Checking the adequacy of a partial linear model

A partial linear model is a model where the response variable depends on some covariates linearly and on others nonparametrically. In this article, we construct an empirical process-based test for examining the adequacy of partial linearity of model. A re-sampling approach, called random symmetrization (RS), is applied to obtain the approximation to the null distribution of the test. The procedure is easy to implement. A simulation study is carried out and application to an example is made.published_or_final_versio

Resampling methods for homogeneity tests of covariance matrices

Testing hypotheses on covariance matrices has long been of interest in statistics. The test of homogeneity is very often a preliminary step in discriminant analysis, cluster analysis, MANOVA, etc. In this article we propose nonparametric tests which are based on the eigenvalues of the differences among the sample covariance matrices after a common rescaling. Three resampling techniques for calculating p-values are shown to be asymptotically valid: Boot-strap, random symmetrization and permutation. Monte Carlo simulations show that the bootstrap performs less satisfactorily than the others in adhering to the nominal level of significance. Some theoretic ground for this phenomenon is given. The simulation results also suggest that the homogeneity tests proposed in this article performs better than the bootstrap version of Bartlett's test.published_or_final_versio

Anisotropic step-flow growth and island growth of GaN(0001) by molecular beam epitaxy

GaN(0001) thin films are grown using radio frequency plasma assisted molecular beam epitaxy. By changing the growth temperature, anisotropic growth rate behavior is observed in both the step-flow growth mode and the 2D island growth mode. Tunneling scanning microscopy reveals, in the step-flow growth mode, strong influences from the growth anisotropy on the shape of the terrace edges, resulting in striking differences between hexagonal and cubic films. In the 2D nucleation growth mode, triangularly shaped islands are formed. The significance of growth anisotropy to growing high quality GaN films is discussed.published_or_final_versio

Failure detection of closed-loop systems and application to SI engines

The existing methods of engine fault detection and isolation are based on open-loop control, which are not applicable to closed-loop control systems. In this paper a new fault detection and isolation method for closed-loop control systems is presented. The validity of this method is verified by simulation results. First, the method was tested on the nonlinear simulation of SI engines, the Mean Value Engine Model (MVEM) with different faults was simulated. The neural network based engine air path model was constructed, which was trained with engine input/output data. Then Radial Basis Function (RBF) neural network was used to model the SI engine. The drawback of the training data acquisition was analyzed and a new data acquisition method was proposed, that greatly improved the model accuracy. © 2017, Editorial Board of Jilin University. All right reserved

Evidence-based obstetrics in four hospitals in China: An observational study to explore clinical practice, women's preferences and provider's views

BACKGROUND: Evidence-based obstetric care is widely promoted in developing countries, but the success of implementation is not known. Using selected childbirth care procedures in four hospitals in Shanghai, we compared practice against evidence-based information, and explored user and provider views about each procedure. METHODS: Observational study. Using the Cochrane Library, we identified six procedures that should be avoided as routine and two that should be encouraged. Procedure rate determined by exit interviews with women, verified using hospital notes. Views of women and providers explored with in depth interviews. The study sites were three hospitals in Shanghai and one in neighbouring province of Jiangsu. 150 women at each centre for procedure rate, and 48 in-depth interviews with women and providers. RESULTS: Vaginal births were 50% (303/599) of the total. Of the six practices where evidence suggests they should be avoided as routine, three were performed with rates above 70%: pubic shaving (3 hospitals), rectal examination (3 hospitals), and episiotomy (3 hospitals). Most women delivered lying down, pain relief was rarely given, and only in the urban district hospital did women routinely have a companion. Most women wanted support or companionship during labour and to be given pain relief; but current practice is insufficient to meet women's needs. CONCLUSION: Obstetric practice is not following best available evidence in the hospitals studied. There is a need to adjust hospital policy to support the use of interventions proven to be of benefit to women during childbirth, and develop approaches that ensure clinical practice changes