12,228 research outputs found
Two-dimensional fluid queues with temporary assistance
We consider a two-dimensional stochastic fluid model with ON-OFF inputs
and temporary assistance, which is an extension of the same model with
in Mahabhashyam et al. (2008). The rates of change of both buffers are
piecewise constant and dependent on the underlying Markovian phase of the
model, and the rates of change for Buffer 2 are also dependent on the specific
level of Buffer 1. This is because both buffers share a fixed output capacity,
the precise proportion of which depends on Buffer 1. The generalization of the
number of ON-OFF inputs necessitates modifications in the original rules of
output-capacity sharing from Mahabhashyam et al. (2008) and considerably
complicates both the theoretical analysis and the numerical computation of
various performance measures
Target Mass Monitoring and Instrumentation in the Daya Bay Antineutrino Detectors
The Daya Bay experiment measures sin^2 2{\theta}_13 using functionally
identical antineutrino detectors located at distances of 300 to 2000 meters
from the Daya Bay nuclear power complex. Each detector consists of three nested
fluid volumes surrounded by photomultiplier tubes. These volumes are coupled to
overflow tanks on top of the detector to allow for thermal expansion of the
liquid. Antineutrinos are detected through the inverse beta decay reaction on
the proton-rich scintillator target. A precise and continuous measurement of
the detector's central target mass is achieved by monitoring the the fluid
level in the overflow tanks with cameras and ultrasonic and capacitive sensors.
In addition, the monitoring system records detector temperature and levelness
at multiple positions. This monitoring information allows the precise
determination of the detectors' effective number of target protons during data
taking. We present the design, calibration, installation and in-situ tests of
the Daya Bay real-time antineutrino detector monitoring sensors and readout
electronics.Comment: 22 pages, 20 figures; accepted by JINST. Changes in v2: minor
revisions to incorporate editorial feedback from JINS
A Primer for Monitoring Water Funds
This document is intended to assist people working on Water Funds to understand their information needs and become familiar with the strengths and weaknesses of various monitoring approaches. This primer is not intended to make people monitoring experts, but rather to help them become familiar with and conversant in the major issues so they can communicate effectively with experts to design a scientifically defensible monitoring program.The document highlights the critical information needs common to Water Fund projects and summarizes issues and steps to address in developing a Water Fund monitoring program. It explains key concepts and challenges; suggests monitoring parameters and an array of sampling designs to consider as a starting-point; and provides suggestions for further reading, links to helpful resources,and an annotated bibliography of studies on the impacts that result from activities commonly implemented in Water Fund projects
Altered perivascular fibroblast activity precedes ALS disease onset
Apart from well-defined factors in neuronal cells1, only a few reports consider that the variability of sporadic amyotrophic lateral sclerosis (ALS) progression can depend on less-defined contributions from glia2,3 and blood vessels4. In this study we use an expression-weighted cell-type enrichment method to infer cell activity in spinal cord samples from patients with sporadic ALS and mouse models of this disease. Here we report that patients with sporadic ALS present cell activity patterns consistent with two mouse models in which enrichments of vascular cell genes preceded microglial response. Notably, during the presymptomatic stage, perivascular fibroblast cells showed the strongest gene enrichments, and their marker proteins SPP1 and COL6A1 accumulated in enlarged perivascular spaces in patients with sporadic ALS. Moreover, in plasma of 574 patients with ALS from four independent cohorts, increased levels of SPP1 at disease diagnosis repeatedly predicted shorter survival with stronger effect than the established risk factors of bulbar onset or neurofilament levels in cerebrospinal fluid. We propose that the activity of the recently discovered perivascular fibroblast can predict survival of patients with ALS and provide a new conceptual framework to re-evaluate definitions of ALS etiology
Water Woes Worsen: Middle Rio Grande Reservoir Modeling Projects Declining Water Availability Under Climate Change Simulations
The Middle Rio Grande is a vital source of water for over 2M people. Climate change is impacting regional hydrology and is likely to put additional stress on a water supply that is already stretched thin. To gain insight on future water availability, a simple water balance model was used to simulate the Elephant Butte-Caballo reservoir system (Southern New Mexico, USA). The water balance model was run under 97 climate simulations derived from Global Climate Models (GCMs) developed under the Intergovernmental Panel on Climate Change\u27s (IPCC) 5th generation Coupled Modeling Intercomparison Project (CMIP5). Results suggest that the percentage of years that water rights allocations are fulfilled over the next 50 years (2021-2070) will decrease compared to the past 50 years (1971-2020). The modeling also projects an increase in multi-year drought events. In most cases, headwaters flow from snowmelt is projected to have a greater influence on water availability downstream of Elephant Butte and Caballo reservoirs than local evaporation and precipitation from the reservoir surfaces
How to Staff when Customers Arrive in Batches
In settings as diverse as autonomous vehicles, cloud computing, and pandemic
quarantines, requests for service can arrive in near or true simultaneity with
one another. This creates batches of arrivals to the underlying queueing
system. In this paper, we study the staffing problem for the batch arrival
queue. We show that batches place a significant stress on services, and thus
require a high amount of resources and preparation. In fact, we find that there
is no economy of scale as the number of customers in each batch increases,
creating a stark contrast with the square root safety staffing rules enjoyed by
systems with solitary arrivals of customers. Furthermore, when customers arrive
both quickly and in batches, an economy of scale can exist, but it is weaker
than what is typically expected. Methodologically, these staffing results
follow from novel large batch and hybrid large-batch-and-large-rate limits of
the general multi-server queueing model. In the pure large batch limit, we
establish the first formal connection between multi-server queues and storage
processes, another family of stochastic processes. By consequence, we show that
the limit of the batch scaled queue length process is not asymptotically
normal, and that, in fact, the fluid and diffusion-type limits coincide. This
is what drives our staffing analysis of the batch arrival queue, and what
implies that the (safety) staffing of this system must be directly proportional
to the batch size just to achieve a non-degenerate probability of customers
waiting
Simulation verification techniques study: Simulation performance validation techniques document
Techniques and support software for the efficient performance of simulation validation are discussed. Overall validation software structure, the performance of validation at various levels of simulation integration, guidelines for check case formulation, methods for real time acquisition and formatting of data from an all up operational simulator, and methods and criteria for comparison and evaluation of simulation data are included. Vehicle subsystems modules, module integration, special test requirements, and reference data formats are also described
Specifications for modelling fuel cell and combustion-based residential cogeneration device within whole-building simulation programs
This document contains the specifications for a series of residential cogeneration device models developed within IEA/ECBCS Annex 42. The devices covered are: solid oxide and polymer exchange membrane fuel cells (SOFC and PEM), and internal combustion and Stirling engine units (ICE and SE). These models have been developed for use within whole-building simulation programs and one or more of the models described herein have been integrated into the following simulation packages: ESP-r, EnergyPlus, TRNSYS and IDA-ICE. The models have been designed to predict the energy performance of cogeneration devices when integrated into a residential building (dwelling). The models account for thermal performance (dynamic thermal performance in the case of the combustion engine models), electrochemical and combustion reactions where appropriate, along with electrical power output. All of the devices are modelled at levels of detail appropriate for whole-building simulation tools
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