Control charts for generalized exponential distribution percentiles

The generalized exponential (GE) distribution, which was introduced by Mudholkar and Srivastava in 1993 Mudholkar, G. S., Srivastava, D. K. (1993). Exponentiated Weibull family for analyzing bathtub failure data. IEEE Transactions on Reliability 42:299–302. [Google Scholar], has been studied for various applications of lifetime modelings. In this article, five control charts, that comprise the Shewhart-type chart and four parametric bootstrap charts based on maximum likelihood estimation method, the moment estimation method, probability plot method, and least-square error method for the GE percentiles, are investigated. An extensive Monte Carlo simulation study is conducted to compare the performance among all five control charts in terms of average run length. Finally, an example is given for illustration.     

Stationary distributions of the R[X]/R/1 cross-correlated queue

We consider an infinite buffer single server queue wherein batch interarrival and service times are correlated having a bivariate mixture of rational (R) distributions, where R denotes the class of distributions with rational Laplace–Stieltjes transform (LST), i.e., ratio of a polynomial of degree at most n to a polynomial of degree n. The LST of actual waiting time distribution has been obtained using Wiener–Hopf factorization of the characteristic equation. The virtual waiting time, idle period (actual and virtual) distributions, as well as inter-departure time distribution between two successive customers have been presented. We derive an approximate stationary queue-length distribution at different time epochs using the Markovian assumption of the service time distribution. We also derive the exact steady-state queue-length distribution at an arbitrary epoch using distributional form of Little’s law. Finally, some numerical results have been presented in the form of tables and figures.     

Multi-class M/PH/1 queues with deterministic impatience times

This article considers computational procedures for the waiting time and queue length distributions in stationary multi-class first-come, first-served single-server queues with deterministic impatience times. There are several classes of customers, which are distinguished by deterministic impatience times (i.e., maximum allowable waiting times). We assume that customers in each class arrive according to an independent Poisson process and a single server serves customers on a first-come, first-served basis. Service times of customers in each class are independent and identically distributed according to a phase-type distribution that may differ for different classes. We first consider the stationary distribution of the virtual waiting time and then derive numerically feasible formulas for the actual waiting time distribution and loss probability. We also analyze the joint queue length distribution and provide an algorithmic procedure for computing the probability mass function of the stationary joint queue length.     

Perinatal and social factors predicting caesarean birth in a 2004 Australian birth cohort

Background

The proportion of babies born by caesarean section in Australia has almost doubled over the last 25 years. Factors known to contribute to caesarean such as higher maternal age, mothers being overweight or obese, or having had a previous caesarean do not completely account for the increased rate and it is clear that other influences exist.

Midwives’ views of an evidence-based intervention to reduce caesarean section rates in Ireland

ProblemA worldwide increase of caesarean section (CS) rates has been estimated at a rate of 4% per year and numerous interventions to reduce the rates have not been successful, perhaps because they are not acceptable to clinicians.BackgroundA caesarean section (CS) can be a life-saving operation, but has been associated with short- and long-term risk factors and shown to affect subsequent pregnancies.AimTo explore midwives’ views on CS rates and evaluate the feasibility and acceptability of an evidence-based intervention programme (REDUCE) designed to decrease overall CS rates in Ireland by 7%.MethodsFollowing ethical approval, a qualitative exploratory design was used to seek midwives’ views of the evidence-based intervention. A total of 28 midwives from one large tertiary maternity hospital took part in four focus group interviews. Data were analysed using thematic analysis.FindingsFive themes emerged, illustrating the midwives’ views of what could be improved in the present system and how CS rates could be reduced in future. The themes included: (i) Induction of labour; (ii) Education; (iii) Auditing of practice; (iv) Clinical practice; (v) Midwife-Obstetrician collaboration.DiscussionThis study noted a rising CS rate year on year, with a rate of 37% at the time of the study, and the midwives voiced their very real concerns over the increased high rates.ConclusionThe study provided support for the evidence based ‘REDUCE’ intervention, which now needs to be tested empirically within this Irish population.     

椭圆气缸内燃机的稳流试验及其性能预测

本次稳流试验用来预测新颖的椭圆气缸往复式内燃机的性能。实测数据和分析结果表明,椭圆截面气缸内燃机此起等容积正圆截面气缸内燃机,增大了进、排气门,从而提高了充气效率;或在充气效率不减的条件下,大幅度提高转速或增压,以实现发动机的高强化。     

无穷直线上含参变未知函数的Hilbert问题

给出了一类参变未知函数Hilbert问题的数学提法,依据解析函数边值问题的经典理论,讨论了此边值问题的可解性条件,给出了该问题的可解性定理.     

Midwifery continuity of care and vaginal birth after caesarean section: A randomised controlled trial

Problem and backgroundCaesarean section (CS) rates in Australia and many countries worldwide are high and increasing, with elective repeat caesarean section a significant contributor.AimTo determine whether midwifery continuity of care for women with a previous CS increases the proportion of women who plan to attempt a vaginal birth in their current pregnancy.MethodsA randomised controlled design was undertaken. Women who met the inclusion criteria were randomised to one of two groups; the Community Midwifery Program (CMP) (continuity across the full spectrum — antenatal, intrapartum and postpartum) (n = 110) and the Midwifery Antenatal Care (MAC) Program (antenatal continuity of care) (n = 111) using a remote randomisation service. Analysis was undertaken on an intention to treat basis. The primary outcome measure was the rate of attempted vaginal birth after caesarean section and secondary outcomes included composite measures of maternal and neonatal wellbeing.FindingsThe model of care did not significantly impact planned vaginal birth at 36 weeks (CMP 66.7% vs MAC 57.3%) or success rate (CMP 27.8% vs MAC 32.7%). The rate of maternal and neonatal complications was similar between the groups.ConclusionModel of care did not significantly impact the proportion of women attempting VBAC in this study. The similarity in the number of midwives seen antenatally and during labour and birth suggests that these models of care had more similarities than differences and that the model of continuity could be described as informational continuity. Future research should focus on the impact of relationship based continuity of care.