The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot,but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently.In this paper,a new type...The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot,but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently.In this paper,a new type of hydraulic filter consisting of a damping hole and a chamber is developed for elimination of fuel pressure fluctuation and multi-injection fuel mass deviation.Linear model of the improved high pressure common-rail system（HPCRS）including injector,the pipe connecting common-rail with injector and the hydraulic filter is built.Fuel pressure fluctuation at injector inlet,on which frequency domain analysis is conducted through fast Fourier transformation,is acquired at different target pressure and different damping hole diameter experimentally.The linear model is validated and can predict the natural frequencies of the system.Influence of damping hole diameter on fuel pressure fluctuation is analyzed qualitatively based on the linear model,and it can be inferred that an optimal diameter of the damping hole for elimination of fuel pressure fluctuation exists.Fuel pressure fluctuation and fuel mass deviation under different damping hole diameters are measured experimentally,and it is testified that the amplitude of both fuel pressure fluctuation and fuel mass deviation decreases first and then increases with the increasing of damping hole diameter.The amplitude of main injection fuel mass deviation can be reduced by 73%at most under pilot-main injection mode,and the amplitude of post injection fuel mass deviation can be reduced by 92%at most under main-post injection mode.Fuel mass of a single injection increases with the increasing of the damping hole diameter.The hydraulic filter proposed by this research can be potentially used to eliminate fuel pressure fluctuation at injector inlet and improve the stability of HPCRS fuel injection.展开更多
The effect of obesity on idiopathic central precocious puberty（ICPP） girls is still under discussion. The relationship between body mass index（BMI） and sexual hormone levels of gonadotropin-releasing hormone（GnRH...The effect of obesity on idiopathic central precocious puberty（ICPP） girls is still under discussion. The relationship between body mass index（BMI） and sexual hormone levels of gonadotropin-releasing hormone（GnRH） stimulation test in ICPP girls is controversial and the underlying mechanism is unclear. This study aims to further explore the independent effect of excess adiposity on peak luteinizing hormone（LH） level of stimulation test in ICPP girls and the role of other related factors. A retrospective cross-sectional study was performed on 618 girls diagnosed as having ICPP, including 355 cases of normal weight, 99 cases of overweight and 164 cases of obese. The results showed that obese group had more progressed Tanner stage and no significant difference（P=0.28） in LH peak was found as basal LH value was used as a covariate. The obese group had higher total testosterone（TT）, adrenocorticotrophic hormone（ACTH）, 17-α hydroxyprogesterone（17-αOHP） and androstendione（AN）, with significantly increased fasting insulin（FIN） and homeostasis model of assessment for insulin resistance index（HOMA-IR）. Stratified analysis showed inconsistency of the relationship between BMI-standard deviation score（BMI-SDS） and LH peak in different Tanner stages（P for interaction=0.017）. Further smoothing plot showed linear and non-linear relationship between BMI-SDS and LH peak in three Tanner stages. Then linear regression model was used to analyze the relationship between BMI-SDS and LH peak in different Tanner stages, with and without different confounding factors being adjusted. In B2 stage, BMI-SDS was negatively associated with LH peak. In B3 stage, when BMI-SDS 〈1.5, as BMI-SDS increased, the level of LH peak decreased（model Ⅰ： β=–1.8, 95% CI=–4.7 to 1.1, P=0.214）. When BMI-SDS ≥1.5, BMI-SDS was significantly positively associated with LH peak（model Ⅰ： β=4.5, 95% CI=1.7 to 7.4, P=0.002）. In B4 stage, when BMI-SDS 〈1.5, BMI-SDS was negatively associated with LH peak（model Ⅰ： β=–11.6, 95% CI=–22.7 to –0.5, P=0.049）. When BMI-SDS ≥1.5, BMI-SDS was positively associated with LH peak（model Ⅰ： β=–4.2, 95% CI=–3.3 to 11.7, P=0.28）. It is concluded that there is an independent correlation between BMI-SDS and LH peak of stimulation test in ICPP girls, their relationships are different in different Tanner stages, and the effect of BMI-SDS can be affected by adrenal androgens, estradiol and glucose metabolism parameters.展开更多
Background: Brain size may affect the probability of invasion of urban habitats if a relatively larger brain entails superior ability to adapt to novel environments. However, once urbanized urban environments may prov...Background: Brain size may affect the probability of invasion of urban habitats if a relatively larger brain entails superior ability to adapt to novel environments. However, once urbanized urban environments may provide poor quality food that has negative consequences for normal brain development resulting in an excess of individuals with small brains.Methods: Here we analyze the independent effects of mean, standard deviation and skewness in brain mass for invasion of urban habitats by 108 species of birds using phylogenetic multiple regression analyses weighted by sample size.Results: There was no significant difference in mean brain mass between urbanized and non-urbanized species or between urban and rural populations of the same species, and mean brain mass was not significantly correlated with time since urbanization. Bird species that became urbanized had a greater standard deviation in brain mass than non-urbanized species, and the standard deviation in brain mass increased with time since urbanization. Brain mass was significantly left skewed in species that remained rural, while there was no significant skew in urbanized species. The degree of left skew was greater in urban than in rural populations of the same species, and successfully urbanized species decreased the degree of left skew with time since urbanization. This is consistent with the hypothesis that sub-optimal brain development was more common in rural habitats resulting in disproportionately many individuals with very smal brains.Conclusions: These findings do not support the hypothesis that large brains promote urbanization, but suggest that skewness has played a role in the initial invasion of urban habitats, and that variance and skew in brain mass have increased as species have become urbanized.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51076014)Research Fund for the Doctoral Program of Higher Education of China(Grant No.20101101110011)
文摘The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot,but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently.In this paper,a new type of hydraulic filter consisting of a damping hole and a chamber is developed for elimination of fuel pressure fluctuation and multi-injection fuel mass deviation.Linear model of the improved high pressure common-rail system（HPCRS）including injector,the pipe connecting common-rail with injector and the hydraulic filter is built.Fuel pressure fluctuation at injector inlet,on which frequency domain analysis is conducted through fast Fourier transformation,is acquired at different target pressure and different damping hole diameter experimentally.The linear model is validated and can predict the natural frequencies of the system.Influence of damping hole diameter on fuel pressure fluctuation is analyzed qualitatively based on the linear model,and it can be inferred that an optimal diameter of the damping hole for elimination of fuel pressure fluctuation exists.Fuel pressure fluctuation and fuel mass deviation under different damping hole diameters are measured experimentally,and it is testified that the amplitude of both fuel pressure fluctuation and fuel mass deviation decreases first and then increases with the increasing of damping hole diameter.The amplitude of main injection fuel mass deviation can be reduced by 73%at most under pilot-main injection mode,and the amplitude of post injection fuel mass deviation can be reduced by 92%at most under main-post injection mode.Fuel mass of a single injection increases with the increasing of the damping hole diameter.The hydraulic filter proposed by this research can be potentially used to eliminate fuel pressure fluctuation at injector inlet and improve the stability of HPCRS fuel injection.
