The dynamic performance of doubly-fed induction generator(DFIG) before and after connection is analyzed based on corresponding mathematical models and transfer functions in decoupled vector control.The parameter tunin...The dynamic performance of doubly-fed induction generator(DFIG) before and after connection is analyzed based on corresponding mathematical models and transfer functions in decoupled vector control.The parameter tuning methods of rotor current regulator before and after connection are given.To reach same dynamic performance the parameters should take different values and be switched before and after connection.However on one hand the closing moment of stator contactor is difficult to get as the feedback signal is usually twenty millisecond delay or so.The delay in parameter switching will affect rotor current and torque dynamics during the delayed period after connection. On the other hand parameter switching is troublesome.Hence a synchronization control strategy without parameter switching is proposed and analyzed in detail,which has linear rising exciting current to avoid current overshooting. The dynamic performance of the proposed strategy is analyzed in frequency domain and implemented on a DFIG experimental platform subsequently.The proposed synchronization strategy is validated by experimental results.展开更多
The thermal performance of a“U”type earth-to-air heat exchanger is presented in this experimental study.The device has a serial-connected vertical configuration.The wells where tubes were installed have a depth of f...The thermal performance of a“U”type earth-to-air heat exchanger is presented in this experimental study.The device has a serial-connected vertical configuration.The wells where tubes were installed have a depth of fewer than 3 m and are separated every 1.5 m,using an installation area of 3m2.The experimentation was carried out in March in Morelos,Mexico when the environmental temperature reaches 35℃ during the day.The performance of the device was measured and compared to the requirements of an office for cooling purposes within a university campus to reproduce the space restrictions found in urbanized areas.By using a small land surface,it is feasible for urbanized areas.The air temperature inside the“U”type earth-to-air heat exchanger,the surrounding soil temperature,the airspeed,and the power consumed by the fan were measured.The air temperature and the fan’s power consumption data were obtained by modifying the airspeed in four constant values,from 1.3 m/s to 6.6 m/s.Results show that the device evaluated in this work has adequate thermal performance for cooling purposes compared to the requirements of an office.A decrease in air temperature was recorded in a range of 5.1℃ to 9.4℃.Over 70%of the total temperature difference was reached in the first well,where the average soil thermal disturbance at 5 cm was 2.8℃.The device achieved a maximum COP of 12.8 and a maximum effectiveness of 88.4%.With these results,it is concluded that the system is suitable for cooling purposes in areas with space restrictions.This work is novel since the dimensions available for installation in urbanized areas are considered and compared with the thermal requirements of an office.In addition to the fact that there are no published works with vertical heat exchangers connected in series.展开更多
This study evaluated the microbial community dynamics and maturation time of two compost systems： biogas slurry compost and cow manure compost, with the aim of evaluating the potential utility of a biogas slurry comp...This study evaluated the microbial community dynamics and maturation time of two compost systems： biogas slurry compost and cow manure compost, with the aim of evaluating the potential utility of a biogas slurry compost system. Denaturing gradient gel electrophoresis （DGGE）, gene clone library, temperature, C/N ratio, and the germination index were employed for the investigation, cow manure compost was used as the control. Results showed that the basic strip and dominant strips of the DGGE bands for biogas slurry compost were similar to those of cow manure compost, but the brightness of the respective strips for each system were different. Shannon-Weaver indices of the two compost systems differed, possessing only 22% similarity in the primary and maturity stages of the compost process. Using bacterial 16S rRNA gene clone library analysis, 88 bacterial clones were detected. Further, 18 and 13 operational taxonomic units （OTUs） were present in biogas slurry and cow manure compost, respectively. The 18 OTUs of the biogas slurry compost belonged to nine bacterial genera, of which the dominant strains were Bacillus sp. and Carnobacterium sp.; the 13 OTUs of the cow manure compost belonged to eight bacterial genera, of which the dominant strains were Psychrobacter sp., Pseudomonas sp., and Clostridium sp. Results demonstrated that the duration of the thermophilic phase （more than 50°C） for biogas slurry compost was 8 d less than the according duration for cow manure compost, and the maturation times for biogas slurry and cow manure compost were 45 and 60 d, respectively. It is an effective biogas slurry assimilate technology by application of biogas slurry as nitrogen additives in the manufacture of organic fertilizer.展开更多
