Unified Power Quality Controller（UPQC） was proposed to comprehensively improve power quality of coal mine power network and its basic structure and operation principle was introduced. In order to overcome time lag o...Unified Power Quality Controller（UPQC） was proposed to comprehensively improve power quality of coal mine power network and its basic structure and operation principle was introduced. In order to overcome time lag of Active Power Filter（APF） in compensating harmonic and reactive current, a novel method based on gray system theory was proposed to predict harmonic current and other distortion component. The mathematical model of component to be compensated was constructed by data sequence of distortion component, which could exactly forecast compensation signal of next period. The optimal control strategy was selected according to the principle of output signal approaching component to be compensated as near as possible. Before predicating each time the oldest data was eliminated while the latest data was added to data sequence. Then new predication model was established once again. The results show that the method can always construct mathematical model with variation of system parameters, reflect the latest state of system and not increase calculation quantity. The feasible and effective control strategy can improve power quality of coal mine power network.展开更多
The shallow hydrogenic donor impurity states in square, V-shaped, and parabolic quantum wells are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The first four impurity...The shallow hydrogenic donor impurity states in square, V-shaped, and parabolic quantum wells are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The first four impurity energy levels and binding energy of the ground state are more easily calculated than with the variation method. The calculation results indicate that impurity energy levels decrease with the increase of the well width and decrease quickly when the well width is small. The binding energy of the ground state increases until it reaches a maximum value, and then decreases as the well width increases. The results are meaningful and can be widely applied in the design of various optoelectronie devices.展开更多
The quality of supply in Spain is regulated by Act 54/1997 as the basic standard and further developed by Royal Decree 1955/2000, among others. Also this law （1997） introduces the division between generators, distri...The quality of supply in Spain is regulated by Act 54/1997 as the basic standard and further developed by Royal Decree 1955/2000, among others. Also this law （1997） introduces the division between generators, distribution companies and retailers. The aim of this paper is to provide an overview of the fundamental parameters to be taken into account when examining the status of national regulations in Spain on the quality of electricity supply, in addition to describing the various agents intervening in these. There are two more aspects to consider： the guarantee of supply and energy is provided at the lowest cost to consumers. The authors propose to include phase-shifting transformers at specific strategic points, in accordance with power flow control principles in parallel circuits. Finally, it can be concluded that Royal Decree 222/2008 needs reviewing and applying effectively, as do modifications to Royal Decree 1995/2000 providing remuneration that effectively induces electricity companies to invest in their networks, and ends with ＂a well-paid electricity company is obliged to invest in network improvements＂.展开更多
This study examines the state of liveability in emerging urban centers of Ago-lwoye and Ijebu-Igbo in Ogun State. The study used primary and secondary data. Both descriptive and inferential statistical techniques were...This study examines the state of liveability in emerging urban centers of Ago-lwoye and Ijebu-Igbo in Ogun State. The study used primary and secondary data. Both descriptive and inferential statistical techniques were used to analyze research questions that bother on urban liveability. Results of the analyses show that in the two urban centres the following are not in very good condition： neighborhood road quality, garbage collection, state of cleanliness, street light, state of security, pollution, water supply, drainage system, and power supply. Most of the residents are not satisfied with the state of liveability in Ago-Iwoye and Ijebu-Igbo towns. Statistical test result shows among others that there is no significant variation in the level of urban dwellers＇ satisfaction with their neighbourhood condition. In order to improve urban liveability in the two urban centres, government should provide all necessary infrastructural facilities and services. While roads are to be improved and maintained, electricity and water supply should be provided. Community associations should also be encouraged. They should be more involved in activities that will improve liveability in the urban centre. They should constitute themselves as pressure groups, working on the government to improve the liveability of the urban centre.展开更多
