In this paper, a delayed SIR model with exponential demographic structure and the saturated incidence rate is formulated. The stability of the equilibria is analyzed with delay: the endemic equilibrium is locally stab...In this paper, a delayed SIR model with exponential demographic structure and the saturated incidence rate is formulated. The stability of the equilibria is analyzed with delay: the endemic equilibrium is locally stable without delay;and the endemic equilibrium is stable if the delay is under some condition. Moreover the dynamical behaviors from stability to instability will change with an appropriate?critical value. At last, some numerical simulations of the model are given to illustrate the main theoretical results.展开更多
A new stochastic epidemic model, that is, a general continuous time birth and death chain model, is formulated based on a deterministic model including vaccination. We use continuous time Markov chain to construct the...A new stochastic epidemic model, that is, a general continuous time birth and death chain model, is formulated based on a deterministic model including vaccination. We use continuous time Markov chain to construct the birth and death process. Through the Kolmogorov forward equation and the theory of moment generating function, the corresponding population expectations are studied. The theoretical result of the stochastic model and deterministic version is also given. Finally, numerical simulations are carried out to substantiate the theoretical results of random walk.展开更多
Network storage provides high scalability, availability and flexibility for storage systems, and is widely applied to many fields. Particularly, I/O performance is of great significance. Its application is wide and ex...Network storage provides high scalability, availability and flexibility for storage systems, and is widely applied to many fields. Particularly, I/O performance is of great significance. Its application is wide and expanding rapidly. I/O performance has already become the bottleneck of the whole performance of computer systems for a long time, and under the condition of the present computer technology, I/O performance optimization method looks especially important. In the paper, I/O performance model was analyzed based on the combination of quasi birth, death process and queuing model, and then solved the model. A number of important related performance indicators and the relationship between them were given. By the way of example, this method can show the I/O performance more accurately. Finally, we got some useful conclusions, which may be used to evaluate network storage performance, and are the basis of confirming I/O scheduling strategy.展开更多
Background: Oral health has been implicated in low birth weight or preterm birth. However, this relationship has not yet been studied in twins. We investigated whether maternal oral health was associated with the birt...Background: Oral health has been implicated in low birth weight or preterm birth. However, this relationship has not yet been studied in twins. We investigated whether maternal oral health was associated with the birth weights of twins by a cross-sectional study conducted at Helsinki University Central Hospital. Methods: Utilizing linear mixed effect models to recognize the correlation between twins from the same mothers and the independence between different mothers. 40 birth weights of twins were modeled as main outcomes. In model 1, poor periodontal health (PPH) was fitted as the main explanatory variable. In model 2, presence of non-specific oral mucositis (NSOM) was fitted as the main predictor. Results: In model 1, babies from mothers with PPH weighed approximately 158.2 grams less than babies of mothers without PPH. However, this association was not statistically significant (p = 0.11). When a stricter criterion for PPH (3 sites of pocket depth > 4 mm) was used, p-value decreased to 0.09 showing a dose response to PPH. In model 2, mothers with NSOM had babies weighing 224.9 grams less than mothers without these lesions. This was nearly significant (p = 0.08). Conclusion: Although not significant, the results from this small data of twins suggest that maternal oral health may be associated with birth weight of twin neonates. Our results are appropriate to generate hypothesis for future studies.展开更多
文摘In this paper, a delayed SIR model with exponential demographic structure and the saturated incidence rate is formulated. The stability of the equilibria is analyzed with delay: the endemic equilibrium is locally stable without delay;and the endemic equilibrium is stable if the delay is under some condition. Moreover the dynamical behaviors from stability to instability will change with an appropriate?critical value. At last, some numerical simulations of the model are given to illustrate the main theoretical results.
