng· h/mL, respectively. After oral administration, the elimination half-lives of Rg1 and its metabolites were 2.25, 6.73, 5.44, and 5.06 h, and the area under the curves were 2363.5, 4185.5, 3774.3, and 396.2 ng· h/mL, respectively. After i.v. administration, Rg1 and its metabolites were well distributed to the tissues analyzed except for the brain. The maximum concentration of Rg1 was reached in all tissues at 5 min post dose, and it was eliminated from most of the tissues except for the kidney faster than it was eliminated from the blood. The maximum concentration of the metabolites was reached in all tissues between 4 and 6 h post dose. After i.v. administration, the recovery of the Rg1 prototype in the urine and bile was 27.96% and 60.77%, respectively. The metabolism of Rg1 in the intestine was via a hydrolization pathway, with the 6-and 20-glucoside bond hydrolyzed gradually under the catalysis of β-glucosaccharase, and then the metabolites were reabsorbed into the blood. Finally, the total recovery of the Rg1 prototype and its metabolites in the urine and feces were 51.31% and 47.46%, respectively.