Scientia Iranica
Volume:18 Issue: 6, 2011

ANSI RBAC is a standard for a consistent and uniform definition on Role Based Access Control features and their functional specifications ANSI (2004) [1]. We analyze both static and dynamic separation of duty constraints specifications in the ANSI RBAC standard and evaluate their reliabilities. We then suggest necessary improvements for making them completely reliable.

In this paper, we present an adaptive method that is a combination of SEU-avoidance in CAD flow and adaptive redundancy to tolerate soft error effects in SRAM-based FPGAs. This method is based on the modification of T-VPack and VPR tools. Three different steps of these tools are modified for SEU-awareness: (1) clustering, (2) placement and (3) routing. Then we use the unused resources as redundancy. We have investigated the effect of this method on several MCNC benchmarks. This investigation has been performed using three experiments: (1) SEU-awareness in clustering with redundancy, (2) SEU-awareness in clustering and placement with redundancy and (3) SEU-awareness in clustering, placement and routing with redundancy. With a confidence level of 95%, the results show that, using each of these three experiments, the system failure rate of ten MCNC circuits has been decreased between 4.52% and 10.42%, between 10.25% and 21.63%, and between 10.48% and 24.39%, respectively.

Due to many applications of multi-objective evolutionary algorithms in real world optimization problems, several studies have been done to improve these algorithms in recent years. Since most multi-objective evolutionary algorithms are based on the non-dominated principle, and their complexity depends on finding non-dominated fronts, this paper introduces a new method for ranking the solutions of an evolutionary algorithm’s population. First, we investigate the relation between the convex hull and non-dominated solutions, and discuss the complexity time of the convex hull and non-dominated sorting problems. Then, we use convex hull concepts to present a new ranking procedure for multi-objective evolutionary algorithms. The proposed algorithm is very suitable for convex multi-objective optimization problems. Finally, we apply this method as an alternative ranking procedure to NSGA-II for non-dominated comparisons, and test it using some benchmark problems.

In this research, we have investigated improvement in the accuracy and robustness of phoneme recognition by refining posterior features extracted from single stream cepstral features. The refinement process is done using Multi Layer Perceptron (MLP) in a cascaded structure. The combination of frame posterior feature vectors, along with the entropy of each frame, as a confidence measure of posterior vectors, in the context window, is used to train a refiner MLP for estimating a new phoneme posterior feature set with the advantage of more accuracy and robustness. The confidence measure, as an informative feature, would enhance the refiner MLP performance in the correction of misclassified frames. The refiner MLP also models language level phonetics and lexical knowledge, using embedded information in the phoneme posteriors of a large context window. The suitability of these refined posterior features is evaluated on the tandem connectionist structures. Results show a significant improvement in both frame classification and phoneme recognition rates on the TIMIT acoustic and phonetic corpus compared to standard posterior features.

Object handover as continually tracking an object across disjoint-view cameras is a necessary part of video-based monitoring systems. While having nonoverlapping cameras is a requirement for monitoring a wide area, there is no common 3D location that can be used to detect multiple views of the same object, in contrast with overlapping cameras. Appearance features play an important role for object handover in such camera networks. This paper focuses on modeling appearance features of moving vehicles by a new major color representation called codebook representation. Toward this end, in each frame, the k-means algorithm is used to cluster major colors of an object. In the subsequent frames, a set of cylinders in the RGB space called codebook keeps the track of these major colors for incremental clustering. Then, in the matching phase, a similarity measurement for comparing different codebook sets discriminates major colors of observations. In addition, a brightness transfer function is developed for mapping cylinders between two camera views. By this mapping, the model can tolerate the illumination change of environments. The method is fast enough to be used in real-time applications. Experimental results show the efficiency of the proposed methods on real datasets.

Self-Organizing Maps (SOMs) are among the most well-known, unsupervised neural network approaches to clustering, which are very efficient in handling large and high dimensional datasets. The original Particle Swarm Optimization (PSO) is another algorithm discovered through simplified social model simulation, which is effective in nonlinear optimization problems and easy to implement. In the present study, we combine these two methods and introduce a new method for anomaly detection. A discussion about our method is presented, its results are compared with some other methods and its advantages over them are demonstrated. In order to apply our method, we also performed a case study on forest fire detection. Our algorithm was shown to be simple and to function better than previous ones. We can apply it to different domains of anomaly detection. In fact, we observed our method to be a generic algorithm for anomaly detection that may need few changes for implementation in different domains.

Multiple ablation technologies are used to provide atrial fibrillation therapy during cardiac surgery. A rigorous search was performed to identify all peer-reviewed papers that provided clinical outcome data following ablation therapy. A META analysis showed significant differences in clinical outcome by ablation technology: clinicians, using temperature-controlled RF power delivery, achieved higher rates of normal sinus rhythm at follow-up, and patients ablated with microwave ablation had lower rates of normal sinus rhythm than the average of all ablation-treated patients. Permanent pacemaker implantation rates were higher than average for patients treated with microwave or argon-based cryoablation technologies, but were lower than the average for patients treated using temperature-controlled RF.

The Tongue Display Unit (TDU) is a 144-channel programmable pulse generator that delivers dc-balanced voltage pulses suitable for electrotactile (electrocutaneous) stimulation of the anterior-dorsal tongue, through a matrix of surface electrodes. This article reviews the theory of operation and a design overview of the TDU, as well as selected applications. These include sensory substitution, tactile information display and neurorehabilitation via induced neuroplasticity.

