Autocalibration of multiprojector CAVE-like immersive environments

In this paper, we present the first method for the geometric autocalibration of multiple projectors on a set of CAVE-like immersive display surfaces including truncated domes and 4 or 5-wall CAVEs (three side walls, floor, and/or ceiling). All such surfaces can be categorized as swept surfaces and multiple projectors can be registered on them using a single uncalibrated camera without using any physical markers on the surface. Our method can also handle nonlinear distortion in the projectors, common in compact setups where a short throw lens is mounted on each projector. Further, when the whole swept surface is not visible from a single camera view, we can register the projectors using multiple pan and tilted views of the same camera. Thus, our method scales well with different size and resolution of the display. Since we recover the 3D shape of the display, we can achieve registration that is correct from any arbitrary viewpoint appropriate for head-tracked single-user virtual reality systems. We can also achieve wallpapered registration, more appropriate for multiuser collaborative explorations. Though much more immersive than common surfaces like planes and cylinders, general swept surfaces are used today only for niche display environments. Even the more popular 4 or 5-wall CAVE is treated as a piecewise planar surface for calibration purposes and hence projectors are not allowed to be overlapped across the corners. Our method opens up the possibility of using such swept surfaces to create more immersive VR systems without compromising the simplicity of having a completely automatic calibration technique. Such calibration allows completely arbitrary positioning of the projectors in a 5-wall CAVE, without respecting the corners.     

Analysis of time-dependent flow-sensitive PC-MRI data

Many flow visualization techniques, especially integration-based methods, are problematic when the measured data exhibit noise and discretization issues. Particularly, this is the case for flow-sensitive phase-contrast magnetic resonance imaging (PC-MRI) data sets which not only record anatomic information, but also time-varying flow information. We propose a novel approach for the visualization of such data sets using integration-based methods. Our ideas are based upon finite-time Lyapunov exponents (FTLE) and enable identification of vessel boundaries in the data as high regions of separation. This allows us to correctly restrict integration-based visualization to blood vessels. We validate our technique by comparing our approach to existing anatomy-based methods as well as addressing the benefits and limitations of using FTLE to restrict flow. We also discuss the importance of parameters, i.e., advection length and data resolution, in establishing a well-defined vessel boundary. We extract appropriate flow lines and surfaces that enable the visualization of blood flow within the vessels. We further enhance the visualization by analyzing flow behavior in the seeded region and generating simplified depictions.     

Analysis of nonlinear electrical circuits using bernstein polynomials

In electrical circuit analysis, it is often necessary to find the set of all direct current (d.c.) operating points (either voltages or currents) of nonlinear circuits. In general, these nonlinear equations are often represented as polynomial systems. In this paper, we address the problem of finding the solutions of nonlinear electrical circuits, which are modeled as systems of n polynomial equations contained in an n-dimensional box. Branch and Bound algorithms based on interval methods can give guaranteed enclosures for the solution. However, because of repeated evaluations of the function values, these methods tend to become slower. Branch and Bound algorithm based on Bernstein coefficients can be used to solve the systems of polynomial equations. This avoids the repeated evaluation of function values, but maintains more or less the same number of iterations as that of interval branch and bound methods. We propose an algorithm for obtaining the solution of polynomial systems, which includes a pruning step using Bernstein Krawczyk operator and a Bernstein Coefficient Contraction algorithm to obtain Bernstein coefficients of the new domain. We solved three circuit analysis problems using our proposed algorithm. We compared the performance of our proposed algorithm with INTLAB based solver and found that our proposed algorithm is more efficient and fast.     

Some investigations on fuzzy P + fuzzy I + fuzzy D controller for non-stationary process

The paper addresses the adaptive behaviour of parallel fuzzy proportional plus fuzzy integral plus fuzzy derivative (FP+FI+FD) controller. The parallel FP+FI+FD controller is actually a non-linear adaptive controller whose gain changes continuously with output of the process under control. Two non-stationary processes, whose characteristics change with time, are considered for simulation study. Simulation is performed using software LabVIEW TM . The set-point tracking response of parallel FP+FI+FD is compared with conventional parallel proportional plus integral plus derivative (PID) controller, tuned with the Ziegler-Nichols (Z-N) tuning technique. Simulation results show that conventional PID controller fails to track the set-point and becomes unstable as the process changes its characteristic with time. But the parallel FP+FI+FD controller shows considerably much better set-point tracking response and does not deviate from steady state. Also, a huge spike is observed in the output of PID controller as the reference set-point and process parameters are changed, while the FP+FI+FD controller gives spike free control signal.     

Automated analysis for scintigraphic evaluation of gastric emptying using invariant moments

This study introduces a method for automated analysis of the standard solid-meal gastric emptying test. The purpose was to develop a diagnostic tool to characterize more reproducibly abnormalities of solid-phase gastric emptying. The processing of gastric emptying is automated using geometrical moments that are invariant to scaling, rotation, and shift. Twenty subjects were studied. The first step was to obtain images of the stomach using a nuclear gamma camera immediately after the subject had eaten a radio-labeled meal. The second step was to process and analyze the images by a recently developed automated gastric emptying analysis (AGEA) method, which determines the gastric contour and the geometrical properties include such parameters as area, centroid, orientation, and moments of inertia. Statistical tests showed that some of the moments were sensitive to the patient's gastric status (normal versus abnormal). The difference between the normal and abnormal patients became noticeable approximately 1 h after meal ingestion.     

