Study of GaN:Eu & delta-InN Based Active Regions For High Efficiency Long Wavelength Emitters

III-nitride alloys and nanostructures have been proved reliable materials for electronic and photonic applications. In particular, indium-gallium-nitride (InGaN) based quantum wells (QW) have been greatly improved over the years exhibiting very high effi

A theoretical study of two-period relaxations for lot-sizing problems with big-bucket capacities

In this paper, we study two-period subproblems proposed by Akartunali et al. (2015) for lot-sizing problems with big-bucket capacities and nonzero setup times, complementing our previous work investigating the special case of zero setup times. In particular, we study the polyhedral structure of the mixed integer sets related to various two-period relaxations. We derive several families of valid inequalities and investigate their facet-defining conditions. We also discuss the separation problems associated with these valid inequalities

Local cuts and two-period convex hull closures for big-bucket lot-sizing problems

Despite the significant attention they have drawn, big bucket lot-sizing problems remain notoriously difficult to solve. Previous work of Akartunali and Miller (2012) presented results (computational and theoretical) indicating that what makes these problems difficult are the embedded single-machine, single-level, multi-period submodels. We therefore consider the simplest such submodel, a multi-item, two-period capacitated relaxation. We propose a methodology that can approximate the convex hulls of all such possible relaxations by generating violated valid inequalities. To generate such inequalities, we separate two-period projections of fractional LP solutions from the convex hulls of the two-period closure we study. The convex hull representation of the two-period closure is generated dynamically using column generation. Contrary to regular column generation, our method is an outer approximation, and therefore can be used efficiently in a regular branch-and-bound procedure. We present computational results that illustrate how these two-period models could be effective in solving complicated problems

Τα αιωρούμενα σωματίδια και οι επιπτώσεις τους στην υγεία

Ο ανθρώπινος οργανισμός εκτίθεται καθημερινά σε διάφορες ουσίες και σωματίδια που αιωρούνται στην ατμόσφαιρα. Το διοξείδιο του άνθρακα (CO2), το διοξείδιο του θείου (SO2), τα οξείδια του αζώτου (NOx), το όζον (O3) και τα αιωρούμενα σωματίδια (PM) είναι ανάμεσα στους πιο γνωστούς και επιβλαβείς αέριους ρύπους. Η δράση τους στον ανθρώπινο οργανισμό εξαρτάται από τη συγκέντρωσή τους στην ατμόσφαιρα. Τα συμπτώματα του ατόμου που εκτίθεται σε αέριους ρύπους μπορούν να κυμαίνονται από ήπια, όπως ερεθισμός των ματιών και του ρινοφάρυγγα έως πολύ σοβαρά, όπως κώμα ή και θάνατος. Οι ατμοσφαιρικοί ρύποι συνυπάρχουν στην ατμόσφαιρα και η δράση τους στον ανθρώπινο οργανισμό είναι συνεργική. Ανάλογα με το βαθμό έκθεσης και την κατάσταση της υγείας του ατόμου, η ατμοσφαιρική ρύπανση προκαλεί διαταραχές στη φυσιολογική λειτουργία πολλών συστημάτων οργάνων ή/και επιδεινώνει ήδη υπάρχουσες νόσους. Ο Π.Ο.Υ. ορίζει την ατμοσφαιρική ρύπανση ως τον πιο σημαντικό περιβαλλοντικό κίνδυνο για την υγεία του ατόμου. Στην τελευταία έκθεσή του αναφέρει μεταξύ άλλων ότι απαιτείται η λήψη μέτρων για τον περιορισμό των αέριων ρύπων, οι οποίοι ευθύνονται για εκατομμύρια θανάτους κάθε χρόνο. Ιδιαίτερη σημασία δίνεται στην επίδραση της ατμοσφαιρικής ρύπανσης στα παιδιά και στα αυξανόμενα περιστατικά βρογχικού άσθματος σε νεαρή ηλικία. Παρά τον περιορισμό των εκπομπών πολλών αέριων ρύπων από κάποιες χώρες, η ατμοσφαιρική ρύπανση, κυρίως στα μεγάλα αστικά κέντρα, εξακολουθεί να βρίσκεται σε υπερβολικά υψηλά επίπεδα (πάνω από τις μέσες τιμές που ορίζει ο Π.Ο.Υ το 2018) με αποτέλεσμα να υποβαθμίζει την ποιότητα ζωής εκατομμυρίων ανθρώπων. Προκαλεί αύξηση της νοσηρότητας και πρόωρη θνησιμότητα.The human body is exposed daily to various substances and suspended particles in the atmosphere. Carbon dioxide (CO2), sulfur dioxide (SO2), nitrogen oxides (NOx), ozone (O3) and particulate matter (PM) are among the most well-known and harmful gaseous pollutants. Their action in the human body depends on their concentration in the atmosphere. The symptoms of the person exposed to gaseous pollutants may range from mild, such as irritation of the eyes and nasopharynx to severe, such as coma and/or death. Atmospheric pollutants coexist in the atmosphere and their action in the human body is synergistic. Depending on the degree of exposure and the state of the individual's health, air pollution causes disturbance to the normal functioning of many organ systems and aggravates existing diseases. WHO defines atmospheric pollution as the most significant environmental hazard to the human health. In its latest report it mentions, among other things, that measures are needed to reduce air pollutants, which are responsible for millions of deaths each year. Particular importance is given to the impact of air pollution on children and the increasing incidences of asthma at an early age. Despite the limitation of emissions of many air pollutants from some countries, air pollution, especially in large urban centers, is still too high (above the average that WHO set in 2018), which degrades the quality of life of millions of people. It causes increased morbidity and premature mortality