Analytical Jacobian, nonlinear least square and three layer artificial neural network models are employed to predict deformation of mouse embryos under needle injection, based on experimental data captured from literature. The Maximum Absolute Error (MAE), coefficient of determination (R2), Relative Error of Prediction (REP), Root Mean Square Error of Prediction (RMSEP), Nash–Sutcliffe coefficient of efficiency (Ef) and accuracy factor (Af) are used as the basis for comparison of these three models. Analytical Jacobian, nonlinear least square and ANN models have yielded the correlation coefficient of 0.9985, 0.9964 and 0.9998, respectively. The REP between the models predicted values and experimental observations are 2.8228(%), 4.7647(%) and 0.4698(%) for the analytical Jacobian, nonlinear least square and ANN methods, respectively. Results showed that ANN performed relatively better than the analytical Jacobian and nonlinear least square methods. Findings indicate that the ANN technique can predict mouse embryo dimple depth by needle injection with considerable accuracy and the least error.

The goal of this study is to investigate the mechanotransduction of an external load to the brain and the causation of concussion and Traumatic Brain Injury (TBI). However, as one step toward this goal, in this paper, the investigation of the material model selection and material properties of the subarachnoid space (SAS) are presented. As the interface between the skull and the brain, the material modeling of SAS plays an important role in the analysis of damping and movement of the brain within the skull, leading to TBI. Based on the histology and morphology of the SAS region, three material types, namely, soft solid, viscous fluid and porous media were proposed. To validate these material models, the relative displacement between the skull and the brain was compared with the experimental study. It was concluded that the optimum material properties of the three material models are for soft solid material,, for viscous fluid,, and for porous media, the permeability of 3.125×10−10 m2. The results indicated that the properties determined in this study for the three material models are appropriate and reliable for future investigations. That is, if one decides to use any of these materials to model the SAS, in local or global FE analyses, these values are suitable.

For monitoring pulmonary edema secondary to Congestive Heart Failure (CHF), we investigated trends of impedance between implanted electrodes. ICDs were implanted in 16 dogs and 5 sheep. Right ventricles were paced (230–250 bpm) for several weeks. Impedance was measured every hour along 4 intrathoracic, 2 intracardiac and 4 cardiogenic vectors. Cardiac function was assessed biweekly by catheterization and echocardiography. Left Atrial Pressure (LAP) was measured daily by an implanted sensor. All animals developed CHF after 2–4 weeks of pacing (EF, 52 vs. 34%; LVEDV, 65 vs. 97 ml; LVEDP, 7 vs. 16 mm Hg; LAV, 17 vs. 33 ml; LAP, 7 vs. 26 mm Hg). Impedance decreased during CHF: LV-Can, 17±9%; LV–RV, 15±8%; LV–RA, 13±6%; RV-Can, 13±8%; RV coil-Can, 8±6%; RA-Can, 6±6%. The LV-Can decrease was greatest and correlated well with LAP (r2=0.73). All impedances were associated with circadian variability at the baseline, which diminished during CHF (5±2% vs. 2±1%). In CHF, cardiogenic impedances displayed reduced peak-to-peak amplitude and increased fractionation. As impedance decreased during CHF, left-heart trends were better correlated with LAP. Left-heart vectors may improve the detection of CHF compared to sensing by right-heart leads alone. This approach has important clinical implications for managing HF patients in ambulatory settings.

Magnetic Resonance Electrical Impedance Tomography (MREIT) aims to produce cross-sectional images of conductivity distributions inside animal and human subjects. In this study, we validate its feasibility by performing conductivity imaging experiments of post-mortem canine bodies. After clipping the hair of a beagle, we attached four carbon–hydrogel electrodes and placed the dog inside our 3T MRI scanner. We injected the imaging current in the form of short pulses into the imaging area, the timing of which was synchronized with a chosen pulse sequence. By obtaining images of the induced magnetic flux density distributions inside the dog, we reconstructed conductivity images using the single-step harmonic Bz algorithm based on the relationship between conductivity and magnetic flux density. Reconstructed conductivity images of heart, kidney, prostate, and other organs exhibited unique contrast information hardly observed in other imaging modalities. By providing cross-sectional conductivity images with a spatial resolution of a few millimeters, MREIT may deliver unique new diagnostic information in future clinical studies.

Biopotential is an electrochemical potential that has been shown to correlate well with the coagulation zone size during cardiac RF catheter ablation. We designed an in vivo experiment to test the hypothesis that a similar correlation exists during hepatic RF ablation. We created coagulation zones, in vivo, in porcine liver, with 17 gauge needle electrodes, using RF ablation (n=56). The power was set constant at 30 W, controlled by impedance, and applied for 60, 120 or 180 s. We measured the biopotential between the electrode and the ground pad with low-pass filtering. The diameter and volume of the coagulation zone were measured and correlated with the change in biopotential between the beginning and end of each ablation procedure. Moderate correlation between biopotential change and both coagulation zone volume (R2=0.43) and diameter (R2=0.31) was observed. The time constant of the biopotential change was not significantly different from the time constant of the ablation zone diameter (36.6 s, p=0.93); the biopotential may, therefore, predict the time course of the ablation zone diameter. The biopotential can potentially be used for intraprocedural monitoring of the progression of the thermal damage zone. It may also allow termination of the procedure, if it can be confirmed that the biopotential reliably correlates with the cessation of ablation zone expansion.