691 research outputs found
A Normal-Mode Approach to Jovian Atmospheric Dynamics
We propose a nonlinear, quasi-geostrophic, baroclinic model of Jovian atmospheric dynamics, in which vertical variations of velocity are represented by a truncated sum over a complete set of orthogonal functions obtained by a separation of variables of the linearized quasi-geostrophic potential vorticity equation. A set of equations for the time variation of the mode amplitudes in the nonlinear case is then derived. We show that for a planet with a neutrally stable, fluid interior instead of a solid lower boundary, the baroclinic mode represents motions in the interior, and is not affected by the baroclinic modes. One consequence of this is that a normal-mode model with one baroclinic mode is dynamically equivalent to a one layer model with solid lower topography. We also show that for motions in Jupiter's cloudy lower troposphere, the stratosphere behaves nearly as a rigid lid, so that the normal-mode model is applicable to Jupiter. We test the accuracy of the normal-mode model for Jupiter using two simple problem forced, vertically propagating Rossby waves, using two and three baroclinic modes and baroclinic instability, using two baroclinic modes. We find that the normal-road model provide qualitatively correct results, even with only a very limited number of vertical degrees of freedom
Density Controlled Divide-and-Rule Scheme for Energy Efficient Routing in Wireless Sensor Networks
Cluster based routing technique is most popular routing technique in Wireless
Sensor Networks (WSNs). Due to varying need of WSN applications efficient
energy utilization in routing protocols is still a potential area of research.
In this research work we introduced a new energy efficient cluster based
routing technique. In this technique we tried to overcome the problem of
coverage hole and energy hole. In our technique we controlled these problems by
introducing density controlled uniform distribution of nodes and fixing optimum
number of Cluster Heads (CHs) in each round. Finally we verified our technique
by experimental results of MATLAB simulations.Comment: 26th IEEE Canadian Conference on Electrical and Computer Engineering
(CCECE2013), Regina, Saskatchewan, Canada, 201
Performance Analysis of Hierarchical Routing Protocols in Wireless Sensor Networks
This work focusses on analyzing the optimization strategies of routing
protocols with respect to energy utilization of sensor nodes in Wireless Sensor
Network (WSNs). Different routing mechanisms have been proposed to address
energy optimization problem in sensor nodes. Clustering mechanism is one of the
popular WSNs routing mechanisms. In this paper, we first address energy
limitation constraints with respect to maximizing network life time using
linear programming formulation technique. To check the efficiency of different
clustering scheme against modeled constraints, we select four cluster based
routing protocols; Low Energy Adaptive Clustering Hierarchy (LEACH), Threshold
Sensitive Energy Efficient sensor Network (TEEN), Stable Election Protocol
(SEP), and Distributed Energy Efficient Clustering (DEEC). To validate our
mathematical framework, we perform analytical simulations in MATLAB by choosing
number of alive nodes, number of dead nodes, number of packets and number of
CHs, as performance metrics.Comment: NGWMN with 7th IEEE International Conference on Broadband and
Wireless Computing, Communication and Applications (BWCCA 2012), Victoria,
Canada, 201
On Energy Efficiency and Delay Minimization in Reactive Protocols in Wireless Multi-hop Networks
In Wireless Multi-hop Networks (WMhNs), routing protocols with energy
efficient and delay reduction techniques are needed to fulfill users demands.
In this paper, we present Linear Programming models (LP_models) to assess and
enhance reactive routing protocols. To practically examine constraints of
respective LP_models over reactive protocols, we select AODV, DSR and DYMO. It
is deduced from analytical simulations of LP_models in MATLAB that quick route
repair reduces routing latency and optimizations of retransmission attempts
results efficient energy utilization. To provide quick repair, we enhance AODV
and DSR. To practically examine the efficiency of enhanced protocols in
different scenarios of WMhNs, we conduct simulations using NS- 2. From
simulation results, enhanced DSR and AODV achieve efficient output by
optimizing routing latencies and routing load in terms of retransmission
attempts
HEER: Hybrid Energy Efficient Reactive Protocol for Wireless Sensor Networks
Wireless Sensor Networks (WSNs) consist of numerous sensors which send sensed
data to base station. Energy conservation is an important issue for sensor
nodes as they have limited power.Many routing protocols have been proposed
earlier for energy efficiency of both homogeneous and heterogeneous
environments. We can prolong our stability and network lifetime by reducing our
energy consumption. In this research paper, we propose a protocol designed for
the characteristics of a reactive homogeneous WSNs, HEER (Hybrid Energy
Efficient Reactive) protocol. In HEER, Cluster Head(CH) selection is based on
the ratio of residual energy of node and average energy of network. Moreover,
to conserve more energy, we introduce Hard Threshold (HT) and Soft Threshold
(ST). Finally, simulations show that our protocol has not only prolonged the
network lifetime but also significantly increased stability period.Comment: 2nd IEEE Saudi International Electronics, Communications and
Photonics Conference (SIECPC 13), 2013, Riyadh, Saudi Arabi
Arctic-North Atlantic interactions and multidecadal variability of the meridional overturning circulation
Analyses of a 500-yr control integration with the non-flux-adjusted coupled atmosphere–sea ice–oceanmodel ECHAM5/Max-Planck-Institute Ocean Model (MPI-OM) show pronounced multidecadal fluctuations of the Atlantic overturning circulation and the associated meridional heat transport. The period of the oscillations is about 70–80 yr. The low-frequency variability of the meridional overturning circulation (MOC) contributes substantially to sea surface temperature and sea ice fluctuations in the North Atlantic.The strength of the overturning circulation is related to the convective activity in the deep-water formation regions, most notably the Labrador Sea, and the time-varying control on the freshwater export from the Arctic to the convection sites modulates the overturning circulation. The variability is sustained by an interplay between the storage and release of freshwater from the central Arctic and circulation changes in the Nordic Seas that are caused by variations in the Atlantic heat and salt transport. The relatively highresolution in the deep-water formation region and the Arctic Ocean suggests that a better representation of convective and frontal processes not only leads to an improvement in the mean state but also introduces new mechanisms determining multidecadal variability in large-scale ocean circulation
The Nature of Domestic Demand for Authentic Ethnic Experiences in Egypt: Exploring Egyptian Visitors’ Perspectives and Assessments of Bedouin Cultural Attractions
Much emphasis in the literature on Bedouin tourism in the Arab world has been given to the demands, perceptions, motivations and experiences of international tourists while domestic demands are not fully understood. Thus, this study challenges the status quo, being one of a few studies in which Egyptians are represented as tourists consuming Egyptian ethnic culture. A mix of qualitative research methods, including 29 semi-structured interviews with domestic visitors, observational data and document analysis, was employed to explore Egyptian visitors’ perspectives and assessments of Bedouin cultural attractions in Egypt. The findings revealed that the concept of experiencing existential authenticity through interactions with the workers and performers appeared to be outside the visitors’ sphere of thought, as they focused almost exclusively on tangible elements of the site offerings. This study has important implications for Bedouin tourism suppliers as well as tourism researchers. Egyptian visitors can be viewed as a powerful potential market for Bedouin attractions. Thus, site management should reconsider their approach to Egyptian visitors, as well as rethink the mission and goals of their site. Theoretically, the findings of this study strongly contest the notion that objective authenticity is no longer essential in ethnic tourism
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