On the simplex algorithm for networks and generalized networks

Bibliography: p. 21-22.by James B. Orlin

Improved primal simplex algorithms for shortest path, assignment and minimum cost flow problems

"November 1988."Includes bibliographical references (p. 24-26).Ravindra K. Ahyja and James B. Orlin

A polynomial time primal network simplex algorithm for minimum cost flows

Cover title.Includes bibliographical references (p. 25-27).Supported by ONR. N00014-94-1-0099 Supported in part by a grant from the UPS foundation.by James B. Orlin

The characterisation and analysis of in-situ and blasted block-size distributions and the blastability of rock masses.

PhDIn this thesis, previous research on discontinuity geometry, in-situ block size distribution (IBSD), blasted block size distribution (BBSD), and blastability of rock mass is discussed. The IBSD with special reference to discontinuities with a fractal spacing distribution is investigated using computer simulation, from which a set of empirical equations is derived for predicting the IBSD of a rock mass with discontinuities of fractal spacing distributions. The goodness-of-fit of theoretical as compared with real spacing distributions is discussed and a grey correlation analysis technique is introduced into the goodness-of-fit. An estimation of mean trace length of discontinuities with lognormal and fractal distributions is derived. A numerical algorithm and associated computer program for estimating the discontinuity size distribution is developed from which empirical equations for estimating the mean size of discontinuities with negative exponential, lognormal and fractal trace length distributions have been derived. A factor which accounts for the discontinuity impersistence is incorporated into the estimation of IBSD. Combining both Ross-Ram and Schuhmann models, a reasonably accurate and user-friendly "photo-scanline" technique is devised for the estimation of BBSD of the blastpile. Blasting results, as a function of both the intact rock properties and the discontinuity structures are investigated, and an energy-block-transition model characterising the blastability of rock masses is developed. It is argued that the blastability of rock mass is governed by a comprehensive range of both intact rock properties and discontinuity parameters, and that the fractal dimension of the IBSD of a rock mass could be an indicator of blastability. Taking into account that blastability is a complex property, a methodology of assessing blastability of rock masses is introduced using a Rock Engineering Systems method. Published data from the literature has been used wherever possible to support the validation of the new techniques of analysis and two case histories in which applications of the developed methodologies and techniques are presented

Suggestions for Genetic A.I.

This paper presents suggestions for "Genetic A.I.": an attempt to model the genesis of intelligence in human infants, particularly as described by Piaget's theory of the Sensorimotor period. The paper includes a synopsis of Sensorimotor intelligence, followed by preliminary suggestions for a mechanism (the "Schema mechanism") for its development, and a hypothetical Scenario which partially reinterprets Sensorimotor development in terms of that mechanism. The Schema mechanism focuses on Piaget's concept of the competition and evolution of mental "schemas." The schema is modelled here as an assertion that one partial state of the mechanism's world-representation is transformable to another via a given action, taken when the schema is "activated". A proposed process of "correlation" allows a schema's assertion to be extended or revised in response to empirically-observed effects of the schema's activation. Correlation uses the the formation and activation of schemas to propose and test hypothesis, in contrast with the passive tabulation characteristic of associationist mechanisms. Further features are proposed to enable schemas to become coordinated into composite structures, "compound actions", which can be used by other schemas; and to synthesize new "items" (state-elements) when existing ones prove inadequate to model the world. The Scenario outlines how the Schema mechanism might begin to make its way through the progression of Sensorimotor stages; development culminating in Piaget's third stage is discussed. This development includes learning about the visual and tactile effects of eye and hand motions-- eg, learning how to look directly at an object, or to move a hand into view; and the organization of that knowledge to designate the tactile properties of "visual objects", and vice versa-- eg knowing how to touch an object which is seen-- paving the way to a sensory-modality-invariant representation of objects and space. The Schema mechanism attempts to "learn from scratch", without built-in expertise or built-in structure in its learning domains. In the past there has been little success among AI programs of this genre. But many such attempts have suffered from mechanisms which were trivial in that they placed the full burden of acquiring and structuring knowledge on one or two simple tricks, whereas, I claim, the present effort shows a willingness to incorporate a multiplicity of elements in a complicated mechanism. In addition, the Schema mechanism benefits from its orientation around a nontrivial theory of development. Piaget gives a comprehensive account of the infant's evolution of primitive problem-solving and domain-specific (chiefly object-manipulation) knowledge; this account is used here as a roadmap that describes the proper course for the mechanism to follow. Thus, there is a nontrivial (or at least nonarbitrary) sequence of target abilities to use as a framework for evaluating and revising the mechanism's performance.MIT Artificial Intelligence Laborator

