An Integer Linear Programming Solution to the Telescope Network Scheduling Problem

Telescope networks are gaining traction due to their promise of higher resource utilization than single telescopes and as enablers of novel astronomical observation modes. However, as telescope network sizes increase, the possibility of scheduling them completely or even semi-manually disappears. In an earlier paper, a step towards software telescope scheduling was made with the specification of the Reservation formalism, through the use of which astronomers can express their complex observation needs and preferences. In this paper we build on that work. We present a solution to the discretized version of the problem of scheduling a telescope network. We derive a solvable integer linear programming (ILP) model based on the Reservation formalism. We show computational results verifying its correctness, and confirm that our Gurobi-based implementation can address problems of realistic size. Finally, we extend the ILP model to also handle the novel observation requests that can be specified using the more advanced Compound Reservation formalism.Comment: Accepted for publication in the refereed conference proceedings of the International Conference on Operations Research and Enterprise Systems (ICORES 2015

A Stochastic Model for Car-Sharing Systems

Vehicle-sharing systems are becoming important for urban transportation. In these systems, users arrive at a station, pick up a vehicle, use it for a while and then return it to another station of their choice. Depending on the type of system, there might be a possibility to book vehicles before picking-up and/or a parking space at the chosen arrival station. Each station has a finite capacity and cannot host more vehicles and reserved parking spaces than its capacity. We propose a stochastic model for an homogeneous car-sharing system with possibility to reserve a parking space at the arrival station when picking-up a car. We compute the performance of the system and the optimal fleet size according to a specific metric. It differs from a similar model for bike-sharing systems because of reservation that induces complexity, especially when traffic increases

Retrial Queuing Models of Multi-Wavelength FDL Feedback Optical Buffers

Cataloged from PDF version of article.Optical buffers based on Fiber Delay Lines (FDL) have been proposed for contention resolution in optical packet/burst switching systems. In this article, we propose a retrial queuing model for FDL optical buffers in asynchronous optical switching nodes. In the considered system, the reservation model employed is of post-reservation type and optical packets are allowed to re-circulate over the FDLs in a probabilistic manner. We combine the MMPP-based overflow traffic models of the classical circuit switching literature and fixed-point iterations to devise an algorithmic procedure to accurately estimate blocking probabilities as a function of various buffer parameters in the system when packet arrivals are Poisson and packet lengths are exponentially distributed. The proposed algorithm is both accurate and fast, allowing one to use the procedure to dimension optical buffers in next-generation optical packet switching systems

Occupancy Estimation Using Low-Cost Wi-Fi Sniffers

Real-time measurements on the occupancy status of indoor and outdoor spaces can be exploited in many scenarios (HVAC and lighting system control, building energy optimization, allocation and reservation of spaces, etc.). Traditional systems for occupancy estimation rely on environmental sensors (CO2, temperature, humidity) or video cameras. In this paper, we depart from such traditional approaches and propose a novel occupancy estimation system which is based on the capture of Wi-Fi management packets from users' devices. The system, implemented on a low-cost ESP8266 microcontroller, leverages a supervised learning model to adapt to different spaces and transmits occupancy information through the MQTT protocol to a web-based dashboard. Experimental results demonstrate the validity of the proposed solution in four different indoor university spaces.Comment: Submitted to Balkancom 201

Perspectives on Unemployment from a General Equilibrium Search Model

Australia has experienced a varied track record on unemployment. For the third quarter of the 20th century unemployment averaged 2.0 per cent. This is bracketed by average unemployment rates of 8.6 and 7.4 per cent in the second and fourth quarter centuries. Explanations of this phenomenon vary. In this paper we explore supply side explanations using a model developed by Ljungqvist and Sargent (LS). We adapt the LS model to the Australian tax and welfare system and calibrate it to the Australian economy. Two simulation experiments are considered. In the first we study the effect of varying the unemployment benefit on the level and composition of unemployment. In the second simulation we examine the effects of increasing the degree of turbulence experienced by the economy. In the former simulation we find that: raising benefits causes a rise in the duration of unemployment; unemployment rates rise; across voluntary and involuntary unemployment classes; the rise is relatively larger in the range of low skill workers whose job-search intensity falls the greatest. Job-search intensity of voluntarily unemployed workers does not change with benefits; and reservation wages of individuals with high skill levels are unaffected by unemployment benefits but the reservation wage low skilled workers increases with the unemployment benefit. In the second simulation increasing turbulence in the economic environment causes an increase in total unemployment and in involuntary unemployment. However, voluntary unemployment falls, because people alter their reservation wages and search intensities in response to increased turbulence; overall the average duration of unemployment rises. Finally, we replicate the LS finding that the adverse consequences of increased turbulence are larger in economies with more generous welfare systems. We interpret the findings reported above as suggesting that the LS model is a useful tool of analysis and in the final version of the paper we propose to calibrate the model to the changes in the level of unemployment benefits and the progressivity of the income tax schedule that occurred towards the end of the third quarter of the 20th century. Our objectives will be to quantify how much of the change in unemployment can be attributed to these factors and to quantify the extent to which higher unemployment is attributable to increased turbulence.Search model; turbulence; unemployment; skill accumulation; tax and welfare system

Forage Inventory and Modeling in Uintah and Ouray Reservation Rangelands

The Uintah and Ouray Reservation in northeastern Utah has not been widely studied, and access to non-tribal members is highly restricted. We sampled vegetation to summarize condition in 300,000 acres of unsurveyed Reservation lands in 2017-2018, combining these data with data collected by the Bureau of Indian Affairs from 2010-2015 to complete an initial rangeland vegetation inventory of the Reservation. This survey was designed to inform management of the area by determining cattle stocking rates and overall ecological condition across the Reservation. Both the density of forage available to cattle and appropriate cattle stocking rates vary greatly throughout management units in the Reservation. We also used the vegetation inventory data to run a model which estimates forage availability in every year from 1984-2018 throughout the Reservation. Whereas the initial inventory only considers the typical forage availability in management units, this method allows us to estimate how forage varies through space and time. The results show that forage availability varies significantly through time, declining and increasing by approximately one-third from median forage availability. Such variability indicates that typical forage availability, the measure used to determine stocking rates in the initial inventory, does not fully address forage availability dynamics. Since actual forage availability can be far lesser or greater than typical forage availability, stocking rates based on typical availability will often be an under or over estimation. The model results therefore lend a fuller picture of appropriate stocking rates. This may improve grazing management by revealing how much forage declines in unfavorable years such as during drought, and improving grazing planning during these years. The forage availability model can continue to be used in the future to monitor trends in vegetation over time, and the modeling method may be applicable to other similar study systems

A noise assessment and prediction system

A system has been designed to provide an assessment of noise levels that result from testing activities at Aberdeen Proving Ground, Md. The system receives meteorological data from surface stations and an upper air sounding system. The data from these systems are sent to a meteorological model, which provides forecasting conditions for up to three hours from the test time. The meteorological data are then used as input into an acoustic ray trace model which projects sound level contours onto a two-dimensional display of the surrounding area. This information is sent to the meteorological office for verification, as well as the range control office, and the environmental office. To evaluate the noise level predictions, a series of microphones are located off the reservation to receive the sound and transmit this information back to the central display unit. The computer models are modular allowing for a variety of models to be utilized and tested to achieve the best agreement with data. This technique of prediction and model validation will be used to improve the noise assessment system