scholarly journals Analysis of Single-Server Multi-Class Queue with Unreliable Service, Batch Correlated Arrivals, Customers Impatience, and Dynamical Change of Priorities

Mathematics ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1257
Author(s):  
Alexander Dudin ◽  
Olga Dudina ◽  
Sergei Dudin ◽  
Konstantin Samouylov
Keyword(s):  
Optimization Problems ◽  
Arrival Rate ◽  
Single Server ◽  
Batch Arrivals ◽  
Arrival Times ◽  
Perishable Goods ◽  
Finite State ◽  
Care Systems ◽  
System States ◽  
The Impact

A single-server non-pre-emptive priority queueing system of a finite capacity with many types of customers is analyzed. Inter-arrival times can be correlated and batch arrivals are allowed. Possible unreliability of the server, implying the loss of a customer or the necessity of its service from the early beginning or some phase of the service, is taken into account. Initial priorities provided to various types of customers at the arrival moment can be varied (increased or decreased) after the random amount of time during the customer stay in the buffer. Such a type of queues arises in the modeling operation of various emergency care systems, information, and perishable goods delivering systems, etc. The stationary behavior of the system is described by the finite state multi-dimensional continuous-time Markov chain with the upper-Hessenberg block structure of the generator. The stationary distribution of the system states and some important characteristics of the system are calculated. The presented numerical examples illustrate opportunities to quantitatively evaluate the impact of the buffer capacity and customers’ mean arrival rate on the most important characteristics of the system. The possibility of solving optimization problems is briefly shown.

scholarly journals The Impact and Implications of The COVID-19 Pandemic on Organ Procurement Outside of an Epicenter

2021 ◽  
pp. 152692482110028
Author(s):  
Janice Jene Hudgins ◽  
Allison Jo Boyer ◽  
Kristen Danielle Orr ◽  
Clint Allen Hostetler ◽  
Jeffrey Paul Orlowski ◽  
...  
Keyword(s):  
Health Care ◽  
Initial Phase ◽  
Organ Procurement ◽  
Health Care Systems ◽  
Health Data ◽  
Organ Procurement Organization ◽  
Care Systems ◽  
The Impact ◽  
Variable Impact ◽  
Single Organ

The COVID-19 pandemic has been well-documented to have a variable impact on individual communities and health care systems. We describe the experience of a single organ procurement organization (OPO), located in an area without a large cluster of cases during the initial phase of the COVID-19 pandemic. A review of community health data describing the impact of COVID-19 nationally and in Oklahoma was conducted. Additionally, a retrospective review of available OPO data from March 2019-May 2020 was performed. While the amount of donor referrals received and organs recovered by the OPO remained stable in the initial months of the pandemic, the observed organs transplanted vs. expected organs transplanted (O:E) decreased to the lowest number in the 15-month period and organs transplanted decreased as well. Fewer organs from Oklahoma donors were accepted for transplant despite staff spending more time allocating organs.

scholarly journals SARS-CoV-2 and Cytomegalovirus Co-Infections—A Case Series of Critically Ill Patients

2021 ◽  
Vol 10 (13) ◽  
pp. 2792
Author(s):  
Patrícia Moniz ◽  
Sérgio Brito ◽  
Pedro Póvoa
Keyword(s):  
Intensive Care Unit ◽  
Critically Ill ◽  
Immune Suppression ◽  
Clinical Course ◽  
Health Care Systems ◽  
Case Series ◽  
Confounding Factors ◽  
Care Systems ◽  
The Impact ◽  
Cmv Reactivation

The SARS-CoV-2 pandemic has placed great strain on the most developed of health care systems, especially in the context of critical care. Although co-infections with cytomegalovirus (CMV) are frequent in the critically ill due to underlying immune suppression of multiple causes, the impact on COVID-19 patients remains unclear. Furthermore, severe COVID-19 has recently been associated with significant immune suppression, and this may in turn impact CMV reactivation, possibly contributing to clinical course. Nevertheless, multiple confounding factors in these patients will certainly challenge upcoming research. The authors present a case series of five patients admitted to the intensive care unit (ICU) in the context of respiratory failure due to severe COVID-19. All patients evolved with CMV reactivation during ICU stay.

scholarly journals Sustainability of Biosimilars in Europe: A Delphi Panel Consensus with Systematic Literature Review