Surface acoustic wave （SAW） resonators are a type of ultraviolet （UV） light sensors with high sensitivity, and they have been extensively studied. Transparent SAW devices are very useful and can be developed into ...Surface acoustic wave （SAW） resonators are a type of ultraviolet （UV） light sensors with high sensitivity, and they have been extensively studied. Transparent SAW devices are very useful and can be developed into various sensors and microfluidics for sensing/monitoring and lab-on-chip applications. We report the fabrication of high sensitivity SAW UV sensors based on piezoelectric （PE） ZnO thin films deposited on glass substrates. The sensors were fabricated and their performances against the post-deposition annealing condition were investigated. It was found that the UV-light sensitivity is improved by more than one order of magnitude after annealing. The frequency response increases significantly and the response becomes much faster. The optimized devices also show a small temperature coefficient of frequency and excellent repeatability and stability, demonstrating its potential for UV-light sensing application.展开更多
With their intrinsic safety and environmental benignity,aqueous Zn-ion batteries(ZIBs)have been considered the most appropriate candidates for replacing alkali metal systems.However,polycrystalline Zn anodes in aqueou...With their intrinsic safety and environmental benignity,aqueous Zn-ion batteries(ZIBs)have been considered the most appropriate candidates for replacing alkali metal systems.However,polycrystalline Zn anodes in aqueous environments still pose enormous issues,such as dendrite growth and side reactions.Although many efforts have been made to address these obstacles through interphase modification and electrolyte design,researchers have not been able to improve the inherent thermodynamic stability and ion deposition behavior of the Zn anode.It is imperative to understand and explore advanced anode construction methods from the perspective of crystallinity.This review delves into the feasibility of precisely regulating the crystallographic features of metallic zinc,examines the challenges and merits of reported strategies for fabricating textured zinc,and offers constructive suggestions for the large-scale production and commercial application of aqueous ZIBs.展开更多
Switch grass was developed as a pioneer energy crop in USA with great industrial prospect. It contains about 60% sugars and 18% lignin. The purpose of this research is to find pretreatment process to fractionate cellu...Switch grass was developed as a pioneer energy crop in USA with great industrial prospect. It contains about 60% sugars and 18% lignin. The purpose of this research is to find pretreatment process to fractionate cellulose, hemicellulose and lignin from switch grass to obtain much more useful chemicals and enhance the residue solid to be hydrolyzed by enzymes. The six different pretreatment methods were studied, such as hot water pretreatment （HWP） alone, dilute acid pretreatment （DAP）, ammonia pretreatment （AP）, lime pretreatment （LP）, organosolv water / ehanol pretreatment （OWEP）, and organosolv water / acetone pretreatment （OWAP）. It was the best method combining DAP with OWEP because the hemicellulose sugars were recovered in the first residual liquid while a varied amount of cellulose was retained in the residual solid and the lignin fraction was obtained by simply adjusting the pH from the second liquid. The result shows the optimal two-stage process consisted of the first stage DAP at 428 K for 7 min with 0.8% sulfuric acid, resulting in 79.82% glucose recovery yield and 98.74% xylose removal and the second stage OWEP at 468K for 20 min in 45% （v / v） ethanol with 0.4% NaOH, resulting in 62% total glucose yield 99% xylose and 80% lignin removal. After enzymatic hydrolysis, the glucose yield was up to 92.6%, compared with 16% yield from untreated switch grass. Scanning electron microscopy （SEM） highlighted the differences in switch grass structure from the various pretreatment methods during biomass fractionation.展开更多
An efficient cellulose degrading bacteria exists in the thermophilic wheat straw-degrading community, WDC2. However, this strain cannot be isolated and cultured using conventional separation techniques under strict an...An efficient cellulose degrading bacteria exists in the thermophilic wheat straw-degrading community, WDC2. However, this strain cannot be isolated and cultured using conventional separation techniques under strict anaerobic conditions. We successfully isolated a strain of effective cellulose degrading bacteria CTL-6 using a wash, heat shock, and solid-liquid alternating process. Analysis of its properties revealed that, although the community containing the strain CTL-6 grew under aerobic conditions, the purified strain CTL-6 only grew under anaerobic culture conditions. The strain CTL-6 had a striking capability of degrading cellulose （80.9% weight loss after 9 days of culture）. The highest efficiency value of the endocellulase （CMCase activity） was 0.404 μmol/（min·mL）, cellulose degradation efficiency by CTL-6 was remarkably high at 50–65°C with the highest degradation efficiency observed at 60°C. The 16S rRNA gene sequence analysis indicated that the closest relative to strain CTL-6 belonged to the genus Clostridium thermocellum. Strain CTL-6 was capable of utilizing cellulose, cellobiose, and glucose. Strain CTL-6 also grew with Sorbitol as the sole carbon source, whereas C. thermocellum is unable to do so.展开更多
