A set of absolute geostrophic current(AGC) data for the period January 2004 to December 2012 are calculated using the P-vector method based on monthly gridded Argo profi les in the world tropical oceans. The AGCs agre...A set of absolute geostrophic current(AGC) data for the period January 2004 to December 2012 are calculated using the P-vector method based on monthly gridded Argo profi les in the world tropical oceans. The AGCs agree well with altimeter geostrophic currents, Ocean Surface Current Analysis-Real time currents, and moored current-meter measurements at 10-m depth, based on which the classical Sverdrup circulation theory is evaluated. Calculations have shown that errors of wind stress calculation, AGC transport, and depth ranges of vertical integration cannot explain non-Sverdrup transport, which is mainly in the subtropical western ocean basins and equatorial currents near the Equator in each ocean basin(except the North Indian Ocean, where the circulation is dominated by monsoons). The identifi ed nonSverdrup transport is thereby robust and attributed to the joint effect of baroclinicity and relief of the bottom(JEBAR) and mesoscale eddy nonlinearity.展开更多
This paper presents a comprehensive charging operation for an electric-drive-reconfigured onboard charger(EDROC)with active power factor correction(APFC).The charging topology exclusively utilizes the three-phase perm...This paper presents a comprehensive charging operation for an electric-drive-reconfigured onboard charger(EDROC)with active power factor correction(APFC).The charging topology exclusively utilizes the three-phase permanent magnet synchronous motor(PMSM)propulsion system as a three-channel boost-type converter in which only a contactor and a small diode bridge are added.First,the operation scenario of the EDROC is introduced.Second,the relationship between electromagnetic torque and rotor position is investigated.Third,the current ripple cancellation of the EDROC is discussed in detail.Moreover,to implement the single-phase APFC along with charging voltage/current regulation of propulsion battery,control strategies including current balancing and synchronous/interleaving PWM strategies are incorporated.Finally,200W proof-of-concept prototype-based tests are conducted under different operation scenarios.展开更多
A generalized single-phase multilevel current source inverter (MCSI) topology with self-balancing current is proposed, which uses the duality transformation from the generalized multilevel voltage source inverter (MVS...A generalized single-phase multilevel current source inverter (MCSI) topology with self-balancing current is proposed, which uses the duality transformation from the generalized multilevel voltage source inverter (MVSI) topology. The existing single-phase 8-and 6-switch 5-level current source inverters (CSIs) can be derived from this generalized MCSI topology. In the proposed topology, each intermediate DC-link current level can be balanced automatically without adding any external circuits; thus, a true multilevel structure is provided. Moreover, owing to the dual relationship, many research results relating to the op- eration, modulation, and control strategies of MVSIs can be applied directly to the MCSIs. Some simulation results are presented to verify the proposed MCSI topology.展开更多
Most of the MHP （micro hydro power） plants use ELC （electronic load controller） for speed control. Various types of ELC have been developed so far. A dummy ballast load is connected across each phase of generator ...Most of the MHP （micro hydro power） plants use ELC （electronic load controller） for speed control. Various types of ELC have been developed so far. A dummy ballast load is connected across each phase of generator terminals and ELC controls the power consumed by the ballast load to result in constant speed operation. The ELC developed so far uses thyristor switches in each phase to control ballast load power. The ELC senses the system frequency and comparing it with reference frequency, it generates a common value of firing angle for all three thyristor pairs of each phase. The performance of such ELC is not perfect for unbalanced consumers load connected in each phase, which overloads the generator. This paper presents an advanced type of ELC which senses frequency as well as consumer＇s load current of each phase and fires the thyristor pairs with different value of firing angles for different phases. This solves the problem of overloading of the generator with unbalanced consumer＇s load. Simutink model is developed to perform transient analysis of the proposed scheme and the prototype of hardware is also fabricated. The simulation results and experimental results are presented.展开更多
Demographic transitions occur at different times and speed across different economies, and age structures consequently differ across regions. Using a solvable four-phase model, we show that economies with a higher pro...Demographic transitions occur at different times and speed across different economies, and age structures consequently differ across regions. Using a solvable four-phase model, we show that economies with a higher proportion of working-age force and a lower dependency ratio tend to have higher savings rates. Because the demographic ＂ center of gravity＂for investment demand falls at a younger point in the age distribution than that of savings supply, countries with a younger age-distribution like those described above generate national savings in excess of domestic investment, resulting in a current account surplus. Numerical simulation supports this hypothesis. But the relative youth or age of a country＇s population reflects temporary demographic trends which change continuously. Therefore, while trade imbalances caused by demographic factors are structural and long-term, they are not permanent, and may be reversed by changes in age structure.展开更多
