A matrix of zeroes and ones is said to have the consecutive ones property if there is a permutation of its rows such that the ones in each column appear consecutively. This paper develops a data structure which may be...
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The interpretation of tracer kinetic data obtained by external monitoring of radioactively-labeled indicators is generally based on mathematical models that ignore recirculation. An important limitation of these model...
The interpretation of tracer kinetic data obtained by external monitoring of radioactively-labeled indicators is generally based on mathematical models that ignore recirculation. An important limitation of these models is that they can be used successfully only in those situations in which the major portion of the response curves are obtainable prior to the onset of the first recirculation. A further complication that limits the usefulness of the models is due to interference from radiotracers carried by recirculation into adjacent perfused regions also within the field of view of the detector. In this paper, we develop a mathematical model applicable for measuring blood flow per unit volume and determining transit-time distributions by external monitoring when recirculation is not a late event and must be taken into consideration. Additionally, the model accounts for interfering recirculation of tracer to adjacent perfused regions in the field of view of the detector. Central to the model is the use of two injections of tracer: one upstream (arterial) and one downstream (venous) of the particular organ or region of interest. Thus, two residue curves are obtained. We develop equations indicating how to employ the two residue curves in order to determine the mean transit time of tracer through the vascular system of interest, as well as higher moments of the transit-time distribution if they are desired. These equations are natural generalizations of Zierler's residue-detection method in that they do not depend for their validity on any model of mass transport within the system of interest. The numerical calculations implied by our equations need not rely on curve-fitting of the data. In addition to mean flow per unit volume, our method can yield compartmental parameters if these are appropriate and desired.
According to behavior of current, equiangular-spiral antenna may be divided into three distinct regions;since positions of these regions are frequency independent, it is possible to obtain complete description of curr...
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According to behavior of current, equiangular-spiral antenna may be divided into three distinct regions;since positions of these regions are frequency independent, it is possible to obtain complete description of current distribution on almost all practical equiangular-spiral antennas by set of curves, which is given in this paper;regions that are characterized by differences in variational formulation of input impedance of antenna are also presented;variational method using approximate current provided by set of curves gives quick, direct means of finding input impedances.
Mathematical and statistical models have played important roles in neuroscience, especially by describing the electrical activity of neurons recorded individually, or collectively across large networks. As the field m...
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Mathematical and statistical models have played important roles in neuroscience, especially by describing the electrical activity of neurons recorded individually, or collectively across large networks. As the field moves forward rapidly, new challenges are emerging. For maximal effectiveness, those working to advance computational neuroscience will need to appreciate and exploit the complementary strengths of mechanistic theory and the statistical paradigm.
Advances in sensing, signal processing, and computer technology during the past half century have stimulated numerous attempts to design general-purpose ma chines that see. These attempts have met with at best m...
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ISBN:
(数字)9781461239840
ISBN:
(纸本)9780387945637;9781461284604
Advances in sensing, signal processing, and computer technology during the past half century have stimulated numerous attempts to design general-purpose ma chines that see. These attempts have met with at best modest success and more typically outright failure. The difficulties encountered in building working com puter vision systems based on state-of-the-art techniques came as a surprise. Perhaps the most frustrating aspect of the problem is that machine vision sys tems cannot deal with numerous visual tasks that humans perform rapidly and effortlessly. In reaction to this perceived discrepancy in performance, various researchers (notably Marr, 1982) suggested that the design of machine-vision systems should be based on principles drawn from the study of biological systems. This "neuro morphic" or "anthropomorphic" approach has proven fruitful: the use of pyramid (multiresolution) image representation methods in image compression is one ex ample of a successful application based on principles primarily derived from the study of biological vision systems. It is still the case, however, that the perfor of computer vision systems falls far short of that of the natural systems mance they are intended to mimic, suggesting that it is time to look even more closely at the remaining differences between artificial and biological vision systems.
One of the methods that are used for increasing accelerator force of projectile in the railgun is the increasing of inductance gradient. Essentially, the inductance gradient is determined by current density in rails a...
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