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The ring-polymer molecular dynamics (RPMD) was used to calculate the thermal rate coefficients and kinetic isotope effects of the heavy-light-heavy abstract reaction Cl+XCl→XCl+Cl (X=H, D, Mu). For the Cl+HCl reaction, the excellent agreement between the RPMD and experimental values provides a strong proof for the accuracy of the RPMD theory. And the RPMD results are also consistent with results from other theoretical methods including improved-canonical-variational-theory and quantum dynamics. The most novel finding is that there is a double peak in Cl+MuCl reaction near the transition state, leaving a free energy well. It comes from the mode softening of the reaction system at the peak of the potential energy surface. Such an explicit free energy well suggests strongly there is an observable resonance. And for the Cl+DCl reaction, the RPMD rate coefficient again gives very accurate results compared with experimental values. The only exception is at the temperature of 312.5 K, results from RPMD and all other theoretical methods are close to each other but slightly lower than the experimental value, which indicates experimental or potential energy surface deficiency. [ABSTRACT FROM AUTHOR]

To ensure the safety of bridges, the comfort of pedestrians and vehicles on bridges, the vortex-induced forces on flat-steel-box girders need to be investigated. The total vortex-induced forces integrated on the surfaces of girders have been studied extensively. This study will be mainly focused on the characteristics of surface distributed vortex-induced force, which can be beneficial to the vortex-induced vibration (VIV) reduction with local aerodynamic optimization. Computational Fluid Dynamics (CFD) method is employed for the simulation of the VIVof a flat-steel-box girder. The simulation results are verified through the comparison with the results of corresponding wind tunnel test. A self-adaptive nonlinear fitting method is proposed to determine the vortex-induced force model. A vortex-induced force contribution factor is defined to account the contribution of the components and the surface location. Based on the surface distributed vortex-induced force analysis, several conclusions are made. The vortex-induced force presents a fairly strong multiple-frequency characteristic, and the high-order terms should be carefully considered. Most energy of the VIV comes from the linear and third-order aerodynamic damping terms. In terms of location, the roof takes most of the aerodynamic damping and the total vortex-induced force. The flow separation around the underside upstream corner, the underside downstream corner and the middle downstream comer lead to large third-order aerodynamic damping term. The flow separation around the underside upstream corner has great contribution to the linear aerodynamic stiffness term. [ABSTRACT FROM AUTHOR]

It is necessary to measure static aerodynamic force coefficients of vehicles and bridge deck in wind-vehicle-bridge coupling vibration analysis. The section of CRH2 train is novel and sensitive to the action of the wind, but the research on aerodynamic characteristics of CRH2 train with cross wind action is rarely introduced. The typical sections of large span railway bridge and small-medium span bridge section are selected to investigate the interaction between vehicles and bridges. The aerodynamic force coefficients of vehicles are tested using the crossed slot system in wind tunnel for the different combination of vehicle and bridge. Aerodynamic coefficients of CRH2 train without bridge deck are analyzed. Reynolds number, the combination condition of vehicle and bridge, the type of bridge deck section are investigated to demonstrate their effects on vehicle wind loads. The test results show that aerodynamic characteristics of CRH2 train with different type bridges are different significantly, the wind load on the vehicle at leeward side may change abruptly when two trains pass each other. The measured aerodynamic parameters of CRH2 train can be used for the coupling vibration analysis of wind-vehicle-bridge systems. [ABSTRACT FROM AUTHOR]

To study the appropriate boundary transition section shape of terrain model for mountains-gorge bridge site, a kind of transition section curves was derived based on the theory of flow around cylinder with ideal fluid. According to the different shapes of the curve transition section with equivalent slope of 0.58 and the ramp transition section with included angle of 30°, an ideal two-dimensional platform terrain was used as the analysis model to comparatively analyze the flow separation behavior and the distribution characteristics of average wind field after airflow flowed along the two transition sections by CFD commercial software FLUENT. Furthermore, the total flow transition lengths of different curve transition section shapes were also compared. The results show that when airflow flows along the curve transition section with equivalent slope of 0.58, the distribution characteristics of wind velocity field after airflow flowed along it are much closer to the distribution characteristics of reference wind velocity field than those when airflow flows along the ramp transition section with included angle of 30°, and its total flow transition length is also the relative shortest. The research conclusions could provide some references for the complex terrain model studies on wind characteristics over the mountains-gorge bridge site by wind tunnel test and CFD methods. [ABSTRACT FROM AUTHOR]

To achieve the equilibrium atmosphere boundary layer in an empty flow field with SST k-ϖ turbulence model, the method of adding source terms to the turbulent kinetic energy transport equation and the specific dissipation rate transport equation respectively was adopted to make the inlet profiles of average wind and turbulence wind consistent with the turbulence model, the consistency of the average wind profiles, turbulent kinetic energy profiles and specific dissipation rate profiles at several different positions with and without considering the source terms were investigated respectively according to the corresponding CFD numerical example. The numerical result shows that when considering the source terms in the turbulence model, the average wind profiles, turbulent kinetic energy profiles and specific dissipation rate profiles at several different positions along the flow field are all maintained very well, which indicates that the equilibrium atmosphere boundary layer in the empty flow field is achieved satisfactorily. The study conclusion proposes a new idea or research method for modeling the equilibrium atmosphere boundary layer and also provides the further CFD simulations in structural wind engineering with theoretical and actual values. [ABSTRACT FROM AUTHOR]

