Classifying between computer generated and natural images: An empirical study from RAW to JPEG format

Computer generated (CG) images have been gradually overspread on the Internet, resulting in difficult discrimination from natural images (NIs) captured by an authentic imaging device. Although some discriminators can deal with NIs in JPEG format, the classification between uncompressed NIs (that are possibly generated in any imaging procedure before compression) and CG ones still remains unknown. Thus, this paper aims to establish multiple discriminators classifying between NIs and CG images. We first describe the main imaging procedure and its intrinsic property, which characterizes the discriminative features for classification. Then, the residual noise (representing intrinsic characteristic) is extracted. Its statistical distribution indeed helps us establish multiple discriminators, consisting of the generalized likelihood ratio test (GLRT) under the framework of hypothesis testing theory. Extensive experiments empirically verify our proposed multiple discriminators outperform many prior arts. Furthermore, the robustness of discriminators is validated with considering some post-processing attacks.     

Model intestinal microflora in computer simulation: a simulation and modeling package for host-microflora interactions

The ecology of the human intestinal microflora and its interaction with the host are poorly understood. Though more and more data are being acquired, in part using modern molecular methods, development of a quantitative theory has not kept pace with this increase in observing power. This is in part due to the complexity of the system and to the lack of simulation environments in which to test what the ecological effect of a hypothetical mechanism of interaction would be, before resorting to laboratory experiments. The MIMICS project attempts to address this through the development of a cellular automaton for simulation of the intestinal microflora. In this paper, the design and evaluation of this simulator is discussed.     

一种穹幕展演空间的CATT声学模拟分析

穹幕展演空间因其视觉效果越来越受到建筑师和业主方的青睐,但这种空间在声学上有一些缺陷,利用CATT声学模拟软件对一种特定的穹幕空间进行声学分析,可以发现单单运用传统的声学计算方法无法发现典型声学参数的分布规律,而计算机声学模拟分析能及早地发现这些潜在声学问题,并且能半定量地解决一大部分的问题,是值得推广的一种技术手段。     

Theoretical study of a channel-doped separate gate Si MOSFET (SG-MOSFET) by two-dimensional computer simulation

A new device structure is proposed for Si MOSFET, featuring an insulated gate structure, channel doping, and finite spacing between gate and source and between gate and drain. Two-dimensional numerical analysis shows that punchthrough is suppressed and that minimum gate length, limited bypunchthrough or VTshift, is extended into the submicrometer range.     

A computer architecture to support qualitative simulation in industrial applications

Monitoring and diagnosis of dynamic systems in industrial environments, like assembly lines and power plants, are challenging tasks. Faulty behaviors must be detected as soon as possible to avoid shutdown or damage. Recently, techniques from artificial intelligence (AI) have been applied to achieve these tasks. To overcome performance problems for the industrial application of the rather new AI technique qualitative simulation, a special-purpose computer architecture has been developed.     

New approach to the manufacturing of power microwave bipolar transistors: A computer simulation

A new manufacturing technology for power microwave silicon npn transistors is evaluated by 2D computer simulation in Silvaco’s SSUPREM4. It enables one to increase the effective emitter area, which makes for better power-handling and frequency capabilities, radiation hardness, and common-emitter output characteristics. Advantages of the new technology over the standard one are demonstrated.     

Revisiting the analytic theory of p-n junction impedance:improvements guided by computer simulation leading to a new equivalentcircuit

We revisit the analytic derivation of the dc and low frequency ac behavior of the p-n step junction and suggest all preexisting treatments are flawed for three important reasons. First, not all contributions to the diode current are included. We derive a rigorous expression for each component of current that can be used to judge the completeness of existing analytic theories. Additionally, wrong boundary conditions for minority carrier concentrations and incorrect equivalent circuit topologies undermine present analytic theories of the diode. We propose a new analytic equivalent circuit model which institutes correct boundary conditions. The resulting circuit model demonstrates excellent dc and ac accuracy for symmetric and asymmetric junctions, for long, short, or intermediate base regimes. Inductive behavior associated with short base diodes at large forward bias is reproduced, as is the decrease in capacitance observed in long base diodes. The assumptions and limitations of our new circuit model are thoroughly investigated     

A recursive free-body approach to computer simulation of human postural dynamics

A recursive, free-body approach to the estimation of joint torques associated with observed motion in linkage mechanisms has recently been shown to be computationally more efficient than any other known approach to this problem. This paper applies this method to the analysis of human postural dynamics and shows how it can also be used to compute accelerations for specified joint torques. The latter calculation, referred to here as the direct dynamics problem, has until now involved symbolic complexity to such an extent as to generally limit computer simulation studies of postural control to very simple models. The model presented in this paper is both straightforward and general, and removes this obstacle to the investigation of possible neural control mechanisms by means of computer simulation. A computationally oriented linearization procedure for the direct dynamics problem is also included in the paper. Finally, example simulation results and corresponding measured body motions for human subjects are presented to validate the method.     

