Exploring the Metabolomic Responses of Bacillus licheniformis to Temperature Stress by Gas Chromatography/Mass Spectrometry

( Zixing Dong ),( Xiaoling Chen ),( Ke Cai ),( Zhixin Chen ),( Hongbin Wang ),( Peng Jin ),( Xiaoguang Liu ),( Kugenthiren Permaul ),( Suren Singh ),( Zhengxiang Wang ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.3

Owing to its high protein secretion capacity, simple nutritional requirements, and GRAS (generally regarded as safe) status, Bacillus licheniformis is widely used as a host for the industrial production of enzymes, antibiotics, and peptides. However, as compared with its close relative Bacillus subtilis, little is known about the physiology and stress responses of B. licheniformis. To explore its temperature-stress metabolome, B. licheniformis strains ATCC 14580 and B186, with respective optimal growth temperatures of 42℃ and 50℃, were cultured at 42℃, 50℃, and 60℃ and their corresponding metabolic profiles were determined by gas chromatography/mass spectrometry and multivariate statistical analyses. It was found that with increased growth temperatures, the two B. licheniformis strains displayed elevated cellular levels of proline, glutamate, lysine, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid, and decreased levels of glutamine and octadecenoic acid. Regulation of amino acid and fatty acid metabolism is likely to be associated with the evolution of protective biochemical mechanisms of B. licheniformis. Our results will help to optimize the industrial use of B. licheniformis and other important Bacillus species.

Driving safety analysis of various types of vehicles on long-span bridges in crosswinds considering aerodynamic interference

Yan Han,Jingwen Huang,C.S. Cai,Suren Chen,Xuhui He 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.4

Strong winds threaten the safety of vehicles on long-span bridges considerably, which could force traffic authorities to reduce speed limits or even close these bridges to traffic. In order to maintain the safe and economic operation of a bridge, a reasonable evaluation of the driving safety on that bridge is needed. This paper aims at carrying outdriving safety analyses for three types of vehicles on a long-span bridge in crosswinds by considering the aerodynamic interference between the bridge and the vehicles based on the wind-vehicle-bridge coupling vibration analysis. Firstly, CFD numerical simulations along with previously obtained wind tunnel testing results were used to determine the aerodynamic force coefficients of the three types of vehicles on the bridge. Secondly, the dynamic responses of the bridge and the vehicles under crosswinds were simulated, and based on those, the driving safety analyses for the three types of vehicles on the bridge were carried out for both cases considering and not considering the aerodynamic interference between the vehicles and the bridge. Finally, the effect of the aerodynamic interference on the safety of the vehicles was investigated. The results show that the aerodynamic interference between the bridge and the vehicles not only affects the accident critical wind speed but also the accident type for all three types of vehicles. Such effects are also different for each of the three types of vehicles being studied.

A coupled wind-vehicle-bridge system and its applications: a review

C.S. Cai,Jiexuan Hu,Suren Chen,Yan Han,Wei Zhang,Xuan Kong 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.2

The performance of bridges under strong wind and traffic is of great importance to set thetraveling speed limit or to make operational decisions for severe weather, such as controlling traffic or evenclosing the bridge. Meanwhile, the vehicle‟s safety is highly concerned when it is running on bridges orhighways under strong wind. During the past two decades, researchers have made significant contributionsto the simulation of the wind-vehicle-bridge system and their interactive effects. This paper aims to providea comprehensive review of the overall performance of the bridge and traffic system under strong wind,including bridge structures and vehicles, and the associated mitigation efforts.

Nonlinear dynamic performance of long-span cable-stayed bridge under traffic and wind

Han, Wanshui,Ma, Lin,Cai, C.S.,Chen, Suren,Wu, Jun Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.20 No.2

