Node discovery in a networked organization

In this paper, I present a method to solve a node discovery problem in a networked organization. Covert nodes refer to the nodes which are not observable directly. They affect social interactions, but do not appear in the surveillance logs which record the participants of the social interactions. Discovering the covert nodes is defined as identifying the suspicious logs where the covert nodes would appear if the covert nodes became overt. A mathematical model is developed for the maximal likelihood estimation of the network behind the social interactions and for the identification of the suspicious logs. Precision, recall, and F measure characteristics are demonstrated with the dataset generated from a real organization and the computationally synthesized datasets. The performance is close to the theoretical limit for any covert nodes in the networks of any topologies and sizes if the ratio of the number of observation to the number of possible communication patterns is large

Mineral composition of ores and silicagel quality

Mineral composition and silica hydrogel properties of Japanese acid clay or

Transport properties of Ag5Pb2O6: a three-dimensional electron-gas-like system with low-carrier-density

We report normal-state transport properties of the single-crystalline samples of the silver-lead oxide superconductor Ag5Pb2O6, including the electrical resistivity, magnetoresistance, and Hall coefficient. From the Hall coefficient measurement, we confirmed that the carrier density of this oxide is as low as 5x10^{21} cm^{-3}, one order of magnitude smaller than those for ordinary alkali metals and noble metals. The magnetoresistance behavior is well characterized by the axial symmetry of the Fermi surface and by a single relaxation time. The T^2 term of the resistivity is scaled with the specific heat coefficient, based on the recent theory for the electron-electron scattering. The present results provide evidence that Ag5Pb2O6 is a low-carrier-density three-dimensional electron-gas-like system with enhanced electron-electron scatterings.Comment: 7 pages, 4 figures. Accepted for publication in Phys. Rev.

Dynamic Behavior of Sand Bed under Oscillating Water Pressure

Under the attack of storm waves, there are many destructions of coastal structures in the forms of sinking and sliding. These types of destructions will be in close relation to the dynamic behavior of sand bed around the structures. From this point of view, in this paper, we investigate the characteristics of the pore water pressure and effective stresses in the highly saturated sand bed under oscillating water pressure theoretically. The results indicate that the oscillating water pressure induce the notable drop of strength of sand bed around the structure under certain condition