A novel iterative approach for mapping local singularities from geochemical data

International audienceThere are many phenomena in nature, such as earthquakes, landslides, floods, and large-scale mineralization that are characterized by singular functions exhibiting scale invariant properties. A local singularity analysis based on multifractal modeling was developed for detection of local anomalies for mineral exploration. An iterative approach is proposed in the current paper for improvement of parameter estimations involved in the local singularity analysis. The advantage of this new approach is demonstrated with de Wijs's zinc data from a sphalerite-quartz vein near Pulacayo in Bolivia. The semivariogram method was used to illustrate the differences between the raw data and the estimated data by the new algorithm. It has been shown that the outcome of the local singularity analysis consists of two components: singularity component characterized by local singularity index and the non-singular component by prefractal parameter

Modelling on seasonal lake ice evolution in central asian arid climate zone : A case study

The seasonal cycle of ice thickness and temperature in Lake Wuliangsuhai, a typical shallow lake in the central Asian arid climate zone, was simulated using the HIGHTSI model and the MERRA-2 data as the meteorological forcing. The average ice growth rate was 0.64 cm·d−1 and −1.65 cm·d−1 for the growth and melting stage of the ice cover, respectively. The ice thickness agreed well with the field observations conducted in winter 2017, with a correlation coefficient of 0.97. The ice temperature field also agreed with observations in both daily variations and the vertical profile, and a better agreement in the daily amplitude and profile shape of ice temperature could be achieved if field data on physical properties of snow cover and melting ice were available. This study proved the feasibility of both the HIGHTSI model and the MERRA-2 data for modeling the ice cover evolution in Lake Wuliangsuhai, providing a basis for a deep insight into the difference of lake ice evolution between central Asian arid climate zone and polar/sub-polar regions.Peer reviewe

Influence of melt-pond depth and ice thickness on Arctic sea-ice albedo and light transmittance

Solar radiation drives the melting of Arctic sea ice in summer, but its parameterization in thermodynamic modeling is difficult due to the large variability of the optical properties of sea ice in space and time. Here, a two-stream radiative transfer model was developed for the propagation of solar radiation in ponded sea ice to investigate the dependence of apparent optical properties (AOPs), particularly albedo and transmittance, on sky conditions, pond depth, ice thickness, and the inherent optical properties (IOPs) of ice and water. The results of numerical experiments revealed that decrease in melt-pond albedo during melting results not only from increase in pond depth but also from decrease in underlying ice thickness, and the latter is more important for thin ice with thickness less than 1.5 m. Hence, a parameterized pond albedo as a function of both pond depth and ice thickness is more suitable for thinning Arctic sea ice than the previously used exponential function of pond depth, which is valid for thicker ice. The increase in broadband transmittance during melting can be explained by the decrease in underlying ice thickness, because its dependence on ice thickness is nearly three times stronger than on pond depth. The spectral dependence of the pond albedo on depth is significant only in the 600-900-nm band, while it depends clearly on ice thickness in the 350-600-nm band. The uncertainty resulting from the absorption coefficient of ice is limited, while the effect of scattering in ice is more important, as determined by a sensitivity study on the influence of the IOPs on the AOPs of sea ice. The two-stream model provides a time-efficient parameterization of the AOPs for ponded sea ice, accounting for both absorption and scattering, and has potential for implementation into sea-ice thermodynamic models to explain the role of melt ponds in the summer decay of Arctic sea ice. (C) 2016 Elsevier B.V. All rights reserved.Peer reviewe

