Program analysis with partial transfer functions

This paper proposes an efficient technique for context-sensitive pointer analysis that is applicable to real C programs. For efficiency, we summarize the effects of procedures using partial transfer functions. A partial transfer function (PTF) describes the behavior of a procedure assuming that certain alias relationships hold when it is called. We can reuse a PTF in many calling contexts as long as the aliases among the inputs to the procedure are the same. Our empirical results demonstrate that this technique is successful—a single PTF per procedure is usually sufficient to obtain completely context-sensitive results. Because many C programs use features such as type casts and pointer arithmetic to circumvent the high-level type system, our algorithm is based on a low-level representation of memory locations that safely handles all the features of C. We have implemented our algorithm in the SUIF compiler system and we show that it runs efficiently for a set of C benchmarks.

It is shown that two properties of rational transfer functions with real coefficients are realized by means of a single complex IIR digital filter. Equivalently, the real and imaginary parts of output from a complex filter for a real input sequence correspond to real coefficient transfer function respectively. In a real signal processing, a delay operator z/sup -1/ corresponds to a real operation. In this case, a complex transfer function is formed by connecting two real transfer functions with an imaginary unit. These real functions are approximated to the desired properties and are expressed by a complex coefficient transfer function.

Physically based realistic direct volume rendering (DVR) is a critical area of research in scientific data visualization. The prevailing realistic DVR methods are primarily rooted in outdated theories of participating media rendering and often lack comprehensive analyses of their applicability to realistic DVR scenarios. As a result, the fidelity of material representation in the rendered output is frequently limited. To address these challenges, we present a novel multi-material radiative transfer model (MM-RTM) designed for realistic DVR, grounded in recent advancements in light transport theories. Additionally, we standardize various transfer function techniques and propose five distinct forms of transfer functions along with proxy volumes. This comprehensive approach enables our DVR framework to accommodate a wide range of complex transfer function techniques, which we illustrate through several visualizations. Furthermore, to enhance sampling efficiency, we develop a new multi-hierarchical volumetric acceleration method that supports multi-level searches and volume traversal. Our volumetric accelerator also facilitates real-time structural updates when applying complex transfer functions in DVR. Our MM-RTM, the unified representation of complex transfer functions, and the acceleration structure for real-time updates are complementary components that collectively establish a comprehensive framework for realistic multi-material DVR. Evaluation from a user study indicates that the rendering results produced by our method demonstrate the most realistic effects among various publicly available state-of-the-art techniques.

Differential mode delay and modal bandwidth measurements of multimode fibers using frequency-domain method

Chapter 9 - Frequency-Domain Approach

Physical structures separate the ears of many mammals, and the ears themselves have complex transfer functions that depend upon the direction of a sound source. Neither of these observations is usually incorporated into standard array analysis. The conventional array problem generally assumes that individual elements are omnidirectional, and there are no physical structures between elements to provide partial isolation. This investigation of binaural angle estimation specifically incorporates the effects of partial isolation and directivity patterns that vary with angle and frequency. Cramér–Rao bounds for the variance of maximum likelihood angle estimates are derived. These bounds, along with a generalized ambiguity function, are used to evaluate the significance of isolation between the ears, angle-dependent magnitude, and phase variations in the spatial transfer functions of the ears, the use of wide-band and narrow-band signals in animal echolocation, symmetry of aural directivity patterns, the transmitted beam patterns that are employed by certain bats, and the angle-dependent signal variations that have been observed in cetacean echolocation. Only two broadband hydrophones are sufficient for accurate, unambiguous azimuth measurement if the width of the signal autocorrelation function is small relative to the distance between hydrophones. The analysis indicates that many past measurements of transmitted beam patterns and aural transfer functions in animals are incomplete, since they do not consider direction-dependent phase variations. It may also be necessary to reinterpret the meaning of time difference and pressure difference cues for localization. These insights can be used not only for better correlation of behavioral and physiological measurements, but also for better design of man-made systems for communication, radar, sonar, and ultrasonic medical diagnosis.

Effect of kinetic regime and axial dispersion on the dynamic response of counter flow extractive reactors

The electrical impedance of trigeminal ganglion cells (in vivo) and hippocampal CA1 neurons (in vitro) of guinea pigs was measured in the frequency range of 5-1250 Hz using intracellular recording techniques with single microelectrodes and computerized methodology. The transfer functions of the electrode and the electrode-neuron system were computed from the ratio of fast Fourier transforms of the output voltage response from the neuron and input current composed of sine waves with rapidly increasing frequency which displaced membrane potential by 2-5 mV. We believe these to be the first measurements of complex impedance and transfer functions in peripheral and central neurons of vertebrates and the first use of such input current functions. The majority of trigeminal ganglion cells did not exhibit electrical behaviour ascribable to a simple resistance-capacitance (RC) circuit but showed a hump at low frequencies (5-250 Hz) in the computed transfer function, probably attributable to resonance. The transfer function in less than 20% of the trigeminal neurons could be fitted approximately to a theoretical transfer function (resistance in series with a parallel RC circuit model) providing values for electrode resistance, effective input resistance, and effective input capacitance. The transfer functions measured in hippocampal CA1 neurons were characterized by a rapid fall-off in the low frequency range (less than 200 Hz). Impedance locus plots approximate the locus corresponding to a series RC circuit in parallel with a parallel RC circuit.

