Stochastic space vibration analysis of a train-bridge coupling system

Li, Xiaozhen,Zhu, Yan Techno-Press 2010 Interaction and multiscale mechanics Vol.3 No.4

The Pseudo-Excitation Method (PEM) is applied to study the stochastic space vibration responses of train-bridge coupling system. Each vehicle is modeled as a four-wheel mass-spring-damper system with two layers of suspension system possessing 15 degrees-of- freedom. The bridge is modeled as a spatial beam element, and the track irregularity is assumed to be a uniform random process. The motion equations of the vehicle system are established based on the d'Alembertian principle, and the motion equations of the bridge system are established based on the Hamilton variational principle. Separate iteration is applied in the solution of equations. Comparisons with the Monte Carlo simulations show the effectiveness and satisfactory accuracy of the proposed method. The PSD of the 3-span simply-supported girder bridge responses, vehicle responses and wheel/rail forces are obtained. Based on the $3{\sigma}$ rule for Gaussian stochastic processes, the maximum responses of the coupling system are suggested.

Temporal dynamics of Bactrocera (Zeugodacus) tau (Diptera: Tephritidae) adults in north Jiangxi, a subtropical area of China revealed by eight years of trapping with cuelure

Xiaozhen Li,Haiyan Yang,Kaiping Hu,Jianguo Wang 한국응용곤충학회 2020 Journal of Asia-Pacific Entomology Vol.23 No.1

Bactrocera (Zeugodacus) tau (Walker) (Diptera: Tephritidae), a quarantine pest of international concern, has become widespread and economically important in South and Southeast Asia. It has been introduced into north Jiangxi from Fujian, China and become a threat to local fruits and vegetables. Field trapping with cuelure (CUE) as lure is needed, not only for monitoring population dynamics of B. tau but also for direct control of population. In this study, we collected weekly tephritids from 4 CUE-baited McPhail traps every year from 2008 to 2015, analysing seasonal and inter-year B. tau population fluctuations. The total number of captured tephritids reached 7811, including B. tau (5321), B. scutellata (Hendel) (2375) and B. cucurbitae (Coquillett) (1 1 5). Among them, B. tau was the dominant species. It had 3–4 generations a year in north Jiangxi with high generation overlapping. The average number of trapped B. tau males did not differ significantly in different years, while the average monthly number showed large variation from June to December. No B. tau males were trapped before June in any year. Adult males were present from mid-June to late December, with distinct peaks between late August and mid-October. This fruit fly can withstand below 13℃ as a monthly minimal temperature under field conditions, and adult capture rates were significantly related to monthly minimal temperature and monthly total precipitation. These results can be used to predict the occurrence time and population size of B. tau in different seasons, enabling growers and extension personnel to take efficient management measures before they damage the host crops.

Aerodynamic Interference and Dynamic Influence of Wind Barrier on Train-bridge Coupling Vibration System

Xiaozhen Li,Yanxi Zhou,Ming Wang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.7

Wind barrier is an important wind-resistant measure for the running performance of trains on long-span bridges. This study aims to clarify how the aerodynamic interference of wind barrier to the train-bridge system affects the dynamic response of the system. The aerodynamic interference and dynamic influence of wind barriers on the train-bridge system are studied by wind tunnel test and coupling vibration analysis. Wind barriers with different ventilation rates are selected to study their wind-resistant performance on trains travelling in four lanes on the bridge. The results show that installing wind barriers can increase the side and lift coefficients of bridge and decrease the side and lift coefficients of train. The maximum difference is that installing a wind barrier with ventilation of 0 can increase the side coefficient of the bridge by 0.6, while reducing the side coefficient of train in Lane 1 from 1.25 to -0.25. Although the wind barrier has changed the aerodynamic coefficient of the bridge, the maximum dynamic response of train-bridge system depends more on its influence on the aerodynamic coefficient of train. Installing a wind barrier with 0% ventilation rate can reduce the maximum lateral displacement at mid span of bridge by 10 mm, the maximum reduction rate of the wheel from 0.38 to 0.1, and the lateral car body acceleration from 1.1 m/s2 to 0.45 m/s2. The vertical dynamic response of train-bridge system is insensitive to wind barrier. The key effect of optimizing train side coefficient on wind-resistant performance of wind barrier is pointed out.