Exercise and redox status responses following alpha-lipoic acid supplementation in G6PD deficient individuals

G6PD deficiency renders cells more susceptible to oxidative insults, while antioxidant dietary supplementation could restore redox balance and ameliorate exercise-induced oxidative stress. To examine the effects of alpha-lipoic acid (ALA) supplementation on redox status indices in G6PD deficient individuals, eight male adults with G6PD deficiency (D) participated in this randomized double-blind placebo-controlled crossover trial. Participants were randomly assigned to receive ALA (600 mg/day) or placebo for 4 weeks separated by a 4-week washout period. Before and at the end of each treatment period, participants exercised following an exhaustive treadmill exercise protocol. Blood samples were obtained before (at rest), immediately after and 1h after exercise for later analysis of total antioxidant capacity (TAC), uric acid, bilirubin, thiobarbituric acid reactive substances (TBARS) and protein carbonyls (PC). ALA resulted in significantly increased resting TAC and bilirubin concentrations. Moreover, TAC increased immediately and 1h after exercise following both treatment periods, whereas bilirubin increased immediately after and 1h after exercise following only ALA. No significant change in uric acid, TBARS or PC was observed at any time point. ALA supplementation for 4 weeks may enhance antioxidant status in G6PD individuals; however, it does not affect redox responses to acute exercise until exhaustion or exercise performance

Decomposition methods for large-scale network expansion problems

Network expansion problems are a special class of multi-period network design problems in which arcs can be opened gradually in different time periods but can never be closed. Motivated by practical applications, we focus on cases where demand between origin-destination pairs expands over a discrete time horizon. Arc opening decisions are taken in every period, and once an arc is opened it can be used throughout the remaining horizon to route several commodities. Our model captures a key timing trade-off: the earlier an arc is opened, the more periods it can be used for, but its fixed cost is higher, since it accounts not only for construction but also for maintenance over the remaining horizon. An overview of practical applications indicates that this trade-off is relevant in various settings. For the capacitated variant, we develop an arc-based Lagrange relaxation, combined with local improvement heuristics. For uncapacitated problems, we develop four Benders decompositi

Targeted Green Recovery Measures in a Post-COVID-19 World Enable the Energy Transition

Despite the significant volume of fiscal recovery measures announced by countries to deal with the COVID-19 crisis, most recovery plans allocate a low percentage to green recovery. We present scenarios exploring the medium- and long-term impact of the COVID-19 crisis and develop a Green Recovery scenario using three well-established global models to analyze the impact of a low-carbon focused stimulus. The results show that a Green Recovery scenario, with 1% of global GDP in fiscal support directed to mitigation measures for 3 years, could reduce global CO 2 emissions by 10.5–15.5% below pre-COVID-19 projections by 2030, closing 8–11.5% of the emissions gap with cost-optimal 2°C pathways. The share of renewables in global electricity generation is projected to reach 45% in 2030, the uptake of electric vehicles would be accelerated, and energy efficiency in the buildings and industry sector would improve. However, such a temporary investment should be reinforced with sustained climate policies after 2023 to put the world on a 2°C pathway by mid-century

Updated nationally determined contributions collectively raise ambition levels but need strengthening further to keep Paris goals within reach

By January 2022, 156 countries had submitted new or updated nationally determined contributions (NDCs) under the Paris Agreement. This study analyses the greenhouse gas (GHG) emissions and macroeconomic impacts of the new NDCs. The total impact of the updated unconditional and conditional NDCs of these countries on global emission levels by 2030 is an additional reduction of about 3.8 and 3.9 GtCO2eq, respectively, compared to the previously submitted NDCs as of October 2020. However, this total reduction must be about three times greater to be consistent with keeping global temperature increase to well below 2 °C, and even seven times greater for 1.5 °C. Nine G20 economies have pledged stronger emission reduction targets for 2030 in their updated NDCs, leading to additional aggregated GHG emission reductions of about 3.3 GtCO2eq, compared to those in the previous NDCs. The socio-economic impacts of the updated NDCs are limited in major economies and largely depend on the emission reduction effort included in the NDCs. However, two G20 economies have submitted new targets that will lead to an increase in emissions of about 0.3 GtCO2eq, compared to their previous NDCs. The updated NDCs of non-G20 economies contain further net reductions. We conclude that countries should strongly increase the ambition levels of their updated NDC submissions to keep the climate goals of the Paris Agreement within reach

Targeted Green Recovery Measures in a Post-COVID-19 World Enable the Energy Transition

Despite the significant volume of fiscal recovery measures announced by countries to deal with the COVID-19 crisis, most recovery plans allocate a low percentage to green recovery. We present scenarios exploring the medium- and long-term impact of the COVID-19 crisis and develop a Green Recovery scenario using three well-established global models to analyze the impact of a low-carbon focused stimulus. The results show that a Green Recovery scenario, with 1% of global GDP in fiscal support directed to mitigation measures for 3 years, could reduce global CO2 emissions by 10.5–15.5% below pre-COVID-19 projections by 2030, closing 8–11.5% of the emissions gap with cost-optimal 2°C pathways. The share of renewables in global electricity generation is projected to reach 45% in 2030, the uptake of electric vehicles would be accelerated, and energy efficiency in the buildings and industry sector would improve. However, such a temporary investment should be reinforced with sustained climate policies after 2023 to put the world on a 2°C pathway by mid-century