The purpose of this paper is to create a comprehensive analysis of the development of foreign trade in the global world, the process of divergence of exports and imports under the influence political and economic chan...The purpose of this paper is to create a comprehensive analysis of the development of foreign trade in the global world, the process of divergence of exports and imports under the influence political and economic changes in Europe and the economic crisis in the world. Data from world public databases are summarized to a clear and understandable form. We analyzed the share of imports and exports （due to the global trade is presented） and its potential impact on the development of current account balance （CAB） for the United States of America （USA）, the European Union （EU）, and China. Correlation coefficient timeline for the last decade of CAB and world trade is also presented to show the influence of trade flow in the world and the EU with respect to current account. The work emphasizes the clear and understandable processing of the required data, which are then formulated to make arguments and then used to make predictions of further development of world trade. From summarized data, future crisis can be predicted and impacts can be evaluated.展开更多
This paper investigated the relationship between demographic structure and international capital flows with panel data of 190 countries over the past 60 years＇ and projection data for the 21st century. As found, from...This paper investigated the relationship between demographic structure and international capital flows with panel data of 190 countries over the past 60 years＇ and projection data for the 21st century. As found, from a global perspective, the current account balance （CAB） is negatively related to the dependency ratio, and orresponding to continuous change, international eapital flows tend to move from ＂adult countries＂ to ＂aged or young countries.＂ Since the middle of the 20th century, the U.S., Europe, Japan, China, Southeast Asia, Central Asia, South Asia, West Asia and Africa took turns in exporting capital to other countries. In the 2lst century, Europe, the U.S., Australia and Singapore will keep importing capital, while China in the 2030s, and Southeast Asia in the 2050s will in turn become the main capital importers. Given the demographic structure of China and the world, the future pattern of the international capital flows requires more serious concern and responses.展开更多
A double input-parallel-output-series hybrid switched-capacitor boost(DIPOS-HSCB)converter is proposed which consists of two different kinds of input-parallel-output-series(IPOS)circuits,i.e.,inner IPOS circuit and ou...A double input-parallel-output-series hybrid switched-capacitor boost(DIPOS-HSCB)converter is proposed which consists of two different kinds of input-parallel-output-series(IPOS)circuits,i.e.,inner IPOS circuit and outer IPOS circuit.Two boost modules and one switched-capacitor network build an inner IPOS circuit based IPOS-HSCB converter and two IPOS-HSCB converters develop the outer IPOS circuit based DIPOS-HSCB converter.With the proposed DIPOS-HSCB converter,a high voltage-gain with low component stress and small input current ripple are achieved.Furthermore,an automatic current balancing function for all input inductor currents can be also achieved using a special carrier phase-shifted modulation scheme.A prototype rated at 200 V/120 W has been developed and the maximum efficiency of the proposed DIPOS-HSCB converter is 95% at 120 W.Both steady and dynamic results are presented to validate the effectiveness of the proposed DIPOS-HSCB converter.展开更多
China＇s emergence as a major player in world trade is well known, but its growing role in global finance might have been underappreciated. China is the second largest creditor in the world today, with a net creditorp...China＇s emergence as a major player in world trade is well known, but its growing role in global finance might have been underappreciated. China is the second largest creditor in the world today, with a net creditorposition of 30 percent of GDP in 2008. We test the importance of the growth differential, demographics, government debt, financial depth and the exchange rate in shaping China＇s net foreign asset position. Our empirical results highlight the sharp fall in the young-age dependence as one key driver behind China ＇s puzzlingly large net lender position and also confirm the neoclassical prediction that faster growth attracts more capital inflows. Looking ahead, our findings suggest that China will unlikely turn into a meaningful net debtor nation over the next two decades.展开更多
