The semi-coke was prepared by solid heat carrier with dry distillation in single factor method. The pore structures of raw coal and semi-coke were characterized by Brunauer-Emmett-Teller (BET) and scanning electron mi...The semi-coke was prepared by solid heat carrier with dry distillation in single factor method. The pore structures of raw coal and semi-coke were characterized by Brunauer-Emmett-Teller (BET) and scanning electron microscope (SEM). The results show that the adsorption and desorption isotherm of semi-coke are not coincident. There was a wide pore distribution on the semi-coke, in which mesopores and micropores account for a considerable proportion. Also there are many more secondary pores. With the increase of the final temperature of heat carrier and constant temperature, as well as the decrease of volume ratio of coal and hot carrier reactor, specific surface area and pore volume of semi-coke increased rapidly first and then decreased and finally increased, along with the rapidly reduction of average pore size. SEM photos show that the surface of semi-coke becomes increasingly rough and glossy.展开更多
The study deals with a new regenerative air heat exchanger with an intermediate heat carrier used in the systems of room ventilation.A physical and mathematical model of the heat transfer process is proposed.The...The study deals with a new regenerative air heat exchanger with an intermediate heat carrier used in the systems of room ventilation.A physical and mathematical model of the heat transfer process is proposed.The influence of design and operating parameters on the temperature efficiency of the heat exchanger is analyzed.The possibility of a significant increase in its efficiency with a decrease in the packing diameter is shown.As a result of calculations,it was found that with a decrease in the filling height,the maximum temperature efficiency shifted towards a decrease in the air flow rate from its value determined from the equality of water equivalents of liquid and air.展开更多
A study has just been carried out on hot electron effects in GaAs/Al0.3Ga0.7As potential well barrier(PWB)diodes using both Monte Carlo(MC)and drift-diffusion(DD)models of charge transport.We show the operation and be...A study has just been carried out on hot electron effects in GaAs/Al0.3Ga0.7As potential well barrier(PWB)diodes using both Monte Carlo(MC)and drift-diffusion(DD)models of charge transport.We show the operation and behaviour of the diode in terms of electric field,mean electron velocity and potential,mean energy of electrons andΓ-valley population.The MC model predicts lower currents flowing through the diode due to back scattering at anode(collector)and carrier heating at higher bias.At a bias of 1.0 V,the current density obtained from experimental result,MC and DD simulation models are 1.35,1.12 and1.77μA/μm^2 respectively.The reduction in current over conventional model,is compensated to a certain extent because less charge settles in the potential well and so the barrier is slightly reduced.The DD model results in higher currents under the same bias and conditions.However,at very low bias specifically,up to 0.3 V without any carrier heating effects,the DD and MC models look pretty similar as experimental results.The significant differences observed in the I-V characteristics of the DD and MC models at higher biases confirm the importance of energy transport when considering these devices.展开更多
基金financial support from the Major State Basic Research Development Program of China (No. 2012CB214902)the National Natural Science Foundation of China (No. 51104159) are greatly appreciated
文摘The semi-coke was prepared by solid heat carrier with dry distillation in single factor method. The pore structures of raw coal and semi-coke were characterized by Brunauer-Emmett-Teller (BET) and scanning electron microscope (SEM). The results show that the adsorption and desorption isotherm of semi-coke are not coincident. There was a wide pore distribution on the semi-coke, in which mesopores and micropores account for a considerable proportion. Also there are many more secondary pores. With the increase of the final temperature of heat carrier and constant temperature, as well as the decrease of volume ratio of coal and hot carrier reactor, specific surface area and pore volume of semi-coke increased rapidly first and then decreased and finally increased, along with the rapidly reduction of average pore size. SEM photos show that the surface of semi-coke becomes increasingly rough and glossy.
基金This work was supported by a state contract with the IT SB RAS№121031800217-8.
文摘The study deals with a new regenerative air heat exchanger with an intermediate heat carrier used in the systems of room ventilation.A physical and mathematical model of the heat transfer process is proposed.The influence of design and operating parameters on the temperature efficiency of the heat exchanger is analyzed.The possibility of a significant increase in its efficiency with a decrease in the packing diameter is shown.As a result of calculations,it was found that with a decrease in the filling height,the maximum temperature efficiency shifted towards a decrease in the air flow rate from its value determined from the equality of water equivalents of liquid and air.
基金supported by the College of Physical Sciences, University of Aberdeen, UK
文摘A study has just been carried out on hot electron effects in GaAs/Al0.3Ga0.7As potential well barrier(PWB)diodes using both Monte Carlo(MC)and drift-diffusion(DD)models of charge transport.We show the operation and behaviour of the diode in terms of electric field,mean electron velocity and potential,mean energy of electrons andΓ-valley population.The MC model predicts lower currents flowing through the diode due to back scattering at anode(collector)and carrier heating at higher bias.At a bias of 1.0 V,the current density obtained from experimental result,MC and DD simulation models are 1.35,1.12 and1.77μA/μm^2 respectively.The reduction in current over conventional model,is compensated to a certain extent because less charge settles in the potential well and so the barrier is slightly reduced.The DD model results in higher currents under the same bias and conditions.However,at very low bias specifically,up to 0.3 V without any carrier heating effects,the DD and MC models look pretty similar as experimental results.The significant differences observed in the I-V characteristics of the DD and MC models at higher biases confirm the importance of energy transport when considering these devices.
