Measurement of air–water CO2 transfer at four coastal sites using a chamber method

We measured the air–water CO₂ flux in four coastal regions (two coral reefs, one estuary, and one coastal brackish lake) using a chamber method, which has the highest spatial resolution of the methods available for measuring coastal air–water gas flux. Some of the measurements were considerably higher than expected from reported wind-dependent relationships. The average k₆₀₀ values for Shiraho Reef, Fukido Reef, Fukido River, and Lake Nakaumi were 1.5 ± 0.6, 3.2 ± 0.3, 0.69 ± 0.26, and 2.2 ± 0.9 (mean ± S.D.) times larger than the wind-dependent relationships. Results were compared with current-dependent relationships and vertical turbulence intensity (VTI). VTI is an index of water-surface stirring and is calculated from near-surface vertical velocity. Although some measurements from the reefs and river closely matched those expected from wind-dependent relationships, others were considerably higher. All data were correlated with VTI and were qualitatively explained by bottom macro-roughness enhancement. In Lake Nakaumi, results tended to differ from the wind-dependent relationships, and the difference between the measured and expected gas-transfer velocity was correlated with biological DO changes and/or the intensity of density stratification. We found these factors to have important effects on coastal gas flux. In addition, the chamber method was an effective tool for evaluating coastal gas flux.     

The combined effect of rain and wind on air–water gas exchange: A feasibility study

A series of experiments were conducted at University of Delaware's Air–Sea Interaction Laboratory to examine the combined effects of rain and wind on air–water gas exchange. During this study, ASIL WRX I, a combination of 3 rain rates and 4 wind speeds were used, for a total of 12 different environmental conditions. The SF₆ evasion method was used to determine the bulk gas transfer velocities, and airside profiles of wind and CO₂ were used to estimate flux–profiles of momentum and carbon dioxide. In addition to measurements of fluxes with and without rain in a wind–wave boundary layer, measurements of wave properties were also obtained. Rain is shown to alter the wind profile in the flume, and dampen surface waves. Also, SF₆ evasion indicates that with the present experimental setup, for most of the experimental conditions, rain and wind combine linearly to influence air–water gas exchange. Flux–profile relationships for marine atmospheric boundary layers, which were performed to scale up to field measurements, were explored by a comparison between SF₆-derived bulk fluxes and airside CO₂ profile measurements.     

Seasonal study of dissolved CH4, CO2 and N2O in a shallow tidal system of the bay of Cádiz (SW Spain)

During 2004, 10 samplings were performed in order to measure dissolved methane (CH₄), carbon dioxide (CO₂) and nitrous oxide (N₂O) in the surface waters of Río San Pedro, a tidal creek in the salt marsh area of the Bay of Cádiz (SW Spain). The inner partvs of the creek is affected by the inputs coming from an intensive fish farm and the drainage of an extensive salt marsh area.Dissolved CH₄, CO₂ and N₂O concentrations ranged from 11 to 88 nM, 36 to 108 μM and 14 to 50 nM, respectively. Surface waters were in all cases oversaturated with respect to the atmosphere, reaching values of up to 5000% for CH₄, 1240% for CO₂ and 840% for N₂O. Dissolved CH₄, CO₂ and N₂O showed a significant tidal and seasonal variability. Over a tidal cycle, concentrations were always highest during low tide, which points to the influence of the inputs from the fish farm effluent and the drainage of the adjacent salt marsh area, as well as in situ production within the system. Dissolved CH₄, CO₂ and N₂O seasonal patterns were similar and showed maximum concentrations in summer conditions. Using four different parameterizations to calculate the gas transfer coefficients [Liss, P.S. and Merlivat, L., 1986. Air-sea exchange rates: introduction and synthesis. In P. Buat-Ménard (Ed.), The Role of Air-Sea Exchanges in Geochemical Cycling. Reidel, Dordrecht, The Netherlands, p. 113–127.; Clark, J.F., Schlosser, P., Simpson, H.J., Stute, M., Wanninkhof, R., and Ho, D.T., 1995. Relationship between gas transfer velocities and wind speeds in the tidal Hudson River determined by the dual tracer technique. In: B. Jähne and E. Monahan (Eds.), Air-Water Gas Transfer: AEON Verlag and Studio, Hanau, Germany, pp. 785–800.; Carini, S., Weston, N., Hopkinson, G., Tucker, J., Giblin, A. and Vallino, J., 1996. Gas exchanges rates in the Parker River estuary, Massachusetts. Biol. Bull., 191: 333–334.; Kremer, J.N., Reischauer, A. and D'Avanzo, C., 2003. Estuary-specific variation in the air-water gas exchange coefficient for oxygen. Estuaries, 26: 829–836.], the averaged air–water fluxes of CH₄, CO₂ and N₂O from the creek to the atmosphere ranged between 34 and 150 μmol CH₄ m^− 2 day^− 1, 73 and 177 mmol CO₂ m^− 2 day^− 1 and 24 and 62 μmol N₂O m⁻² day⁻¹, respectively.     

