Approximation of the two-dimensional output process of a retrial queue with MMPP input

In this paper, we review a retrial queue with MMPP input and two-way communication. Incoming requests arriving at the server and finding it busy join the source of retrial calls and try to enter the server again after some exponentially distributed time. While idle, the server makes outgoing calls and serves them with another delay parameter. MMPP (Markov Modulated Poisson Process) is an input process in which control is driven by a continuous Markov chain. Changing its state entails a change in the intensity of the input process. For this model, we present an asymptotic approximation of the two-dimensional characteristic function under the condition of a long delay of requests in the source of retrial calls. For this approximation, we carried out a numerical experiment, where asymptotic results were compared to computations obtained via simulation

Engineering in a crisis : observing students’ perceived roles of engineers during pandemics and natural disasters

Engineers have a responsibility to use their skills to protect the welfare of communities. When these ethical responsibilities are discussed in classrooms, the focus is usually on microethics, which focuses on individual decision-making, rather than macroethics that address broad societal concerns. The COVID-19 pandemic has presented a unique opportunity to assess macroethics attitudes because unjust social, economic, and environmental systems have been brought to the forefront amidst the response (e.g., inequitable healthcare systems). In this paper, we consider the COVID-19 pandemic and natural disasters through the lens of engineering macroethics. We aim to understand students’ macroethics attitudes and perceptions about the responsibilities of engineers. In Fall 2020, we deployed a survey to undergraduate engineering students at two universities (n = 520). We asked students to discuss what they perceived to be the role of the engineering profession in response to the global COVID-19 pandemic and natural disasters. We used qualitative content analyses to explore responses in which macroethics attitudes are present and to evaluate the actions that students believe engineers should take in the wake of a crisis. Many of these responses include considerations of infrastructure resilience, resource distribution, and community equity. Logit models were then used to assess the presence of macroethics attitudes in relation to sociodemographic factors of respondents, revealing that factors, including family size, major, and gender influenced these attitudes. Implications from this study include recommendations on curricular content and identifying which student demographic groups would benefit most from intentional macroethical content in coursework.Civil, Architectural, and Environmental Engineerin

FORGING THE MINOAN PAST

oai:ojs.www.cretaantica.unict.it:article/134‘Cretenses semper mendaces’ was an ancient tag-line, and forgers on Crete produced fake ‘antiquities’ from an early date. Excavation and publication of prehistoric remains at Knossos vastly increased the value of Cretan artefacts. The romantic associations of the island’s early civilisations with mythological figures, and the excitement created by the new discoveries engendered an eager market for objects that could be linked to what was lauded as the first high culture of Europe. Although not nearly so well known as the series of ivory figurines that began to surface a decade later, ‘Minoan’ terracottas, bronzes, carved horn, and engraved rings and gemstones produced in the first years of the 20th century were likewise fashioned to satisfy the desires of private collectors and foreign museum curators. Forgers relied on a variety of factors as they attempted to ensure the marketability of their products and increase their value. They employed precious or semi-precious materials, devised appealing iconographies, suggested plausible find spots, and invented colourful stories of recovery. This chapter contextualises some of these forgeries and explores their active effects: not just how they were designed to satisfy the desires of intended buyers, but also how they engendered new ideas about the distant past and yet simultaneously reinforced prevalent conceptions of it

Dielectric spectroscopy of perfluorosulfonic membranes in proton- and terbium-substituted forms

The present study was aimed to reveal the mechanisms of electrical conductivity of the perfluorosulfonic membrane (MF-4SK) in the proton-substituted form and an effect of Tb ions modified this matrix on these mechanisms. The frequency dependences of the complex permittivity at a temperature of 293 K and the temperature dependences of it at a frequency of 1 kHz for samples of the both forms have been measured. An increase in the permittivity ε´ value with decreasing frequency and increasing temperature was brought out. The maxima of the dielectric loss factor were obtained for the layers of the studied systems at different temperatures. The obtained experimental data allowed us to assume that there were distributions over relaxation times for relaxation oscillators. A transition from classical to quantum mechanical charge transfer was discovered and interpreted for the original and modified membranes

Mathematical model of Scheduler with Semi-Markov input and bandwidth sharing discipline

In this paper, we consider single server queueing system with multiple semi-Markov inputs and buffers. Each request of the flows brings to the system some random amount of information. According to the bandwidth sharing discipline, each buffer has its own part of the throughput and the server transmits the information from buffers simultaneously. The aim of the current research is to derive the probability distribution of the amount of information in single buffer