Unidirectional block in cardiac fibers: effects of discontinuitiesin coupling resistance and spatial changes in resting membrane potentialin a computer simulation study

The mechanisms for conduction and unidirectional block (UDB) in cardiac tissue under spatial changes in cell-to-cell coupling resistivity (Ri) and resting potential (Vrest) were studied. Cable theory was used to simulate the cardiac fiber, and the Beeler and Reuter model, or a modified model based on the Ebihara-Johnson formulation was used to describe the ionic currents. The effects of discontinuities in Ri as would result from collagenous or fibrotic tissue on propagation characteristics were studied. We were especially interested in the effects on propagation characteristics of discontinuities in Ri in the border zone between normal and ischemic tissue. We found that conduction block is more likely to occur when an abrupt decrease in Ri is encountered as compared to an abrupt increase in Ri. Discontinuities in Ri were found to cause changes in propagation characteristics, changing regions of bidirectional block to UDB or bidirectional propagation. Spatial changes in Vrest were also studied. We found that when Vrest alone was altered, block was not likely to occur, while discontinuities in Ri superimposed with Vrest gradients increased the likelihood of block. We also found that Ri discontinuities located in the border zone between normal and ischemic tissue can create exit block or propagation of a parasystolic focus.     

Higher-order (nonlinear) diffraction tomography: reconstructionalgorithms and computer simulation

The usual propagation transform of diffraction tomography is generalized into higher-order (nonlinear) propagation transforms via use of the Born series as the data-generating model in scattering experiments. Nonlinear tomographic reconstruction algorithms are developed for inversion of scattered field data modeled up to an arbitrarily large (possibly infinite) number of terms in the Born series. A computer simulation study is included to illustrate the performance of the algorithms for the case of scattering objects with cylindrical symmetry.     

Part I: A computer program for the simulation of telecommunication systems: application to optical transmission systems

The conception and analysis of optical transmission systems employing various optical devices (semiconductor lasers, optical fibre, optical amplifiers, photo-diodes,…) require the support supplied by simulation software dedicated to the new components. The objective of thecnet/ipsis collaboration is to respond to this need. In this first article we present the simulation tools which characterize the quality of a digital transmission system, as well as the modelling of the optical elements. In order to show its full range of capabilities in the optical domain, a second article describes the results obtained from the simulation of digital transmission system using wavelength multiplexing.     

Analysis of firm-level computer investments: a comparative study ofthree Pacific-rim economies

The impact of information technology (IT) on firm level productivity has been a subject of considerable research. Although a number of empirical studies have been reported, results are far from conclusive. Almost all of these studies are based on secondary data collected in the United States, which makes it impossible to compare productivity impacts under different economic and demographic settings. It remains unclear whether empirical findings obtained from US firms are also applicable to firms residing in other parts of the world. To answer this question, an empirical study was conducted to assess the impact of IT investment in firms operating in three economies (Hong Kong, Singapore, and Malaysia) in the Pacific Rim from 1983 to 1991. Our results indicate that while still small as a percentage of total capital compared with the United States, computer capital stock increased substantially in all economies during the period. Our production function estimates suggest that there are positive and excess returns in one of the three economies. Results of the analysis provide the basis to address issues such as national IT policy and the effect of economic dynamics on IT adoption     

Dynamic performance of ALOHA-type VSAT channels: a simulation study

A simulation study is presented of the dynamic behavior of ALOHA-type protocols used in interactive-data very small aperture terminal (VSAT) networks. A simulation model for quantitative evaluation of random access channel stability in terms of the transient response to a traffic overload pulse is described, and the usefulness of a single performance measure called backlog fall time is established. The variation of backlog fall time with selectable protocol parameters (such as average retransmission delay for nonadaptive systems or retransmission backoff policy parameters for adaptive systems) is investigated, for example, for ALOHA and selective reject ALOHA channels. A methodology for joint optimization of steady-state and dynamic performance based on obtaining contours of average delay versus backlog fall time over the variation range of selectable protocol parameters is outlined and demonstrated. It is shown that, generally speaking, a suitable operating point is easily identified from these contours because they exhibit a characteristic knee region in which both delay and fall time are close to the minimum values that can be independently obtained     