For a variable speed large scale wind turbine, the vibration issues become a key problem that cannot be ignored in the turbine＇s life cycle. Wind turbine tower vibration will cause superfluous mechanical loads. To re...For a variable speed large scale wind turbine, the vibration issues become a key problem that cannot be ignored in the turbine＇s life cycle. Wind turbine tower vibration will cause superfluous mechanical loads. To resolve the vibration issue, a method for constructng the energy function V is proposed to meet the demands of safe operation. The Lyapunov theorem has been em- bedded in a wind turbine control algorithm, proving the theoretical feasibility of stability control based on function V. Accord- ing to an analysis of this complex nonlinear model for the wind turbine, the general method of constructing an energy function suitable for a wind turbine is presented explicitly. The feasibility of applying an energy function to wind turbine vibration con- trol is verified experimentally using a 3.0-MW direct drive wind turbine model. The experimental results indicate that the dy- namic performance of the tested wind turbine model with energy function control is significantly better than that of the uncon- trolled structure in terms of the reduction of nacelle acceleration, velocity, and displacement response.展开更多
Ecotechnology,quintessential for crafting sustainable socio-environmental strategies,remains tantalizingly uncharted.Our analysis,steered by the nuances of machine learning and augmented by bibliometric insights,delin...Ecotechnology,quintessential for crafting sustainable socio-environmental strategies,remains tantalizingly uncharted.Our analysis,steered by the nuances of machine learning and augmented by bibliometric insights,delineates the expansive terrain of this domain,elucidates pivotal research themes and conundrums,and discerns the vanguard nations in this field.Furthermore,we deftly connect our discoveries to the United Nations'2030 Sustainable Development Goals,thereby accentuating the profound societal ramifications of ecotechnology.展开更多
文摘The dynamic performance of doubly-fed induction generator(DFIG) before and after connection is analyzed based on corresponding mathematical models and transfer functions in decoupled vector control.The parameter tuning methods of rotor current regulator before and after connection are given.To reach same dynamic performance the parameters should take different values and be switched before and after connection.However on one hand the closing moment of stator contactor is difficult to get as the feedback signal is usually twenty millisecond delay or so.The delay in parameter switching will affect rotor current and torque dynamics during the delayed period after connection. On the other hand parameter switching is troublesome.Hence a synchronization control strategy without parameter switching is proposed and analyzed in detail,which has linear rising exciting current to avoid current overshooting. The dynamic performance of the proposed strategy is analyzed in frequency domain and implemented on a DFIG experimental platform subsequently.The proposed synchronization strategy is validated by experimental results.
文摘The thermal performance of a“U”type earth-to-air heat exchanger is presented in this experimental study.The device has a serial-connected vertical configuration.The wells where tubes were installed have a depth of fewer than 3 m and are separated every 1.5 m,using an installation area of 3m2.The experimentation was carried out in March in Morelos,Mexico when the environmental temperature reaches 35℃ during the day.The performance of the device was measured and compared to the requirements of an office for cooling purposes within a university campus to reproduce the space restrictions found in urbanized areas.By using a small land surface,it is feasible for urbanized areas.The air temperature inside the“U”type earth-to-air heat exchanger,the surrounding soil temperature,the airspeed,and the power consumed by the fan were measured.The air temperature and the fan’s power consumption data were obtained by modifying the airspeed in four constant values,from 1.3 m/s to 6.6 m/s.Results show that the device evaluated in this work has adequate thermal performance for cooling purposes compared to the requirements of an office.A decrease in air temperature was recorded in a range of 5.1℃ to 9.4℃.Over 70%of the total temperature difference was reached in the first well,where the average soil thermal disturbance at 5 cm was 2.8℃.The device achieved a maximum COP of 12.8 and a maximum effectiveness of 88.4%.With these results,it is concluded that the system is suitable for cooling purposes in areas with space restrictions.This work is novel since the dimensions available for installation in urbanized areas are considered and compared with the thermal requirements of an office.In addition to the fact that there are no published works with vertical heat exchangers connected in series.
