A new two-part test based on density ratio model for zero-inflated continuous distributions

In this paper,we consider testing the hypothesis concerning the means of two independent semicontinuous distributions whose observations are zero-inflated,characterized by a sizable number of zeros and positive observations from a continuous distribution.The continuous parts of the two semicontinuous distributions are assumed to follow a density ratio model.A new two-part test is developed for this kind of data.The proposed test takes the sum of one test for equality of proportions of zero values and one conditional test for the continuous distribution.The test is proved to follow a 2 distribution with two degrees of freedom.Simulation studies show that the proposed test controls the type I error rates at the desired level,and is competitive to,and most of the time more powerful than two popular tests.A real data example from a dietary intervention study is used to illustrate the usefulness of the proposed test.

A Hurdle Negative Binomial Regression Model for Non-Marital Fertility in Namibia

The rise of non-marital fertility, which seems to defy the Bongaarts model by decoupling marriage from fertility, has become a subject of interest in both the developed and developing world. Consequences of non-marital fertility are mostly negative particularly in developing countries. In Namibia, although premarital childbearing has been reported to be high and increasing, no studies have explicitly analyzed factors influencing non-marital fertility. This paper uses data from the 2006/7 Namibia DHS to establish the determinants of non-marital fertility among women by applying a two-part model, with one part to describe the presence of non-marital birth and the other part to explain its intensity （number of children born）. Using the number of children ever born as an outcome, we explored various count data models. Based on the Voung statistics model comparison, we settled for the Hurdle logit Negative Binomial regression to model the number of non-marital births. Non-marital fertility in Namibia is associated with the age, with young women likely to have lower fertility compared to older women. Women with secondary or higher education had lower fertility compared those with no formal education. Findings also show that rural women higher fertility propensity compared to their urban counterparts even though there was no significant difference in fertility intensity. With regard to socio-economic status, fertility intensity decreased as the women got richer. Intervention efforts should focus on promoting education among girls and women especially in rural areas to improve their socio-economic status, reduce teenage pregnancy and non-marital fertility.

公立医疗机构比私立医疗机构更利他吗？

为了研究不同所有制医疗机构的利他性,本文使用相关调查数据对农村地区新农合受访者门诊费用、药品费用及其各自付比进行回归分析。结果显示:在基层公立医疗机构看门诊所产生的医疗总费用、总费用自付额均显著地高于基层非公立医疗机构,而这一差异可能源自总费用中的非药品费用;相比基层非公立医疗机构,患者在基层公立医疗机构看门诊拥有更高的总费用报销比。以上结论不满足公立医疗机构降低患者医疗费用利他性假设,因此本文建议更加深化医疗改革,促进非公立医疗机构发展、提升患者福利。

Internet Usage and Household Investment on Risky Financial Assets

Using panel data from the China Family Panel Studies for 2010,2014 and 2016,this paper uses a two-part model,with the first part using a fixed-effects panel logit model and the second part using a linear logit fixed-effects model to study the impact of Internet usage on Chinese households’participation in risky financial markets and the intensity of investment in risky assets after participation.The results find that Internet usage can promote household participation in the risky finance market and increase household investment in risky assets.Therefore,accelerating Internet usage can promote Chinese households’participation in the risk finance market.

Deep-reinforcement-learning-based UAV autonomous navigation and collision avoidance in unknown environments

In some military application scenarios,Unmanned Aerial Vehicles(UAVs)need to perform missions with the assistance of on-board cameras when radar is not available and communication is interrupted,which brings challenges for UAV autonomous navigation and collision avoidance.In this paper,an improved deep-reinforcement-learning algorithm,Deep Q-Network with a Faster R-CNN model and a Data Deposit Mechanism(FRDDM-DQN),is proposed.A Faster R-CNN model(FR)is introduced and optimized to obtain the ability to extract obstacle information from images,and a new replay memory Data Deposit Mechanism(DDM)is designed to train an agent with a better performance.During training,a two-part training approach is used to reduce the time spent on training as well as retraining when the scenario changes.In order to verify the performance of the proposed method,a series of experiments,including training experiments,test experiments,and typical episodes experiments,is conducted in a 3D simulation environment.Experimental results show that the agent trained by the proposed FRDDM-DQN has the ability to navigate autonomously and avoid collisions,and performs better compared to the FRDQN,FR-DDQN,FR-Dueling DQN,YOLO-based YDDM-DQN,and original FR outputbased FR-ODQN.

Numerical modeling of sediment transport based on unsteady and steady flows by incompressible smoothed particle hydrodynamics method

The purpose of the present paper is to introduce a simple two-part multi-phase model for the sediment transport problems based on the incompressible smoothed particle hydrodynamics（ISPH） method. The proposed model simulates the movement of sediment particles in two parts. The sediment particles are classified into three categories, including the motionless particles, moving particles behave like a rigid body, and moving particles with a pseudo fluid behavior. The criterion for the classification of sediment particles is the Bingham rheological model. Verification of the present model is performed by simulation of the dam break waves on movable beds with different conditions and the bed scouring under steady flow condition. Comparison of the present model results, the experimental data and available numerical results show that it has good ability to simulate flow pattern and sediment transport.

Application of a weakly compressible smoothed particle hydrodynamics multi-phase model to non-cohesive embankment breaching due to flow overtopping

The subject of present study is the application of mesh free Lagrangian two-dimensional non-cohesive sediment transport model applied to a two-phase flow over an initially trapezoidal-shaped sediment embankment. The governing equations of the present model are the Navier-Stocks equations solved using Weakly Compressible Smoothed Particle Hydrodynamics （WCSPH） method. To simulate the movement of sediment particles, the model considers a powerful two-part technique; when the sediment phase has rigid behavior, only the force term due to shear stress in the Navier-Stokes equations is used for simulation of sediment particles＇ movement. Otherwise, all the Navier-Stokes force terms are used for transport simulation of sediment particles. In the present model, the interactions between different phases are calculated automatically, even with considerable difference between the density and viscosity of phases. Validation of the model is performed using simulation of available laboratory experiments, and the comparison between computational results and experimental data shows that the model generally predicts well the flow propagation over movable beds, the induced sediment transport and bed changes, and temporal evolution of embankment breaching.

The Impact of Multimorbidity on Healthcare Utilization and Expenditure:Evidence from China

Objective To investigate the impact of multimorbidity on China’s healthcare utilization and expenditure.Methods A two-part model was used to analyze the outpatient cares based on the data from CHARLS 2015 wave.Results and Conclusion As the prevalence of multimorbidity was 36.6%among 15523 middle-aged and elderly respondents in China,the multimorbidity increased the likelihood of outpatient service,while the total outpatient expenditure did not increase significantly as well as the OOP expenditure.Secondly,although there was a similar probability of outpatient visit,the patients with multimorbidity excluding diabetes and(or)hypertension,had not been concerned by China’s Chronic Condition Management Programs(CCCMP)yet.Thirdly,the patients with multimorbidity increased the outpatient visits to different types of hospitals.Under CCCMP intervention,the patients did not switch from the county/city hospital to primary healthcare centers and township hospital.A costeffective strategy for providing services to patients with multimorbid conditions is needed,the focus of CCCMP should be switched from the single chronic disease to the multimorbidity.