The effects of the Electrical Double Layer （EDL） on the liquid mean flow and the flow stability in microchannels are investigated by solving the Poisson-Boltzmann equation. The models of the traditional streaming El...The effects of the Electrical Double Layer （EDL） on the liquid mean flow and the flow stability in microchannels are investigated by solving the Poisson-Boltzmann equation. The models of the traditional streaming Electrical Current Balance （ECB） and the newly introduced streaming Electrical Current Density Balance （ECDB） are applied to determine the electrical streaming current. The numerical results show that the electrical streaming current backflow in the ECB model near the wall can be removed by using the ECDB model, which is suitable to study the effects of the EDL on the mean flow and the flow stability in microchannels. The flow is found more unstable if the ECDB model is applied.展开更多
基金Supported by the National Basic Research Program of China(973 Program)(No.2012CB956001)the CMA(No.GYHY201306018)+2 种基金the Chinese Academy of Sciences(CAS)(No.XDA11010301)the National Natural Science Foundation of China(Nos.41176019,41421005,U1406401)the State Oceanic Administration(SOA)(No.GASI-03-01-01-05)
文摘A set of absolute geostrophic current(AGC) data for the period January 2004 to December 2012 are calculated using the P-vector method based on monthly gridded Argo profi les in the world tropical oceans. The AGCs agree well with altimeter geostrophic currents, Ocean Surface Current Analysis-Real time currents, and moored current-meter measurements at 10-m depth, based on which the classical Sverdrup circulation theory is evaluated. Calculations have shown that errors of wind stress calculation, AGC transport, and depth ranges of vertical integration cannot explain non-Sverdrup transport, which is mainly in the subtropical western ocean basins and equatorial currents near the Equator in each ocean basin(except the North Indian Ocean, where the circulation is dominated by monsoons). The identifi ed nonSverdrup transport is thereby robust and attributed to the joint effect of baroclinicity and relief of the bottom(JEBAR) and mesoscale eddy nonlinearity.
基金This work was supported in part by the National Natural Science Foundation of China(51807098,61673226)and the Six Talent Peaks Project in Jiangsu Province(2015-JY-028).
文摘This paper presents a comprehensive charging operation for an electric-drive-reconfigured onboard charger(EDROC)with active power factor correction(APFC).The charging topology exclusively utilizes the three-phase permanent magnet synchronous motor(PMSM)propulsion system as a three-channel boost-type converter in which only a contactor and a small diode bridge are added.First,the operation scenario of the EDROC is introduced.Second,the relationship between electromagnetic torque and rotor position is investigated.Third,the current ripple cancellation of the EDROC is discussed in detail.Moreover,to implement the single-phase APFC along with charging voltage/current regulation of propulsion battery,control strategies including current balancing and synchronous/interleaving PWM strategies are incorporated.Finally,200W proof-of-concept prototype-based tests are conducted under different operation scenarios.
文摘A generalized single-phase multilevel current source inverter (MCSI) topology with self-balancing current is proposed, which uses the duality transformation from the generalized multilevel voltage source inverter (MVSI) topology. The existing single-phase 8-and 6-switch 5-level current source inverters (CSIs) can be derived from this generalized MCSI topology. In the proposed topology, each intermediate DC-link current level can be balanced automatically without adding any external circuits; thus, a true multilevel structure is provided. Moreover, owing to the dual relationship, many research results relating to the op- eration, modulation, and control strategies of MVSIs can be applied directly to the MCSIs. Some simulation results are presented to verify the proposed MCSI topology.
文摘Most of the MHP （micro hydro power） plants use ELC （electronic load controller） for speed control. Various types of ELC have been developed so far. A dummy ballast load is connected across each phase of generator terminals and ELC controls the power consumed by the ballast load to result in constant speed operation. The ELC developed so far uses thyristor switches in each phase to control ballast load power. The ELC senses the system frequency and comparing it with reference frequency, it generates a common value of firing angle for all three thyristor pairs of each phase. The performance of such ELC is not perfect for unbalanced consumers load connected in each phase, which overloads the generator. This paper presents an advanced type of ELC which senses frequency as well as consumer＇s load current of each phase and fires the thyristor pairs with different value of firing angles for different phases. This solves the problem of overloading of the generator with unbalanced consumer＇s load. Simutink model is developed to perform transient analysis of the proposed scheme and the prototype of hardware is also fabricated. The simulation results and experimental results are presented.
基金This research is supported by： National Social Science Foundation ＂ Study on China＇s imbalanced foreign trade from the perspective of intra-product specialization＂ （10BJY079）.