基金supported by the National 863 Program of China(2012AA101803)the National Key Technology R&D Program of China(2012BAD14B06,2012BAD14B01)
文摘This study evaluated the microbial community dynamics and maturation time of two compost systems： biogas slurry compost and cow manure compost, with the aim of evaluating the potential utility of a biogas slurry compost system. Denaturing gradient gel electrophoresis （DGGE）, gene clone library, temperature, C/N ratio, and the germination index were employed for the investigation, cow manure compost was used as the control. Results showed that the basic strip and dominant strips of the DGGE bands for biogas slurry compost were similar to those of cow manure compost, but the brightness of the respective strips for each system were different. Shannon-Weaver indices of the two compost systems differed, possessing only 22% similarity in the primary and maturity stages of the compost process. Using bacterial 16S rRNA gene clone library analysis, 88 bacterial clones were detected. Further, 18 and 13 operational taxonomic units （OTUs） were present in biogas slurry and cow manure compost, respectively. The 18 OTUs of the biogas slurry compost belonged to nine bacterial genera, of which the dominant strains were Bacillus sp. and Carnobacterium sp.; the 13 OTUs of the cow manure compost belonged to eight bacterial genera, of which the dominant strains were Psychrobacter sp., Pseudomonas sp., and Clostridium sp. Results demonstrated that the duration of the thermophilic phase （more than 50°C） for biogas slurry compost was 8 d less than the according duration for cow manure compost, and the maturation times for biogas slurry and cow manure compost were 45 and 60 d, respectively. It is an effective biogas slurry assimilate technology by application of biogas slurry as nitrogen additives in the manufacture of organic fertilizer.
基金supported by the National Natural Science Foundation of China(Grant Nos.61274037 and 61301046)the Research Fund for the Doctoral Program of Higher Education of China(Grant Nos.20120101110031 and 20120101110054)
文摘Surface acoustic wave （SAW） resonators are a type of ultraviolet （UV） light sensors with high sensitivity, and they have been extensively studied. Transparent SAW devices are very useful and can be developed into various sensors and microfluidics for sensing/monitoring and lab-on-chip applications. We report the fabrication of high sensitivity SAW UV sensors based on piezoelectric （PE） ZnO thin films deposited on glass substrates. The sensors were fabricated and their performances against the post-deposition annealing condition were investigated. It was found that the UV-light sensitivity is improved by more than one order of magnitude after annealing. The frequency response increases significantly and the response becomes much faster. The optimized devices also show a small temperature coefficient of frequency and excellent repeatability and stability, demonstrating its potential for UV-light sensing application.
基金This work was supported by National Key Research and Development Program of China(No.2021YFB2500100)National Natural Science Foundation of China[Grant No.51872196 and 22109114],the Carbon Peaking and Carbon Neutrality Technology Innovation Special Fund of Jiangsu Province(Grant number:BE2022041)Open Foundation of Shanghai Jiao Tong University Shaoxing Research Institute of Renewable Energy and Molecular Engineering(Grant number:JDSX2022023).
文摘With their intrinsic safety and environmental benignity,aqueous Zn-ion batteries(ZIBs)have been considered the most appropriate candidates for replacing alkali metal systems.However,polycrystalline Zn anodes in aqueous environments still pose enormous issues,such as dendrite growth and side reactions.Although many efforts have been made to address these obstacles through interphase modification and electrolyte design,researchers have not been able to improve the inherent thermodynamic stability and ion deposition behavior of the Zn anode.It is imperative to understand and explore advanced anode construction methods from the perspective of crystallinity.This review delves into the feasibility of precisely regulating the crystallographic features of metallic zinc,examines the challenges and merits of reported strategies for fabricating textured zinc,and offers constructive suggestions for the large-scale production and commercial application of aqueous ZIBs.
基金Acknowledgments This research was supported by Hubei Provincal Department of Education （No. CXY2009B2008）, Angel Yeast Co.Ltd （SDH200800230）, the Science Foundation of Yichang City （No. A2007103-1）, the Alan G. MacDiarmid Institute of Renewable Energy, Yichang, China and the USDA Western Regional Research Center （WRRC）. The authors thank WRRC Center Director James N. Seiber, Artur, Klamczynski and Charles Lee for the thoughtful discussions and technical insights, and Miss Tina William for the SEM imagines.
