The understanding of reaction mechanisms of electrode materials is of significant importance for the development of advanced batteries.The LiMn2O4 cathode has a voltage plateau around 2.8 V(vs.Li^+/Li),which can provi...The understanding of reaction mechanisms of electrode materials is of significant importance for the development of advanced batteries.The LiMn2O4 cathode has a voltage plateau around 2.8 V(vs.Li^+/Li),which can provide an additional capacity for Li storage,but it suffers from a severe capacity degradation.In this study,operando X-ray diffraction is carried out to investigate the structural evolutions and degradation mechanisms of LiMn2O4 in different voltage ranges.In the range of 3.0-4.3 V(vs.Li^+/Li),the LiMn2O4 cathode exhibits a low capacity but good cycling stability with cycles up to 100 cycles and the charge/discharge processes are associated with the reversible extraction/insertion of Li^+from/into LixMn2O4(0≤x≤1).In the range of 1.4-4.4 V(vs.Li^+/Li),a capacity higher than 200 mAh/g is achieved,but it rapidly decays during the cycling.The voltage plateau around 2.8 V(vs.Li^+/Li)is related to the transformation of the cubic LiMn2O4 phase to the tetragonal Li2Mn2O4 phase,which leads to the formation of cracks as well as the performance degradation.展开更多
The hydrothermal wave was investigated numerically for large-Prandtl-number fluid (Pr = 105.6) in a shallow cavity with different heated sidewalls. The traveling wave appears and propagates in the direction opposite t...The hydrothermal wave was investigated numerically for large-Prandtl-number fluid (Pr = 105.6) in a shallow cavity with different heated sidewalls. The traveling wave appears and propagates in the direction opposite to the surface flow (upstream) in the case of zero gravity when the applied temperature difference grows and over the critical value. The phase relationships of the disturbed velocity,temperature and pressure demonstrate that the traveling wave is driven by the disturbed tem-perature,which is named hydrothermal wave. The hydrothermal wave is so weak that the oscillatory flow field and temperature distribution can hardly be observed in the liquid layer. The exciting mechanism of hydrothermal wave is analyzed and discussed in the present paper.展开更多
The open-circuit fault of the power switches in shunt active power filter(SAPF) would exacerbate the harmonic pollution of power grid, and degrade the reliability of the devices and system. A fault diagnosis method is...The open-circuit fault of the power switches in shunt active power filter(SAPF) would exacerbate the harmonic pollution of power grid, and degrade the reliability of the devices and system. A fault diagnosis method is proposed based on reference model and an over-modulation strategy under hardware fault tolerance for SAPF. First, a mathematic model is established for SAPF. Second, the residuals are generated by comparing the outputs of reference model and those of actual model, and open-switch fault is detected and diagnosed by residual evaluation. After that, hardware fault tolerance is performed with the three-phase four-switch(TPFS) topology to isolate the faulty phase. Finally, the over-modulation strategy is proposed to increase the voltage transfer ratio of the TPFS topology. Simulation and experimental results verified the feasibility and effectiveness of the proposed method.展开更多
In recent years,the popularity increased for nutritional supplements and herbal products.Prescription drugs,but not herbal therapies are paid by health insurances.They are sold over-the-counter(OTC)on the patients’ow...In recent years,the popularity increased for nutritional supplements and herbal products.Prescription drugs,but not herbal therapies are paid by health insurances.They are sold over-the-counter(OTC)on the patients’own expense.However,there are potential risks of self-medication,e.g.incorrect self-diagnosis,severe adverse reactions,dangerous drug interactions,risk of addiction etc.They are often used by patients at their own discretion without knowledge of and control by their physicians.Certain users are at risk of intoxication.Multiple medications taken by older patients increase the risk for adverse drug reactions,drug-drug interactions,and compliance problems for this age group(polypharmacy).Herbals should be discontinued prior to operations to avoid interactions with anesthetics or anticoagulants.Herbal preparations may also be carcinogenic or interfere with cancer treatments.Pregnant women use various OTC preparations.However,in many cases,it is unclear whether their use is safe for mother or baby.Self-medication with herbals is also largely distributed among anxious and depressive patients,and patients with other conditions and symptoms.The popularity of herbal products has also brought concerns on quality,efficacy and safety.Cases of botanical misidentification,contaminations with heavy metals,pesticides,radioactivity,organic solvents,microbials as well as adulteration with chemical drugs necessitate the establishment of international quality control standards.Hepatotoxic effects have been reported for more than 300 plant species,and some commonly used herbs have been demonstrated to interact with Western medication.Health care professionals have a critical responsibility assessing the self-care ability of their patients.Databases are available for pharmacists with information on action,side effects and toxicities as well as herbdrug interactions.There is a need for established guidelines regarding the correct use of nutritional supplements and herbal OTC preparations(phytovigilance).Physicians,pharmacis展开更多
