804 research outputs found
Generalized selfish bin packing
Standard bin packing is the problem of partitioning a set of items with
positive sizes no larger than 1 into a minimum number of subsets (called bins)
each having a total size of at most 1. In bin packing games, an item has a
positive weight, and given a valid packing or partition of the items, each item
has a cost or a payoff associated with it. We study a class of bin packing
games where the payoff of an item is the ratio between its weight and the total
weight of items packed with it, that is, the cost sharing is based linearly on
the weights of items. We study several types of pure Nash equilibria: standard
Nash equilibria, strong equilibria, strictly Pareto optimal equilibria, and
weakly Pareto optimal equilibria. We show that any game of this class admits
all these types of equilibria. We study the (asymptotic) prices of anarchy and
stability (PoA and PoS) of the problem with respect to these four types of
equilibria, for the two cases of general weights and of unit weights. We show
that while the case of general weights is strongly related to the well-known
First Fit algorithm, and all the four PoA values are equal to 1.7, this is not
true for unit weights. In particular, we show that all of them are strictly
below 1.7, the strong PoA is equal to approximately 1.691 (another well-known
number in bin packing) while the strictly Pareto optimal PoA is much lower. We
show that all the PoS values are equal to 1, except for those of strong
equilibria, which is equal to 1.7 for general weights, and to approximately
1.611824 for unit weights. This last value is not known to be the (asymptotic)
approximation ratio of any well-known algorithm for bin packing. Finally, we
study convergence to equilibria
More Than a Meal: Pilot Research Study
The national Meals on Wheels network continues to face limited funding, rising costs, unprecedented demand and need and increasing for-profit competition. That is why Meals on Wheels America set out to compare the experience and health outcomes realized by older adults who receive three different levels of service: daily traditional meal delivery, once-weekly frozen delivery and individuals on a waiting list. This study, funded by AARP Foundation and conducted by researchers at Brown University, implemented a groundbreaking approach to investigating the impact of meal service delivery on homebound seniors receiving Meals on Wheels. The study's findings validate what we've all known for decades anecdotally through firsthand experience: that Meals on Wheels does in fact deliver so much more than just a meal
Technology utilization program report, 1974
The adaptation of various technological innovations from the NASA space program to industrial and domestic applications is summarized
Compressed Air Network Calculus Using Computer Program
This paper presents the results obtained in developing a computer program for the calculus of compressed air network
A Soft-Switched Three-Port DC-DC Converter for a PV/ Battery System
This thesis proposed a soft-switched three-port bidirectional DC-DC converter for managing the power flow of a photovoltaic (PV) and battery system. The proposed converter consists of three ports connected to a PV panel, battery, and load. These three ports are interfaced through the high-frequency transformer and use phase-shift control to achieve soft-switching for all converter switches. Compared with the traditional multiport converters, the proposed three-port converter uses the least number of power switches, and zero-voltage switching (ZVS). Simulation and experimental results validate the design and effectiveness of soft switching and power flow control. The converter can work in different scenarios regardless of the availability of renewable energy and the battery\u27s state of charge. In addition, maximum power point tracking (MPPT) for renewable energy sources can be achieved for the renewable energy source while managing the power flow between three ports
Power Plant Waste Heat Recovery for Household Heating Using Heat Pumps
This paper presents a model of a power plant condenser cooling circuit which has in addition to the classical cooling scheme heat pumps for waste heat recovery. Major source of loss for a thermal power plant is the heat rejected by the condenser which can be up to 48.9% of thermal energy at turbine inlet, depending on technology used for power generation. Heat rejected by the cooling water of condenser will end up in the environment through the use of a cooling tower or directly in rivers depending on the cooling scheme employed, producing thermal pollution. Based on the mathematical model, a study on the effect of heat recovery using power plant waste heat as heat source for heat pumps was carried out. The reference heat source temperature for the heat pump was 5 °C, while the condenser cooling water temperature at outlet was in the range of 22.96 °C in April to 14.99 °C in December. As expected high cooling water temperatures at condenser outlet will generate the highest practical COP which is 3.35 comparative to 2.84 for the reference case. Accordingly the smallest amount of work that needs to be supplied to the heat pump is 8.359 kW comparative to 9.861 kW for the reference case, resulting 1.502 kW savings. For the heating period from October to April the worst case scenario is for the temperatures in December when temperature of water at the outlet of condenser was minimal 14.99 °C. Even in this case, practical COP is 3.11 higher than 2.84 for reference case, and the amount of savings with the work supplied to heat pump is 0.869 kW. In closed loop operation, the temperature of returned water at the steam condenser inlet can be theoretically 5 °C (temperature at the outlet of heat pump evaporator) with all the benefits resulting from proper condenser cooling
Nanostructured ceria-based catalysts for automotive application - Formulation of nanostructured systems for diesel and gasoline-type engines
L'abstract è presente nell'allegato / the abstract is in the attachmen
Efectos distorsionadores de la ayuda internacional: una evaluación empírica para el África Subsahariana
RESUMEN. La región de África Subsahariana (ASS) es clave para el éxito de la Agenda 2030 para el Desarrollo Sostenible. Sobre la base de las diferencias de las distintas modalidades de ayuda, analizamos el efecto generado por la Ayuda Oficial al Desarrollo (AOD) sobre el ritmo de crecimiento y la reducción de la
pobreza en ASS en el periodo 1991-2014. Para ello construimos un modelo analístico sobre los efectos distorsionadores de la ayuda, cuya estimación proporciona cuatro resultados relevantes: i) la ayuda externa ejerce tanto efectos estimulantes como distorsionadores sobre el crecimiento, pero los primeros compensan los segundos; ii) un aumento en ambas modalidades de ayuda y una reasignación entre donaciones y préstamos podría inducir un mayor crecimiento; iii) sin embargo, dicha reasignación sólo sería positiva en países con niveles sostenibles de endeudamiento; y iv) aunque la ayuda es eficaz a nivel agregado, no contribuyó significativamente a aumentar el ingreso medio corregido por la desigualdad, lo que revela una grave carencia
distributiva.ABSTRACT. Sub-Saharan Africa (SSA) is a key region for the success of the 2030 Agenda for Sustainable Development. However, there is no consensus about the contribution of Official Development Assistance (ODA) in the promotion of economic growth and the reduction of extreme poverty in this region. We therefore build an analytical framework of the distorting effects of foreign aid, and make the subsequent estimations during the period 1991?2014 for SSA. We find four main results: i) ODA to SSA has exerted both distorting and stimulating effects on growth but the latter effects were larger than the former; ii) increasing both aid grants and aid loans, and increasing the ratio of loans to grants, may induce higher growth; iii) however, such a reallocation may only be positive in countries with sustainable debt burdens; and iv) although ODA was effective in aggregate terms, it did not significantly boost the mean income corrected from inequality, which reveals a grave distributional deficiency
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