The influence of caprock on blast fragmentation distribution

This dissertation describes the development of a small-scale model of a caprock-laden quarry blast and discusses the results from that testing. The purpose of this testing was to provide insight into the reasons for poor caprock breakage during blasting. Small-scale test blocks were poured using a weak mortar mix to represent a limestone formation at a small scale. A cold joint was created in the upper portion of the test specimens to represent the bedding plane that separates caprock and substrate layers in a caprock-laden limestone bench. The scale-model test blocks were blasted using detonating cord. The primary configuration for this work was a single blast hole at a 4” burden and spacing from the outside corner of the test block. The blocks were loaded with detonating cord, and initiated from the bottom. Following blasting, surface breakage of the cap layer was photographed and collected for sizing. Following collection of the cap fragments, substrate breakage was photographed and collected for sieving as well. Test blocks fragmented well in the substrate portion and poorly in the cap layers. Cap breakage was typically limited to single-digit fragment populations. Annular fracturing sometimes created uncharacteristically large fragments that exceeded the burden and spacing of the blast hole and explains the presence of uncharacteristically large boulders in the field. This testing provided insight into how a massive, solid layer reacts when blasted from below. Cap breakage remained poor regardless of typical blast hole design. The results of this work indicated that the caprock fragmentation and the substrate fragmentation need to be treated separately by blasters and engineers --Abstract, page iii

Adaptation of perceived depth related to changes of the effective interpupuillary distance in computer-graphic steroscopic displays

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.Includes bibliographical references (p. 260-268).by David Walter Schloerb.Ph.D

The effect of alcohol intoxication on haemodynamic physiology of acute cardiac tamponade

It is generally accepted that alcohol impairs haemodynamic physiology in normal subjects. Alcohol is also thought to have a detrimental effect in shock states. However, most research has concentrated on haemorrhagic shock, whereas in cardiac tamponade, the pathophysiology of shock is very different. Although some studies have mentioned alcohol as a negative factor in patients with cardiac tamponade, none have adequately assessed its effect. In a clinical study of 50 patients who presented to Groote Schuur Hospital Trauma Unit with acute cardiac tamponade due to penetrating chest injury, those who were intoxicated fared the same as their sober counterparts. Although more patients in the intoxicated group were "moribund" or "in extremis" on admission, this did not lead to a higher overall mortality. Haemodynamic parameters and results of special investigations in the two groups were also similar. These findings suggested that intoxicated patients with cardiogenic shock, specifically acute cardiac tamponade, behaved differently from intoxicated patients with haemorrhagic shock. However, the multitude of variables and the stress involved in treating patients with life-threatening acute conditions, makes studies such as this difficult. Because of these limitations, an animal model of acute cardiac tamponade was developed, so that actions of alcohol on haemodynamic physiology could be studied in a controlled environment. Fourteen young pigs were randomly assigned to receive either 30% alcohol or tap-water via a gastrostomy. The former resulted in blood alcohol levels which were compatible with moderate to severe intoxication. Cardiac tamponade was then induced by instilling warmed plasmalyte-8 into the pericardia! sac using a pressure-cycled system. Despite the fact that animals in the tamponade/alcohol group were more hypotensive, and reflex increase in heart rate was inhibited, cardiac output was similar in the two groups. The actions of alcohol in isolation were also studied in eight sham-operated pigs. The only noticeable effect in this instance were higher pulmonary artery wedge pressures in the sham/non-alcohol group. In other words, cardiac performance in both the tamponade/alcohol and sham/alcohol groups was at least equal to, or even better than that in animals that did not receive alcohol. It would seem therefore, that alcohol does not have a negative effect on haemodynamic physiology of acute cardiac tamponade. Theoretically, alcohol may "protect" patients with acute cardiac tamponade by decreasing peripheral vascular resistance and "afterload". It is also possible that inhibitory actions on the respiratory centre may prevent hyperpnoea or tachypnoea, and thereby diminish competitive filling of the right and left ventricles. However, further studies of cardiac function in intoxicated subjects with tamponade using more sophisticated techniques are necessary, before mechanisms will become apparent. In practice, an aggressive approach should be adopted towards moribund patients with penetrating chest injuries; if they have acute cardiac tamponade and are intoxicated, their prognosis is not necessarily dismal. This is of particular relevance in Cape Town, where both alcohol abuse and assault are endemic. As for a therapeutic effect of alcohol, these studies do not support its use for pharmacological manipulation of cardiac tamponade