Partitioning of solar radiation in Arctic sea ice during melt season

Summary The partitioning of solar radiation in the Arctic sea ice during the melt season is investigated using a radiative transfer model containing three layers of melt pond, underlying sea ice, and ocean beneath ice. The wavelength distribution of the spectral solar irradiance clearly narrowed with increasing depth into ice, from 350–900 nm at the pond surface to 400–600 nm in the ocean beneath. In contrast, the net spectral irradiance is quite uniform. The absorbed solar energy is sensitive to both pond depth (Hp) and the underlying ice thickness (Hi). The solar energy absorbed by the melt pond (Ψp) is proportional only to Hp. However, the solar energy absorbed by the underlying ice (Ψi) is more complicated due to the counteracting effects arising from the pond and ice to the energy absorption. In September, Ψp decreased by 10% from its August value, which is attributed to more components in the shortwave band (<530 nm) of the incident solar radiation in September relative to August. The absorption coefficient of the sea ice only enhances the absorbed energy in ice, while an increase in the ice scattering coefficient only enhances the absorbed energy in the melt pond, although the resulted changes in Ψp and Ψi are smaller than that in the albedo and transmittance. The energy absorption rate with depth depends strongly on the incident irradiance and ice scattering, but only weakly on pond depth. Our results are comparable to previous field measurements and numerical simulations. We conclude that the incident solar energy was largely absorbed by the melt pond rather than by the underlying sea ice.Peer reviewe

Factors Driving Mobile App Users to Pay for Freemium Services

With the popularity of smart mobile devices, mobile applications (most commonly referred to as an App) have gradually grown up to be a huge commercial market. Therefore, as the variety and download counts of Apps in the application stores of the two biggest operating systems increase, how to make a profit from Apps has become the most concerned issue for developers. Today the freemium strategy is widely observed in mobile App markets. Freemium is a business model by which an App is offered free of charge, but a premium is charged for advanced features. Hence, the purpose of this study is to explore the factors driving mobile App users to pay for freemium services based on value-based adoption model. An online survey was conducted to collect empirical data in order to test the research model. The results of PLS analysis indicate that an App user’s intention to pay is determined by perceived value, a thorough comparison of benefits and sacrifices, and trust of developer. Furthermore, perceived value will be affected by perceived effort and perceived usefulness while the App user has no experience on premium service. Finally, the implications for practitioners and researchers are discussed

Program Dependence Net and On-demand Slicing for Property Verification of Concurrent System and Software

When checking concurrent software using a finite-state model, we face a formidable state explosion problem. One solution to this problem is dependence-based program slicing, whose use can effectively reduce verification time. It is orthogonal to other model-checking reduction techniques. However, when slicing concurrent programs for model checking, there are conversions between multiple irreplaceable models, and dependencies need to be found for variables irrelevant to the verified property, which results in redundant computation. To resolve this issue, we propose a Program Dependence Net (PDNet) based on Petri net theory. It is a unified model that combines a control-flow structure with dependencies to avoid conversions. For reduction, we present a PDNet slicing method to capture the relevant variables' dependencies when needed. PDNet in verifying linear temporal logic and its on-demand slicing can be used to significantly reduce computation cost. We implement a model-checking tool based on PDNet and its on-demand slicing, and validate the advantages of our proposed methods.Comment: 17 pages, 3 figure

Application of local singularity in prospecting potential oil/gas Targets

International audienceTogether with generalized self-similarity and the fractal spectrum, local singularity analysis has been introduced as one part of the new 3S principle and technique for mineral resource assessment based on multifractal modeling, which has been demonstrated to be useful for anomaly delineation. Local singularity is used in this paper to characterize the property of multifractal distribution patterns of geochemical indexes to delineate potential areas for oil/gas exploration using the advanced GeoDAS GIS technology. Geochemical data of four oil/gas indexes, consisting of acid-extracted methane (SC1), ethane (SC2), propane (SC3), and secondary carbonate (?C), from 9637 soil samples amassed within a large area of 11.2×104 km2 in the Songpan-Aba district, Sichuan Province, southwestern China, were analyzed. By eliminating the interference of geochemical oil/gas data with the method of media-modification and Kriging, the prospecting area defined by the local singularity model is better identified and the results show that the subareas with higher singularity exponents for the four oil/gas indexes are potential targets for oil/gas exploration. These areas in the shape of rings or half-rings are spatially associated with the location of the known producing drilling well in this area. The spatial relationship between the anomalies delineated by oil/gas geochemical data and distribution patterns of local singularity exponents is confirmed by using the stable isotope of ?13C

Impact of Microstructure on Solar Radiation Transfer Within Sea Ice During Summer in the Arctic : A Model Sensitivity Study

