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In this study, a stochastic tropical cyclone (TC) intensity model based on a deterministic fast physics-based TC intensity model is developed for potential applications in the TC hazard assessment. To account for the effect of randomness, an error term is introduced to the ordinary differential equation for the TC intensity. The error term is assumed to be the summation of a mean part and a white noise. The geographically weighted summary statistics method is adopted to estimate the geographically varying mean and white noise intensity of the error term using the 1,010 historical tropical cyclone records from the western North Pacific. The effects of the mean and random parts of the error term on the model's performance are investigated in terms of the individual samples and the probabilistic characteristics of TC intensity evolution. The results show that, by introducing the error term, the difference of the 25-, 50-, and 100-year recurrence interval values between the model and observation can be largely reduced from the level of 10% to less than 4%, validating the adequacy of the proposed model in the TC hazard assessment. [ABSTRACT FROM AUTHOR]

High-momentum jets, which are the key parameter to achieve moderate or intense low-oxygen dilution (MILD) combustion may lead to insufficient residence time and high CO emissions, especially for furnaces with a forward-flow configuration. A reflector for application in the furnace was proposed by two-dimensional numerical simulations to reduce the CO emissions and maintain low NOx emissions. The prediction showed a remarkable agreement with measurements. The effects of the reflector height H, the excess air factor λ (changes in the inlet methane-mass flow rate), and the hydrogen content in the blended gas were investigated. The numerical results indicate that the reflector blocks the reactant's flow, intensifies the combustion before it, and prolongs the residence time of flue gases both before and behind it. The added hydrogen in methane can intensify combustion, increase reaction temperature and NO emissions, and reduce CO emissions. The reaction rates of thermal, prompt, NNH, and N2O-intermediate routes increase with the decrease of λ. The addition of hydrogen decreases the rate of the prompt route, but the rates of NNH and thermal routes increase. MILD combustion is achieved under the reflector conditions, considering the nearly uniform temperature distribution and the low pollutants. [ABSTRACT FROM AUTHOR]

Three-dimensional numerical simulations were carried out to study fuel-staged low-NOx burners (LNB). The effect of the number of staged guns (four and six) and quarl style (Venturi and boss) on the performance of the LNBs was investigated. The flow field, flame temperature, OH radical field, and NO emission were analyzed. The turbulence, radiation, and chemical reactions were simulated with the standard k-ε model, discrete ordinate (DO) model, and probability density function mixture fraction model, respectively, using a commercial computational fluid dynamics code. The numerical model was validated with experimental measurements at different excess air conditions. The agreement of the calculated and measured NO emission is remarkable; therefore, the present model is considered reliable. The results indicate that the number of staged guns has little effect on the NO emission; the boss quarl increases mean air velocity, changes staged gas flow direction, and reduces peak flame temperature and peak OH mole fraction. The boss quarl reduces more than 60% of the NO emission compared with the Venturi quarl. [ABSTRACT FROM AUTHOR]

The vibration isolation and mitigation of a platform, such as aerospace or precision instrument platforms, is an important research topic. However, previous studies only address high-frequency excitations; they disregard the control effect of low-frequency excitations. Thus, a new vibration control scheme for a platform is proposed to reduce the dynamic responses of a platform that is subjected to wide-frequency excitations, which range from 0 to 500 Hz, using vibration isolation and mitigation devices, magnetorheological (MR) dampers, and viscoelastic (VE) dampers. The motion equations of a complex dynamic system with these three different types of dampers are deduced considering seven degree-of-freedom coupling vibration. The idea of multistate control is adopted to control the inputting currents of the MR damper, and the dynamic responses of the platform to sinusoidal excitation, white noise excitation, and load spectrum excitation are calculated, respectively. The analysis results indicate that the proposed vibration control scheme is effective and suitable for vibration control of the platform [ABSTRACT FROM AUTHOR]

A newly built roller-compacted concrete gravity dam is located on the Yalongjiang River in southwest China. Complex geological conditions greatly puzzled the designers of the project. There are abundant joints within the riverbed that form the double- inclined wedge foundation. This is a typical mode of instability of concrete gravity dams. The equal-K method, which falls into the category of conventional limit-equilibrium methods, is provided in the design codes of gravity dams to evaluate the stability of a dam against sliding along deep failure surfaces. The factor of safety calculated by the equal-K method is determined by the angle of the force acting on the interface of the two inclined wedges, denoted by φ, which is unspecified in the design codes. On the basis of Sarma's assumption, this study proposes an algorithm for the determination of ∅, which needs only slight improvement of the algorithm in the existing codes. The justification of the proposed procedure is demonstrated by showing that the results from the proposed procedure are very close to those from a rigorous limit-equilibrium method in which all equilibrium conditions are satisfied. [ABSTRACT FROM AUTHOR]