Figs (Moracea: Ficus) and fig wasps (Hymenoptera: Chlocloids: Agaonideae) depend on each other to complete their reproduction. Monoecious fig species and their pollinating wasps are in conflict over the use of fig ov...Figs (Moracea: Ficus) and fig wasps (Hymenoptera: Chlocloids: Agaonideae) depend on each other to complete their reproduction. Monoecious fig species and their pollinating wasps are in conflict over the use of fig ovaries which can either produce one seed or one wasp. From observation on Ficus virens Ait., we showed that female flowers with outer layer of ovaries (near to the wall of syconium) had no significant difference from that with inner and interval layer of ovaries (near to the syconium cavity), in which most seeds and wasps were produced. This meant that fig tree provided the same potential resource for seed and wasps production. Observation indicated that there was usually only one foundress in syconium at female flower phase and no com- petition pollinators. Measurement of the style length of female flowers and the ovipositor of pollinators indicated that most ovaries could be reached by pollinator’s ovipositor. However, at the male flower phase, production of seeds was significantly more than that of wasps including non-pollinating wasps but there was no significant difference between seed and pollinating wasp production when without non-pollinating wasps produced. This result indicated that non-pollinating wasps competed ovaries not with seeds but with pollinating wasps for ovipositing. Bagged experiment showed that the sampling fig species was not self-sterile which was important for figs and wasps to survive bad season. Seed production in self-pollinated figs was not significantly different from total wasps in- cluding non-pollinating ones. This might be related with the weaker competition among wasps since bagged figs were not easy to reach by wasps from outside.展开更多
A two-dimensional Ohm heating theoretic model in the magnetizing ionosphere and a ray-tracing model in a discrete ionosphere background are used to analyze quantitatively the characteristics(mainly the Doppler shift a...A two-dimensional Ohm heating theoretic model in the magnetizing ionosphere and a ray-tracing model in a discrete ionosphere background are used to analyze quantitatively the characteristics(mainly the Doppler shift and the phase shift)of the over-the-horizon radar(OTHR)wave,which propagates through the ionospheric region heated by high frequency radio wave.The simulation results about the Doppler and the phase shift are obtained within two minutes after the heater is on.Preliminary conclusions are given by comparing the numerical results with experimental data.展开更多
基金the financial support by the National Natural Science Foundation of China (51871133, 51671115)support by the Department of Science and Technology of the Shandong Province for the Young Tip-Top Talent Support Project.
文摘The understanding of reaction mechanisms of electrode materials is of significant importance for the development of advanced batteries.The LiMn2O4 cathode has a voltage plateau around 2.8 V(vs.Li^+/Li),which can provide an additional capacity for Li storage,but it suffers from a severe capacity degradation.In this study,operando X-ray diffraction is carried out to investigate the structural evolutions and degradation mechanisms of LiMn2O4 in different voltage ranges.In the range of 3.0-4.3 V(vs.Li^+/Li),the LiMn2O4 cathode exhibits a low capacity but good cycling stability with cycles up to 100 cycles and the charge/discharge processes are associated with the reversible extraction/insertion of Li^+from/into LixMn2O4(0≤x≤1).In the range of 1.4-4.4 V(vs.Li^+/Li),a capacity higher than 200 mAh/g is achieved,but it rapidly decays during the cycling.The voltage plateau around 2.8 V(vs.Li^+/Li)is related to the transformation of the cubic LiMn2O4 phase to the tetragonal Li2Mn2O4 phase,which leads to the formation of cracks as well as the performance degradation.
基金Supported by the National Natural Science Foundation of China (Grant No. 10432060)
文摘The hydrothermal wave was investigated numerically for large-Prandtl-number fluid (Pr = 105.6) in a shallow cavity with different heated sidewalls. The traveling wave appears and propagates in the direction opposite to the surface flow (upstream) in the case of zero gravity when the applied temperature difference grows and over the critical value. The phase relationships of the disturbed velocity,temperature and pressure demonstrate that the traveling wave is driven by the disturbed tem-perature,which is named hydrothermal wave. The hydrothermal wave is so weak that the oscillatory flow field and temperature distribution can hardly be observed in the liquid layer. The exciting mechanism of hydrothermal wave is analyzed and discussed in the present paper.