2020 ◽  
Vol 13 (11) ◽  
pp. 400
Author(s):  
Arnold G. Vulto ◽  
Jackie Vanderpuye-Orgle ◽  
Martin van der Graaff ◽  
Steven R. A. Simoens ◽  
Lorenzo Dagna ◽  
...  
Keyword(s):  
Health Care ◽  
Literature Review ◽  
Systematic Literature Review ◽  
Health Care Systems ◽  
Delphi Panel ◽  
The European Union ◽  
Modified Delphi ◽  
Care Systems ◽  
Supply Risks ◽  
The Impact

Introduction: Biosimilars have the potential to enhance the sustainability of evolving health care systems. A sustainable biosimilars market requires all stakeholders to balance competition and supply chain security. However, there is significant variation in the policies for pricing, procurement, and use of biosimilars in the European Union. A modified Delphi process was conducted to achieve expert consensus on biosimilar market sustainability in Europe. Methods: The priorities of 11 stakeholders were explored in three stages: a brainstorming stage supported by a systematic literature review (SLR) and key materials identified by the participants; development and review of statements derived during brainstorming; and a facilitated roundtable discussion. Results: Participants argued that a sustainable biosimilar market must deliver tangible and transparent benefits to the health care system, while meeting the needs of all stakeholders. Key drivers of biosimilar market sustainability included: (i) competition is more effective than regulation; (ii) there should be incentives to ensure industry investment in biosimilar development and innovation; (iii) procurement processes must avoid monopolies and minimize market disruption; and (iv) principles for procurement should be defined by all stakeholders. However, findings from the SLR were limited, with significant gaps on the impact of different tender models on supply risks, savings, and sustainability. Conclusions: A sustainable biosimilar market means that all stakeholders benefit from appropriate and reliable access to biological therapies. Failure to care for biosimilar market sustainability may impoverish biosimilar development and offerings, eventually leading to increased cost for health care systems and patients, with fewer resources for innovation.

scholarly journals Optimal Pricing Strategy of Electric Vehicle Charging Station for Promoting Green Behavior Based on Time and Space Dimensions

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Xiaomin Xu ◽  
Dongxiao Niu ◽  
Yan Li ◽  
Lijie Sun
Keyword(s):  
Electric Vehicles ◽  
Optimization Problems ◽  
Power Grid ◽  
Economic Benefits ◽  
Pricing Strategy ◽  
Optimal Pricing ◽  
Electricity Pricing ◽  
Optimal Pricing Strategy ◽  
Charging Stations ◽  
The Impact

Considering that the charging behaviors of users of electric vehicles (EVs) (including charging time and charging location) are random and uncertain and that the disorderly charging of EVs brings new challenges to the power grid, this paper proposes an optimal electricity pricing strategy for EVs based on region division and time division. Firstly, by comparing the number of EVs and charging stations in different districts of a city, the demand ratio of charging stations per unit is calculated. Secondly, according to the demand price function and the principle of profit maximization, the charging price between different districts of a city is optimized to guide users to charge in districts with more abundant charging stations. Then, based on the results of the zonal pricing strategy, the time-of-use (TOU) pricing strategy in different districts is discussed. In the TOU pricing model, consumer satisfaction, the profit of power grid enterprises, and the load variance of the power grid are considered comprehensively. Taking the optimization of the comprehensive index as the objective function, the TOU pricing optimization model of EVs is constructed. Finally, the nondominated sorting genetic algorithm (NSGA-II) is introduced to solve the above optimization problems. The specific data of EVs in a municipality directly under the Central Government are taken as examples for this analysis. The empirical results demonstrate that the peak-to-valley ratio of a certain day in the city is reduced from 56.8% to 43% by using the optimal pricing strategy, which further smooth the load curve and alleviates the impact of load fluctuation. To a certain extent, the problem caused by the uneven distribution of electric vehicles and charging stations has been optimized. An orderly and reasonable electricity pricing strategy can guide users to adjust charging habits, to ensure grid security, and to ensure the economic benefits of all parties.

