Ensemble forecasting has become the prevailing method in current operational weather forecasting. Although ensemble mean forecast skill has been studied for many ensemble prediction systems（EPSs） and different cases...Ensemble forecasting has become the prevailing method in current operational weather forecasting. Although ensemble mean forecast skill has been studied for many ensemble prediction systems（EPSs） and different cases, theoretical analysis regarding ensemble mean forecast skill has rarely been investigated, especially quantitative analysis without any assumptions of ensemble members. This paper investigates fundamental questions about the ensemble mean, such as the advantage of the ensemble mean over individual members, the potential skill of the ensemble mean, and the skill gain of the ensemble mean with increasing ensemble size. The average error coefficient between each pair of ensemble members is the most important factor in ensemble mean forecast skill, which determines the mean-square error of ensemble mean forecasts and the skill gain with increasing ensemble size. More members are useful if the errors of the members have lower correlations with each other, and vice versa. The theoretical investigation in this study is verified by application with the T213 EPS. A typical EPS has an average error coefficient of between 0.5 and 0.8; the 15-member T213 EPS used here reaches a saturation degree of 95%（i.e., maximum 5% skill gain by adding new members with similar skill to the existing members） for 1–10-day lead time predictions, as far as the mean-square error is concerned.展开更多
NICFED expert system-a rule-based"non-invasive cardiac function evaluationand cardiac diseases diagnosing expert system"-is discussed in this paper.The sys-tem can be regarded as an interpretation expert sys...NICFED expert system-a rule-based"non-invasive cardiac function evaluationand cardiac diseases diagnosing expert system"-is discussed in this paper.The sys-tem can be regarded as an interpretation expert system and as a diagnostic expertsystem.When it is applied to evaluate cardiac function,it can explain more than onehundred parameters detected by"MCA-Ⅲ cardiac function device of multi-domainand multidemension".With these parameters the cardiac function in time domain,fre-展开更多
Physiological and metabolic processes of ectotherms are markedly influenced by ambient temperature. Previous studies have shown that the abdominal black-speckled area becomes larger with increased elevation in plateau...Physiological and metabolic processes of ectotherms are markedly influenced by ambient temperature. Previous studies have shown that the abdominal black-speckled area becomes larger with increased elevation in plateau Phrynocephalus, however, no studies have verified the hypothesis that this variation is correlated with the lizard＇s thermoregulation. In this study, infrared thermal imaging technology was first used to study the skin temperature variation of torsos, heads, limbs and tails of a cold-climate agamid lizard, Phrynocephalus guinanensis. The heating rates of the central abdominal black-speckled skin area and peripheral non-black-speckled skin area under solar radiation were compared. Our results showed that the heating rates of limbs and tails were relatively faster than the torsos, as heating time was extended, rates gradually slowed before stabilizing under solar radiation. Under the environment without solar radiation, the cooling rates of limbs and tails were also relatively faster than the torsos of lizards, the rates slowed down and finally became stable as the cooling time was extended. We also found that the heating rate of the abdominal black-speckled skin area was faster than the nearby non-black-speckled skin area. These results increased our insights into the functional significance of these phenotypic traits and help explain their covariation with the thermal environment in these cold-climate agamid lizards.展开更多
The two factors which influence the low temperature performance of deformable mirrors（DMs） are the piezoelectric stroke of the actuators and the thermally induced surface deformation of the DM. A new theory was prop...The two factors which influence the low temperature performance of deformable mirrors（DMs） are the piezoelectric stroke of the actuators and the thermally induced surface deformation of the DM. A new theory was proposed to explain the thermally induced surface deformation of the DM： because the thermal strain between the actuators and the base leads to an additional moment according to the theory of plates, the base will be bent and the bowing base will result in an obvious surface deformation of the facesheet. The finite element method（FEM） was used to prove the theory. The results showed that the thermally induced surface deformation is mainly caused by the base deformation which is induced by the coefficient of thermal expansion（CTE） mismatching; when the facesheet has similar CTE with the actuators, the surface deformation of the DM would be smoother. Then an optimized DM design was adopted to reduce the surface deformation of the DMs at low temperature. The low temperature tests of two 61-element discrete PZT actuator sample deformable mirrors and the corresponding optimized DMs were conducted to verify the simulated results. The results showed that the optimized DMs perform well.展开更多
For microfluidic systems, interfacial phenomena in micro-reactors are of great importance because they control the transfer and reaction characteristics. This paper dwells on how the surface property and geometry infl...For microfluidic systems, interfacial phenomena in micro-reactors are of great importance because they control the transfer and reaction characteristics. This paper dwells on how the surface property and geometry influence the mass flux in a complex microchannel. The lattice Boltzmann method(LBM) with a pseudo potential model and the Shan–Chen model for the interaction between fluid and hydrophobic surface were built up, so a boundary slip effect was added and verified. On this basis, a microchannel with variable-section geometry was simulated. The results indicate that the optimal design and the flow pattern are quite different under hydrophilic and hydrophobic conditions. A microchannel with sequential hydrophilic and hydrophobic surface was also simulated. The numerical results indicate that the hydrophobic wall can improve the mass flux, irrespective of microchannel geometry. Particularly, an empirical correlation with a linearly relationship between length of hydrophobic segment and mass flux was obtained for the straight microchannel.展开更多
