Based on the cross-layer design, the power-optimization problem of Macro-Femto Heterogeneous Networks （HetNets） has been formulated. The constraints of power and re-source block allocation in the physical layer, del...Based on the cross-layer design, the power-optimization problem of Macro-Femto Heterogeneous Networks （HetNets） has been formulated. The constraints of power and re-source block allocation in the physical layer, delay and target data rate in the medium ac-cess control layer, urgent queue length in the network layer, and packet error rate in the transport layer, have been considered. The original problem is non-deterministic polyno-mial time hard, which cannot be solved practi-cally. After the restrictions of upper layers are translated into constraints with physical layer parameters, and the integer restrictions are relaxed, the original problem can be decom- posed into convex optimization subproblems. The optimal solutions of resource block allo-cation and power allocation can be obtained by using the Lagrangian optimization. Simula-tion results show that the proposed scheme is better than both the round robin algorithm and the max-rain one in terms of energy efficiency, throughput and service fairness. The round robin algorithm and the max-min one only focus on the user fairness rather than quality of service fairness. Compared to the round robin scheme （the max-min one）, the proposed scheme improves the energy efficiency 58.85% （62.41%）, the throughput 19.09% （25.25%）, the service fairness 57.69% （35.48%）.展开更多
Flue gases exhausted from thermal power plants contain more than 50% of the fuel thermal energy. In the present work, experimental investigation was carried out to study the utilization of thermal energy in flue gases...Flue gases exhausted from thermal power plants contain more than 50% of the fuel thermal energy. In the present work, experimental investigation was carried out to study the utilization of thermal energy in flue gases to enhance the performance of modified solar chimney consisting of Savonius wind rotor. A modified solar chimney model was designed and fabricated to carry out experimental measurement. The model consists of thermal energy conversion unit; Savonius wind rotor and a chimney. The thermal energy in the flue gas transfers to the air particles in the air channel across the absorber plate and results in upward air stream due to the buoyancy effect. With an 9 absorber area of 2.36 re＇and flue gas mass flow rate of0.18 kg/s, air velocity＇ of 4.1 m/s was achieved at the top of the thermal unit. Increasing the mass flow rate of the flue gas to 0.24 kg/s enhances the air velocity to be 4.6 m/s. The results have demonstrated the possibility＇ of utilizing the thermal energy in the waste flue gas to enhance the performance of a solar chimney and facilitate the continuous operation during the absence of the sun.展开更多
基金supported in part by the project of National Natural Science Foundation of China under Grant No. 61071075National Science and Technology Major Project of China under Grant No. 2010ZX03003-001-02+1 种基金National Science and Technology Major Project of China under Grant No. 2011ZX03004003the Chinese Ministry of Education in the project of the Fundamental Research Funds for the Central Universities under Grant No.2011YJS216
文摘Based on the cross-layer design, the power-optimization problem of Macro-Femto Heterogeneous Networks （HetNets） has been formulated. The constraints of power and re-source block allocation in the physical layer, delay and target data rate in the medium ac-cess control layer, urgent queue length in the network layer, and packet error rate in the transport layer, have been considered. The original problem is non-deterministic polyno-mial time hard, which cannot be solved practi-cally. After the restrictions of upper layers are translated into constraints with physical layer parameters, and the integer restrictions are relaxed, the original problem can be decom- posed into convex optimization subproblems. The optimal solutions of resource block allo-cation and power allocation can be obtained by using the Lagrangian optimization. Simula-tion results show that the proposed scheme is better than both the round robin algorithm and the max-rain one in terms of energy efficiency, throughput and service fairness. The round robin algorithm and the max-min one only focus on the user fairness rather than quality of service fairness. Compared to the round robin scheme （the max-min one）, the proposed scheme improves the energy efficiency 58.85% （62.41%）, the throughput 19.09% （25.25%）, the service fairness 57.69% （35.48%）.
文摘Flue gases exhausted from thermal power plants contain more than 50% of the fuel thermal energy. In the present work, experimental investigation was carried out to study the utilization of thermal energy in flue gases to enhance the performance of modified solar chimney consisting of Savonius wind rotor. A modified solar chimney model was designed and fabricated to carry out experimental measurement. The model consists of thermal energy conversion unit; Savonius wind rotor and a chimney. The thermal energy in the flue gas transfers to the air particles in the air channel across the absorber plate and results in upward air stream due to the buoyancy effect. With an 9 absorber area of 2.36 re＇and flue gas mass flow rate of0.18 kg/s, air velocity＇ of 4.1 m/s was achieved at the top of the thermal unit. Increasing the mass flow rate of the flue gas to 0.24 kg/s enhances the air velocity to be 4.6 m/s. The results have demonstrated the possibility＇ of utilizing the thermal energy in the waste flue gas to enhance the performance of a solar chimney and facilitate the continuous operation during the absence of the sun.
