Denial of service attacks and challenges in broadband wireless networks

Broadband wireless networks are providing internet and related services to end users. The three most important broadband wireless technologies are IEEE 802.11, IEEE 802.16, and Wireless Mesh Network (WMN). Security attacks and vulnerabilities vary amongst these broadband wireless networks because of differences in topologies, network operations and physical setups. Amongst the various security risks, Denial of Service (DoS) attack is the most severe security threat, as DoS can compromise the availability and integrity of broadband wireless network. In this paper, we present DoS attack issues in broadband wireless networks, along with possible defenses and future directions

Methods of calculation of magnetic fields and static characteristics of linear step motors for control rod drives of nuclear reactors

The performance of linear step motors (LSMs) which are being developed for control rod drives in nuclear reactors is governed by their static characteristics. The reliability of control rod drive mechanisms and the safety of the reactor depend on reliable performance of these motors. The authors describe methods of calculation of magnetic fields and static characteristics of LSMs. Two methods have been developed, approximate and accurate. The first method, less computationally intensive, could be used for small currents and weak iron saturation, while the second, based on accurate field modeling, takes into account saturation effects which considerably affect motor performance

Agricultural Growth in China and Sub-Saharan African Countries

Agriculture remains a dominant sector in the economies of most African and several Asian countries. However, the poor performance of agriculture in Africa stands in sharp contrast to the robust agricultural growth in many Asian countries.2 In this regard, the experience of China is perhaps as impressive as it is relevant to many countries in Sub-Saharan Africa. A general observation is that the productivity of land and labour has to rise through intensive agriculture, given the limited area of arable land (in China and Africa) and the high rates of growth of population (as in Africa). In many African countries, labour productivity has fallen and land productivity has not increased significantly. In China, productivities of both land and labour have increased significantly since at least the early 1980s. Agricultural output can increase in three ways: (i) get more from the same quantities of inputs through better utilisation of the existing capacity; (ii) use increased quantities of inputs; and (iii) use new techniques to raise the productivity of each input or raise the total product curve. All of these may require changes in tenurial arrangements, levels of investment in infrastructure and support services, and policies that affect the prices of outputs and inputs. A close examination of factors underlying the contrasting experiences in China and African countries reveals important differences in the institutional and policy environments affecting the individual behaviour with regard to the adoption and use of new (profitable) technologies to raise the land and labour productivities.

Calculation of static characteristics of linear step motors for control rod drives of nuclear reactors-an approximate approach

This paper describes an approximate method for calculating the static characteristics of linear step motors (LSM), being developed for control rod drives (CRD) in large nuclear reactors. The static characteristic of such a LSM which is given by the variation of electromagnetic force with armature displacement determines the motor performance in its standing and dynamic modes. The approximate method of calculation of these characteristics is based on the permeance analysis method applied to the phase magnetic circuit of LSM. This is a simple, fast and efficient analytical approach which gives satisfactory results for small stator currents and weak iron saturation, typical to the standing mode of operation of LSM. The method is validated by comparing theoretical results with experimental ones

Finite element modelling of electrostatic fields in process tomography capacitive electrode systems for flow response evaluation

Various aspects and results of 2-D finite element (FE) modeling of electrostatic fields in 12-electrode capacitive systems for two-phase flow imaging are described. The capacitive technique relies on changes in capacitances between electrodes (mounted on the outer surface of the flow pipe) due to the change in permittivities of flow components. The measured capacitances between various electrode pairs and the field computation data are used to reconstruct the cross sectional image of the flow components. FE modeling of the electric field is necessary to optimize design variables and evaluate the system response to various flow regimes, likely to be encountered in practice. Results are presented in terms of normalized capacitances for various flow regimes. The effects of key geometric parameters of the electrode system are presented and analyzed

Large-scale QRPA calculation of E1-strength and its impact on the neutron capture cross section

Large-scale QRPA calculations of the E1-strength are performed as a first attempt to microscopically derive the radiative neutron capture cross sections for the whole nuclear chart. A folding procedure is applied to the QRPA strength distribution to take the damping of the collective motion into account. It is shown that the resulting E1-strength function based on the SLy4 Skyrme force is in close agreement with photoabsorption data as well as the available experimental E1-strength at low energies. The increase of the E1-strength at low energies for neutron-rich nuclei is qualitatively analyzed and shown to affect the corresponding radiative neutron capture cross section significantly. A complete set of E1-strength function is made available for practical applications in a table format for all 7<Z<111 nuclei lying between the proton and the neutron drip lines.Comment: 17 pages, 8 figures, accepted for publication in Nucl. Phys.

Real-time cross-layer design for large-scale flood detection and attack trace-back mechanism in IEEE 802.11 wireless mesh networks

IEEE 802.11 WMN is an emerging next generation low-cost multi-hop wireless broadband provisioning technology. It has the capability of integrating wired and wireless networks such as LANs, IEEE 802.11 WLANs, IEEE 802.16 WMANs, and sensor networks. This kind of integration: large-scale coverage, decentralised and multi-hop architecture, multi-radios, multi-channel assignments, ad hoc connectivity support the maximum freedom of users to join or leave the network from anywhere and at anytime has made the situation far more complex. As a result broadband resources are exposed to various kinds of security attacks, particularly DoS attacks

Validation of Finite Element Modelling of Multielectrode Capacitive System for Process Tomography Flow Imaging

Finite element modelling of process tomography sensor systems is necessary for their CAD both for performance evaluation and design optimization. This paper involves the validation of finite element models of a 12-electrode capacitive sensor system for multiphase flow imaging. Various results of modelling have been compared in the form of standing mode capacitances and sensor sensitivity distribution with experimental data obtained from UMIST. There is good agreement between simulation results and experiments especially for high sensitivity regions inside the pipe