基金supported by grants from 12th five-year Plan National Key Technology R&D Program(No.2012BAI09B04)Program for Changjiang Scholars and Innovative Research Team in University(No.PCSIRT1131)
文摘The effect of obesity on idiopathic central precocious puberty（ICPP） girls is still under discussion. The relationship between body mass index（BMI） and sexual hormone levels of gonadotropin-releasing hormone（GnRH） stimulation test in ICPP girls is controversial and the underlying mechanism is unclear. This study aims to further explore the independent effect of excess adiposity on peak luteinizing hormone（LH） level of stimulation test in ICPP girls and the role of other related factors. A retrospective cross-sectional study was performed on 618 girls diagnosed as having ICPP, including 355 cases of normal weight, 99 cases of overweight and 164 cases of obese. The results showed that obese group had more progressed Tanner stage and no significant difference（P=0.28） in LH peak was found as basal LH value was used as a covariate. The obese group had higher total testosterone（TT）, adrenocorticotrophic hormone（ACTH）, 17-α hydroxyprogesterone（17-αOHP） and androstendione（AN）, with significantly increased fasting insulin（FIN） and homeostasis model of assessment for insulin resistance index（HOMA-IR）. Stratified analysis showed inconsistency of the relationship between BMI-standard deviation score（BMI-SDS） and LH peak in different Tanner stages（P for interaction=0.017）. Further smoothing plot showed linear and non-linear relationship between BMI-SDS and LH peak in three Tanner stages. Then linear regression model was used to analyze the relationship between BMI-SDS and LH peak in different Tanner stages, with and without different confounding factors being adjusted. In B2 stage, BMI-SDS was negatively associated with LH peak. In B3 stage, when BMI-SDS 〈1.5, as BMI-SDS increased, the level of LH peak decreased（model Ⅰ： β=–1.8, 95% CI=–4.7 to 1.1, P=0.214）. When BMI-SDS ≥1.5, BMI-SDS was significantly positively associated with LH peak（model Ⅰ： β=4.5, 95% CI=1.7 to 7.4, P=0.002）. In B4 stage, when BMI-SDS 〈1.5, BMI-SDS was negatively associated with LH peak（model Ⅰ： β=–11.6, 95% CI=–22.7 to –0.5, P=0.049）. When BMI-SDS ≥1.5, BMI-SDS was positively associated with LH peak（model Ⅰ： β=–4.2, 95% CI=–3.3 to 11.7, P=0.28）. It is concluded that there is an independent correlation between BMI-SDS and LH peak of stimulation test in ICPP girls, their relationships are different in different Tanner stages, and the effect of BMI-SDS can be affected by adrenal androgens, estradiol and glucose metabolism parameters.
文摘Background: Brain size may affect the probability of invasion of urban habitats if a relatively larger brain entails superior ability to adapt to novel environments. However, once urbanized urban environments may provide poor quality food that has negative consequences for normal brain development resulting in an excess of individuals with small brains.Methods: Here we analyze the independent effects of mean, standard deviation and skewness in brain mass for invasion of urban habitats by 108 species of birds using phylogenetic multiple regression analyses weighted by sample size.Results: There was no significant difference in mean brain mass between urbanized and non-urbanized species or between urban and rural populations of the same species, and mean brain mass was not significantly correlated with time since urbanization. Bird species that became urbanized had a greater standard deviation in brain mass than non-urbanized species, and the standard deviation in brain mass increased with time since urbanization. Brain mass was significantly left skewed in species that remained rural, while there was no significant skew in urbanized species. The degree of left skew was greater in urban than in rural populations of the same species, and successfully urbanized species decreased the degree of left skew with time since urbanization. This is consistent with the hypothesis that sub-optimal brain development was more common in rural habitats resulting in disproportionately many individuals with very smal brains.Conclusions: These findings do not support the hypothesis that large brains promote urbanization, but suggest that skewness has played a role in the initial invasion of urban habitats, and that variance and skew in brain mass have increased as species have become urbanized.
