We present an equivalent circuit model for a silicon carrier-depletion single-drive push–pull Mach–Zehnder modulator(MZM)with its traveling wave electrode made of coplanar strip lines.In particular,the partialcapaci...We present an equivalent circuit model for a silicon carrier-depletion single-drive push–pull Mach–Zehnder modulator(MZM)with its traveling wave electrode made of coplanar strip lines.In particular,the partialcapacitance technique and conformal mapping are used to derive the capacitance associated with each layer.The PN junction is accurately modeled with the fringe capacitances taken into consideration.The circuit model is validated by comparing the calculations with the simulation results.Using this model,we analyze the effect of several key parameters on the modulator performance to optimize the design.Experimental results of MZMs confirm the theoretical analysis.A 56 Gb/s on–off keying modulation and a 40 Gb/s binary phase-shift keying modulation are achieved using the optimized modulator.展开更多
Surplus rural workers seek employment through inter-provincial migration, which was once a path to urbanization in labor export regions, and contributed a lot to the economic and social development of both the labor e...Surplus rural workers seek employment through inter-provincial migration, which was once a path to urbanization in labor export regions, and contributed a lot to the economic and social development of both the labor export regions and labor import regions. But in recent years the labor shortage in eastern regions indicates new changes of the Chinese population structure and migration. Based on the macro statistical analysis and f ield survey, this paper analyzes Huaiyuan County in northern Anhui Province by using the push-and-pull model as the analytical framework. Then it explores the mechanism of population migration and the tendency of urbanization from the aspects of the pull from labor import regions and the push from labor export regions. The study shows that both the pull from labor import regions and the push from labor export regions are decreasing, and reverse population migration may occur. Therefore, to accommodate such changes, labor export regions should transfer from "Laborers Migrating for Employment" to "Industry Transfer for Laborers" to promote healthy urbanization. Finally, it proposes further discussions in combination with the National New Urbanization Plan(2014 – 2020).展开更多
This paper documents design and modeling of a grid-connected emergency back-up power supply for medium power applications. Back-up power supplies are very important in regard to support electrical loads in the events ...This paper documents design and modeling of a grid-connected emergency back-up power supply for medium power applications. Back-up power supplies are very important in regard to support electrical loads in the events of grid power outage. However, grid-integration of a back-up power supply substantiates continual power transfer to the loads, especially to the critical loads, which should not suffer from power interruptions. Therefore, design and circuit modeling of switching converters based reliable grid-tied emergency back-up power supply are presented in this paper. There are a rectifier-link boost derived battery charging circuit and a 4-switch push-pull power inverter circuit which are controlled by high frequency pulse width modulation (PWM) signals. This paper presents a state averaging model and Laplace domain transfer function of the charging circuit and a switching converter model of the power inverter circuit. A changeover relay based transfer switch controls the power flow towards the utility loads. During off-grid situations, loads are fed power by the proposed inverter circuit and during on-grid situations, battery is charged by an ac-link rectifier-fed boost converter. However, there is a relay switching circuit to control the charging phenomenon of the battery. The proposed design is simulated in PLECS and the simulation results corroborate the reliability of the presented framework.展开更多
基金National Natural Science Foundation of China(NSFC)(61422508,61535006,61661130155)Shanghai Rising-Star Program(14QA1402600)
文摘We present an equivalent circuit model for a silicon carrier-depletion single-drive push–pull Mach–Zehnder modulator(MZM)with its traveling wave electrode made of coplanar strip lines.In particular,the partialcapacitance technique and conformal mapping are used to derive the capacitance associated with each layer.The PN junction is accurately modeled with the fringe capacitances taken into consideration.The circuit model is validated by comparing the calculations with the simulation results.Using this model,we analyze the effect of several key parameters on the modulator performance to optimize the design.Experimental results of MZMs confirm the theoretical analysis.A 56 Gb/s on–off keying modulation and a 40 Gb/s binary phase-shift keying modulation are achieved using the optimized modulator.
文摘Surplus rural workers seek employment through inter-provincial migration, which was once a path to urbanization in labor export regions, and contributed a lot to the economic and social development of both the labor export regions and labor import regions. But in recent years the labor shortage in eastern regions indicates new changes of the Chinese population structure and migration. Based on the macro statistical analysis and f ield survey, this paper analyzes Huaiyuan County in northern Anhui Province by using the push-and-pull model as the analytical framework. Then it explores the mechanism of population migration and the tendency of urbanization from the aspects of the pull from labor import regions and the push from labor export regions. The study shows that both the pull from labor import regions and the push from labor export regions are decreasing, and reverse population migration may occur. Therefore, to accommodate such changes, labor export regions should transfer from "Laborers Migrating for Employment" to "Industry Transfer for Laborers" to promote healthy urbanization. Finally, it proposes further discussions in combination with the National New Urbanization Plan(2014 – 2020).
文摘This paper documents design and modeling of a grid-connected emergency back-up power supply for medium power applications. Back-up power supplies are very important in regard to support electrical loads in the events of grid power outage. However, grid-integration of a back-up power supply substantiates continual power transfer to the loads, especially to the critical loads, which should not suffer from power interruptions. Therefore, design and circuit modeling of switching converters based reliable grid-tied emergency back-up power supply are presented in this paper. There are a rectifier-link boost derived battery charging circuit and a 4-switch push-pull power inverter circuit which are controlled by high frequency pulse width modulation (PWM) signals. This paper presents a state averaging model and Laplace domain transfer function of the charging circuit and a switching converter model of the power inverter circuit. A changeover relay based transfer switch controls the power flow towards the utility loads. During off-grid situations, loads are fed power by the proposed inverter circuit and during on-grid situations, battery is charged by an ac-link rectifier-fed boost converter. However, there is a relay switching circuit to control the charging phenomenon of the battery. The proposed design is simulated in PLECS and the simulation results corroborate the reliability of the presented framework.
