Limited Energy Capacity Research Articles

Numerical estimation of the influence of natural convection in liquid on the conditions of ignition by a local heat source

Peculiarities of natural convection in a liquid condensed substance at ignition by a typical local energy source, that is, a small hot metal particle, are numerically investigated. The proposed model takes into account the whole complex of the main processes of heat and mass transfer with phase transitions, chemical reaction, and hydrodynamic processes during interaction between a liquid substance and a source with a limited energy capacity. The influence of convective streams in liquid during the ignition delay time on the process characteristics is analyzed.

Reliability based design of frames with limited residual strain energy capacity

The aim of this paper is to create new type of plastic limit design procedures where the influence of the limited load carrying capacity of the beam-to-column connections of elasto-plastic steel (or composite) frames under multi-parameter static loading and probabilistically given conditions are taken into consideration. In addition to the plastic limit design to control the plastic behaviour of the structure, bound on the complementary strain energy of the residual forces is also applied. If the design uncertainties (manufacturing, strength, geometrical) are taken into consideration at the computation of the complementary strain energy of the residual forces the reliability based extended plastic limit design problems can be formed. Two numerical procedures are elaborated. The formulations of the problems yield to nonlinear mathematical programming which are solved by the use of sequential quadratic algorithm.

Reliability based limit design of steel frames with limited residual strain energy capacity

AbstractThe aim of this paper is to take into consideration the influence of the limited load carrying capacity of the connections on the plastic limit state of elasto‐plastic steel (or composite) framed structures under multi‐parameter stochastic loading and probabilistically given conditions. In addition to the plastic limit design to control the plastic behaviour of the structure, bound on the complementary strain energy of the residual forces is also applied. This bound has significant effect for the load parameter. If the design uncertainties (manufacturing, strength, geometrical) are expressed by the calculation of the complementary strain energy of the residual forces a reliability based extended limit design problem is formed. The formulations of the problems yield to nonlinear mathematical programming which are solved by the use of sequential quadratic algorithm. The bi‐level optimization procedure governed by the reliability index calculation. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

On Balancing Energy Consumption in Wireless Sensor Networks

Wireless sensor networks (WSNs) require protocols that make judicious use of the limited energy capacity of the sensor nodes. In this paper, the potential performance improvement gained by balancing the traffic throughout the WSN is investigated. We show that sending the traffic generated by each sensor node through multiple paths, instead of a single path, allows significant energy conservation. A new analytical model for load-balanced systems is complemented by simulation to quantitatively evaluate the benefits of the proposed load-balancing technique. Specifically, we derive the set of paths to be used by each sensor node and the associated weights (i.e., the proportion of utilization) that maximize the network lifetime.

Reliability based limit analysis of steel frames with limited residual strain energy capacity

AbstractThe main structural elements of steel framed multi–storey structures are the columns, the beams and their connectionsmagenta, which can be considered rigid, pinned or semi–rigid. The aim of this paper is to analyze the effect of the semi–rigid connections on the limit analysis of steel structures under multi–parameter static loading where to control the plastic behavior of the structure a bound on the complementary strain energy of the residual forces is applied. The bound value is assumed to be uncertain and is modelled by a random variable. By the use of this constraint a reliability based problem formulation is constructed. The formulation of the problem yields a nonlinear mathematical programming with a nested algorithm. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Efficient index and data allocation for wireless broadcast services

The periodic broadcasting of frequently requested data can reduce the workload of uplink channels and improve data access for users in a wireless network. Since mobile devices have limited energy capacities associated with their reliance on battery power, it is important to minimize the time and energy spent on accessing broadcast data. The indexing and scheduling of broadcast data play a key role in this problem. In this paper, we formulate the index and data allocation problem and propose a solution that can adapt to any number of broadcast channels. We first restrict the considered problem to a scenario with no index/data replication, and introduce an optimal solution and a heuristic solution to the single-channel and multichannel cases, respectively. Then, we discuss how to replicate indexes on the allocation to further improve the performance. The results from some experiments demonstrate the superiority of our proposed approach.

SCON: Secure management of continuity in sensor networks

Due to limited energy capacity of batteries, the function lifetime of sensor networks in general is longer than the operational lifetime of single nodes. Therefore, to keep the network working, multiple deployments of sensor nodes are needed. Due to their nature and their operational resource constraints, sensor networks are vulnerable to various types of attacks. Key pre-distribution has been shown to be an effective way to establish secure communication in sensor networks. However, existing schemes of key pre-distribution assume the use of the same pools in various deployments of sensors. We analyzed the vulnerability of the existing key pre-distribution schemes arising out of the repeated use of fixed key information through multiple deployments. We also developed SCON, an approach for key management that provides a significant improvement in security through the use of a unique key pool for each phase of deployment. Nodes of different deployments connect through special nodes called bridge nodes which have keys from adjacent key pools of respective deployments. Furthermore, we show that SCON can perform better by taking advantage of more powerful nodes used as bridge nodes.

Gateway Selection Review in Ad hoc Networks

The nature of wireless mobile ad hoc networks depend on batteries or other fatiguing means for their energy. A limited energy capacity may be the most significant performance constraint. Therefore, radio resource and power management is an important issue of any wireless network. There is a need to reduce interference by controlling transmit power of the Mobile Terminals (MTs). Power aware design and estimation of transmit power requires familiarity with the energy consumption behavior, path loss, and interference of wireless systems. Moreover, selection of gateways, in case of availability of more than one gateway, has not been introduced thoroughly. Gateways maintain connectivity of the network and integrate two types of networks with each other. This paper introduces a mathematical analysis of power adjustment to control the transmit power using maximum transmission range and intermediate node methods for sending packets. We use these equations in selecting gateways in the simulation experiments according to two different criteria: the gateway with the highest energy level and the gateway with the least number of neighbors.

Some General Basic Planning Characteristics of Pump-Storage Hydro Capacity

This paper first discusses the effect of limited energy hydro capacity, including pump-storage hydro capacity, on system installed capacity requirements, showing that, for a combined thermal and hydro system, the capacity value of the hydro depends primarily on the reduction in the maximum thermal generation requirements that can be effected over the heavier daily peak load hours. Such determinations are inseparable from the load characteristics and the effect of prior installed limited energy capacity. Second, a mathematical basis is presented for the evaluation of the relative economics of alternative potential pump-storage sites based on operating requirements, and for the determination of the most economical size of development for various conditions.