Long-span cable-stayed bridges exhibit some features which are more critical than typical long span bridges such as geometric and aerodynamic nonlinearities, higher probability of the presence of multiple vehicles on the bridge, and more significant influence of wind loads acting on the ultra high pylon and super long cables. A three-dimensional nonlinear fully-coupled analytical model is developed in this study to improve the dynamic performance prediction of long cable-stayed bridges under combined traffic and wind loads. The modified spectral representation method is introduced to simulate the fluctuating wind field of all the components of the whole bridge simultaneously with high accuracy and efficiency. Then, the aerostatic and aerodynamic wind forces acting on the whole bridge including the bridge deck, pylon, cables and even piers are all derived. The cellular automation method is applied to simulate the stochastic traffic flow which can reflect the real traffic properties on the long span bridge such as lane changing, acceleration, or deceleration. The dynamic interaction between vehicles and the bridge depends on both the geometrical and mechanical relationships between the wheels of vehicles and the contact points on the bridge deck. Nonlinear properties such as geometric nonlinearity and aerodynamic nonlinearity are fully considered. The equations of motion of the coupled wind-traffic-bridge system are derived and solved with a nonlinear separate iteration method which can considerably improve the calculation efficiency. A long cable-stayed bridge, Sutong Bridge across the Yangze River in China, is selected as a numerical example to demonstrate the dynamic interaction of the coupled system. The influences of the whole bridge wind field as well as the geometric and aerodynamic nonlinearities on the responses of the wind-traffic-bridge system are discussed.

A coupled wind-vehicle-bridge system and its applications: a review

Cai, C.S.,Hu, Jiexuan,Chen, Suren,Han, Yan,Zhang, Wei,Kong, Xuan Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.20 No.2

The performance of bridges under strong wind and traffic is of great importance to set the traveling speed limit or to make operational decisions for severe weather, such as controlling traffic or even closing the bridge. Meanwhile, the vehicle's safety is highly concerned when it is running on bridges or highways under strong wind. During the past two decades, researchers have made significant contributions to the simulation of the wind-vehicle-bridge system and their interactive effects. This paper aims to provide a comprehensive review of the overall performance of the bridge and traffic system under strong wind, including bridge structures and vehicles, and the associated mitigation efforts.

Nonlinear dynamic performance of long-span cable-stayed bridge under traffic and wind

Wanshui Han,Lin Ma,C.S. Cai,Suren Chen,Jun Wu 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.2

Long-span cable-stayed bridges exhibit some features which are more critical than typical longspan bridges such as geometric and aerodynamic nonlinearities, higher probability of the presence ofmultiple vehicles on the bridge, and more significant influence of wind loads acting on the ultra high pylonand super long cables. A three-dimensional nonlinear fully-coupled analytical model is developed in thisstudy to improve the dynamic performance prediction of long cable-stayed bridges under combined trafficand wind loads. The modified spectral representation method is introduced to simulate the fluctuating windfield of all the components of the whole bridge simultaneously with high accuracy and efficiency. Then, theaerostatic and aerodynamic wind forces acting on the whole bridge including the bridge deck, pylon, cablesand even piers are all derived. The cellular automation method is applied to simulate the stochastic trafficflow which can reflect the real traffic properties on the long span bridge such as lane changing, acceleration,or deceleration. The dynamic interaction between vehicles and the bridge depends on both the geometricaland mechanical relationships between the wheels of vehicles and the contact points on the bridge deck. Nonlinear properties such as geometric nonlinearity and aerodynamic nonlinearity are fully considered. Theequations of motion of the coupled wind-traffic-bridge system are derived and solved with a nonlinearseparate iteration method which can considerably improve the calculation efficiency. A long cable-stayedbridge, Sutong Bridge across the Yangze River in China, is selected as a numerical example to demonstratethe dynamic interaction of the coupled system. The influences of the whole bridge wind field as well as thegeometric and aerodynamic nonlinearities on the responses of the wind-traffic-bridge system are discussed.

Experimental study on wake-induced vibrations of two circular cylinders with two degrees of freedom

Xiaoqing Du,Benjian Jiang,Chin Dai,Guoyan Wang,Suren Chen 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.26 No.2

Wind tunnel tests are conducted to investigate wake-induced vibrations of two circular cylinders with a center-to-center spacing of 4 diameters and attack angle varying from 0 to 20 for Reynolds numbers between 18,000 and 168,800. Effects of structural damping, Reynolds number, attack angle and reduced velocity on dynamic responses are examined. Results show that wake-induced vortex vibrations of the downstream cylinder occur in a wider range of the reduced velocity and have higher amplitudes in comparison to the vortex-induced vibration of a single circular cylinder. Two types of wake-induced instability phenomena with distinct dynamic characteristics are observed, which may be due to different generation mechanisms. For small attack angles like 5 and 10, the instability of the downstream cylinder characterizes a one-degree-of-freedom (1-DOF) oscillation moving in the across-wind direction. For a large attack angle like 20, the instability characterizes a two-degree-of-freedom (2-DOF) oscillation with elliptical trajectories. For an attack angle of 15, the instability can transform from the 1-DOF pattern to the 2-DOF one with the increase of the Reynolds number. Furthermore, the two instabilities show different sensitivity to the structural damping. The 1-DOF instability can be either completely suppressed or reduced to an unsteady oscillation, while the 2-DOF one is relatively less sensitive to the damping level. Reynolds number has important effects on the wake-induced instabilities.

