CO observations of the expanding envelope of IRC plus 10216

High-sensitivity emission profiles were observed for the transition of C12O16 and C13O16 towards IRC + or - 10216. It appears that the spherically symmetric uniform mass-outflow model proposed by Morris is necessary to describe the line profiles. The outflow appears to be slightly accelerated, having a velocity of 15 km/sec at the edges of the CO cloud, compared with 12 km/sec for the more centrally confined molecules

Measurement of the sizes of circumstellar dust shells around evolved stars with high mass loss rates

The research supported by the NASA ADP contract NAG5-1153 has been completed. The attached paper, which will be submitted for publication in the Astrophysical Journal in January 1992, presents the results of this work. Here is a summary of the project and its results. A set of computer programs was developed to process the raw 60 micron and 100 micron IRAS survey data. The programs were designed to detect faint extended emission surrounding a bright unresolved source. Candidate objects were chosen from a list of red giant stars and young planetary nebulae which have been detected in millimeter/submillimeter lines of CO. Of the 279 stars examined, 55 were resolved at 60 microns. The principle results of the study are given. The average age for the shells surrounding the 9 Mira-type stars which are extended is 6 x 10(exp 4) yr. This suggests that the period during which these stars lose mass lasts for approx 10(exp 5) yr. The oldest shell found surrounds U Ori, and the youngest surrounds Mira itself. Some shells appear to be detached from the central star. This phenomenon is more common among older stars, suggesting that the mass loss becomes more episodic as the star sheds its envelope. Although all 8 stars less distant than 200 pc are resolved in the IRAS 60 micron data, 29 stars within 500 pc were not. These stars probably have younger circumstellar shells than those which were resolved. Almost all the carbon stars with distances of 500 pc or less have resolved shells, while only 1/2 of the oxygen-rich stars do. The resolved carbon star shells also are older on average than the oxygen-rich ones. These facts imply that carbon stars have been losing mass for a longer period, on average, than oxygen-rich red giants. Large circumstellar shells tend to be found at large distances from the galactic plane, confirming that the ISM density limits the size to which a dust shell can grow. Surprisingly, even very large shells seem to be nearly spherical, and do not appear to be distorted by ram-pressure caused by the star's motion with respect to the ISM. Radiative transfer models and the value of I sub 60 microns/I sub 100 microns allow the average dust temperature in the outer regions of a circumstellar shell to be estimated. The typical value obtained in about 35 K

Psychological and physiological correlates of stress: Performance on a cooperative task

The relationship of personality dimensions to performance was investigated. The personality measure used to select subjects, the Barratt impulsiveness scale, is hypothesized to be related to a style of behavior which should affect the trend of choices which various subjects will make. Personality dimensions were specifically examined during performance of a cooperative task, the Prisoner's Dilemma

Centrifugal-Pump Performance as Affected by Design Features

This paper presents some of the results of a study of Grand Coulee pumping-plant characteristics. The research program was conducted for the Bureau of Reclamation by the California Institute of Technology in its hydraulic machinery laboratory (1) and has been in progress since January, 1938. While the principal object was to determine the operating features for pumping units to be installed at the Grand Coulee project, the results obtained are somewhat more generally applicable than might be expected. It is believed by the author that investigations of a somewhat similar nature offer the most reliable means for securing the characteristics desired in hydraulic units, both pump and turbine, for practically any given set of conditions

Complete Characteristics of Centrifugal Pumps and Their Use in the Prediction of Transient Behavior

This paper describes the technique of determining the complete operating characteristics of a hydraulic machine such as a centrifugal pump or a turbine, together with a method of presenting these characteristics in a convenient manner on a single diagram. The characteristics of a modern, high-head, high-efficiency pump are analyzed and presented in the manner proposed. The use of these complete characteristics for the prediction of the behavior of the machine during operating transients is discussed and the analytical background is presented. The assumptions involved are investigated and experimental checks of their validity are offered. The interrelationships between the hydraulic characteristics of the machine and the pipe line are indicated

The Hydraulic-Machinery Laboratory at the California Institute of Technology

This paper gives a description of the arrangement, equipment, and instrumentation of the hydraulic-machinery laboratory at the California Institute of Technology. This laboratory was designed essentially to work with problems involving high heads, high speeds, and moderately large powers and rates of flow. The instruments and equipment permit both speed and precision in testing, an overall accuracy of O.l per cent being attainable. For the past two years the laboratory has been used for the study of pumping problems of the Colorado River aqueduct, a project which will have pumps totaling 350,000 hp when completed

Accelerated Field Tests of Cavitation Intensity

The purpose of this paper is to describe a new technique for measuring the intensity of the cavitation attack in a piece of hydraulic equipment operating in the field, and to present the results and conclusions of a preliminary trial of this method in a 30,000-kw hydraulic turbine. This technique has been referred to as an accelerated test because the time required for the test run is measured in minutes, and by careful planning the total outage time required for installation and removal of the test plates is short

An Institutional Framework for Heterogeneous Formal Development in UML

We present a framework for formal software development with UML. In contrast to previous approaches that equip UML with a formal semantics, we follow an institution based heterogeneous approach. This can express suitable formal semantics of the different UML diagram types directly, without the need to map everything to one specific formalism (let it be first-order logic or graph grammars). We show how different aspects of the formal development process can be coherently formalised, ranging from requirements over design and Hoare-style conditions on code to the implementation itself. The framework can be used to verify consistency of different UML diagrams both horizontally (e.g., consistency among various requirements) as well as vertically (e.g., correctness of design or implementation w.r.t. the requirements)