Magnetic resonance driven electrical impedance tomography: a simulation study

Magnetic resonance electrical impedance tomography (MREIT) is a method for reconstructing a three-dimensional image of the conductivity distribution in a target volume using magnetic resonance (MR). In MREIT, currents are applied to the volume through surface electrodes and their effects on the MR induced magnetic fields are analyzed to produce the conductance image. However, current injection through surface electrodes poses technical problems such as the limitation on the safely applicable currents. In this paper, we present a new method called magnetic resonance driven electrical impedance tomography (MRDEIT), where the magnetic resonance in each voxel is used as the applied magnetic field source, and the resultant electromagnetic field is measured through surface electrodes or radio-frequency (RF) detectors placed near the surface. Because the applied magnetic field is at the RF frequency and eddy currents are the integral components in the method, a vector wave equation for the electric field is used as the basis of the analysis instead of a quasi-static approximation. Using computer simulations, it is shown that complex permittivity images can be reconstructed using MRDEIT, but that improvements in signal detection are necessary for detecting moderate complex permittivity changes.     

Infinite-failure models for a finite world: a simulation study offault discovery

Many software reliability growth models have been published since the 1970s. Each one has been justified on theoretical or empirical evidence. A particularly interesting way of classifying these models is based on whether the asymptotic (time approaches infinity) mean number of total failures is infinite or finite. Theoretical and, especially, empirical justification for the appropriateness of infinite-failure models came after justification of finite-failure models. Infinite-failure models were associated with weak fault-repair systems or possibly with highly nonuniform usage. This paper demonstrates, through simulations of black-box testing and/or field use, that infinite-failure models are appropriate where there is perfect and near-perfect repair and where usage is uniform for the vast majority of the system, Therefore, infinite-failure software-reliability growth models have a place in the finite world of software and do not have to be associated with unusual and especially undesirable software characteristics     

The role of intramyocardial pressure during coronary sinusinterventions: a computer model study

A model consisting of an arterial, a capillary, and a venous compartment was developed to reproduce experimentally determined hemodynamic results of the arterial and venous sides of the coronary circulation. From the model, intramyocardial flow between capillaries and veins, which is inaccessable to measurement, was then estimated. Results are given for normal perfusion and coronary sinus occlusion conditions. For both conditions, intramyocardial pressure was varied within the model in order to study its impact on intramyocardial flow. For low and moderate intramyocardial pressures under coronary sinus occlusion, retrograde flow from veins to capillaries was seen to increase with increasing intramyocardial pressure. However, for very high values of intramyocardial pressure, which are close to left ventricular pressure, retrograde flow declined.     

Ad hoc routing protocol's performance: a realistic simulation based study

Multiple wireless devices jointly create and maintain ad hoc networks; their employment is favored to happen in a variety of environments with distinct topological characteristics. Diversified environmental conditions are expected to vary network performance. In fact, obstacles, buildings and/or mountains may act as either barriers, or source of noise for the radio signals. Nevertheless, most of the previous performance evaluation studies based on simulation, neglected this consideration; they used simulation models that were too simplistic, and too narrow (i.e. idealistic) in their scopes. With this paper we propose a new, complete and realistic Urban Mobility Model (UMM). It models realistically users motion, and radio signals propagation in a city-like scenario. Our aim is to study the effects of realistic network simulation on routing performance. The results prove that a realistic scenario with roads and buildings has a significant impact on routing.     

The sarnoff engine: A massively parallel computer for high definition system simulation

This paper describes the Sarnoff Engine, a 1.6 TeraFLOP, real-time, high definition, video and image processing computer. It is a second generation, scalable, linear array, multiuser, MIMD architecture focused on the applications of real-time high definition video and image processing (data compression encoders and decoders), 3D/4D data visualization, and neural network development.     

Generalized likelihood ratio tests for complex fMRI data: a simulation study

Statistical tests developed for the analysis of (intrinsically complex valued) functional magnetic resonance time series, are generally applied to the data's magnitude components. However, during the past five years, new tests were developed that incorporate the complex nature of fMRI data. In particular, a generalized likelihood ratio test (GLRT) was proposed based on a constant phase model. In this work, we evaluate the sensitivity of GLRTs for complex data to small misspecifications of the phase model by means of simulation experiments. It is argued that, in practical situations, GLRTs based on magnitude data are likely to perform better compared to GLRTs based on complex data in terms of detection rate and constant false alarm rate properties.