267 research outputs found
Jackknife empirical likelihood tests for error distributions in regression models
AbstractRegression models are commonly used to model the relationship between responses and covariates. For testing the error distribution, some classical test statistics such as KolmogorovâSmirnov test and CramĂ©râvon-Mises test suffer from the complicated limiting distribution due to the plug-in estimate for the unknown parameters. Hence some ad hoc procedure such as bootstrap method is needed to obtain critical points. Recently, Khmaladze and Koul (2004) [7] have proposed an asymptotically distribution free test via some Martingale transforms. However, the calculation of such a test becomes quite involved, which usually requires numeric integration when the CramĂ©râvon-Mises type of test is employed. In this paper we propose a novel jackknife empirical likelihood method which is easy to compute and has a chi-square limit so that critical values are ready at hand. A simulation study confirms that the new test has an accurate size and is powerful too
A Discussion on the Detachment Structural Deformation and Its Influence on Pore Structure Evolution in Shale on the Western of the Xuefeng Mountain, South China
Detachment structures occur widely in the crust, and it is the commonest and most important deformation type developed in the region between orogenic belts and basins. Organic-rich shale, as the weak layers, usually acts as slippery layers in detachment structural deformation systems. The âcomb-likeâ and âtough-likeâ fold belts on the western side of the Xuefeng Mountain result from the multilayer detachment, and their formation is different from the typical Jura type structures. The reason is that there are several detachment layers and detachment systems in the stratigraphic column from the Neoproterozoic upwards to the Mesozoic in the study area. As the stress decoupling role, the shale slippery layers tend to undergo strong deformation in the detachment systems and impacted on pore structure evolution in the shale. In order to obtain the detachment structural deformation and its influence on pore structure evolution in shale on the Middle and Upper Yangtze, the structural and textural, geochemical and mineralogical properties analysis, porosity and pore structure feature investigations are performed using shale samples collected from the same shale bed of the Longmaxi Formations (Lower Silurian) of Western of the Xuefeng Mountain, South China
Data-driven method of solving computationally expensive combined economic/emission dispatch problems in large-scale power systems: an improved kriging-assisted optimization approach
Combined economic/emission dispatch (CEED) is generally studied using analytical objective functions. However, for large-scale, high-dimension power systems, CEED problems are transformed into computationally expensive CEED (CECEED) problems, for which existing approaches are time-consuming and may not obtain satisfactory solutions. To overcome this problem, a novel data-driven surrogate-assisted method is introduced firstly. The fuel cost and emission objective functions are replaced by improved Kriging-based surrogate models. A new infilling sampling strategy for updating Kriging-based surrogate models online is proposed, which improves their fitting accuracy. Through this way, the evaluation time of the objective functions is significantly reduced. Secondly, the optimization of CECEED is executed by an improved non-dominated sorting genetic algorithm-II (NSGA-II). The above infilling sampling strategy is also used to reduce the number of evaluations for original mathematic fitness functions. To improve their local convergence ability and global search abilities, the individuals that exhibit excellent performance in a single objective are cloned and mutated. Finally, information about the Pareto front is used to guide individuals to search for better solutions. The effectiveness of this optimization method is demonstrated through simulations of IEEE 118-bus test system and IEEE 300-bus test system
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Designing nano-aluminum laden fuel pump for aviation applications
In view of the fact that traditional liquid propellants cannot meet the design requirements of large-thrust flight vehicle, it has become a new trend to add nano-metal powder to liquid propellants to greatly increase density and specific impulse. In order to achieve the variable flow-rate and variable-proportion transportation of aviation fuel with nano-aluminum, a new type of solid-liquid mixing pumping system is designed, including powder conveying device, stirring device, pump and corresponding drive and transmission system. For the purpose of avoiding the frictional contact between the rotors, which will bring potential hazard to nano-aluminum powder, a non-contact twin-screw pump with synchronous gears is designed. Among them, based on the considerations of flow pulsation, volumetric efficiency and manufacturing difficulty, cycloid profile is adopted for screw rotors. After completing the functional design, geometric parameter design, structural design, 3D modeling, prototype manufacturing and preliminary performance estimation of the mixing pumping system, the performance of the screw feeder, agitator, screw pump was tested through experiments to meet the expected design requirements. The designed agitator can achieve sufficient mixing at 500 rpm in less than 10 s. Even though 50-micron clearances are designed with a relatively small rotor diameter, the volumetric efficiency of screw pump can reach above 50% when the discharge pressure is below 450 kPa and the flow rate is set as 10 L/min, the power of the screw pump is less than 700 W. This design facilitates the rapid real-time preparation of metallized propellants and provides a reference for further improving the design and control methods of nanoparticle two-phase flow pumping
Observer-based Hâ control of networked systems with stochastic communication protocol: The finite-horizon case
This paper is concerned with the H â control problem for a class of linear time-varying networked control systems (NCSs) with stochastic communication protocol (SCP). The sensor-to-controller network (the controller-to-actuator network) is considered where only one sensor (one actuator) obtains access to the communication network at each transmission instant. The SCP is applied to determine which sensor (actuator) should be given the access to the network at a certain instant. The aim of the problem addressed is to design an observer-based controller such that the H â performance of the closed-loop system is guaranteed over a given finite horizon. For the purpose of simplifying the NCS model, a new Markov chain is constructed to model the SCP scheduling of communication networks. Then, both the methods of stochastic analysis and completing squares are utilized to establish the sufficient conditions for the existence of the desired controller. The controller parameters are characterized by solving two coupled backward recursive Riccati difference equations subject to the scheduled SCP. Finally, a numerical example is given to illustrate the effectiveness of the proposed controller design scheme
Even high normal blood pressure affects live birth rate in women undergoing fresh embryo transfer
STUDY QUESTION
Do differences in blood pressure within the normal range have any impacts on the live birth rate (primary outcome) or biochemical pregnancy rate (beta-hCG positivity), clinical pregnancy rate (heart beating in ultrasound), abortion rate and ectopic pregnancy rate (secondary outcomes) of fresh embryo transfer in women undergoing their IVF/ICSI treatment?