Semi-Markov resource flow as a bit-level model of traffic

In this paper, we consider semi-Markov flow as a bit-level model of traffic. Each request of the flow brings some arbitrary distributed amount of information to the system. The current paper aims to investigate the amount of information received in semi-Markov flow during time unit. We use the asymptotic analysis method under the limit condition of growing time of observation to derive the limiting probability distribution of the amount of information received in the flow and build the approximation of its prelimit distribution function

Evaluation of the integrated intervention for dual problems and early action among latino immigrants with co-occurring mental health and substance misuse symptoms: A randomized clinical trial

Importance: Immigrants are at an increased risk for co-occurring mental health and substance misuse symptoms; however, effective treatments are lacking. Objective: To evaluate the effectiveness of the Integrated Intervention for Dual Problems and Early Action (IIDEA) program compared with enhanced usual care. Design, Setting, and Participants: This effectiveness randomized clinical trial was conducted from September 2, 2014, to February 2, 2017, in 17 clinics or emergency departments and 24 community sites in Boston, Massachusetts, as well as in Madrid and Barcelona, Spain. Equal randomization (1:1) in 2-person blocks was used, assigning participants to either the IIDEA treatment group (n = 172) or the enhanced usual care control group (n = 169). Intent-to-treat analyses assessed effectiveness, and post hoc analyses examined whether results varied by symptom severity or treatment dose. Eligible participants were between 18 and 70 years of age, self-identified as Latino, screened positive for co-occurring symptoms, and were not receiving specialty behavioral health services. Interventions: Participants were randomized to a 10-session IIDEA treatment or to enhanced usual care. Main Outcomes and Measures: Primary outcomes were changes in alcohol and drug misuse and results of a urine test for drug metabolites but not for alcohol misuse. Secondary outcomes were symptoms of depression, generalized anxiety, posttraumatic stress disorder, and overall mental health. Results: In total, 341 participants were randomized to either the IIDEA treatment group (n = 172; 94 [54.7%] female, mean [SD] age, 33.5 [11.6] years) or the enhanced usual care control group (n = 169; 80 [47.3%] female, mean [SD] age, 34.3 [11.8] years). No statistically significant effects of IIDEA were found for primary drug and alcohol outcomes (ASI Lite-drug score: β = -0.02 [SE, 0.69; P = .88; Cohen d, 0.00; 95% CI, -0.17 to 0.17]; ASI Lite-alcohol score: β = -0.01 [SE, 1.19; P = .66; Cohen d, 0.00; 95% CI, -0.12 to 0.12]; urine drug test result: β = -0.36 [SE, 0.43; P = .50; OR, 0.70; 95% CI, 0.30-1.61]), but statistically significant effects were observed for secondary mental health outcomes. The IIDEA treatment was effective in reducing depressive symptoms per the Public Health Questionnaire-9 score (β = -1.14; SE, 0.47; P = .02; Cohen d, 0.20 [95% CI, 0.04-0.36]), posttraumatic stress disorder symptoms per the Posttraumatic Stress Disorder Checklist-5 score (β = -3.23; SE, 1.59; P = .04; Cohen d, 0.25 [95% CI, 0.01-0.37]), and overall mental health symptoms per the Hopkins Symptom Checklist-20 (β = -0.20; SE, 0.07; P = .01; Cohen d, 0.25 [95% CI, 0.08-0.42]) and composite mental health (β = -3.70; SE, 1.75; P = .04; Cohen d, 0.19 [95% CI, 0.01-0.36]) scores at the 6-month follow-up. Exploratory analyses suggested that 6-month treatment effects occurred for patients whose drug misuse was moderate to severe at the baseline assessment. Among patients with moderate to severe substance misuse, IIDEA substantially reduced substance use per the urine test results (odds ratio, 0.25 [95% CI, 0.09-0.67]; P = .01). Treatment dose showed small to large effect sizes by outcome. Conclusions and Relevance: The IIDEA treatment did not change drug misuse but did improve secondary mental health and substance misuse outcomes for a heterogeneous population with moderate to severe symptoms; this finding provides a path for treating Latino immigrants with co-occurring mental health and substance misuse symptoms. Trial Registration: ClinicalTrials.gov Identifier: NCT02038855.This study was funded in part by grant R01DA034952 from NIDA of the National Institutes of Health; grant R01MH100155-01S1 from NIMH; and grants ISCII PI13/02200 and PI16/01852 from Instituto de Salud Carlos III, grant 20151073 from Delegación del Gobierno para el Plan Nacional de Drogas, and grant LSRG-1-005-16 from the American Foundation for Suicide Prevention (Dr Baca-García