文摘Demographic transitions occur at different times and speed across different economies, and age structures consequently differ across regions. Using a solvable four-phase model, we show that economies with a higher proportion of working-age force and a lower dependency ratio tend to have higher savings rates. Because the demographic ＂ center of gravity＂for investment demand falls at a younger point in the age distribution than that of savings supply, countries with a younger age-distribution like those described above generate national savings in excess of domestic investment, resulting in a current account surplus. Numerical simulation supports this hypothesis. But the relative youth or age of a country＇s population reflects temporary demographic trends which change continuously. Therefore, while trade imbalances caused by demographic factors are structural and long-term, they are not permanent, and may be reversed by changes in age structure.
文摘The purpose of this paper is to create a comprehensive analysis of the development of foreign trade in the global world, the process of divergence of exports and imports under the influence political and economic changes in Europe and the economic crisis in the world. Data from world public databases are summarized to a clear and understandable form. We analyzed the share of imports and exports （due to the global trade is presented） and its potential impact on the development of current account balance （CAB） for the United States of America （USA）, the European Union （EU）, and China. Correlation coefficient timeline for the last decade of CAB and world trade is also presented to show the influence of trade flow in the world and the EU with respect to current account. The work emphasizes the clear and understandable processing of the required data, which are then formulated to make arguments and then used to make predictions of further development of world trade. From summarized data, future crisis can be predicted and impacts can be evaluated.
文摘This paper investigated the relationship between demographic structure and international capital flows with panel data of 190 countries over the past 60 years＇ and projection data for the 21st century. As found, from a global perspective, the current account balance （CAB） is negatively related to the dependency ratio, and orresponding to continuous change, international eapital flows tend to move from ＂adult countries＂ to ＂aged or young countries.＂ Since the middle of the 20th century, the U.S., Europe, Japan, China, Southeast Asia, Central Asia, South Asia, West Asia and Africa took turns in exporting capital to other countries. In the 2lst century, Europe, the U.S., Australia and Singapore will keep importing capital, while China in the 2030s, and Southeast Asia in the 2050s will in turn become the main capital importers. Given the demographic structure of China and the world, the future pattern of the international capital flows requires more serious concern and responses.
文摘A double input-parallel-output-series hybrid switched-capacitor boost(DIPOS-HSCB)converter is proposed which consists of two different kinds of input-parallel-output-series(IPOS)circuits,i.e.,inner IPOS circuit and outer IPOS circuit.Two boost modules and one switched-capacitor network build an inner IPOS circuit based IPOS-HSCB converter and two IPOS-HSCB converters develop the outer IPOS circuit based DIPOS-HSCB converter.With the proposed DIPOS-HSCB converter,a high voltage-gain with low component stress and small input current ripple are achieved.Furthermore,an automatic current balancing function for all input inductor currents can be also achieved using a special carrier phase-shifted modulation scheme.A prototype rated at 200 V/120 W has been developed and the maximum efficiency of the proposed DIPOS-HSCB converter is 95% at 120 W.Both steady and dynamic results are presented to validate the effectiveness of the proposed DIPOS-HSCB converter.
文摘China＇s emergence as a major player in world trade is well known, but its growing role in global finance might have been underappreciated. China is the second largest creditor in the world today, with a net creditorposition of 30 percent of GDP in 2008. We test the importance of the growth differential, demographics, government debt, financial depth and the exchange rate in shaping China＇s net foreign asset position. Our empirical results highlight the sharp fall in the young-age dependence as one key driver behind China ＇s puzzlingly large net lender position and also confirm the neoclassical prediction that faster growth attracts more capital inflows. Looking ahead, our findings suggest that China will unlikely turn into a meaningful net debtor nation over the next two decades.
基金Project supported by the National Natural Science Foundation of China (Grant No. 20676093)
文摘The effects of the Electrical Double Layer （EDL） on the liquid mean flow and the flow stability in microchannels are investigated by solving the Poisson-Boltzmann equation. The models of the traditional streaming Electrical Current Balance （ECB） and the newly introduced streaming Electrical Current Density Balance （ECDB） are applied to determine the electrical streaming current. The numerical results show that the electrical streaming current backflow in the ECB model near the wall can be removed by using the ECDB model, which is suitable to study the effects of the EDL on the mean flow and the flow stability in microchannels. The flow is found more unstable if the ECDB model is applied.