文摘A new stochastic epidemic model, that is, a general continuous time birth and death chain model, is formulated based on a deterministic model including vaccination. We use continuous time Markov chain to construct the birth and death process. Through the Kolmogorov forward equation and the theory of moment generating function, the corresponding population expectations are studied. The theoretical result of the stochastic model and deterministic version is also given. Finally, numerical simulations are carried out to substantiate the theoretical results of random walk.
基金Sponsored by the National Natural Science Foundation of China(Grant No. 61073047)the Fundamental Research Funds for the Central Universities(Grant No.HEUCFT1007andHEUCF100607)the State Key Laboratory of High-End Server & Storage Technology(Grant No.2009HSSA08)
文摘Network storage provides high scalability, availability and flexibility for storage systems, and is widely applied to many fields. Particularly, I/O performance is of great significance. Its application is wide and expanding rapidly. I/O performance has already become the bottleneck of the whole performance of computer systems for a long time, and under the condition of the present computer technology, I/O performance optimization method looks especially important. In the paper, I/O performance model was analyzed based on the combination of quasi birth, death process and queuing model, and then solved the model. A number of important related performance indicators and the relationship between them were given. By the way of example, this method can show the I/O performance more accurately. Finally, we got some useful conclusions, which may be used to evaluate network storage performance, and are the basis of confirming I/O scheduling strategy.
文摘Background: Oral health has been implicated in low birth weight or preterm birth. However, this relationship has not yet been studied in twins. We investigated whether maternal oral health was associated with the birth weights of twins by a cross-sectional study conducted at Helsinki University Central Hospital. Methods: Utilizing linear mixed effect models to recognize the correlation between twins from the same mothers and the independence between different mothers. 40 birth weights of twins were modeled as main outcomes. In model 1, poor periodontal health (PPH) was fitted as the main explanatory variable. In model 2, presence of non-specific oral mucositis (NSOM) was fitted as the main predictor. Results: In model 1, babies from mothers with PPH weighed approximately 158.2 grams less than babies of mothers without PPH. However, this association was not statistically significant (p = 0.11). When a stricter criterion for PPH (3 sites of pocket depth > 4 mm) was used, p-value decreased to 0.09 showing a dose response to PPH. In model 2, mothers with NSOM had babies weighing 224.9 grams less than mothers without these lesions. This was nearly significant (p = 0.08). Conclusion: Although not significant, the results from this small data of twins suggest that maternal oral health may be associated with birth weight of twin neonates. Our results are appropriate to generate hypothesis for future studies.
基金The Scientific Research Projet of Ningde Normal University(2021Q202,2022ZX415)the Natural Science Foundation of Fujian Province(2021J011555 FJ2021B031)。
文摘目的 分析早产儿入院24 h内低体温发生的危险因素并构建风险预测模型,为临床制订干预措施预防早产儿入院低体温提供参考。方法 将307例早产儿随机按照7∶3比例分为训练集(215例)和验证集(92例)。分析早产儿入院低体温发生情况及影响因素,绘制列线图并评估其区分度和一致性。结果 307例早产儿中,209例(训练集146例,验证集63例)发生入院低体温,发生率68.08%。训练集logistic回归分析结果显示,低出生体质量、早期早产儿、出生5 min Apgar评分≤7分、并存新生儿呼吸窘迫综合征是早产儿发生入院低体温的独立危险因素。训练集ROC曲线下面积0.809(95%CI:0.744~0.875),校准曲线斜率接近1,且Hosmer-Lemeshow拟合优度检验χ^(2)=8.761、P=0.363。验证集ROC曲线下面积0.844(95%CI:0.755~0.933),校准曲线斜率接近1,且Hosmer-Lemeshow拟合优度检验χ^(2)=7.911、P=0.442。结论 早产儿入院低体温发生率较高,需重视低出生体质量、早期早产儿、出生5 min Apgar评分≤7分及并存新生儿呼吸窘迫综合征的高危早产儿,构建的风险预测模型显示出较好的预测性能,可采用预测模型早期识别早产儿入院低体温风险。
