This paper presents evaluation and comparison of the TCP performance in different mobile scenarios generated by Random Waypoint (RW) and Social Network (SN) mobility models. To our knowledge, TCP performance in SN mob...This paper presents evaluation and comparison of the TCP performance in different mobile scenarios generated by Random Waypoint (RW) and Social Network (SN) mobility models. To our knowledge, TCP performance in SN mobility is discussed for the first time. The impact of AODV and DSDV routing protocols on the TCP goodput, delay and drop rate per- formance is also discussed. Extensive simulation results and analysis showed that TCP has better performance over AODV than over DSDV and has more stable performance in SN mobility than in RW mobility. We suggest using more mobility models, in particular, such as SN, in the evaluations of the transport layer or routing layer protocols because the mobility patterns have impacts on the protocol performance.展开更多
Algeria registers only 0.25 ha of agricultural surface per capita. This indicates very low agricultural capacities. Otherwise agricultural activities are concentrated in a narrow fringe of the Northern part of the cou...Algeria registers only 0.25 ha of agricultural surface per capita. This indicates very low agricultural capacities. Otherwise agricultural activities are concentrated in a narrow fringe of the Northern part of the country where the dominant climate is semi-arid with very irregular rainfalls. A majority of farms produces its main part of income from cereal crops--livestock association system. However, the diversity of the climate and the physical environment, on one hand, and the agricultural policies on the other hand, induce major transformations in this system. Transformations are also the result of a significant demographic growth in rural area. In this context, significant issues appear in term of resource＇s uses and systems＇ sustainability. To shed light in the actual situation, this study, based on a survey of 90 owners, shows that： the intensification can constitute a threat on the pastoral resources; the weakness of the farms encourages the generalization of practices characterised by a weak feed autonomy and a bad management of stock fodders; the animal interspecific integration and partial intensification are positive if they follow models which ensure autonomy, performance and optimal pastoral resource management.展开更多
The environmental problems can not be addressed in all their depth and complexity, and the most viable solutions can be made only by direct and continuous reference to the large issues of the development of the societ...The environmental problems can not be addressed in all their depth and complexity, and the most viable solutions can be made only by direct and continuous reference to the large issues of the development of the society as a whole. Environment and economic development are indissoluble, the first is where we all live, and development is what we all do to improve our fate in this environment. A main cause is the attitude of economic operators towards the environment, an attitude according to which profit should be pursued immediately, while nature protection is left for later. Ecological crisis is a new phenomenon, but derived from anthropological crisis. This reflects, at a global level, man＇s inner crisis. Every man in part, and not people or humanity in general, is responsible for this crisis. Individual responsibility is not a question of quality, but a question of quantity. The ecological crisis is linked to the personal and social life of man as a whole. The convenience, lack of respect for things, irrational waste, lack of measure, irresponsibility, injustice, exploitation, winning dirty money, eudemonism, which manifest on all aspects of life and human activity, are factors that provoke it. And, unfortunately, they maintain it.展开更多
基金Project supported by the National Natural Science Foundation of China (No. 90412010), the National Basic Research Program (973) of China (No. 2003CB317003), and the Research Grants Council of Hong Kong, China under the Area of Excellence (AoE) Scheme (No. AoE/E-01/99)
文摘This paper presents evaluation and comparison of the TCP performance in different mobile scenarios generated by Random Waypoint (RW) and Social Network (SN) mobility models. To our knowledge, TCP performance in SN mobility is discussed for the first time. The impact of AODV and DSDV routing protocols on the TCP goodput, delay and drop rate per- formance is also discussed. Extensive simulation results and analysis showed that TCP has better performance over AODV than over DSDV and has more stable performance in SN mobility than in RW mobility. We suggest using more mobility models, in particular, such as SN, in the evaluations of the transport layer or routing layer protocols because the mobility patterns have impacts on the protocol performance.
文摘Algeria registers only 0.25 ha of agricultural surface per capita. This indicates very low agricultural capacities. Otherwise agricultural activities are concentrated in a narrow fringe of the Northern part of the country where the dominant climate is semi-arid with very irregular rainfalls. A majority of farms produces its main part of income from cereal crops--livestock association system. However, the diversity of the climate and the physical environment, on one hand, and the agricultural policies on the other hand, induce major transformations in this system. Transformations are also the result of a significant demographic growth in rural area. In this context, significant issues appear in term of resource＇s uses and systems＇ sustainability. To shed light in the actual situation, this study, based on a survey of 90 owners, shows that： the intensification can constitute a threat on the pastoral resources; the weakness of the farms encourages the generalization of practices characterised by a weak feed autonomy and a bad management of stock fodders; the animal interspecific integration and partial intensification are positive if they follow models which ensure autonomy, performance and optimal pastoral resource management.
文摘The environmental problems can not be addressed in all their depth and complexity, and the most viable solutions can be made only by direct and continuous reference to the large issues of the development of the society as a whole. Environment and economic development are indissoluble, the first is where we all live, and development is what we all do to improve our fate in this environment. A main cause is the attitude of economic operators towards the environment, an attitude according to which profit should be pursued immediately, while nature protection is left for later. Ecological crisis is a new phenomenon, but derived from anthropological crisis. This reflects, at a global level, man＇s inner crisis. Every man in part, and not people or humanity in general, is responsible for this crisis. Individual responsibility is not a question of quality, but a question of quantity. The ecological crisis is linked to the personal and social life of man as a whole. The convenience, lack of respect for things, irrational waste, lack of measure, irresponsibility, injustice, exploitation, winning dirty money, eudemonism, which manifest on all aspects of life and human activity, are factors that provoke it. And, unfortunately, they maintain it.
