1,447 research outputs found

    Network Marketing on a Small-World Network

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    We investigate a dynamic model of network marketing in a small-world network structure artificially constructed similarly to the Watts-Strogatz network model. Different from the traditional marketing, consumers can also play the role of the manufacturer's selling agents in network marketing, which is stimulated by the referral fee the manufacturer offers. As the wiring probability α\alpha is increased from zero to unity, the network changes from the one-dimensional regular directed network to the star network where all but one player are connected to one consumer. The price pp of the product and the referral fee rr are used as free parameters to maximize the profit of the manufacturer. It is observed that at α=0\alpha=0 the maximized profit is constant independent of the network size NN while at α0\alpha \neq 0, it increases linearly with NN. This is in parallel to the small-world transition. It is also revealed that while the optimal value of pp stays at an almost constant level in a broad range of α\alpha, that of rr is sensitive to a change in the network structure. The consumer surplus is also studied and discussed.Comment: 12 pages, to appear in Physica

    Engineering criticality analysis on an offshore structure using the first- and second-order reliability method

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    AbstractDue to the uncertainties related to the flaw assessment parameters, such as flaw size, fracture toughness, loading spectrum and so on, the probability concept is preferred over deterministic one in flaw assessment. In this study, efforts have been made to develop the reliability based flaw assessment procedure which combines the flaw assessment procedure of BS7910 and first- and second-order reliability methods (FORM/SORM). Both crack length and depth of semi-elliptical surface crack at weld toe were handled as random variable whose probability distribution was defined as Gaussian with certain means and standard deviations. Then the limit state functions from static rupture and fatigue perspective were estimated using FORM and SORM in joint probability space of crack depth and length. The validity of predicted limit state functions were checked by comparing it with those obtained by Monte Carlo simulation. It was confirmed that the developed methodology worked perfectly in predicting the limit state functions without time-consuming Monte Carlo simulation

    Self-consistent inference formulation of gravity model

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    The gravity model has been a useful framework to describe macroscopic flow patterns in geographically correlated systems. In the general framework of the gravity model, the flow between two nodes decreases with distance and has been set to be proportional to the suitably defined mass of each node. Despite the frequent successful applications of the gravity model and its alternatives, the existing models certainly possess a serious logical drawback from a theoretical perspective. In particular, the mass in the gravity model has been either assumed to be proportional to the total in- and out-flow of the corresponding node or simply assigned the other node attribute external to the gravity model formulation. In the present work, we propose a general novel framework in which the mass as well as the distance-dependent deterrence function can be computed iteratively in a self-consistent manner within the framework only based on the flow data as input. We validate our suggested methodology in an artificial synthetic flow data to find the near-perfect agreement between the input information and the results from our framework. We also apply our method to the real international trade network data and discuss implications of the results.Comment: 8 pages, 6 figure

    Effects of strobe light stimulation on postnatal developing rat retina

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    The nature and intensity of visual stimuli have changed in recent years because of television and other dynamic light sources. Although light stimuli accompanied by contrast and strength changes are thought to have an influence on visual system development, little information is available on the effects of dynamic light stimuli such as a strobe light on visual system development. Thus, this study was designed to evaluate changes caused by dynamic light stimuli during retinal development. This study used 80 Sprague-Dawley rats. From eye opening (postnatal day 14), half of the rats were maintained on a daily 12-h light/dark cycle (control group) and the remaining animals were raised under a 12-h strobe light (2 Hz)/dark cycle (strobe light-reared group). Morphological analyses and electroretinogram (ERG) were performed at postnatal weeks 3, 4, 6, 8, and 10. Among retinal neurons, tyrosine hydroxylase-immunoreactive (TH-IR, dopaminergic amacrine cells) cells showed marked plastic changes, such as variations in numbers and soma sizes. In whole-mount preparations at 6, 8, and 10 weeks, type I TH-IR cells showed a decreased number and larger somata, while type II TH-IR cells showed an increased number in strobe-reared animals. Functional assessment by scotopic ERG showed that a-wave and b-wave amplitudes increased at 6 and 8 weeks in strobe-reared animals. These results show that exposure to a strobe light during development causes changes in TH-IR cell number and morphology, leading to a disturbance in normal visual functions

    Optical switching of the Dirac point in graphene multilayer field-effect transistors functionalized with spiropyran

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    A facile method for achieving optical switching of the Dirac point and conductance in reduced graphene oxide multilayer FETs that are non-covalently functionalized with a photoresponsive spiropyran derivative is presented. The photoresponsive transition from spiropyran to merocyanine induces the reversible optical switching in graphene based FETs.close6

    Design of Process Parameters in Electromagnetic Forming Apparatus by FEM

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    Electromagnetic forming (EMF) process is one of a high-speed forming process, which uses an electromagnetic body (Lorentz) force to deform work-piece. Advantages of EMF are summarized as improvement of formability, reduction in wrinkling, non-contact forming. In this study, the spiral coil is considered to evaluate formability in terms of pressure distribution of the forming process. It also is represented forming results of numerical analysis using ANSYS code. In the numerical simulation, RLC circuit coupled with spiral coil was made to consider the design parameters such as system input current and electromagnetic force. The simulation results show that even though input peak currents level are same level in each case, forming condition is certainly different because of frequency of input current and magnitude of current density and magnetic flux density. Finally, the simulation results appear that electromagnetic forming force apparently affected by input current frequency which determines magnitude of current density and magnetic flux density
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