The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets （GNPs） composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electri...The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets （GNPs） composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electrical conductivity enhancements of GNP-oil nanofluids and GNP-polyimide composites are measured. By taking into account the particle shape, the volume fraction, the thermal conductivity of filling particles and the base fluids, the thermal and electrical conductivity enhancements of GNP nanofluids are theoretically predicted by the generalized effective medium theory. Both the nonlinear dependence of effective thermal conductivity on the GNP volume fraction in nanofhiids and the very low percolation threshold for GNP-polyimide composites are well predicted. The theoretical predications are found to be in reasonably good agreement with the experimental data. The generalized effective medium theory can be used for predicting the thermal and electrical properties of GNP composites and it is still available for most of the thermal/electrical modifications in two-phase composites.展开更多
A new instrument for upper ocean survey, namely the UCTD （Underway Conductivity-Temperature- Depth）, which combines some of the advantages of other underway instruments, is introduced in this paper. The Introduction...A new instrument for upper ocean survey, namely the UCTD （Underway Conductivity-Temperature- Depth）, which combines some of the advantages of other underway instruments, is introduced in this paper. The Introduction section presents a description of the construction and function of the UCTD, and the experiments conducted in the South China Sea on board the R/V Dong Fang Hong 2 in July 2007 and August 2008. The UCTD system, with pressure and temperature sensors in the probe, is con- veniently portable, cost-effective and environment-friendly. It is hopefully suitable for future cruises. An intercomparison based on regressing with the experiment temperature data from both SeaBird plus911 CTD and the UCTD showed that the standard deviation is 0.88~C and the correlation coefficient is 0.96, achieving the goals set for the current oceanography uses. In the hydrodynamic experiments, the descending velocities and depths were calculated for different ship speeds. A pulling test was designed with a tensiorneter to measure the magnitude of the pull. The maximal tension of the line was found to be 66.2 kg, which is far lower than the bearing limit of the Hollow Spectra line. Finally, some improvement suggestions are put forward for future experiments and production.展开更多
The characteristics of low frequency electrical noise, voltage current ( V I ) and electrical derivation for 980 nm InGaAsP/InGaAs/GaAs high power double quantum well lasers(DQWLs) are measured under different conditi...The characteristics of low frequency electrical noise, voltage current ( V I ) and electrical derivation for 980 nm InGaAsP/InGaAs/GaAs high power double quantum well lasers(DQWLs) are measured under different conditions. The correlation of the low frequency electrical noise with surface non radiative current of devices is discussed. The results indicate the low frequency electrical noise of 980 nm DQWLs with high power is mainly 1/ f noise and has good relation with the device surface current at low injection.展开更多
As the quality of power LED improves and the cost of power LED reduces, semiconductor lighting will replace incandescent and fluorescent lighting gradually, causing another revolution on the lighting history. And its ...As the quality of power LED improves and the cost of power LED reduces, semiconductor lighting will replace incandescent and fluorescent lighting gradually, causing another revolution on the lighting history. And its driving solution has been greatly accelerated. Based on the white power LED I-V characteristics and the application ambiance, proposed is a new LED lighting solution, suiting indoor and outdoor illumination. According to the test results, the design is optimized, and the electrical efficiency is 95% and the output current deviation is 13.0%.展开更多
A novel high step-down non-isolated DC-DC converter has been proposed. The proposed converter consists of highly efficient non-isolated cell converters using bidirectional semiconductor power devices, and these cell c...A novel high step-down non-isolated DC-DC converter has been proposed. The proposed converter consists of highly efficient non-isolated cell converters using bidirectional semiconductor power devices, and these cell converters are connected in ISOP （input series and output parallel）. The non-isolated ISOP converter achieves high step-down ratio of D/N, operating N cell converters under the duty ratio olD. Availability of the proposed converter has been shown by developing the 48 V-12 V laboratory prototype using two 24 V-12 V cell converters. Design consideration for the 48 V-3 V multicellular converter using four 12 V-3 V cell converters has been also conducted, and the potential to approach the efficiency of 97% has been discussed. The proposed topology is suitable for the POL （point of load） converters in the highly efficient next generation DC distribution system for data centers.展开更多
Due to rapidly development of high power semiconductor devices with fast control features have made possible to control the power flow more efficiently and effectively. The Flexible AC Transmission Systems （FACTS） i...Due to rapidly development of high power semiconductor devices with fast control features have made possible to control the power flow more efficiently and effectively. The Flexible AC Transmission Systems （FACTS） in this category introduces several innovative operating control devices. One of the recent devices is Advanced Unified Power Flow Controller （AUPFC） or multi-converter UPFC, which can control bus voltage and real and reactive power flows of more than one line or even a sub-network. This paper presents performance analysis of AUPFC based on d-q axis model theory. Based on the analysis, a new fuzzy logic rules based control algorithm has been developed in this paper which improves the system performance. The control rules are structured depending upon the relationship between series inserted voltages in multi-line and the desired changes of real and reactive power flows in the control network. The impacts of different controllers along with parameters of series connected transformers and transmission lines have been investigated through developed control block models in SIMULINK. The effectiveness of the proposed scheme is demonstrated by a case study.展开更多
基金The National Natural Science Foundation of China(No.50906073,31070517)China Postdoctoral Science Foundation(No.20110491332)+1 种基金Jiangsu Planned Projects for Postdoctoral Research Funds(No.1101009B)the Science and Technology Development Plan of North Jiangsu(No.BC2012444)
文摘The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets （GNPs） composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electrical conductivity enhancements of GNP-oil nanofluids and GNP-polyimide composites are measured. By taking into account the particle shape, the volume fraction, the thermal conductivity of filling particles and the base fluids, the thermal and electrical conductivity enhancements of GNP nanofluids are theoretically predicted by the generalized effective medium theory. Both the nonlinear dependence of effective thermal conductivity on the GNP volume fraction in nanofhiids and the very low percolation threshold for GNP-polyimide composites are well predicted. The theoretical predications are found to be in reasonably good agreement with the experimental data. The generalized effective medium theory can be used for predicting the thermal and electrical properties of GNP composites and it is still available for most of the thermal/electrical modifications in two-phase composites.
