Supporting disconnection operations through cooperative hoarding

Mobile clients often need to operate while disconnected from the network due to limited battery life and network coverage. Hoarding supports this by fetching frequently accessed data into clients' local caches prior to disconnection. Existing work on hoarding have focused on improving data accessibility for individual mobile clients. However, due to storage limitations, mobile clients may not be able to hoard every data object they need. This leads to cache misses and disruption to clients' operations. In this paper, a new concept called cooperative hoarding is introduced to reduce the risks of cache misses for mobile clients. Cooperative hoarding takes advantage of group mobility behaviour, combined with peer cooperation in ad-hoc mode, to improve hoard performance. Two cooperative hoarding approaches are proposed that take into account access frequency, connection probability, and cache size of mobile clients so that hoarding can be performed cooperatively. Simulation results show that the proposed methods significantly improve cache hit ratio and provides better support for disconnected operations compared to existing schemes

Multipath aware TCP (MATCP)

On the Internet many different paths exist between each source and destination. When single path routing is used these paths can be under utilized, not used fairly or not used at all. One way to overcome this is to allow multipath routing. But when multiple paths are used TCP congestion control can be negatively affected and cause poor goodput performance due to the reordering of packets. We proposeMATCP (Multipath Aware TCP) which makes modifications to TCP that allows it to monitor and select which path it takes through the network for each flow. MATCP is compared to single path routing and is validated using extensive simulation. MATCP is found to greatly improve fairness between flows while providing equal or better utilization of links than single best path networks

An adaptive membership management algorithm for application layer multicast

Due to deployment difficulty of network layer multicast, application layer multicast is considered to be a good substitute for massive P2P video/audio streaming in large networks. However, in application layer multicast, the participating users join and leave the on-going session at will. Therefore, a scalable and reliable group membership management algorithm is necessary due to the highly dynamic nature of the overlay network, built on top of the Internet. Gossip-based algorithms seem to be a solution. However, most gossip-based membership management algorithms lack flexibility, and are unable to adapt to the everchanging network dynamics, imposing roughly the same amount of overhead on the network. A new adaptive gossip-based membership management algorithm is proposed to bridge the gap. This algorithm captures the changes of the network and adjusts the parameter settings dynamically, bringing adaptivity and reducing overhead. Simulation results indicate a maximum of 50% reduction can be achieved in terms of network overhead on core network components, such as backbone links and attached routers, without sacrificing reliability and scalabilit

Location-aware cache replacement for mobile environments

Traditional cache replacement policies rely on the temporal locality of users' access pattern to improve cache performance. These policies, however, are not ideal in supporting mobile clients. As mobile clients can move freely from one location to another, their access pattern not only exhibits temporal locality, but also exhibits spatial locality. In order to ensure efficient cache utilisation, it is important to take into consideration the location and movement direction of mobile clients when performing cache replacement. In this paper. we propose a mobility-aware cache replacement policy, called MARS, suitable for wireless environments. MARS takes into account important factors (e.g. client access rate, access probability, update probability and client location) in order to improve the effectiveness of onboard caching for mobile clients. Test results show that MARS consistently outperforms existing cache replacement policies and significantly improves mobile clients' cache hit ratio

Factors Influencing Nigeria’s Trade

This paper examined factor influencing Nigeria’s trade with the rest of the world using standard time series analysis technique on annual data spanning 1981 to 2012. Focus was on industrial and agricultural production. The stylized facts showed the increasing neglect the non-oil sector has suffered over the years. On average, oil trade dominates total trade and is about three times non-oil trade. Oil trade is also more volatile, about 2 times more volatile than non-oil trade. Also, oil balance of trade is comparatively two times more unstable. Nigeria’s export on average has been larger and more volatile than import due to the dominance of oil-export. All the variables were I(1) and cointegrated. The error correction results showed that in industrial output growth is more important in explaining balance of trade and total trade adjustments to equilibrium. This could be misleading, because the Nigerian industrial sector is dominated by activities in the petroleum (oil) sector which predominantly is an extractive industry. This implies primary product trade drives the Nigerian economy. This underscores why fluctuations in the crude oil market has had significant effect on the Nigerian economy in time past and in contemporary times. It was concluded that Nigeria’s trade pattern does not conform to the Hescher-Ohlin theory of factor endowment. Amongst others, it was recommended that the Nigerian state should come up with a consumption theory, where citizens and foreign nationals domiciled in the country are encouraged to consume more of made – in – Nigeria goods. Keywords: Factors, Nigeria, oil, non-oil, Trade JEL Classification: C22 F1

Correlated Differential Privacy: Feature Selection in Machine Learning

© 2005-2012 IEEE. Privacy preserving in machine learning is a crucial issue in industry informatics since data used for training in industries usually contain sensitive information. Existing differentially private machine learning algorithms have not considered the impact of data correlation, which may lead to more privacy leakage than expected in industrial applications. For example, data collected for traffic monitoring may contain some correlated records due to temporal correlation or user correlation. To fill this gap, in this article, we propose a correlation reduction scheme with differentially private feature selection considering the issue of privacy loss when data have correlation in machine learning tasks. The proposed scheme involves five steps with the goal of managing the extent of data correlation, preserving the privacy, and supporting accuracy in the prediction results. In this way, the impact of data correlation is relieved with the proposed feature selection scheme, and moreover the privacy issue of data correlation in learning is guaranteed. The proposed method can be widely used in machine learning algorithms, which provide services in industrial areas. Experiments show that the proposed scheme can produce better prediction results with machine learning tasks and fewer mean square errors for data queries compared to existing schemes

