Problem Of Particular Interest Research Articles

An adaptive automaton controller for discrete-time markov processes

The computation of an optimal feedback controller characteristic for a non-linear stochastic system may be facilitated by the use of a stochastic automaton as a system model. A problem of particular interest is that of a long duration stationary Markov process in which the state is observable but the process dynamics and disturbance characteristics are initially unknown. The determination of a suitable control algorithm, in the form of an adaptive automation in the feedback loop, is considered in this paper for such a process. Since the algorithm is to be used on-line to perform simultaneously the functions of estimation and control, it must constitute an efficient convergent multi-stage dual control strategy. It is shown that an existing method for dual control of a repetitive single-stage stochastic process may be extended to apply to the present case. A method is introduced of calculating successive policy estimates recursively, so that the task of updating the estimated optimal feedback policy at each stage of the process is rendered feasible. The application of the automaton controller is illustrated by the simulated adaptive control of a non-linear conditionally stable heat treatment process disturbed by multiplicative noise.

Photon Counting Statistics of Gaussian Light

It is well known that the photocount distribution associated with the photoelectric detection of fluctuating light beams carries information about the probability density of the light intensity. In this paper, we present an exact solution to a problem of particular interest which arises in connection with the photoelectric detection of narrow-band Gaussian (thermal or pseudothermal) light, namely, the problem of determining the photocount distribution when the counting-time interval is not necessarily short compared to the coherence time of the light. The method developed in this paper is applied to the case where the spectral profile of the light is Lorentzian; it leads to an exact expression for the photocount generating function and it provides simple recurrence relations for the photocount distribution and for its factorial moments.

Radiation hazard to man and animals from fallout in the Arctic

The radiation hazards to humans in certain northern regions, and to reindeer, caribou and moose, due to radioactive materials from fallout in their diets, have been discussed recently in numerous publications. The following factors make this problem of particular interest:i. The peculiarity of lichens to absorb and retain larger quantities of radioactive fallout than other plants. This peculiarity of lichens is exemplified by some measurements of Paakkiola and Miettinen made during 1960 and 1961. They found that the strontium-90 content of lichens in northern Finland varied between 350 and 4500 SU, whereas for grass and other plants from the same area the figures varied between 43 and 273 SU.

Drug automatism — A problem of particular interest in alcoholics and narcomania cases

Drug automatism — A problem of particular interest in alcoholics and narcomania cases

Clean surfaces and sorption of gases

Chemisorption studies have progressively shown the importance of having available truly clean surfaces to obtain valuable results. To this end in the past few years extensive use has been made of evaporated films: however, recent trends seem to prefer the use of bulk materials (filaments, foils, tips) which can be degassed at high temperature. Such materials are much more versatile than films, and give a useful basis to the development of new techniques for the study of surface phenomena. These surfaces can be used any number of times; they further permit the elimination of secondary phenomena, not strictly related to the surface, such as diffusion within the discontinuous structure of evaporated films. Techniques employing bulk materials are necessarily restricted to those metals which do not possess an appreciable vapour pressure at the degassing temperatures required. However, the results which have recently been obtained with this type of sorbent, by field emission microscopy, field ion microscopy and flash filament technique, are of great theoretical interest and can be applied to most of the other metals. We limit ourselves to quote the information obtained about the existence of: (a) various types of atoms on the metal surface, characterized by different sorption properties; (b) different coefficients of surface diffusion for the different crystal faces; (c) different states of the gas adsorbed on the metal. Concerning this latter point, useful information can be obtained from infrared spectroscopy of the adsorbed molecules. This complex picture of the observed phenomena is confirmed by our results for the adsorption of nitrogen and carbon monoxide on tungsten. The technique used to measure the velocity of adsorption, based on the flow of gas through a capillary of known conductance, is similar to that used in the field of getters; the adsorbent is a tungsten lamina having a thickness of 0.0025 cm and a surface area of 27.5 cm 2; the measurements have been carried out in the pressure range of 10 -7 to 10 -8 Torr, and in the temperature interval between 90 and 480°K. A problem of particular interest arises from the immeasurably low temperature coefficients and from the fact that the velocity of adsorption is initially independent of the surface coverage. The theoretical hypotheses put forward concerning this problem are briefly examined. The correct interpretation of such complex surface phenomena seems to be necessary even for the study of gas sorption by evaporated metal films.

The shadow of a straight edge

In his anniversary address on 30 November 1935, the President of the Royal Society paid a tribute to the work of HECTOR MUNRO MACDONALD. In the course of his address he made particular reference to MACDONALD’s solution of the difficult, and analytically very attractive, problem of diffraction by a prism, perhaps better known as the Wedge Problem. A few years ago the author of the present paper, who was much impressed by the work of MACDONALD and had the privilege of corresponding with him, made some notes upon this problem and upon an associated problem of particular interest. Arising from these notes, which were recalled upon reading the President’s address, certain ideas, which would appear to be of a fundamental nature, have been developed to form the subject of the following communication. The problem of the half-plane had been previously treated by two distinguished mathematicians, but the first complete solution of the wedge problem was given by MACDONALD. The two mathematicians were POINCARE and SOMMERFELD. Subsequently to the publication of MACDONALD’s work, BROMWICH published a paper which gives a slightly more general treatment of the problem. References are given at the end of the paper.

DELAYED TRAUMATIC SERRATUS PARALYSIS

The deformity of scapula alata or winged scapula caused by paralysis of the posterior thoracic nerve, resulting from trauma, presents a problem of particular interest to men engaged in practice that necessitates the assignment of the role of trauma in the production of paralyses alleged to be produced by mechanical injury. The treatment of this condition also deserves particular attention. Isolated traumatic paralysis of the serratus is generally stated to be much more frequent in men than in women; according to Berger, it is eight times as common in the former, and according to Gowers, it is six times as frequent. These investigators tabulated the reports of about thirty cases from the literature. It occurs most frequently in laborers, in muscular persons during the active period of life, between 25 and 45 years of age. The reason that it is most frequent during this period, and that a predilection is