Towards Unifying Scheduling and Location Problems: A Non-Stationary Hypercube Model

Purpose – this paper aims to develop a non-stationary hypercube model capable of uniting the properties that models for both problems seek (location and shift-scheduling problems). Theoretical framework – We present the proposed model using a mixed discrete-continuous time Markov chain and compares it to a discrete-event simulation through an illustrative example. Design/methodology/approach – The method used in this paper is quantitative with a comparison between an approach of simulation and an exact model. Findings – The results show a high similarity between both models. However, the proposed model does not present noise in performance measures such as waiting times and travel times. Nevertheless, the study of their residuals revealed that the proposed model has a lower sensitivity to events, such as shift endings and imperfections in dispatch preferences. Further studies may reduce such a variation by improvements in the calculations of performance measurements. Research, Practical & Social implications – The mentioned results suggest that the proposed model may become an option for applications uniting location and shift-scheduling problems. Originality/value – When developing location problems, we seek models that are capable of representing the pertinent geographic characteristics to the problem. On the other hand, when developing shift-scheduling problems, we seek models capable of capturing transient fluctuations in the components (such as demand, service times, available workforce, among others) of such a system. Therefore, in the search to improve the daily operations of systems, such as emergency service systems (ambulances, police, firefighters) using either of the two problems individually, it may lead to flawed conclusions. Keywords - Emergency Service Systems; Queueing Theory; Hypercube non-stationary; Discrete Event Simulation; Performance Measurement.

The Dynamic Hypercube as a Niche Community Model

Different models of community dynamics, such as the MacArthur–Wilson theory of island biogeography and Hubbell’s neutral theory, have given us useful insights into the workings of ecological communities. Here, we develop the niche-hypervolume concept of the community into a powerful model of community dynamics. We describe the community’s size through the volume of the hypercube and the dynamics of the populations in it through the fluctuations of the axes of the niche hypercube on different timescales. While the community’s size remains constant, the relative volumes of the niches within it change continuously, thus allowing the populations of different species to rise and fall in a zero-sum fashion. This dynamic hypercube model reproduces several key patterns in communities: lognormal species abundance distributions, 1/f-noise population abundance, multiscale patterns of extinction debt and logarithmic species-time curves. It also provides a powerful framework to explore significant ideas in ecology, such as the drift of ecological communities into evolutionary time.

A simulation-optimization algorithm for return strategies in emergency medical systems

In an emergency medical system, the locations of ambulance stations has a direct impact on response time. In this paper, two location models are presented in combination with the hypercube queuing model to maximize coverage probability. In the first model, the locations of free and busy ambulances are considered in the system states, and the hypercube model can be analyzed accurately. The model contains a large number of states, and cannot be used for large-sized problems. For this reason, the second model is presented with the same assumptions as in the first model, except that the locations of busy ambulances are not included in the system state, but approximated based on the arrival rates. Both models are offline and dynamic, in which an ambulance does not necessarily return to the station from which it has been dispatched. Two strategies are defined for returning ambulances to the stations from the customer’s location. In the first strategy, the ambulance is returned to the nearest station after completion of its mission, and in the second strategy, it returns to the empty station that covers the highest demand rate. For evaluation of the performance of the proposed models, small-sized examples are solved for both return strategies using the GAMS software. A simulation-optimization approach combined with a simulated annealing algorithm and a discrete-event simulation are used for solving large-sized problems. Moreover, real data from a case study are used to demonstrate the performance of the models in the real world.

An Efficient Exact Hypercube Model with Fully Dedicated Servers

The hypercube model is a useful descriptive tool to evaluate emergency services such as firefighters, police, and emergency medical services where geographically distributed vehicles and personnel serve users in emergencies. This study proposes an extension of the hypercube model to represent a dispatch policy in which advanced equipped servers serve solely life-threatening calls (called dedicated servers). The proposed approach is applied to two case studies of public medical emergency services in two different cities in Brazil and validated with discrete-event simulations. The computational experiments show the proposed model as more sensitive to respond to more life-threatening requests than other hypercube models in the literature, serving more of these requests under increased demand. In addition, to reduce the number of equilibrium equations and, consequently, the computational effort of the hypercube model, an aggregate model is shown based on the grouping of homogeneous servers located in the same station. The aggregation policy does not generate additional losses in the accuracy of the model, as shown through several experiments.

Distributed HPC UFS ACM Optimizing the Risk for All the Time on Every Time

The access control mechanism is one of the well advance controls for all the time on every time on recent pervasive computing for protection of data and services from the hacker, thefts and unauthorized users. This paper contributes to the development of an optimization model that aims to determine the optimal cost to be implementing into DOOS security mechanisms on the measure component of UFS attribute. Our objective should be design in such way, that the Read, Write & Execute automatically protect to our web services on DOOS. We have to make high simplification, unification and step by step normalization by implementing UFS ACM mechanism based on distributed object oriented system on N dimensional hypercube model. Finally, we have to maximize the qualities of services & minimize the cost and time of the Business, Resources and Technology. The subject and object can able communicate through read, write and execute over a UFS on N Dimensional HPC. We have to apply these ACM utilities over a anti-fragile technology to make robust and high secure for all the time. Our objective will be resolve the unstable, uncertainty, un-order, un safe and unset up (U^4) problems of complex technology on right time and right place for all the time in around the globe to take care of accountabilities, action abilities and manage abilities. Meanwhile, it will be more accountable for performance, fault tolerance, throughput, bench marking and risk optimization on any web services for all the time.