This study is to understand the impact of operating condition, especially initial operation temperature （Tini） which is set in high temperature range, on the temperature profile of the interface between PEM （polyme...This study is to understand the impact of operating condition, especially initial operation temperature （Tini） which is set in high temperature range, on the temperature profile of the interface between PEM （polymer electrolyte membrane） and catalyst layer at the cathode （i.e., the reaction surface） in a single PEFC （polymer electrolyte fuel cell）. A 1D multi-plate heat transfer model based on the temperature data of separator measured using thermograph in a power generation experiment was developed to evaluate the reaction surface temperature （Treact）. This study investigated the effects of flow rate, relative humidity and type of supply gas as well as Tini on the temperature distribution on reaction surface. The results obtained in 02 supply case show that, the temperature rise at the segments near the outlet of cell decreases with increasing Tini irrespective of relative humidity of supply gas （RH）, while it is not seen in air supply case. Regarding the segments except near the outlet in 02 supply case, Treact - Tini increases with increasing Tini for 40% RH. The temperature distribution on reaction surface in 02 supply case is wider with increasing Tini as well as decreasing RH, though that in air supply case is relatively even.展开更多
The district heating company ＂Rigas siltums＂ operates biomass fuelled boiler in Riga city. Three systems consisting ofbiomass boilers having a comparatively similar heat capacity and particle abatement units like mu...The district heating company ＂Rigas siltums＂ operates biomass fuelled boiler in Riga city. Three systems consisting ofbiomass boilers having a comparatively similar heat capacity and particle abatement units like multicyclons, electrostatic precipitators and flue gas condensers are compared. The main goal of the study is to evaluate the boiler plant as a system where solid particles are both emitted and caught. The results show that, the particulate matter can be efficiently trapped from flue gases by the particle abatement technologies, and the electrostatic precipitator with sufficiently large collection surfaces is able to provide appropriate flue gas treatment of the particulate matter in the biomass boilers also without pre-cleaning of the flue gas in multieyelons.展开更多
The likely goal of nanotectulology is the integration of individual nanodevices into a nanosystem, which includes the nanodevice（s）, power harvesting unit, data processing logic system, and possibly wireless communi...The likely goal of nanotectulology is the integration of individual nanodevices into a nanosystem, which includes the nanodevice（s）, power harvesting unit, data processing logic system, and possibly wireless communication unit. A nanosystem requires a nanoscale power source to make the entire package extremely small and high performance. The nanofuel and nanobiofuel cells developed here represent a new self-powering approach in nanotechnology, and their power output is high enough to drive nanodevices for performing self-powered sensing. This study shows the feasibility of building self-powered nanosystems for biological sciences, environmental monitoring, defense technology and even personal electronics.展开更多
文摘Unified Power Quality Controller（UPQC） was proposed to comprehensively improve power quality of coal mine power network and its basic structure and operation principle was introduced. In order to overcome time lag of Active Power Filter（APF） in compensating harmonic and reactive current, a novel method based on gray system theory was proposed to predict harmonic current and other distortion component. The mathematical model of component to be compensated was constructed by data sequence of distortion component, which could exactly forecast compensation signal of next period. The optimal control strategy was selected according to the principle of output signal approaching component to be compensated as near as possible. Before predicating each time the oldest data was eliminated while the latest data was added to data sequence. Then new predication model was established once again. The results show that the method can always construct mathematical model with variation of system parameters, reflect the latest state of system and not increase calculation quantity. The feasible and effective control strategy can improve power quality of coal mine power network.
基金Supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (PRC)Foundation of Qufu Normal University under Grant No. XJ0622
文摘The shallow hydrogenic donor impurity states in square, V-shaped, and parabolic quantum wells are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The first four impurity energy levels and binding energy of the ground state are more easily calculated than with the variation method. The calculation results indicate that impurity energy levels decrease with the increase of the well width and decrease quickly when the well width is small. The binding energy of the ground state increases until it reaches a maximum value, and then decreases as the well width increases. The results are meaningful and can be widely applied in the design of various optoelectronie devices.
