International audienceThe MAVEN spacecraft launched in November 2013, arrived at Mars in September 2014, and completed commissioning and began its one-Earth-year primary science mission in November 2014. The orbiter’s science objectives are to explore the interactions of the Sun and the solar wind with the Mars magnetosphere and upper atmosphere, to determine the structure of the upper atmosphere and ionosphere and the processes controlling it, to determine the escape rates from the upper atmosphere to space at the present epoch, and to measure properties that allow us to extrapolate these escape rates into the past to determine the total loss of atmospheric gas to space through time. These results will allow us to determine the importance of loss to space in changing the Mars climate and atmosphere through time, thereby providing important boundary conditions on the history of the habitability of Mars. The MAVEN spacecraft contains eight science instruments (with nine sensors) that measure the energy and particle input from the Sun into the Mars upper atmosphere, the response of the upper atmosphere to that input, and the resulting escape of gas to space. In addition, it contains an Electra relay that will allow it to relay commands and data between spacecraft on the surface and Earth
A 59-year-old man with a known breast cancer type 1 gene mutation and a 2-year history of metastatic prostate cancer to bone and lymph nodes presented with a sudden onset of thunderclap headache, photophobia and a left sided facial droop. He was being treated at the time with the poly ADP ribose polymerase inhibitor Rucaparib. Of note, 6 weeks prior to this presentation, he had been diagnosed with malignant spinal cord compression at T3–T6, he underwent an emergency decompressive laminectomy and had received palliative postoperative radiotherapy. An urgent CT brain revealed dural metastases from his prostate cancer, with extensive oedema and midline shift. He underwent palliative whole brain radiotherapy but died 2 weeks later.
Webb, S.,* Lehigh U. Bogucz, E.,** Lehigh U. Levy, E., Lehigh U. Barrett, M.L., Pennsylvania Power & Light Co. Pennsylvania Power & Light Co. Snyder, C., Pennsylvania Power & Light Co. Pennsylvania Power & Light Co. Waters, C., Pennsylvania Power & Light Co. Pennsylvania Power & Light Co. Copyright 1987 Society of Petroleum Engineers Summary. This paper describes an analysis developed to model the inert gas displacement process for evacuating a high-pour-point oil from a long pipeline. The governing equations were derived from the basic conservation pipeline. The governing equations were derived from the basic conservation equations for mass. momentum, and energy. The resultant computer program accounts for such effects as pipeline elevation changes, laminar and turbulent oil flow, temperature-dependent oil viscosity, and heat loss from the oil to the ground. Results of computations for an 84-mile [135-km] residual oil pipeline operated by the Pennsylvania Power and Light Co. are presented and compared with pressure measurements obtained during a trial presented and compared with pressure measurements obtained during a trial purge of the system. Calculations show that the minimum N volume required purge of the system. Calculations show that the minimum N volume required for a successful pipeline evacuation increases considerably with increased delay time. In addition, theoretical results indicate that for this case, the pipeline purge operation must begin within 20 hours of a shutdown to avoid evacuation difficulties. Introduction The development of procedures for shutting down an oil pipeline carrying a high-pour-point oil represents a pipeline carrying a high-pour-point oil represents a complex interaction of technical and economic issues. At ambient temperatures, these oils are virtually impossible to pump. To be moved at all, they must be heated and the pump. To be moved at all, they must be heated and the pipe insulated to reduce heat loss and excessive cooling pipe insulated to reduce heat loss and excessive cooling of the oil as it flows along the length of the pipe. Shutdowns of these pipelines occur periodically during periods of low demand or because of a loss -of power to the periods of low demand or because of a loss -of power to the pipeline pumps during emergency power outages. pipeline pumps during emergency power outages. During such shutdowns, the oil must be evacuated from the line before it cools below the pour point and becomes unpumpable. An unsuccessful evacuation of the oil would result in a clogged line and a very high cleaning bill. One approach commonly used for planned shutdowns is to displace the high-pour-point oil with a high-grade oil that can be pumped easily at ambient temperature. Unfortunately, this approach requires that a large quantity of expensive oil be maintained in storage for use during a shutdown. An alternative is to use a pressurized inert gas to drive a pig through the line to force the oil out. For scheduled shutdowns, this approach may have economic advantages over the high-grade-oil displacement approach. In addition, it is the only feasible technique for emergency situations when power to the pipeline pumps is lost. In such emergencies, liquid N is delivered to the pipeline by truck. The N is then pumped to high pressure, vaporized, and fed into the pipeline to evacuate the line before the oil cools. A number of important questions concerning inert gas displacement relate to the maximum length of time a pipeline can be shut down before initiation of the evacuation pipeline can be shut down before initiation of the evacuation process, the best operational strategy for purging the line, process, the best operational strategy for purging the line, and the minimum amount of N required to do the job. This paper describes an analysis developed for modeling the inert gas displacement process. A description of the analysis is given in the next section and is followed by a discussion of the results of computations for an 84-mile [135-km] residual oil pipeline operated by the Pennsylvania Power and Light Co. Pennsylvania Power and Light Co. Analytical Model The gas and oil volumes are treated separately in this analysis. Because the pig position is a function of time, the sizes of the gas and oil volumes change, making a deformable control-volume approach convenient to use. The control volumes are depicted in Fig. 1. In the subsequent analysis, slippage of gas or oil past the pig is assumed negligible. Gas Conservation Equations. The general deformable control-volume continuity equation is Using an average gas density. This equation can be written as (1) where y is the length of the gas control volume. SPEPE P. 45
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.