SUMMARY An s-t ow in a directed network is called \un-controllable", when the ow is representable as a positive sum of elementary s-t path ows. In this paper, we discuss the problem \Is a given ow uncontrollable?". We show that the problem is NP-complete. 1. Introduction Recently, Iri proposed a new type of network ow theory [1], where only those ows which are representable as a positive sum of...

We show that if a ow network has k input/output terminals (for the traditional maximum-ow problem , k = 2), its external ow pattern (possible values of ow at the terminals) has two characterizations of size independent of the total number of vertices: a set of at most 2 k inequalities in k variables representing ow values at the terminals, and a mimicking network with at most 2 2 k vertices and...

This paper reports on Web users' optimal ̄ow experiences (Csikszentmihalyi, 1975b) in the Web environment. The concept of ̄ow was employed to see if there were some positive aspects of Web experiences that could be linked to theory applied to other media and then incorporated into Web design to enhance its utility to users. The notions of the Web as a `multi-activity medium' and a view of the W...

In this paper we will present a method for computation of optical ow elds in which we take advantage of the concept of scale. We believe that it is possible to extract optical ow elds from normal ow elds, by tting the normal components of a local polynomial model of the optic ow to the normal ow eld. This tting is based on an analytically solvable variational optimisation problem, in which an i...

The Sparse Evaluation Graph has emerged over the past several years as an intermediate representation that captures the data ow information in a program compactly and helps perform data ow analysis e ciently. The contributions of this paper1 are three-fold: We present a linear time algorithm for constructing a variant of the Sparse Evaluation Graph for any data ow analysis problem. Our algorith...

Abstract The rising generation of organic waste (OW) can be a concern, representing at the same time valuable opportunity for phosphorous (P) recycling; however, yet little is known about plant-available P release from this source. In work, two anaerobic digestates, agro- (AW D ) and bio-waste (BW ), their respective composts C BW were selected to assess P-release via sequential chemical extrac...

Background Individuals with overweight and obesity (OW/OB) have poor performance in weight-bearing exercises, resulting low functional capacity. The dynamic neuromuscular stabilization (DNS) technique was created to engage the core-postural chain conjunction core muscles, generating enough intra-abdominal pressure dynamically support spine through muscular activity. DNS is a strategy that empha...

We show that if a ow network has k input/output terminals (for the traditional maximum-ow problem, k = 2), its external ow pattern (the possible values of ow into and out of the terminals) has two characterizations of size independent of the total number of vertices: a set of 2 k + 1 inequalities in k variables representing ow values at the terminals, and a mimicking network with at most 2 2 k ...

Pedestrian counter $ow is investigated by experiment and simulation. The experiment is performed for the channel with open boundaries. Two types of walkers, going to the right and to the left, are taken into account. The video recordings and measurements of individual arrival times are evaluated. The pattern formation and jamming transition are discussed. The experiment is mimicked by the latti...

This model is motivated by the need to explain anomalous features associated with production from reservoirs of so-called foamy oils. These oils are described by some of their properties of response to pressure declines; it is noted that they nucleate dispersed gas bubbles and display obvious foaminess in well head samples produced by solution gas drive in which oil and gas is produced by the d...