Updating free speed models through mechanistic principles for Indian conditions

The prediction of free speeds of vehicles is an integral part of the economic appraisal of highways. It is to be noted that speeds not only govern the travel time costs, but also have major impacts on Vehicle Operating Costs (VOC). The World Bank has proposed a mechanistic free speed model based on the limiting speed concept for Highway Design and Maintenance (HDM)‐III. This model along with some refinements has been included in HDM‐4. The underlying assumption in the HDM free speed prediction model is that the free speed at any given point of time is the minimum of possible constraining speeds. This paper mainly addresses the methodology considered to update the free speed models through mechanistic principles (based on HDM‐4). This is accomplished by calibration of the model using the current data on free speeds, road and vehicle characteristics. Subsequently, the validation of the developed models has been carried out.     

利用直接边界元法求解兴波问题

本文描述了利用直接边界元法求解定常兴波问题的理论和数值方法，本方法利用线性化自由面条件，辐射条件基于Dawson的四点差分格式进行处理。本文给出了Wigley船的兴波阻力和波高的数值结果，并与Dawson方法和试验结果进行了比较，结果显示本文的结果合理可靠。     

A computational approach for fatigue crack propagation in ship structures under random sequence of clustered loading

The authors have developed a simulation program, CP-System, for multiple cracks propagating in a three-dimensional stiffened panel structure, where through-the-thickness crack propagation is formulated as a two-dimensional in-plane problem, and the crack propagation behavior is simulated by step-by-step finite element analyses. In order to evaluate the fatigue lives of marine structures accurately, it is necessary to take into account the load histories induced by sea waves, which may be composed of a random sequence of certain clustered loads with variable stress range. In the proposed crack growth model, the crack opening and closure behavior is simulated by using the modified strip yielding model, and the effective tensile plastic stress intensity range, ΔK _RP, is calculated by considering the contact of plastic wake along the crack surfaces. The adequacy of the proposed crack growth model is examined by comparison with fatigue tests under non-constant-amplitude loading. The usefulness of the developed method is demonstrated for a ship structural detail under certain simulated load sequences. It is shown that the fatigue crack growth of a ship structure is significantly retarded due to the load interaction effects, so that the conventional method for fatigue life assessment may predict a relatively conservative fatigue life of a structure.     

Numerical weight function method for the structural analysis of ships: a speedy direct calculation with condensed structural information

The weight function method was originally derived for crack problems to calculate stress intensity factors for arbitrary loading conditions. In this article, a numerical weight function method has been extended to formulate the structural response analyses of two-dimensional elasticity, plate-bending, and three-dimensional plate-structures by using the finite-element method. The solution procedure is based on the well-known Maxwell–Betti reciprocal theorem, which is applied to the original and properly defined auxiliary problems. The present numerical weight function may be considered as a finite-element version of a Green’s function in an integral equation solution scheme. Although ship structures are certainly analysed by the finite-element method in a practical design procedure, the weight function approach has not yet been realized. The method is very useful for the analysis of structures subjected to a vast range of loading conditions, because structural responses can simply be calculated by the inner product of the universal weight function and load vectors. The validity and convergence characteristics of the present method are investigated by two-dimensional elastic and plate-bending problems, respectively. Finally, the method is applied to the calculation of the response amplitude operator of a stress component at a critical structural detail of a double-hull tanker, and the speed and efficiency of the method are quantitatively discussed based on the practical results.     

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电力是现今大部份铁道系统的动力来源． 可靠、有效率及安全的电力输送对整体铁道服务质素尤为重要，跟其它大型工程系统一样，铁道供电系统的设计，运作及筹划相当倚重计算机仿真．本文将回顾铁道供电系统仿真的模型及一般常规，并通过模拟结果例子及实际应用，介绍最新的模拟方式发展．本文亦对铁道供电系统仿真的未来挑战作出评论．     

REGULATED PHOSPHORYLATION OF THE GATA－2 DNA BINDINGPROTEIN IN ENDOTHELIAL CELLS

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Majorization of working parameters for non-thermal plasma reactor and impact on no oxidation of diesel engine

The main target of this work is to realize the function of pre-oxidizing NO from diesel engine’s exhaust by using self-designed double-dielectric Non-thermal Plasma (NTP) reactor. The majorized discharge frequency and discharge peak to peak voltage (V_p-p) range for NTP reactor were obtained through air discharge test. The diesel engine test bench was established to observe the effect of NTP on the volume fraction of NO. The results showed that there were more active substances and fewer by-products in NTP reactor when discharge frequency was 9 kHz and V_p-p was between 9 kV and 23 kV; Exhaust flows had insignificant effect on the performance of NTP pre-oxidizing NO; The ability of NTP to pre-oxidize NO gradually weakened with the increase of engine load, and when the engine load were 0 % and 25 %, the ratio of NO/NO₂ could reach 1. In such working conditions, SCR system could improve the conversion rate of the NO_x at low-temperature zone through quick reaction combined with NTP.