scholarly journals The impact of chronic disease and disability on the elderly

1999 ◽  
Vol 55 (3) ◽  
pp. 9-14
Author(s):  
C. J. Eales
Keyword(s):  
Health Care ◽  
Chronic Disease ◽  
Chronic Diseases ◽  
Health Care Systems ◽  
The Elderly ◽  
Therapeutic Interventions ◽  
Elderly Persons ◽  
Care Systems ◽  
And Function ◽  
The Impact

Health care systems for elderly people should aim to delay the onset of illness, reducing the final period of infirmity and illness to the shortest possible time. The most effective way to achieve this is by health education and preventative medicine to maintain mobility and function. Changes in life style even in late life may result in improved health, effectively decreasing the incidence of chronic diseases associated with advancing age. This paper presents the problems experienced by elderly persons with chronic diseases and disabilities with indications for meaningful therapeutic interventions.

Methodology to Evaluate the Fuel Economy of a Multimode Combustion Engine With Three-Way Catalytic Converter

2014 ◽  
Author(s):  
Sandro P. Nüesch ◽  
Anna G. Stefanopoulou ◽  
Li Jiang ◽  
Jeffrey Sterniak
Keyword(s):  
Fuel Economy ◽  
Combustion Engine ◽  
Catalytic Converter ◽  
Oxygen Storage ◽  
Nox Emissions ◽  
Combustion Mode ◽  
Mode Switch ◽  
Drive Cycle ◽  
Finite State ◽  
The Impact

Highly diluted, low temperature homogeneous charge compression ignition (HCCI) combustion leads to ultra-low levels of engine-out NOx emissions. A standard drive cycle, however, would require switches between HCCI and spark-ignited (SI) combustion modes. In this paper a methodology is introduced, investigating the fuel economy of such a multimode combustion concept in combination with a three-way catalytic converter (TWC). The TWC needs to exhibit unoccupied oxygen storage sites in order to show acceptable performance. But the lean exhaust gas during HCCI operation fills the oxygen storage and leads to a drop in NOx conversion efficiency. Eventually the levels of NOx become unacceptable and a mode switch to a fuel rich combustion mode is necessary in order to deplete the oxygen storage. The resulting lean-rich cycling leads to a penalty in fuel economy. In order to evaluate the impact of those penalties on fuel economy, a finite state model for combustion mode switches is combined with a longitudinal vehicle model and a phenomenological TWC model, focused on oxygen storage. The aftertreatment model is calibrated using combustion mode switch experiments from lean HCCI to rich spark-assisted HCCI and back. Fuel and emissions maps acquired in steady state experiments are used. Two depletion strategies are compared in terms of their influence on drive cycle fuel economy and NOx emissions.

A QUEUE WITH POSITIVE AND NEGATIVE ARRIVALS GOVERNED BY A MARKOV CHAIN

2003 ◽  
Vol 17 (4) ◽  
pp. 487-501 ◽  
Author(s):  
Yang Woo Shin ◽  
Bong Dae Choi
Keyword(s):  
Markov Chain ◽  
Transient State ◽  
Single Server ◽  
Negative Customers ◽  
Service Distribution ◽  
Finite State ◽  
Sojourn Time Distribution ◽  
Absorbing States ◽  
Negative Arrivals ◽  
Selection Of

We consider a single-server queue with exponential service time and two types of arrivals: positive and negative. Positive customers are regular ones who form a queue and a negative arrival has the effect of removing a positive customer in the system. In many applications, it might be more appropriate to assume the dependence between positive arrival and negative arrival. In order to reflect the dependence, we assume that the positive arrivals and negative arrivals are governed by a finite-state Markov chain with two absorbing states, say 0 and 0′. The epoch of absorption to the states 0 and 0′ corresponds to an arrival of positive and negative customers, respectively. The Markov chain is then instantly restarted in a transient state, where the selection of the new state is allowed to depend on the state from which absorption occurred.The Laplace–Stieltjes transforms (LSTs) of the sojourn time distribution of a customer, jointly with the probability that the customer completes his service without being removed, are derived under the combinations of service disciplines FCFS and LCFS and the removal strategies RCE and RCH. The service distribution of phase type is also considered.

