Fixed points for multi-class queues

Burke's theorem can be seen as a fixed-point result for an exponential single-server queue; when the arrival process is Poisson, the departure process has the same distribution as the arrival process. We consider extensions of this result to multi-type queues, in which different types of customer have different levels of priority. We work with a model of a queueing server which includes discrete-time and continuous-time M/M/1 queues as well as queues with exponential or geometric service batches occurring in discrete time or at points of a Poisson process. The fixed-point results are proved using interchangeability properties for queues in tandem, which have previously been established for one-type M/M/1 systems. Some of the fixed-point results have previously been derived as a consequence of the construction of stationary distributions for multi-type interacting particle systems, and we explain the links between the two frameworks. The fixed points have interesting "clustering" properties for lower-priority customers. An extreme case is an example of a Brownian queue, in which lower-priority work only occurs at a set of times of measure 0 (and corresponds to a local time process for the queue-length process of higher priority work).Comment: 25 page

Small engine emissions testing laboratory development and emissions sampling system verification

With the recent scrutiny of engine emissions and a focus towards higher fuel efficiencies, there has been an increase in demand for small, efficient engines and small engine emissions testing. Small engines have proven to provide high efficiency performance for systems including refrigeration units, generators, compressors and numerous other off-road applications. In the past, the existing emissions testing facilities at West Virginia University\u27s (WVU) Center for Alternative Fuels, Engines and Emissions (CAFEE) have been focused towards the testing of heavy duty diesel engines.;In order to expand the emissions testing capabilities at CAFEE, a new small engine emissions testing laboratory was needed. Over a two year period a new small engine emissions laboratory (SEEL) was designed and built at CAFEE\u27s Westover facility. The new SEEL used a 40 hp alternating current (AC) dynamometer with an in-line slip ring torque sensor. It included full dynamometer and engine cooling capabilities. Custom built software provided the control algorithms to allow for engine mapping, steady state, and transient emissions tests. Safety systems including shaft guards and an automatic kill switch provided a safe working environment and would isolate damage in case of a mechanical failure.;The SEEL was designed to be used with existing raw and dilute emissions sampling systems. The raw emissions sampling system was recently developed at WVU and needed to be verified against a trusted dilute emissions sampling system in order to prepare it for testing with the SEEL. A set of tests were performed which included simultaneous sampling of one engine by both sampling systems. The results from these tests showed that raw sampling system CO, CO2, and NOx passed their verification criteria of 2%, 2%, and 5% difference respectfully. The HC measurement systems did not pass the 10% verification criteria. The verification of HC was a complex issue that was beyond the scope of this study

Mutagenicity and Carcinogenicity Prediction of Compounds from Cardamom (\u3cem\u3eElettaria cardamom\u3c/em\u3e Maton)

In silico approaches are currently not employed in any of the spices to study the toxicity. The aim of this study is to find the most efficacious molecule which does not have any adverse effects. In the present study one hundred and eight compounds from cardamom were used to predict mutagenicity and carcinogenecity. The results of these studies indicate that only four compounds are non-mutagenic and non-carcinogenic. The rest of the compounds do not have the characteristics necessary to become therapeutic agents have been identified early and prevented (i.e., the fail early, fail fast approach) from entering the drug development process