Experimental study on wake-induced vibrations of two circular cylinders with two degrees of freedom

Du, Xiaoqing,Jiang, Benjian,Dai, Chin,Wang, Guoyan,Chen, Suren Techno-Press 2018 Wind and Structures, An International Journal (WAS Vol.26 No.2

Wind tunnel tests are conducted to investigate wake-induced vibrations of two circular cylinders with a center-to-center spacing of 4 diameters and attack angle varying from $0^{\circ}$ to $20^{\circ}$ for Reynolds numbers between 18,000 and 168,800. Effects of structural damping, Reynolds number, attack angle and reduced velocity on dynamic responses are examined. Results show that wake-induced vortex vibrations of the downstream cylinder occur in a wider range of the reduced velocity and have higher amplitudes in comparison to the vortex-induced vibration of a single circular cylinder. Two types of wake-induced instability phenomena with distinct dynamic characteristics are observed, which may be due to different generation mechanisms. For small attack angles like $5^{\circ}$ and $10^{\circ}$, the instability of the downstream cylinder characterizes a one-degree-of-freedom (1-DOF) oscillation moving in the across-wind direction. For a large attack angle like $20^{\circ}$, the instability characterizes a two-degree-of-freedom (2-DOF) oscillation with elliptical trajectories. For an attack angle of $15^{\circ}$, the instability can transform from the 1-DOF pattern to the 2-DOF one with the increase of the Reynolds number. Furthermore, the two instabilities show different sensitivity to the structural damping. The 1-DOF instability can be either completely suppressed or reduced to an unsteady oscillation, while the 2-DOF one is relatively less sensitive to the damping level. Reynolds number has important effects on the wake-induced instabilities.

The influence of vehicles on the flutter stability of a long-span suspension bridge

Yan Han,Shuqian Liu,C.S. Cai,Jianren Zhang,Suren Chen,Xuhui He 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.2

The presence of traffic on a slender long-span bridge deck will modify the cross-section profileof the bridge, which may influence the flutter derivatives and in turn, the critical flutter wind velocity of thebridge. Studies on the influence of vehicles on the flutter derivatives and the critical flutter wind velocity ofbridges are rather rare as compared to the investigations on the coupled buffeting vibration of thewind-vehicle-bridge system. A typical streamlined cross-section for long-span bridges is adopted for bothexperimental and analytical studies. The scaled bridge section model with vehicle models distributed on thebridge deck considering different traffic flow scenarios has been tested in the wind tunnel. The flutterderivatives of the modified bridge cross section have been identified using forced vibration method and theresults suggest that the influence of vehicles on the flutter derivatives of the typical streamlined cross-sectioncannot be ignored. Based on the identified flutter derivatives, the influence of vehicles on the flutter stabilityof the bridge is investigated. The results show that the effect of vehicles on the flutter wind velocity isobvious.

The influence of vehicles on the flutter stability of a long-span suspension bridge

Han, Yan,Liu, Shuqian,Cai, C.S.,Zhang, Jianren,Chen, Suren,He, Xuhui Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.20 No.2

The presence of traffic on a slender long-span bridge deck will modify the cross-section profile of the bridge, which may influence the flutter derivatives and in turn, the critical flutter wind velocity of the bridge. Studies on the influence of vehicles on the flutter derivatives and the critical flutter wind velocity of bridges are rather rare as compared to the investigations on the coupled buffeting vibration of the wind-vehicle-bridge system. A typical streamlined cross-section for long-span bridges is adopted for both experimental and analytical studies. The scaled bridge section model with vehicle models distributed on the bridge deck considering different traffic flow scenarios has been tested in the wind tunnel. The flutter derivatives of the modified bridge cross section have been identified using forced vibration method and the results suggest that the influence of vehicles on the flutter derivatives of the typical streamlined cross-section cannot be ignored. Based on the identified flutter derivatives, the influence of vehicles on the flutter stability of the bridge is investigated. The results show that the effect of vehicles on the flutter wind velocity is obvious.