Synthesis with Mandatory Stop Actions

2021 ◽  
Author(s):  
Giuseppe De Giacomo ◽  
Antonio Di Stasio ◽  
Giuseppe Perelli ◽  
Shufang Zhu
Keyword(s):  
Model Checking ◽  
Finite State Automata ◽  
Deep Impact ◽  
Synthesis Technique ◽  
Büchi Automata ◽  
Finite State ◽  
Ltl Synthesis ◽  
Buchi Automata ◽  
The Impact

We study the impact of the need for the agent to obligatorily instruct the action stop in her strategies. More specifically we consider synthesis (i.e., planning) for LTLf goals under LTL environment specifications in the case the agent must mandatorily stop at a certain point. We show that this obligation makes it impossible to exploit the liveness part of the LTL environment specifications to achieve her goal, effectively reducing the environment specifications to their safety part only. This has a deep impact on the efficiency of solving the synthesis, which can sidestep handling Buchi determinization associated to LTL synthesis, in favor of finite-state automata manipulation as in LTLf synthesis. Next, we add to the agent goal, expressed in LTLf, a safety goal, expressed in LTL. Safety goals must hold forever, even when the agent stops, since the environment can still continue its evolution. Hence the agent, before stopping, must ensure that her safety goal will be maintained even after she stops. To do synthesis in this case, we devise an effective approach that mixes a synthesis technique based on finite-state automata (as in the case of LTLf goals) and model-checking of nondeterministic Buchi automata. In this way, again, we sidestep Buchi automata determinization, hence getting a synthesis technique that is intrinsically simpler than standard LTL synthesis.

‘Untying the Knot’: Achieving Integrative and Collaborative Care within Trauma and Fear Saturated Systems – A Practice-Focused Discussion Paper

2017 ◽  
Vol 42 (2) ◽  
pp. 104-107 ◽  
Author(s):  
Dilip Balu
Keyword(s):  
Child Protection ◽  
Health Care Systems ◽  
Traumatic Experience ◽  
Ripple Effect ◽  
Discussion Paper ◽  
Care Systems ◽  
Trauma Informed ◽  
The Impact ◽  
The Brain ◽  
Mental Health Care Systems

The author's clinical experience with the Child Protection and Mental Health Care systems informs this brief practice-focused paper. The author posits that Secondary Traumatic Stress and Vicarious Trauma are central to understanding the impact of relationally traumatic material and the experience of individuals, families, team and the wider ecology of care systems. In particular, the author hypothesises that the tendency of systems to become fragmented in operation, with silos of sub-parts working parallel to each other, may be a natural adaptation to the ways in which traumatic experience ripples across system boundaries. This ‘ripple effect’ may lead to increasing emotional and relational reactivity, and survival-oriented inward focus of energies and efforts. The metaphor of the brain and nervous system is used to explore ideas of connection and integration in care systems. Trauma-informed leadership by individuals and teams is also touched upon in relation to reducing fear-driven clinical practice.

Development of metaheuristics to solve a transportation inventory location routing problem considering lost sale for perishable goods

2019 ◽  
Vol 14 (1) ◽  
pp. 175-198 ◽  
Author(s):  
S.M.T. Fatemi Ghomi ◽  
B. Asgarian
Keyword(s):  
Mathematical Model ◽  
Distribution Systems ◽  
Hybrid Approach ◽  
Rational Approach ◽  
Location Routing Problem ◽  
Routing Problem ◽  
Content Type ◽  
Location Routing ◽  
Perishable Goods ◽  
The Impact

PurposeFinding a rational approach to maintain a freshness of foods and perishable goods and saving their intrinsic attributes during a distribution of these products is one of the main issues for distribution and logistics companies. This paper aims to provide a framework for distribution of perishable goods which can be applied for real life situations.Design/methodology/approachThis paper proposes a novel mathematical model for transportation inventory location routing problem. In addition, the paper addresses the impact of perishable goods age on the demand of final customers. The model is optimally solved for small- and medium-scale problems. Moreover, regarding to NP-hard nature of the proposed model, two simple and one hybrid metaheuristic algorithms are developed to cope with the complexity of problem in large scale problems.FindingsNumerical examples with different scenarios and sensitivity analysis are conducted to investigate the performance of proposed algorithms and impacts of important parameters on optimal solutions. The results show the acceptable performance of proposed algorithms.Originality/valueThe authors formulate a novel mathematical model which can be applicable in perishable goods distribution systems In this regard, the authors consider lost sale which is proportional to age of products. A new hybrid approach is applied to tackle the problem and the results show the rational performance of the algorithm.

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