ALBERT

Description: The outbreak of waterborne disease cholera has been associated with rainfall and flooding events by contamination of potable water with environmental Vibrio cholerae. The continuation of the epidemic in a region, however, is often due to secondary transmission of the initial outbreak strain through human waste. This paper reports, on the contrary, a rapid shift of genotype from one V. cholerae strain to another one in an epidemic region. V. cholerae isolated from patients during 2005 cholera epidemic in Chennai, India were characterized using PCR identification of toxin genes, antibiogram, and genomic fingerprinting analysis. The results showed that in spite of the similarity of toxin genes and antibiogram, the Vibrio isolates grouped into two different clusters based on the ERIC-PCR fingerprinting. Each cluster corresponded to a distinct peak of cholera outbreak, which occurred after separate heavy rainfall. The results suggest that the rainfall event can bring various genotypes of V. cholerae strains causing multiple outbreaks.

Description: We describe the setup of testing regions for the China Earthquake Forecast Testing Center and provide preliminary forecast results in the scope of the Collaboratory for the Study of Earthquake Predictability (CSEP) project. We investigate the spatiotemporal variations of the completeness magnitude M c by using the frequency-magnitude distribution of the China Earthquake Networks Center (CENC) catalog. We find three periods of significantly different M c histories: (I) 1 January 1970–30 September 2001, (II) 1 October 2001–30 September 2008, and (III) 1 October 2008–31 August 2011. M c mapping provides median values , 2.2, and 1.6 for the three periods of time, respectively, showing the improvement in catalog completeness over time. We recommend using data from periods II and III to define a baseline long enough for retrospective forecast testing. Small magnitude events from period I should be used with caution due to important fluctuations in completeness. For period III, coordinates of all national and regional seismic stations are available, and we therefore apply the Bayesian magnitude of completeness (BMC) technique, mapping M c continuously by using prior information on the relationship between M c and the density of seismic stations. We define four potential testing/collection areas for CSEP-China: (A) All China, (B) North–South Seismic Belt (NSSB), (C) North and West Xinjiang Seismic Region, and (D) North China Seismic Region. In the current phase of CSEP-China, only the NSSB (region B) is considered. To demonstrate the type of earthquake predictability experiment that will be performed in the Chinese Testing Center, we present a series of retrospective forecast experiments with TripleS, a smoothed seismicity model. Online Material: The CENC earthquake catalog (1 January 1970–31 August 2011, restricted to magnitudes M ≥3.0) as well as completeness magnitude M c ( x , y ) spatial grids.

Description: 〈span〉〈div〉ABSTRACT〈/div〉The subjectivity in the artificial selection of calculation rules for seismicity parameters is an important factor that constrains the scientific results of calculations and their application in other fields. In this article, we apply the idea of a data‐driven approach to seismicity parameter calculation and propose a parameter‐free method to estimate the spatial distribution of parameters for the Ogata–Katsura 1993 (OK1993) model. This model is currently widely used and expressed in continuous function form. To verify the feasibility of this data‐driven approach and to explore the rules of model selection, we generate a synthetic catalog according to three sets of different parameters for the OK1993 model and perform large‐scale calculations and method testing. In the calculation, we use a total of 5,049,000 randomly generated models with various numbers of Voronoi nodes (ranging from 2 to 100) and cell meshes generated from 1000 random throws for each number of nodes. Next, we construct a penalized function to select the optimal model based on the Bayesian information criterion (BIC). The results of the median (Q2) and median absolute deviation for the β, μ, and σ values in the OK1993 model show that the initial input parameters can be well recovered for a synthetic catalog. Additionally, we see that our calculation is optimized with an effective node number Nv=20–100 and the best 1000 BIC values. We apply this data‐driven approach and the corresponding model selection rules to an actual earthquake catalog in the Shimian–Mianning–Xichang region in southwest China. The results show that the Gutenberg–Richter magnitude–frequency b‐values, converted from the moment‐frequency β values, are quite different from results obtained by previous studies using traditional methods. The low β values in the northern segment of the Anninghe fault and in the Daliangshan fault may indicate a higher stress accumulation in these regions. This new data‐driven and nonparametric calculation method for the OK1993 model can provide estimations of seismicity parameters that are potentially useful in many fields, including earthquake engineering, seismic hazard assessment, and geodynamics.〈/span〉

