497,445 research outputs found
Optimization of insulation thickness of external walls of residential buildings in hot summer and cold winter zone of China
It is important to reduce primary energy consumption and greenhouse gas emissions associated with residential buildings in the hot summer and cold winter (HSCW) zone of China. Changing the insulation thickness of the external walls of residential buildings (ITEWB) is regarded as an effective way to manage such problems within a budget. This paper aims at developing an innovative way to select the optimal insulation thickness of external walls for residential buildings (OTWRB) in the HSCW zone of China, considering economic, energy and greenhouse gas emissions issues associated with the ITEWB. Four different cities and two different operation modes of the air conditioners (continuous and intermittent) are considered in this study. To explain the selection process, typical hypothetical buildings are simulated in Wuhan, Changsha, Hangzhou and Chengdu. Expanded polystyrene is chosen as the material of the insulation layer while split air conditioners are selected as the equipment for space heating and cooling. Integrated Environmental Solutions-Virtual Environment is used for the dynamic operational energy consumption of buildings. Life cycle cost method is adopted to calculate the economic impact of ITEWB on building performance. The Chinese life cycle database is used to quantize the impacts of ITEWB on building performance in the aspect of energy and greenhouse gas emissions based on the life cycle theory. The most appreciated insulation thickness is chosen from the thickness range of 30 mm to 150 mm. We find that for continuous operation mode of air conditioners in Wuhan, the optimal economic insulation thickness is 70 mm, whereas when considering only energy and environmental aspects, the OTWRB is 150 mm. These are all larger than the current insulation thickness which is 30 mm. When the weighting efficiencies of the economy, energy, and greenhouse gas emissions are different, the OTWRB varies from 70 mm to 150 mm for continuous operation mode. The different cities have little influence on the OTWRB while the different operation modes of air conditioners have some influence on the OTWRB
Dependence of X-Ray Burst Models on Nuclear Reaction Rates
X-ray bursts are thermonuclear flashes on the surface of accreting neutron
stars and reliable burst models are needed to interpret observations in terms
of properties of the neutron star and the binary system. We investigate the
dependence of X-ray burst models on uncertainties in (p,),
(,), and (,p) nuclear reaction rates using fully
self-consistent burst models that account for the feedbacks between changes in
nuclear energy generation and changes in astrophysical conditions. A two-step
approach first identified sensitive nuclear reaction rates in a single-zone
model with ignition conditions chosen to match calculations with a
state-of-the-art 1D multi-zone model based on the {\Kepler} stellar evolution
code. All relevant reaction rates on neutron deficient isotopes up to mass 106
were individually varied by a factor of 100 up and down. Calculations of the 84
highest impact reaction rate changes were then repeated in the 1D multi-zone
model. We find a number of uncertain reaction rates that affect predictions of
light curves and burst ashes significantly. The results provide insights into
the nuclear processes that shape X-ray burst observables and guidance for
future nuclear physics work to reduce nuclear uncertainties in X-ray burst
models.Comment: 24 pages, 13 figures, 4 tables, submitte
A Common Election Day for Euro Zone Member States?
This paper tests for the Euro zone the hypothesis put forward by Sapir and Sekkat (1999) that synchronizing elections might improve welfare. After identifying a political budget cycle in the Euro zone we build a politico-macroeconomic model and simulate the effects of adopting a common election day in the 12 Euro zone member states. The results support most of the theoretical predictions by Sapir-Sekkat: (i) Synchronizing the elections could enhance GDP growth, reduce unemployment, but leads to increased inflation and in some countries to a deterioration of the budget; higher inflation forces ECB to monetary restrictions. (ii) If the synchronization happens asymmetrically - either only in the large or only in the small Euro zone countries - the result depends on the size of the spillovers. (iii) As anticipated in Sapir -Sekkat a common election day is a further step towards the desired "European business cycle", however, at the cost of increasing its amplitude. Harmonizing elections is another method of policy coordination. Whether this leads to higher welfare is a matter of weighting the different macroeconomic outcomes and it also depends on the model applied. (author's abstract)Series: EI Working Papers / Europainstitu
Impact of inter-cell interference on flow level performance of scheduling schemes for the UMTS EUL
The UMTS Enhanced Uplink (EUL) is expected to provide higher capacity, increased data rates, and smaller latency on the communication link from users towards the network. A key mechanism in EUL traffic handling is the packet scheduler, for which a number of basic schemes can be identified (one-by- one, partial parallel, and full parallel). In this paper we analyze the interaction between the EUL scheduling scheme deployed in the network and the inter-cell interference. On the one hand, different scheduling schemes cause different inter-cell interference patterns on neighbouring cells. On the other hand, the different schemes are affected by inter-cell interference in different ways. The scheduling schemes are evaluated and compared under different approaches for reserving part of the allowed noise rise at the base station for inter-cell interference. For our analysis, we have developed a hybrid analytical/simulation approach allowing for fast evaluation of performance measures such as the mean flow transfer time and fairness expressing how the performance depends on the user’s location. This approach takes into account both the packet-level characteristics and the flow-level dynamics due to the random user behaviour
Analysis of packet scheduling for UMTS EUL - design decisions and performance evaluation
The UMTS Enhanced Uplink (EUL) provides higher capacity, increased data rates and smaller latency on the communication link from users towards the network. In this paper we present a performance comparison of three distinct EUL scheduling schemes (one-by-one, partial parallel and full parallel) taking into account both the packet level characteristics and the flow level dynamics due to the (random) user behaviour.\ud
Using a very efficient hybrid analytical and simulation approach we analyse the three schemes with respect to performance measures such as mean file transfer time and fairness. In UMTS, a significant part of the system capacity will be used to support non-elastic voice traffic. Hence, part of our investigation is dedicated to the effects that the volume of voice traffic has on the performance of the elastic traffic supported by the EUL. Finally, we evaluate the impact that implementation specifics of a full parallel scheduler has on these measures.\ud
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Our main conclusion is that our partial parallel scheduler, which is a hybrid between the one-by-one and full parallel, outperforms the other two schedulers in terms of mean flow transfer time, and is less sensitive to volume and nature of voice traffic. However, under certain circumstances, the partial parallel scheduler exhibits a somewhat lower fairness than the alternatives
The Global Warming Potential of Building Materials: An Application of Life Cycle Analysis in Nepal
open6siThis paper analyzes the global-warming potential of materials used to construct the walls of 3 building types—traditional, semimodern, and modern—in Sagarmatha National Park and Buffer Zone in Nepal, using the life-cycle assessment approach. Traditional buildings use local materials, mainly wood and stone, while semimodern and modern buildings use different amounts of commercial materials, such as cement and glass wool. A comparison of the greenhouse gas emissions associated with the 3 building types, using as the functional unit 1 m2 of wall, found that traditional buildings release about one-fourth of the greenhouse gas emissions released by semimodern buildings and less than one-fifth of the emissions of modern buildings. However, the use of thermal insulation in the modern building walls helps to reduce the energy consumption for space heating and consequently to reduce the global warming potential. In 25 years, the total global warming potential of a traditional building will be 20% higher than that of a modern building. If local materials, such as wood, are used in building construction, the emissions from production and transportation could be dramatically reduced.openBhochhibhoya, Silu; Zanetti, Michela; Pierobon, Francesca; Gatto, Paola; Maskey, R. K.; Cavalli, RaffaeleBhochhibhoya, Silu; Zanetti, Michela; Pierobon, Francesca; Gatto, Paola; Maskey, R. K.; Cavalli, Raffael
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