The recent rapid changes in Arctic sea ice have occurred not only in ice thickness and extent, but also in the microstructure of ice. To understand the role of microstructure on partitioning of incident solar shortwave radiation within the ice and upper ocean, this study investigated the sensitivity of the optical properties of summer sea ice on ice microstructures such as the volume fraction, size, and vertical distribution of gas bubbles, brine pockets, and particulate matter (PM). The results show that gas bubbles are the predominant scatterers within sea ice. Their effects on the scattering coefficient and ice albedo are 5 and 20 times stronger respectively than the effect of brine pockets. Albedo and transmittance of ice decrease with higher concentration and larger size of PM particles. A 4-cm top layer of ice with high PM concentration (50 g/m(3)) results in a 10% increase in radiation absorption. The role of ice microstructure in the partitioning of radiation transfer is more important for seasonal than for multiyear ice, and more important for ponded than for snow-covered ice. Varying ice microstructure can obviously alter solar radiation transfer in the ice-ocean system, even with a constant ice thickness. Our results suggest that numerical models should take the variable microstructure of sea ice into account to improve model accuracy and to understand the interaction between internal variations in Arctic sea ice and the ocean, especially in summer.Peer reviewe

Distribución del tamaño y variación mensual del desarrollo ovárico del cangrejo azul hembra, Portunus pelagicus en el golfo de Beibu, frente al sur de China

The present study was conducted to investigate the size distribution and seasonality variation of ovarian development for females of the blue swimmer crab, Portunus pelagicus, from Beibu Gulf, China. The results show that, based on pubertal moult, gonadosomatic index (GSI), morphology and histological configurations, the ovarian development cycle of P. pelagicus can be divided into five stages; Stage I, dominated by oogonia with some previtellogenic oocytes and endogenous vitellogeic oocytes; Stage II, dominated by endogenous vitellogenic oocytes with some previtellogeic oocytes and oogonia; Stage III, dominated by exogenous vitellogeic oocytes; Stage IV, of nearly mature oocytes; and Stage V, of mature oocytes with fully ripened ovary. GSI increased significantly during the ovarian development (P < 0.05), while the hepatosomatic index (HSI) appeared to decrease. Thus, a significant negative correlation was found between GSI and HSI (P < 0.01). The smallest carapace width of a mature female and that at which 50% of females reach maturity were 79.2 mm and 108.2 mm, respectively. The carapace width and body weight of the dominant size class ranged between 86 and 115 mm and 40 and 120 g, respectively. Furthermore, the highest GSI of female P. pelagicus was found in March, while the peak of ovigerous females was found in April.Este estudio se realizó para investigar la distribución del tamaño y la estacionalidad de desarrollo ovárico del cangrejo azul hembra, Portunus pelagicus en el golfo de Beibu, China. Los resultados muestran que, sobre la base de la muda de la pubertad, el GSI (índice gonadosomático), la morfología y las configuraciones histológicos y el ciclo del desarrollo ovárico de P. pelagicus puede dividirse en cinco etapas. Etapa I: La fase de oogonia (OG) dominaba con algunos ovocitos previtelogeicos (PR) y ovocitos vitelogeicos endógenos (EN); Etapa II: fase de EN dominaba con algunos PR y OG; Etapa III: la fase de ovocitos vitelogeicos exógenos (EX) era dominante; Etapa IV: fase de ovocitos casi maduros (NO); Etapa V: fase de ovocitos maduros (MO) y maduración completa del ovario. El índice gonadosomático (GSI) aumentó significativamente durante el desarrollo del ovario (P < 0.05), mientras que el índice hepatosomático (HSI) parecía disminuir. Por lo tanto, se encontró una correlación negativa significativa entre GSI y HSI (P < 0.01). La menor anchura del caparazón (CW) de una hembra madura y CW del 50% de las hembras maduras eran 79.2 mm y 108.2 mm, respectivamente. La CW y el peso corporal de la clase de tamaño dominante oscilaban entre 86-115 mm y 40-120 g respectivamente. Por otra parte, el GSI de la hembra más grande de P. pelagicus se encontró en marzo, mientras que el pico de las hembras ovígeras se produjo en abril en la población del golfo de Beibu