With long spans and weak stiffness, cable-stayed-suspension systems are susceptible to both vehicles and wind. An Aerobus system which will be built in China is regarded as an engineering practice example of long span cable-stayed-suspension system in this paper. Based on the interactions among wind, vehicle and guideway, the nonlinear three-dimensional analysis model is established for the coupling vibration of the wind-vehicle-guideway system. With the wind load and vehicle load imposed automatically, the secondary development of the finite element software ANSYS has been carried Out to simulate the process of vehicle running on the guideway. The dynamic response of both vehicle and cable-stayed-suspension system can be obtained by the developed software. The analysis results of the engineering example indicate that the location and stiffness of the stayed cables are important to the vertical acceleration response of vehicles. The research conclusions can provide a basis for the design optimization of long span cable-stayed-suspension system. [ABSTRACT FROM AUTHOR]

Objective: To investigate the efficacy of acupoint injection of Ropivacaine for labor analgesia and its effect on breastfeeding and prolactin secretion., Methods: A total of 80 primipara who asked to receive labor analgesia were randomized into epidural analgesia group ( n ＝35) and acupoint injection group ( n ＝36), and other 36 primipara who refused to receive labor analgesia were subjected to the control group. The labor analgesia began to be performed when the puerpera's uterine orifice opened about ≥3 cm (the first stage of labor), including puerpera controlled epidural analgesia (PCEA, Sufentainil ＋ 0.1% Ropivacaine hydrochloride, 5 µg/mL at L3-L4 interspace, till the birth of fetus) or acupoint injection of Ropivacaine (0.2%, 1 mL/acupoint) at bilateral Hegu (LI4) and Sanyinjiao (SP6). The delivery situations such as the duration of labor, and number of cases who used oxytocin, obstetric-forceps-aided delivery, cesarean delivery were recorded. The serum prolactin concentration was assayed by using ELISA. The visual analogue scale (VAS) scores at the time points of T 0 (about 3 cm widening of the orifice of uterus and before performing analgesia), T 1 (30 min after labor analgesia), T 2 (about 10 cm widening of the orifice of uterus) and T 3 (coming out of fetal head). The duration of labor, ratio of use of oxytocin, onset time of breastfeeding, and times of breastfeeding within 24 postpartum hours were recorded accordingly., Results: The VAS scores at time-points of T 1, T 2 and T 3 were significantly lower in both epidural analgesia and acupoint injection groups in comparison with their own T 0 and the control group ( P <0.05), and were also considerably higher in the acupoint injection group than in the epidural analgesia group ( P <0.05). The duration of the 2 nd stage of labor (from complete opening of the uterus orifice to complete birth of the fetus) was significantly longer, ( P <0.05) and the number of oxytocin-using puerpera was obviously bigger in the epidural analgesia group than in the control group ( P <0.05). After partum, the 1 st breastfeeding time was obviously earlier and the frequency of breastfeeding notably increased in both epidural analgesia and acupoint injection groups than in the control group ( P <0.05), the serum prolactin content was remarkably higher in the acupoint injection group than in the epidural analgesia group ( P <0.05). No significant differences were found between the acupoint injection and the control groups in the duration of the 1 st and 2 nd stages of labor, and in the numbers of oxytocin-using puerpera, obstetric forceps-aided birth and cesarean delivery ( P >0.05), and between the epidural analgesia group and control group in the serum prolactin levels ( P >0.05)．., Conclusion: Injection of Ropivacaine at LI4 and SP6 is effective for labor analgesia and raising prolactin level, and favorable to breastfeeding in the early postpartum period.

Objective: To observe the anesthetic effect and safety of different doses of dexmedetomidine combined with ropivacaine for brachial plexus nerve block in children undergoing polydactyly surgery., Methods: Eighty children undergoing polydactyly surgery were randomized into 4 groups to receive brachial plexus nerve block with dexmedetomidine at 0.25, 0.50 or 0.75 µg/kg combined with 0.25% ropivacaine (0.20 mL/kg) (D1, D2, and D3 groups, respectively) or with 0.25% ropivacaine (0.20 mL/kg) only (control group). The onset time, duration of brachial plexus nerve block, awakening time, success rate, and incidence of complications were compared among the groups. Results In D2 and D3 groups, the onset time and awakening time were shorter and anesthesia lasted longer than those in the control group. The onset time and awakening time were shorter and anesthesia maintenance time was longer in D3 group than in D1 group. The success rates of brachial plexus nerve block were significantly higher in D1-3 groups than in the control group (P<0.05). Hematoma was found in one of the patients. In each of the 4 groups, laryngeal nerve block occurred in 1 child and respiratory depression in another; 2 or 3 patients had Horner syndrome, and 1 patient in D3 group experienced an episode of lowered heart beat to below 70 min -1 . All the complications were managed properly and the patients all recovered uneventfully., Conclusion: Brachial plexus nerve block with 0.5 µg/kg dexmedetomidine combined with 0.25% ropivacaine (0.20 mL/kg) is safe for effective anesthesia in children undergoing surgery for polydactyly.