Teachers’ technology literacy in Iran’s national curriculum on education and training in work and technology

Background and Objectives:Technology is changing rapidly, and as new technologies are created, existing technologies are being improved and developed. The technologies of the 21st century have brought possibilities to mankind, and the advances that have taken place surround human life today from all sides. Among these changes are the impact of technological advances in education and the resulting changes in the teaching-learning process. In today's world, educational systems are looking for new approaches to help them rebuild in the face of global changes. For this reconstruction, they need a rich curriculum, flexible education, effective educational leadership, a suitable learning environment and educational content, and capable and professional teachers. Readiness to use technology and knowledge of how technology supports students' learning should be one of the basic skills of teachers. Teachers' ability in the field of technology literacy enables them to use new technologies in the teaching-learning process, especially information and communication technology, thereby improving the quality of their education and the level of information literacy of students and access to a wide range of information learning resources The purpose of this study was to investigate teachers’ technology literacy in the national curriculum on Education and Training in Work and Technology. Method and Materials: This research is conducted as a descriptive study using content analysis technique. The population was three main education documents including National Comprehensive Scientific Map; The Fundamental Transformation of Education Document; and The National Curriculum Document. Data collection instruments were checklists. Descriptive and inferential statistics were used to determine the frequencies and test the results of univariate t-test and Kruskal-Wallis test. Gutmann factor was used to test the reliability. Findings: The results show agreement between .48 to .95 coefficients for the validity checklists using content validity. The findings of the study show that the level of attention to teacher technology literacy in National Curriculum in the Domain of Teaching and Education Work and Technology was higher than average; and to a largely extent it is appropriately cared for. There is no significant difference between technology literacy standards in terms of compliance with the competencies intended for teachers. Conclusion: The results show that there is no significant difference between teachers' technology literacy standards and their compliance with the required competencies. Optimal implementation of the national curriculum in the relevant field requires the special assistance and attention of teachers and the use of appropriate professional competencies provided in this program; so its provisions should be taken seriously into account in human resource engineering and in training programs, recruitment and empowerment and retraining teachers before and during service Due to the comprehensive national curriculum in the field of training and learning work and technology, in the field of technology literacy, the content should be included in the preparation and compilation of all educational content, including textbooks, curriculum guide and production of educational packages, etc

Magneto-elastic coupling and competing entropy changes in substituted CoMnSi metamagnets

We use neutron diffraction, magnetometry and low temperature heat capacity to probe giant magneto-elastic coupling in CoMnSi-based antiferromagnets and to establish the origin of the entropy change that occurs at the metamagnetic transition in such compounds. We find a large difference between the electronic density of states of the antiferromagnetic and high magnetisation states. The magnetic field-induced entropy change is composed of this contribution and a significant counteracting lattice component, deduced from the presence of negative magnetostriction. In calculating the electronic entropy change, we note the importance of using an accurate model of the electronic density of states, which here varies rapidly close to the Fermi energy.Comment: 11 pages, 9 figures. Figures 4 and 6 were updated in v2 of this preprint. In v3, figures 1 and 2 have been updated, while Table II and the abstract have been extended. In v4, Table I has updated with relevant neutron diffraction dat

Giant crystal-electric-field effect and complex magnetic behavior in single-crystalline CeRh3Si2

Single-crystalline CeRh3Si2 was investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, electrical resistivity, and specific heat measurements carried out in wide temperature and magnetic field ranges. Moreover, the electronic structure of the compound was studied at room temperature by cerium core-level x-ray photoemission spectroscopy (XPS). The physical properties were analyzed in terms of crystalline electric field and compared with results of ab-initio band structure calculations performed within the density functional theory approach. The compound was found to crystallize in the orthorhombic unit cell of the ErRh3Si2 type (space group Imma -- No.74, Pearson symbol: oI24) with the lattice parameters: a = 7.1330(14) A, b = 9.7340(19) A, and c = 5.6040(11) A. Analysis of the magnetic and XPS data revealed the presence of well localized magnetic moments of trivalent cerium ions. All physical properties were found to be highly anisotropic over the whole temperature range studied, and influenced by exceptionally strong crystalline electric field with the overall splitting of the 4f1 ground multiplet exceeding 5700 K. Antiferromagnetic order of the cerium magnetic moments at TN = 4.70(1)K and their subsequent spin rearrangement at Tt = 4.48(1) K manifest themselves as distinct anomalies in the temperature characteristics of all investigated physical properties and exhibit complex evolution in an external magnetic field. A tentative magnetic B-T phase diagram, constructed for B parallel to the b-axis being the easy magnetization direction, shows very complex magnetic behavior of CeRh3Si2, similar to that recently reported for an isostructural compound CeIr3Si2. The electronic band structure calculations corroborated the antiferromagnetic ordering of the cerium magnetic moments and well reproduced the experimental XPS valence band spectrum.Comment: 32 pages, 12 figures, to appear in Physical Review