基金Project(2012AA051601)supported by the High-Tech Research and Development Program of China
文摘The open-circuit fault of the power switches in shunt active power filter(SAPF) would exacerbate the harmonic pollution of power grid, and degrade the reliability of the devices and system. A fault diagnosis method is proposed based on reference model and an over-modulation strategy under hardware fault tolerance for SAPF. First, a mathematic model is established for SAPF. Second, the residuals are generated by comparing the outputs of reference model and those of actual model, and open-switch fault is detected and diagnosed by residual evaluation. After that, hardware fault tolerance is performed with the three-phase four-switch(TPFS) topology to isolate the faulty phase. Finally, the over-modulation strategy is proposed to increase the voltage transfer ratio of the TPFS topology. Simulation and experimental results verified the feasibility and effectiveness of the proposed method.
文摘In recent years,the popularity increased for nutritional supplements and herbal products.Prescription drugs,but not herbal therapies are paid by health insurances.They are sold over-the-counter(OTC)on the patients’own expense.However,there are potential risks of self-medication,e.g.incorrect self-diagnosis,severe adverse reactions,dangerous drug interactions,risk of addiction etc.They are often used by patients at their own discretion without knowledge of and control by their physicians.Certain users are at risk of intoxication.Multiple medications taken by older patients increase the risk for adverse drug reactions,drug-drug interactions,and compliance problems for this age group(polypharmacy).Herbals should be discontinued prior to operations to avoid interactions with anesthetics or anticoagulants.Herbal preparations may also be carcinogenic or interfere with cancer treatments.Pregnant women use various OTC preparations.However,in many cases,it is unclear whether their use is safe for mother or baby.Self-medication with herbals is also largely distributed among anxious and depressive patients,and patients with other conditions and symptoms.The popularity of herbal products has also brought concerns on quality,efficacy and safety.Cases of botanical misidentification,contaminations with heavy metals,pesticides,radioactivity,organic solvents,microbials as well as adulteration with chemical drugs necessitate the establishment of international quality control standards.Hepatotoxic effects have been reported for more than 300 plant species,and some commonly used herbs have been demonstrated to interact with Western medication.Health care professionals have a critical responsibility assessing the self-care ability of their patients.Databases are available for pharmacists with information on action,side effects and toxicities as well as herbdrug interactions.There is a need for established guidelines regarding the correct use of nutritional supplements and herbal OTC preparations(phytovigilance).Physicians,pharmacis
基金Supported by the Knowledge Innovation Research Program,Chinese Academy of Sciences (KSCX2-SW-105)
文摘Figs (Moracea: Ficus) and fig wasps (Hymenoptera: Chlocloids: Agaonideae) depend on each other to complete their reproduction. Monoecious fig species and their pollinating wasps are in conflict over the use of fig ovaries which can either produce one seed or one wasp. From observation on Ficus virens Ait., we showed that female flowers with outer layer of ovaries (near to the wall of syconium) had no significant difference from that with inner and interval layer of ovaries (near to the syconium cavity), in which most seeds and wasps were produced. This meant that fig tree provided the same potential resource for seed and wasps production. Observation indicated that there was usually only one foundress in syconium at female flower phase and no com- petition pollinators. Measurement of the style length of female flowers and the ovipositor of pollinators indicated that most ovaries could be reached by pollinator’s ovipositor. However, at the male flower phase, production of seeds was significantly more than that of wasps including non-pollinating wasps but there was no significant difference between seed and pollinating wasp production when without non-pollinating wasps produced. This result indicated that non-pollinating wasps competed ovaries not with seeds but with pollinating wasps for ovipositing. Bagged experiment showed that the sampling fig species was not self-sterile which was important for figs and wasps to survive bad season. Seed production in self-pollinated figs was not significantly different from total wasps in- cluding non-pollinating ones. This might be related with the weaker competition among wasps since bagged figs were not easy to reach by wasps from outside.
文摘A two-dimensional Ohm heating theoretic model in the magnetizing ionosphere and a ray-tracing model in a discrete ionosphere background are used to analyze quantitatively the characteristics(mainly the Doppler shift and the phase shift)of the over-the-horizon radar(OTHR)wave,which propagates through the ionospheric region heated by high frequency radio wave.The simulation results about the Doppler and the phase shift are obtained within two minutes after the heater is on.Preliminary conclusions are given by comparing the numerical results with experimental data.
