veruse of cesarean delivery can jeopardize maternal and child health. 1,2 Concerns about "alarming" 3 rates in China increased after the World Health Organization (WHO) 4 reported that 46.2% of births were delivered by cesarean in the years 2007 and 2008, based on an analysis of 14 541 deliveries in 21 hospitals in 3 provinces. With a population of approximately 1.37 billion in 2014, China's health care use is of substantial global interest. Over the past 2 decades, the nation has invested in improving maternal and child health. The Law on Maternal and Infant Health Care was passed in 1995 to provide a high-quality hospital delivery to all women. 5 Health insurance expansion began in 2003, to provide better financial access to maternity care. 6 In 2009, a comprehensive health care reform plan included subsidies for in-hospital delivery to pregnant women in rural areas. 7 In 2008, 89.9% of deliveries occurred in hospitals, and 87.9% of families had health insurance. 6 By 2014, 99.6% of deliveries occurred in hospitals. 8 China's increasing cesarean rate has been spurred by many factors, including expanded access to hospital care, medicolegal concerns, financial incentives for physicians to perform cesareans, and parents' focus on having a "perfect baby" under the one-child policy. 9,10 Since 2002, reducing the cesarean rate has been a national priority, 11 and a variety of policies, programs, and activities have emerged at the central government, 12 provincial or municipal, 13 city, 14 and city district or county levels. 15 There is no national IMPORTANCE The increasing use of cesarean delivery is an emerging global health issue. Prior estimates of China's cesarean rate have been based on surveys with limited geographic coverage. OBJECTIVE To provide updated information about cesarean rates and geographic variation in cesarean use in China. DESIGN, SETTING, AND DATA SOURCES Descriptive study, covering every county (n = 2865) in mainland China's 31 provinces, using county-level aggregated information on the number of live births, cesarean deliveries, maternal deaths, and perinatal deaths, collected by the Office for National Maternal & Child Health Statistics of China, from 2008 through 2014. EXPOSURES Live births. MAIN OUTCOMES AND MEASURES Annual rate of cesarean deliveries. RESULTS Over the study period, there were 100 873 051 live births, of which 32 947 229 (32.7%) were by cesarean delivery. In 2008, there were 13 160 634 live births, of which 3 788 029 (28.8%) were by cesarean delivery and in 2014 there were 15 123 276 live births, of which 5 280 124 (34.9%) were by cesarean delivery. Rates varied markedly by province, from 4.0% to 62.5% in 2014. Despite the overall increase, by 2014 rates of cesarean delieries in 14 of the nation's 17 "super cities" had declined by 4.1 to 17.5 percentage points from their earlier peak values (median, 11.4; interquartile range, 6.3-15.4). In 4 super cities with the largest decreases, there was no increase in maternal or perinatal mortality. CONCLUSIONS AND RELEVANCE Between 2...

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An electro-absorption optical modulator based on dual-graphene-on-graphene configuration is presented and investigated. Four graphene layers are embedded in a silicon-on-insulator (SOI) waveguide, the total metal-graphene contact resistance of this structure is reduced 50% by the graphene layers co-electrode design. By optimizing the position of each graphene-on-graphene (GOG) layer in the waveguide, a strong interaction between graphene layers and light is obtained, which leads to a significant change of the effective mode index (EMI) in the waveguide. Calculations show that an electro-absorption optical modulator can achieve 34 dB extinction ratio (ER) and 100 GHz modulation bandwidth with 5 µm-long active region and 17.6 fJ/bit consumption.

The interaction between free surface flow and structure is investigated using a new level set immersed boundary method. The incorporation of an improved immersed boundary method with a free surface capture scheme implemented in a Navier-Stokes solver allows the interaction between fluid flow with free surface and moving body/bodies of almost arbitrary shape to be modelled. A new algorithm is proposed to locate exact forcing points near solid boundaries, which provides an accurate numerical solution. The discretized linear system of the Poisson pressure equation is solved using the Generalized Minimum Residual (GMRES) method with incomplete LU preconditioning. Uniform flow past a cylinder at Reynolds number Re=100 is modelled using the present model and results agree well with the experiment and numerical data in the literature. Water exit and entry of a cylinder at the prescribed velocity is also investigated. The predicted slamming coefficient is in good agreement with experimental data and previous numerical simulations using a ComFlow model. The vertical slamming force and pressure distribution for the free falling wedge is also studied by the present model and comparisons with available theoretical solutions and experimental data are made.

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SUMMARYA new numerical method that couples the incompressible Navier-Stokes equations with the global mass correction level-set method for simulating fluid problems with free surfaces and interfaces is presented in this paper. The finite volume method is used to discretize Navier-Stokes equations with the two-step projection method on a staggered Cartesian grid. The free-surface flow problem is solved on a fixed grid in which the free surface is captured by the zero level set. Mass conservation is improved significantly by applying a global mass correction scheme, in a novel combination with third-order essentially nonoscillatory schemes and a five stage Runge-Kutta method, to accomplish advection and re-distancing of the level-set function. The coupled solver is applied to simulate interface change and flow field in four benchmark test cases: (1) shear flow; (2) dam break; (3) travelling and reflection of solitary wave and (4) solitary wave over a submerged object. The computational results are in excellent agreement with theoretical predictions, experimental data and previous numerical simulations using a RANS-VOF method. The simulations reveal some interesting free-surface phenomena such as the free-surface vortices, air entrapment and wave deformation over a submerged object.

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