This paper deals with simplified mathematical models of the dynamic systems with weak non-linearities and described by complex continuous transfer functions without jumping. We consider only the first approximation of the steady state forced vibration where the complex amplitude corresponds to the same frequency as the harmonic excitation. The iterative smoothing of the above system from the measured transfer function at discrete frequency points and especially from their moduli is proposed. The aim of this method is to determine the complex eigenvalues of the systems with Duffing-type stiffness behaviour (only their imaginary parts depend on the squares of the absolute values of the amplitudes) and real modal parameters in situations when no-phase difference between output and input is known. If the complex transfer function is completely known, the identified complex eigenvalues are assumed to be linear and quadratic functions of absolute values of amplitudes and the modal parameters are complex.

To study the importance of certain factors involved in the genesis of the ballistocardiogram, the transfer function relating the blood flow in the ascending aorta and the velocity ballistocardiogram has been measured in dogs. This complex transfer function is determined by the characteristics of the arterial system such as pulse wave velocity, anatomical distribution of the blood vessels etc. The transfer function is also a function of the mutual coupling of body parts and the supporing platform. A similar study has been performed on an electrical analogue of the human systemic arterial tree. A striking similarity between the moduli of the transfet functions obtained from the animal study and from the study on the analogue was found.

Many methods have been proposed for small-signal stability analysis of power-electronic-based power systems. As one common method, the sequence impedance model stands on that the disturbances are in the form of harmonics, which seems not consistent with the basic small-signal stability theory. In this paper, firstly small disturbances of any forms are applied to the three-phase voltage. By a rigorous Laplace transform, the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\alpha\beta$</tex> impedance of the power electronic device is obtained, both in the form of transfer function matrix and complex transfer function. Then, the equivalence between the proposed model, the sequence impedance model, and the complex transfer function model are obtained. Finally, the open-loop response of a voltage source converter (VSC) and the stability of its grid connected system are verified by simulation. Based on the detailed analysis in the paper, it has been proved that the sequence impedance model is suitable for small-signal stability analysis of power-electronic-based power systems under not only harmonic disturbances but also any forms of disturbances, standing on a more rigorous mathematical basis.

The effect on the photographic image due to complex types of relative motions between the image and the film during the time of exposure can be expressed in terms of complex transfer functions.The complex transfer functions have been found for both quadratic relative motion and uniform accelerated relative motion with superimposed oscillations. In case of quadratic motion it is seen that there is further image degradation due to the presence of the quadratic component of velocity but the general nature of degradation is basically the same. In the second case the basic nature of image degradation is found to be different from that due to quadratic motion, and the transfer

The article deals with the problem of using the method of optical spatial filtration, applied at present in radiodiagnosis for solving a number of problems connected with image processing in order to reduce the influence of disturbances, to compensate the transfer functions, etc. The process of the formation of roentgen shadow projection is described by integral equations. In this way the possibility for correcting a posteriori the transfer characteristics of the processes of the formation and fixation of roentgenograms has been revealed, and the maximum dimensions of objects capable of being successfully processed by spatial filtration, as well as the necessary filtering functions of the correction filter, have been determined. The problem of measuring the transfer characteristics of radiodiagnostic systems is discussed, and the method of measuring the complex transfer function, suitable for the spatial variant system, is proposed. On the basis of a short review of publications on this problem, and taking into consideration the above analysis, the trends of using the methods of optical filtration are determined. The authors believe that these methods used within the determined trends may improve the quality of roentgen images and, in the end, the diagnostic value of roentgenograms.

Analysis of complex transfer functions poles (CTFP) is formulated in this paper to complete the application of complex transfer function (CTF) in 3-phase current control analysis. It serves as a straightforward tool to directly compare and analyze the transient responses of various current control strategies implemented on different reference frames, which conventional pole analysis of real transfer functions (RTFs) or bode diagram fail to capture.

The implementation of paraxial diffractive elements with complex transfer functions is a difficult problem since current technologies impose restrictions to certain modulation domains. In optical information processing, addressable spatial light modulators are already used to implement diffractive elements. The spatial resolution of such modulators is strongly limited. Moreover, they are restricted to a certain modulation domain. In this paper, we examine how to make optimal use of the available space-bandwidth product of an SLM to realize optical functions on the basis of encoding methods in diffractive optics. Theoretical considerations are documented by an example, where a classical matched filter is encoded into a diffractive phase element.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.