Ultrasonic phased-array scanner with digital echo synthesis for Doppler echocardiography

For the purpose of the quantitative assessment of subtle disease processes in the cardiovascular system an electronically steered sector scanner that combines echographic imaging and Doppler blood velocity measurements has been developed. The integrated operation of a fast Fourier transform (FFT) Doppler signal processor for the simultaneous blood velocity evaluation of 64 individual gates is among the specific design goals. The instrument incorporates an unusually high degree of digital signal processing, which allows for high integration density, easy manufacturing and high reliability in future designs. The complex Doppler spectra are determined for each of the 64 Doppler gates in real time, and the subsequent computation of the first moment provides a reliable estimate of the mean blood flow velocities at the respective locations. The instantaneous velocity profile along the Doppler beam is displayed together with the calculated volume flow rate and a range-selected complete frequency spectrum. Results of both in vitro and in vivo tests indicate that in the future, a higher degree of digital signal processing could be implemented in complex ultrasonic systems.     

A new mechanism of ultrasonic absorption in aqueous solutions of rigid macromolecules

The temperature- and frequency-dependences of the ultrasonic absorption in lyotropic liquid crystals of rod-like FD virus particles have been measured with the ultrasonic beam being parallel or perpendicular to the rod axis. The experimental results show a strongly anisotropic ultrasonic absorption in the lyotropic liquid crystals, which varies with temperature exactly as the shear viscosity of water. Experimental results are in good agreement with the following model for the absorption process. The authors believe that the absorption arises from differential flow of water between the relatively long and rigid rod-like macromolecules. This mechanism of ultrasonic absorption becomes dominant for frequencies of 1-100 MHz. The validity of this mechanism is, however, not restricted to the special lyotropic crystals discussed here. Instead, this absorption process is expected to be important also for other macromolecular solutions whenever the dissolved macromolecular objects have a sufficiently large linear dimension in the direction parallel to the sound beam.     

Unusual W-shaped Galvanic Cell Model of ISCC of α-brass in Neutral Mattsson''''s Solution

Intergranular stress corrosion cracking(ISCC) of α-brass in neutral Mattsson's solutionwas found to be controlled by an unusual"W"-shaped galvanic cell whose cathode is thegrain boundary oxide film (G.B.0. film) andsurface film and the anode is fresh metal atthe cracked tip on both sides of the G.B.0.film. Redox reactions involved in the cellhave been proposed here. According to thismdel, initidtion of ISCC is caused by therupturing of surface film along grain boundaries,thus forming a galvanic cell. Propagation ofISCC resulted from alternate advances of G.B.0.film and dissolution on both sides of G.B.0.film caused by the effect of electrochemicalreaction. This work developed an effective approachto investigate the embrittlement process atthe tip of the crack, by increasing the lengthof the embrittlement region through constantstrain test and distinguishing the morphologyand the nature of the corrosion products byoptical microscopy and scanning electronmicroscopy (SEH).     

Portability of three consumer products

Three consumer products (a television set, a personal computer and a typewriter), all considered portable by their respective manufacturers, were evaluated experimentally for portability. Products were not considered portable if the physical and subjective workloads resulting from carrying them over specified distances were excessive. Twenty-two males and six females participated in the experimental investigation and carried the three products for distances of 45·72, 91·44. 137·16 and 182·88 m. Their pulse and ratings of perceived exertion (RPE) of the arms and whole body were recorded and used as measures of physical and perceived workloads. Both physiological and subjective responses to carrying products were significantly influenced by the type of product and carrying distance, regardless of the gender of the person performing the carrying. The results of this study and the design guidelines provided in the literature for one-handed and two-handed carrying tasks led to the conclusion that, of the three products, only the television set could be considered portable.     

Effect of added water, sodium erythorbate and storage time on the functional properties of prerigor beef preblends in a model system

Singular and combined effects of added water, sodium erythorbate and storage time on salt soluble protein extractability, bacteriological and chemical characteristics of preblended hot-boned beef were evaluated. Waterholding and gel forming capacities of preblended hot-boned beef containing either 0, 10 or 20% added water were determined. Significant interactions between added water level and storage time on microbial counts and between sodium erythorbate level and storage time on thiobarbituric acid values and residual nitrite levels were noted. The presence of sodium erythorbate resulted in a more (P < 0·05) rapid rate of nitrite disappearance, but it did not affect (P > 0·05) microbial counts. Salt-soluble protein extractability was not affected (P > 0·05) by added water, but more protein could be extracted with increasing storage time. A trend existed to suggest that the presence of added water in the meat preblends slightly improved the gel formation and waterholding capacities.