基金supported by the National Basic Research (973) Program of China (Grant No. 2013CB430106)the R&D Special Fund for Public Welfare Industry (Meteorology) (Grant Nos. GYHY201306002 and GYHY201206005)+2 种基金the National Natural Science Foundation of China (Grant Nos. 40830958 and 41175087)the Jiangsu Collaborative Innovation Center for Climate Changethe High Performance Computing Center of Nanjing University
文摘Ensemble forecasting has become the prevailing method in current operational weather forecasting. Although ensemble mean forecast skill has been studied for many ensemble prediction systems（EPSs） and different cases, theoretical analysis regarding ensemble mean forecast skill has rarely been investigated, especially quantitative analysis without any assumptions of ensemble members. This paper investigates fundamental questions about the ensemble mean, such as the advantage of the ensemble mean over individual members, the potential skill of the ensemble mean, and the skill gain of the ensemble mean with increasing ensemble size. The average error coefficient between each pair of ensemble members is the most important factor in ensemble mean forecast skill, which determines the mean-square error of ensemble mean forecasts and the skill gain with increasing ensemble size. More members are useful if the errors of the members have lower correlations with each other, and vice versa. The theoretical investigation in this study is verified by application with the T213 EPS. A typical EPS has an average error coefficient of between 0.5 and 0.8; the 15-member T213 EPS used here reaches a saturation degree of 95%（i.e., maximum 5% skill gain by adding new members with similar skill to the existing members） for 1–10-day lead time predictions, as far as the mean-square error is concerned.
文摘NICFED expert system-a rule-based"non-invasive cardiac function evaluationand cardiac diseases diagnosing expert system"-is discussed in this paper.The sys-tem can be regarded as an interpretation expert system and as a diagnostic expertsystem.When it is applied to evaluate cardiac function,it can explain more than onehundred parameters detected by"MCA-Ⅲ cardiac function device of multi-domainand multidemension".With these parameters the cardiac function in time domain,fre-
基金supported by the National Natural Science Foundation of China (31372183, 41541002)
文摘Physiological and metabolic processes of ectotherms are markedly influenced by ambient temperature. Previous studies have shown that the abdominal black-speckled area becomes larger with increased elevation in plateau Phrynocephalus, however, no studies have verified the hypothesis that this variation is correlated with the lizard＇s thermoregulation. In this study, infrared thermal imaging technology was first used to study the skin temperature variation of torsos, heads, limbs and tails of a cold-climate agamid lizard, Phrynocephalus guinanensis. The heating rates of the central abdominal black-speckled skin area and peripheral non-black-speckled skin area under solar radiation were compared. Our results showed that the heating rates of limbs and tails were relatively faster than the torsos, as heating time was extended, rates gradually slowed before stabilizing under solar radiation. Under the environment without solar radiation, the cooling rates of limbs and tails were also relatively faster than the torsos of lizards, the rates slowed down and finally became stable as the cooling time was extended. We also found that the heating rate of the abdominal black-speckled skin area was faster than the nearby non-black-speckled skin area. These results increased our insights into the functional significance of these phenotypic traits and help explain their covariation with the thermal environment in these cold-climate agamid lizards.
基金Project supported by the National Natural Science Foundation of China(Grant No.11178004)
文摘The two factors which influence the low temperature performance of deformable mirrors（DMs） are the piezoelectric stroke of the actuators and the thermally induced surface deformation of the DM. A new theory was proposed to explain the thermally induced surface deformation of the DM： because the thermal strain between the actuators and the base leads to an additional moment according to the theory of plates, the base will be bent and the bowing base will result in an obvious surface deformation of the facesheet. The finite element method（FEM） was used to prove the theory. The results showed that the thermally induced surface deformation is mainly caused by the base deformation which is induced by the coefficient of thermal expansion（CTE） mismatching; when the facesheet has similar CTE with the actuators, the surface deformation of the DM would be smoother. Then an optimized DM design was adopted to reduce the surface deformation of the DMs at low temperature. The low temperature tests of two 61-element discrete PZT actuator sample deformable mirrors and the corresponding optimized DMs were conducted to verify the simulated results. The results showed that the optimized DMs perform well.
基金Supported by National Key Research and Development Program(2016YFB0301701)the National Natural Science Foundation of China(21276256,21490584,91534105)
文摘For microfluidic systems, interfacial phenomena in micro-reactors are of great importance because they control the transfer and reaction characteristics. This paper dwells on how the surface property and geometry influence the mass flux in a complex microchannel. The lattice Boltzmann method(LBM) with a pseudo potential model and the Shan–Chen model for the interaction between fluid and hydrophobic surface were built up, so a boundary slip effect was added and verified. On this basis, a microchannel with variable-section geometry was simulated. The results indicate that the optimal design and the flow pattern are quite different under hydrophilic and hydrophobic conditions. A microchannel with sequential hydrophilic and hydrophobic surface was also simulated. The numerical results indicate that the hydrophobic wall can improve the mass flux, irrespective of microchannel geometry. Particularly, an empirical correlation with a linearly relationship between length of hydrophobic segment and mass flux was obtained for the straight microchannel.