文摘Switch grass was developed as a pioneer energy crop in USA with great industrial prospect. It contains about 60% sugars and 18% lignin. The purpose of this research is to find pretreatment process to fractionate cellulose, hemicellulose and lignin from switch grass to obtain much more useful chemicals and enhance the residue solid to be hydrolyzed by enzymes. The six different pretreatment methods were studied, such as hot water pretreatment （HWP） alone, dilute acid pretreatment （DAP）, ammonia pretreatment （AP）, lime pretreatment （LP）, organosolv water / ehanol pretreatment （OWEP）, and organosolv water / acetone pretreatment （OWAP）. It was the best method combining DAP with OWEP because the hemicellulose sugars were recovered in the first residual liquid while a varied amount of cellulose was retained in the residual solid and the lignin fraction was obtained by simply adjusting the pH from the second liquid. The result shows the optimal two-stage process consisted of the first stage DAP at 428 K for 7 min with 0.8% sulfuric acid, resulting in 79.82% glucose recovery yield and 98.74% xylose removal and the second stage OWEP at 468K for 20 min in 45% （v / v） ethanol with 0.4% NaOH, resulting in 62% total glucose yield 99% xylose and 80% lignin removal. After enzymatic hydrolysis, the glucose yield was up to 92.6%, compared with 16% yield from untreated switch grass. Scanning electron microscopy （SEM） highlighted the differences in switch grass structure from the various pretreatment methods during biomass fractionation.
基金supported by the Key Projects in the National Science&Technology Pillar Program during the Eleventh Five-Year Plan Period(No.2006BAD10B05-02,2006BAD07A01)the National Public Benefit Research Sector(No.200803033)
文摘An efficient cellulose degrading bacteria exists in the thermophilic wheat straw-degrading community, WDC2. However, this strain cannot be isolated and cultured using conventional separation techniques under strict anaerobic conditions. We successfully isolated a strain of effective cellulose degrading bacteria CTL-6 using a wash, heat shock, and solid-liquid alternating process. Analysis of its properties revealed that, although the community containing the strain CTL-6 grew under aerobic conditions, the purified strain CTL-6 only grew under anaerobic culture conditions. The strain CTL-6 had a striking capability of degrading cellulose （80.9% weight loss after 9 days of culture）. The highest efficiency value of the endocellulase （CMCase activity） was 0.404 μmol/（min·mL）, cellulose degradation efficiency by CTL-6 was remarkably high at 50–65°C with the highest degradation efficiency observed at 60°C. The 16S rRNA gene sequence analysis indicated that the closest relative to strain CTL-6 belonged to the genus Clostridium thermocellum. Strain CTL-6 was capable of utilizing cellulose, cellobiose, and glucose. Strain CTL-6 also grew with Sorbitol as the sole carbon source, whereas C. thermocellum is unable to do so.
基金supported by the Pearl River Talent Recruitment Program of Guangdong(China)(2019QN01C693)Guangdong Innovative and Entrepreneurial Research Team Program(2021ZT09L392)+1 种基金Guangzhou Basic Science and Applied Basic Research Foundation(SL2024A04J00594)the National Natural Science Foundation of China(22179039 and 22005105)。
文摘For a variable speed large scale wind turbine, the vibration issues become a key problem that cannot be ignored in the turbine＇s life cycle. Wind turbine tower vibration will cause superfluous mechanical loads. To resolve the vibration issue, a method for constructng the energy function V is proposed to meet the demands of safe operation. The Lyapunov theorem has been em- bedded in a wind turbine control algorithm, proving the theoretical feasibility of stability control based on function V. Accord- ing to an analysis of this complex nonlinear model for the wind turbine, the general method of constructing an energy function suitable for a wind turbine is presented explicitly. The feasibility of applying an energy function to wind turbine vibration con- trol is verified experimentally using a 3.0-MW direct drive wind turbine model. The experimental results indicate that the dy- namic performance of the tested wind turbine model with energy function control is significantly better than that of the uncon- trolled structure in terms of the reduction of nacelle acceleration, velocity, and displacement response.
基金.Ricardo Ruíz-Sanchez was partially supported by the UNAM-DGAPA postdoctoral fellowship program。
文摘Ecotechnology,quintessential for crafting sustainable socio-environmental strategies,remains tantalizingly uncharted.Our analysis,steered by the nuances of machine learning and augmented by bibliometric insights,delineates the expansive terrain of this domain,elucidates pivotal research themes and conundrums,and discerns the vanguard nations in this field.Furthermore,we deftly connect our discoveries to the United Nations'2030 Sustainable Development Goals,thereby accentuating the profound societal ramifications of ecotechnology.