基金support of the National High Technology Research and Development Program of China (Nos.2006AA09A314 and 2006AA09A307)the National Natural Science Fund (40706006)+2 种基金China’s Na-tional Basic Research Priorities Programmer (2005CB- 422303 and 2007CB411804)the key project of the In-ternational Science and Technology Cooperation Program of China (2006DFB21250)the Ministry of Educa-tion’s 111 Project (B07036)
文摘A new instrument for upper ocean survey, namely the UCTD （Underway Conductivity-Temperature- Depth）, which combines some of the advantages of other underway instruments, is introduced in this paper. The Introduction section presents a description of the construction and function of the UCTD, and the experiments conducted in the South China Sea on board the R/V Dong Fang Hong 2 in July 2007 and August 2008. The UCTD system, with pressure and temperature sensors in the probe, is con- veniently portable, cost-effective and environment-friendly. It is hopefully suitable for future cruises. An intercomparison based on regressing with the experiment temperature data from both SeaBird plus911 CTD and the UCTD showed that the standard deviation is 0.88~C and the correlation coefficient is 0.96, achieving the goals set for the current oceanography uses. In the hydrodynamic experiments, the descending velocities and depths were calculated for different ship speeds. A pulling test was designed with a tensiorneter to measure the magnitude of the pull. The maximal tension of the line was found to be 66.2 kg, which is far lower than the bearing limit of the Hollow Spectra line. Finally, some improvement suggestions are put forward for future experiments and production.
文摘The characteristics of low frequency electrical noise, voltage current ( V I ) and electrical derivation for 980 nm InGaAsP/InGaAs/GaAs high power double quantum well lasers(DQWLs) are measured under different conditions. The correlation of the low frequency electrical noise with surface non radiative current of devices is discussed. The results indicate the low frequency electrical noise of 980 nm DQWLs with high power is mainly 1/ f noise and has good relation with the device surface current at low injection.
文摘As the quality of power LED improves and the cost of power LED reduces, semiconductor lighting will replace incandescent and fluorescent lighting gradually, causing another revolution on the lighting history. And its driving solution has been greatly accelerated. Based on the white power LED I-V characteristics and the application ambiance, proposed is a new LED lighting solution, suiting indoor and outdoor illumination. According to the test results, the design is optimized, and the electrical efficiency is 95% and the output current deviation is 13.0%.
文摘A novel high step-down non-isolated DC-DC converter has been proposed. The proposed converter consists of highly efficient non-isolated cell converters using bidirectional semiconductor power devices, and these cell converters are connected in ISOP （input series and output parallel）. The non-isolated ISOP converter achieves high step-down ratio of D/N, operating N cell converters under the duty ratio olD. Availability of the proposed converter has been shown by developing the 48 V-12 V laboratory prototype using two 24 V-12 V cell converters. Design consideration for the 48 V-3 V multicellular converter using four 12 V-3 V cell converters has been also conducted, and the potential to approach the efficiency of 97% has been discussed. The proposed topology is suitable for the POL （point of load） converters in the highly efficient next generation DC distribution system for data centers.
文摘Due to rapidly development of high power semiconductor devices with fast control features have made possible to control the power flow more efficiently and effectively. The Flexible AC Transmission Systems （FACTS） in this category introduces several innovative operating control devices. One of the recent devices is Advanced Unified Power Flow Controller （AUPFC） or multi-converter UPFC, which can control bus voltage and real and reactive power flows of more than one line or even a sub-network. This paper presents performance analysis of AUPFC based on d-q axis model theory. Based on the analysis, a new fuzzy logic rules based control algorithm has been developed in this paper which improves the system performance. The control rules are structured depending upon the relationship between series inserted voltages in multi-line and the desired changes of real and reactive power flows in the control network. The impacts of different controllers along with parameters of series connected transformers and transmission lines have been investigated through developed control block models in SIMULINK. The effectiveness of the proposed scheme is demonstrated by a case study.