Physicochemical properties and energy content of yellow dent corn from different climatic origins in growing pigs

Wenxuan Dong,Juntao Li,Zhongchao Li,Shuo Zhang,Xiaozhen Li,Chundi Yang,Ling Liu,Shuai Zhang 아세아·태평양축산학회 2020 Animal Bioscience Vol.33 No.11

Objective: The objective of this study was to determine the digestible energy (DE) and metabolizable energy (ME) of yellow dent corn sourced from different meteorological origins fed to growing pigs and develop equations to predict the DE and ME of yellow dent corn from southwestern China. Methods: Sixty crossbred barrows were allotted to 20 treatments in a triplicate 20×2 incomplete Latin square design with 3 replicated pigs per dietary treatment during 2 consecutive periods. Each period lasted for 12 days, and total feces and urine during the last 5 days of each period were collected to calculate the energy contents. Results: On dry matter (DM) basis, the DE and ME in 20 corn grain samples ranged from 15.38 to 16.78 MJ/kg and from 14.93 to 16.16 MJ/kg, respectively. Selected best-fit prediction equations for DE and ME (MJ/kg DM basis) for yellow dent corn (n = 16) sourced from southwestern China were as follows: DE = 28.58–(0.12×% hemicellulose)+(0.35×% ether extract)–(0.83×MJ/kg gross energy)+(0.20×% crude protein)+(0.49×% ash); ME = 30.42–(0.11×% hemicellulose)+(0.31×% ether extract)–(0.81×MJ/kg gross energy). Conclusion: Our results indicated that the chemical compositions, but not the meteorological conditions or physical characteristics could explain the variation of energy contents in yellow dent corn sourced from southwestern China fed to growing pigs.

Development and application of EST-SSR to evaluate the genetic diversity of Southeast Asian rice planthoppers

Yongfu Qiu,Xiaozhen Jiao,Dehui Hu,Fang Liu,Fengkuan Huang,Rongbai Li 한국응용곤충학회 2016 Journal of Asia-Pacific Entomology Vol.19 No.3

A total of 320 ESTs (Expressed Sequence Tags, 12.8%) of rice planthoppers were identified to carry SSR (Simple Sequence Repeat) motifs from2491 ESTs downloaded frompublic database, and 397 pairs of brown planthopper (BPH; Nilaparvata lugens Stål) and 25 pairs ofwhite-backed planthopper (WBPH; Sogatella furcifera) (Hemiptera: Delphacidae) EST-SSR were detected based on the motifs. The dinucleotide repeat was the dominant type with repeat motif AG/GA/TC/CT; and the trinucleotide repeat was the style of AAG/AGA/GAA/TTC/TCT/CTT among the BPH repeat motifs. A total of 20 EST-SSRs (16 developed in the present study and four fromprevious studies) were applied to survey the genetic diversity of the 15 rice planthoppers. Consequently, 18 pairs of primer amplifies clear, dominant and polymorphic gel bands among the collected planthoppers population; one ESTSSR amplified a single gel band; and one had no result. Furthermore, a total of 227 bands were produced by the selected 19 pairs of primers, of which 207 bands (91.2%) were polymorphic among the test insect populations. Genetic diversity analysis suggested that the BPH populations from Cuu Long, Thailand and Ho Chi Minh were clustered, respectively; and Hue and Long Xuyen were composed into one class; the others were clustered together when the similar coefficient was 0.76. The results show that it is an effective and available approach to develop SSR markers based on ESTs in rice planthoppers; and also the developed EST-SSR markers could detect the genetic diversity of the planthoppers population, which would be beneficial for rice planthoppers control strategy. ©

Acoustic Radiation and Dynamic Study of a Steel Beam Damped with Viscoelastic Material

Quanmin Liu,Xiaozhen Li,Peipei Xu,Linya Liu,Yun-Lai Zhou 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.7

Steel structures subject to dynamic loads are prior to generate excessive vibration and noise. Viscoelastic treatment is an effective measure to mitigate the vibration and noise from thin-walled structures in a broad frequency range. H-shaped steel beams are widely used in civil engineering. So an experiment system is established and a series of impact hammer tests are conducted to assess the modal parameters, dynamic response and acoustic behaviour of an H-shaped steel beam coated with various viscoelastic treatments. Firstly, the spectra of the velocity response and acoustic radiation of the bare beam are analysed based on the tested data. Secondly, the resonance frequencies and modal loss factors of the beam with various viscoelastic treatments derived from the frequency response function are compared. Finally, the effect of the layout and thickness of viscoelastic patches on the mitigation of vibration and noise is discussed experimentally. It is shown that the modal loss factor of the first mode increases from 0.012 to 0.191 when the web is treated with 5 mm thick constrained layer damping (CLD). The viscoelastic patches on the web of the H-shaped beam are more effective to control the vibration and noise of the beam than the patches on the flanges. The viscoelastic treatment has distinct effect on the reduction of structural vibration and noise owing to the different dominant frequencies of vibration and noise as well as the frequency-dependent radiation efficiency. The normal velocity level of the H-shaped beam with an 8 mmthick web can be reduced by more than 10 dB and the sound pressure level around the beam about 8 dB when the web is partially covered with the constrained layer damping composed of 2.0 mm thick damping layer and 3.0 mm thick constraining layer.