文摘The quality of supply in Spain is regulated by Act 54/1997 as the basic standard and further developed by Royal Decree 1955/2000, among others. Also this law （1997） introduces the division between generators, distribution companies and retailers. The aim of this paper is to provide an overview of the fundamental parameters to be taken into account when examining the status of national regulations in Spain on the quality of electricity supply, in addition to describing the various agents intervening in these. There are two more aspects to consider： the guarantee of supply and energy is provided at the lowest cost to consumers. The authors propose to include phase-shifting transformers at specific strategic points, in accordance with power flow control principles in parallel circuits. Finally, it can be concluded that Royal Decree 222/2008 needs reviewing and applying effectively, as do modifications to Royal Decree 1995/2000 providing remuneration that effectively induces electricity companies to invest in their networks, and ends with ＂a well-paid electricity company is obliged to invest in network improvements＂.
文摘This study examines the state of liveability in emerging urban centers of Ago-lwoye and Ijebu-Igbo in Ogun State. The study used primary and secondary data. Both descriptive and inferential statistical techniques were used to analyze research questions that bother on urban liveability. Results of the analyses show that in the two urban centres the following are not in very good condition： neighborhood road quality, garbage collection, state of cleanliness, street light, state of security, pollution, water supply, drainage system, and power supply. Most of the residents are not satisfied with the state of liveability in Ago-Iwoye and Ijebu-Igbo towns. Statistical test result shows among others that there is no significant variation in the level of urban dwellers＇ satisfaction with their neighbourhood condition. In order to improve urban liveability in the two urban centres, government should provide all necessary infrastructural facilities and services. While roads are to be improved and maintained, electricity and water supply should be provided. Community associations should also be encouraged. They should be more involved in activities that will improve liveability in the urban centre. They should constitute themselves as pressure groups, working on the government to improve the liveability of the urban centre.
文摘This study is to understand the impact of operating condition, especially initial operation temperature （Tini） which is set in high temperature range, on the temperature profile of the interface between PEM （polymer electrolyte membrane） and catalyst layer at the cathode （i.e., the reaction surface） in a single PEFC （polymer electrolyte fuel cell）. A 1D multi-plate heat transfer model based on the temperature data of separator measured using thermograph in a power generation experiment was developed to evaluate the reaction surface temperature （Treact）. This study investigated the effects of flow rate, relative humidity and type of supply gas as well as Tini on the temperature distribution on reaction surface. The results obtained in 02 supply case show that, the temperature rise at the segments near the outlet of cell decreases with increasing Tini irrespective of relative humidity of supply gas （RH）, while it is not seen in air supply case. Regarding the segments except near the outlet in 02 supply case, Treact - Tini increases with increasing Tini for 40% RH. The temperature distribution on reaction surface in 02 supply case is wider with increasing Tini as well as decreasing RH, though that in air supply case is relatively even.
文摘The district heating company ＂Rigas siltums＂ operates biomass fuelled boiler in Riga city. Three systems consisting ofbiomass boilers having a comparatively similar heat capacity and particle abatement units like multicyclons, electrostatic precipitators and flue gas condensers are compared. The main goal of the study is to evaluate the boiler plant as a system where solid particles are both emitted and caught. The results show that, the particulate matter can be efficiently trapped from flue gases by the particle abatement technologies, and the electrostatic precipitator with sufficiently large collection surfaces is able to provide appropriate flue gas treatment of the particulate matter in the biomass boilers also without pre-cleaning of the flue gas in multieyelons.
基金Acknowledgements The authors thank the National Program on key Basic Research Project （973 Program）, the Chinese National Natural Science Foundation, and the National Centre for Nanoscience and Technology of China for support. This work made use of the resources of the Beijing National Center for Electron Microscopy.
文摘The likely goal of nanotectulology is the integration of individual nanodevices into a nanosystem, which includes the nanodevice（s）, power harvesting unit, data processing logic system, and possibly wireless communication unit. A nanosystem requires a nanoscale power source to make the entire package extremely small and high performance. The nanofuel and nanobiofuel cells developed here represent a new self-powering approach in nanotechnology, and their power output is high enough to drive nanodevices for performing self-powered sensing. This study shows the feasibility of building self-powered nanosystems for biological sciences, environmental monitoring, defense technology and even personal electronics.