Description: With increasing and more stringent requirements for advanced vehicle integration, including vehicle dynamics and control, traditional control and optimization strategies may not qualify for many applications. This is because, among other factors, they do not consider the nonlinear characteristics of practical systems. Moreover, the vehicle wheel model has some inadequacies regarding the sideslip angle, road adhesion coefficient, vertical load, and velocity. In this paper, an adaptive neural wheel network is introduced, and the interaction between the lateral and vertical dynamics of the vehicle is analyzed. By means of nonlinear analyses such as the use of a bifurcation diagram and the Lyapunov exponent, the vehicle is shown to exhibit complicated motions with increasing forward speed. Furthermore, electric power steering (EPS) and active suspension system (ASS), which are based on intelligent control, are used to reduce the nonlinear effect, and a negotiation algorithm is designed to manage the interdependences and conflicts among handling stability, driving smoothness, and safety. Further, a rapid control prototype was built using the hardware-in-the-loop simulation platform dSPACE and used to conduct a real vehicle test. The results of the test were consistent with those of the simulation, thereby validating the proposed control.

Description: 〈span〉〈div〉ABSTRACT〈/div〉The subjectivity in the artificial selection of calculation rules for seismicity parameters is an important factor that constrains the scientific results of calculations and their application in other fields. In this article, we apply the idea of a data‐driven approach to seismicity parameter calculation and propose a parameter‐free method to estimate the spatial distribution of parameters for the Ogata–Katsura 1993 (OK1993) model. This model is currently widely used and expressed in continuous function form. To verify the feasibility of this data‐driven approach and to explore the rules of model selection, we generate a synthetic catalog according to three sets of different parameters for the OK1993 model and perform large‐scale calculations and method testing. In the calculation, we use a total of 5,049,000 randomly generated models with various numbers of Voronoi nodes (ranging from 2 to 100) and cell meshes generated from 1000 random throws for each number of nodes. Next, we construct a penalized function to select the optimal model based on the Bayesian information criterion (BIC). The results of the median (Q2) and median absolute deviation for the β, μ, and σ values in the OK1993 model show that the initial input parameters can be well recovered for a synthetic catalog. Additionally, we see that our calculation is optimized with an effective node number Nv=20–100 and the best 1000 BIC values. We apply this data‐driven approach and the corresponding model selection rules to an actual earthquake catalog in the Shimian–Mianning–Xichang region in southwest China. The results show that the Gutenberg–Richter magnitude–frequency b‐values, converted from the moment‐frequency β values, are quite different from results obtained by previous studies using traditional methods. The low β values in the northern segment of the Anninghe fault and in the Daliangshan fault may indicate a higher stress accumulation in these regions. This new data‐driven and nonparametric calculation method for the OK1993 model can provide estimations of seismicity parameters that are potentially useful in many fields, including earthquake engineering, seismic hazard assessment, and geodynamics.〈/span〉

Description: This paper investigates behaviors of flows driven by tangential velocity and shear stress on their boundaries such as solid walls and water surfaces. In a steady flow between two parallel plates with one of them in motion, analytic solutions are the same when a velocity and a shear stress boundary condition are applied on the moving plate. For an unsteady, impulsively started flow, however, analysis shows that solutions for velocity profiles as well as energy transferring and dissipation are different under the two boundary conditions. In an air-water flow, if either a velocity or a stress condition is imposed at the air-water interface, the problem becomes ill-posed because it has multiple solutions. Only when both of the conditions are specified, it will have a unique solution. Numerical simulations for cavity flows are made to confirm the theoretical results; a tangential velocity and a shear stress boundary condition introduce distinct flows if one considers an unsteady flow, whereas the two conditions lead to a same solution if one simulates a steady flow. The results in this paper imply that discretion is needed on selection of boundary conditions to approximate forcing on fluid boundaries such as wind effects on surfaces of coastal ocean waters.