A Novel 3-D Imaging Configuration Exploiting Synthetic Aperture Ladar

Liang Guo,Yinli Huang,Xiaozhen Li,Xiaodong Zeng,Yu Tang,Mengdao Xing 한국광학회 2017 Current Optics and Photonics Vol.1 No.6

Traditional three-dimensional (3-D) laser imaging systems are based on real aperture imaging technology,whose resolution decreases as the range increases. In this paper, we develop a novel 3-D imaging techniquebased on the synthetic aperture technology in which the imaging resolution is significantly improved anddoes not degrade with the increase of the range. We consider an imaging laser radar (ladar) system usingthe floodlight transmitting mode and multi-beam receiving mode. High 3-D imaging resolutions areachieved by matched filtering the linear frequency modulated (LFM) signals respectively in range, syntheticaperture along-track, and the real aperture across-track. In this paper, a novel 3-D imaging signal modelis given first. Because of the motion during the transmission of a sweep, the Doppler shift induced bythe continuous motion is taken into account. And then, a proper algorithm for the 3-D imaging geometryis given. Finally, simulation results validate the effectiveness of the proposed technique.

Dynamic analysis of coupled wind-train-bridge system considering tower shielding and triangular wind barriers

Zhang, Nan,Ge, Guanghui,Xia, He,Li, Xiaozhen Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.21 No.3

A method for analyzing the coupled wind-vehicle-bridge system is proposed that also considers the shielding effect of the bridge tower with triangular wind barriers. The static wind load and the buffeting wind load for both the bridge and the vehicle are included. The shielding effects of the bridge tower and the triangular wind barriers are incorporated by taking the surface integral of the wind load. The inter-history iteration is adopted to solve the vehicle-bridge dynamic equations with time-varying external loads. The results show that after installing the triangular wind barriers in the area of the bridge tower, the bridge response and the vehicle safety factors change slightly. The peak value of the train car body acceleration is significantly reduced when the wind barrier size is increased.

Broad Activity against Porcine Bacterial Pathogens Displayed by Two Insect Antimicrobial Peptides Moricin and Cecropin B

Han Hu,Qigai He,Chunmei Wang,Xiaozhen Guo,Wentao Li,Yang Wang 한국분자세포생물학회 2013 Molecules and cells Vol.35 No.2

In response to infection, insects produce a variety of antimicrobial peptides (AMPs) to kill the invading patho-gens. To study their physicochemical properties and bioactivities for clinical and commercial use in the porcine industry, we chemically synthesized the mature peptides Bombyx mori moricin and Hyalophora cecropia cecropin B. In this paper, we described the antimicrobial activity of the two AMPs. Moricin exhibited antimicrobial activity on eight strains tested with minimal inhibitory concentration values (MICs) ranging between 8 and 128 g/ml, while cecropin B mainly showed antimicrobial activity against the Gram-negative strains with MICs ranging from 0.5 to 16 g/ml. Compared to the potent antimicrobial activity these two AMPs displayed against most of the bacterial pathogens tested, they exhibited limited hemolytic activity against porcine red blood cells. The activities of moricin and cecropin B against Haemophilus parasuis SH 0165 were studied in further detail. Transmission electron microscopy (TEM) of moricin and cecropin B treated H. parasuis SH 0165 indicated extensive damage to the membranes of the bacteria. Insights into the probable mechanism utilized by moricin and cecropin B to eliminate pathogens are also presented. The observations from this study are important for the future application of AMPs in the porcine industry.

Dynamic analysis of coupled wind-train-bridge system considering tower shielding and triangular wind barriers

Nan Zhang,Guanghui Ge,He Xia,Xiaozhen Li 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.3

A method for analyzing the coupled wind-vehicle-bridge system is proposed that also considers the shielding effect of the bridge tower with triangular wind barriers. The static wind load and the buffeting wind load for both the bridge and the vehicle are included. The shielding effects of the bridge tower and the triangular wind barriers are incorporated by taking the surface integral of the wind load. The inter-history iteration is adopted to solve the vehicle-bridge dynamic equations with time-varying external loads. The results show that after installing the triangular wind barriers in the area of the bridge tower, the bridge response and the vehicle safety factors change slightly. The peak value of the train car body acceleration is significantly reduced when the wind barrier size is increased.