SUMMARY ANSWER
Even rather small differences in baseline blood pressure in women with normal blood pressure according to current guidelines undergoing fresh embryo transfer after IVF/ICSI affects substantially the live birth rate.
WHAT IS KNOWN ALREADY
Pre-pregnancy hypertension is a well-known risk factor for adverse pregnancy events such as preeclampsia, fetal growth restriction, placental abruption and adverse neonatal events. It is likewise well known that hypertension during pregnancy in women undergoing ART is associated with adverse pregnancy outcomes. However, whether blood pressure at the high end of the normal range has an impact on ART is unknown.
STUDY DESIGN, SIZE, DURATION
It is a prospective observational cohort study based on a single IVF center between January 2017 and December 2018.
PARTICIPANTS/MATERIALS, SETTING, METHODS
Two thousand four hundred and eighteen women with normal blood pressure undergoing fresh embryo transfer after IVF/ICSI at the Reproductive and Genetic Hospital of CITIC-Xiangya were enrolled in this study.
MAIN RESULTS AND THE ROLE OF CHANCE
Blood pressure was measured at the first visit when women consulted the IVF center due to infertility. In women with a successful pregnancy outcome (1487 live births out of 2418 women undergoing fresh embryo transfer after IVF/ICSI), systolic blood pressure (SBP) (114.1â±â9.48âmmHg versus 115.4â±â9.8âmmHg, Pâ=â0.001) and diastolic blood pressure (DBP) (74.5â±â7.5âmmHg versus 75.3â±â7.34âmmHg, Pâ=â0.006) were lower than in those who did not achieve live births. Multivariate logistic regression analysis revealed that SBP (OR: 0.987, 95% CI: 0.979â0.996, Pâ=â0.004) and DBP (OR: 0.986, 95% CI: 0.975â0.998, Pâ=â0.016) were negatively associated with live birth. Similarly, SBP was significantly negatively related to clinical pregnancy rate (OR: 0.990, 95% CI: 0.981â0.999, Pâ=â0.033), while for DBP the association was not statistically significant (OR: 0.994, 95% CI: 0.982â1.006, Pâ=â0.343). However, both SBP and DBP were positively associated with miscarriage OR: 1.021 (95% CI: 1.004â1.037, Pâ=â0.013) and OR: 1.027 (95% CI: 1.005â1.049, Pâ=â0.014), respectively. Both SBP and DBP were unrelated to biochemical pregnancy (hCG positivity), implantation and ectopic pregnancy rate.
LIMITATIONS, REASONS FOR CAUTION
Whether lowering blood pressure before initiating ART treatment in women with SBP or DBP higher than the thresholds defined in our study will confer a benefit is unknown. Also, we cannot exclude bias due to different ethnicities. Moreover, participants in our study only received fresh embryo transfer, whether the results could apply to frozen embryo transfer is unclear.
WIDER IMPLICATIONS OF THE FINDINGS
Our study challenges the current blood pressure goals in women undergoing fresh embryo transfer after IVF/ICSI. Further studies are needed to figure out the mechanism and effective approach to increase IVF/ICSI pregnancy outcomes.
STUDY FUNDING/COMPETING INTEREST(S)
Hunan Provincial Grant for Innovative Province Construction (2019SK4012). The authors declare that there were no conflicts of interest in this study.
TRIAL REGISTRATION NUMBER
N/A
Macrophageâderived MMPâ9 enhances the progression of atherosclerotic lesions and vascular calcification in transgenic rabbits
Matrix metalloproteinaseâ9 (MMPâ9), or gelatinase B, has been hypothesized to be involved in the progression of atherosclerosis. In the arterial wall, accumulated macrophages secrete considerable amounts of MMPâ9 but its pathophysiological functions in atherosclerosis have not been fully elucidated. To examine the hypothesis that macrophageâderived MMPâ9 may affect atherosclerosis, we created MMPâ9 transgenic (Tg) rabbits to overexpress the rabbit MMPâ9 gene under the control of the scavenger receptor A enhancer/promoter and examined their susceptibility to cholesterol dietâinduced atherosclerosis. Tg rabbits along with nonâTg rabbits were fed a cholesterol diet for 16 and 28Â weeks, and their aortic and coronary atherosclerosis was compared. Gross aortic lesion areas were significantly increased in female Tg rabbits at 28Â weeks; however, pathological examination revealed that all the lesions of Tg rabbits fed a cholesterol diet for either 16 or 28Â weeks were characterized by increased monocyte/macrophage accumulation and prominent lipid core formation compared with those of nonâTg rabbits. Macrophages isolated from Tg rabbits exhibited higher infiltrative activity towards a chemoattractant, MCPâ1 in vitro and augmented capability of hydrolysing extracellular matrix in granulomatous tissue. Surprisingly, the lesions of Tg rabbits showed more advanced lesions with remarkable calcification in both aortas and coronary arteries. In conclusion, macrophageâderived MMPâ9 facilitates the infiltration of monocyte/macrophages into the lesions thereby enhancing the progression of atherosclerosis. Increased accumulation of lesional macrophages may promote vascular calcification.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154927/1/jcmm15087-sup-0001-FigS1-S13.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154927/2/jcmm15087.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154927/3/jcmm15087_am.pd
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