High-dimensional robust approximated M-estimators for mean regression with asymmetric data

Asymmetry along with heteroscedasticity or contamination often occurs with the growth of data dimensionality. In ultra-high dimensional data analysis, such irregular settings are usually overlooked for both theoretical and computational convenience. In this paper, we establish a framework for estimation in high-dimensional regression models using Penalized Robust Approximated quadratic M-estimators (PRAM). This framework allows general settings such as random errors lack of symmetry and homogeneity, or the covariates are not sub-Gaussian. To reduce the possible bias caused by the data's irregularity in mean regression, PRAM adopts a loss function with a flexible robustness parameter growing with the sample size. Theoretically, we first show that, in the ultra-high dimension setting, PRAM estimators have local estimation consistency at the minimax rate enjoyed by the LS-Lasso. Then we show that PRAM with an appropriate non-convex penalty in fact agrees with the local oracle solution, and thus obtain its oracle property. Computationally, we demonstrate the performances of six PRAM estimators using three types of loss functions for approximation (Huber, Tukey's biweight and Cauchy loss) combined with two types of penalty functions (Lasso and MCP). Our simulation studies and real data analysis demonstrate satisfactory finite sample performances of the PRAM estimator under general irregular settings

Electrical poling below coercive field for large piezoelectricity

Isotropic polycrystalline ferroelectric ceramics have to be electrically poled to develop a net macroscopic polarization and hence piezoelectricity. It is well accepted that a sufficient poling can only be realized under an electric field that is much higher than the coercive field. In this study, we observed in (Bi1/2 Na 1/2)TiO3-BaTiO3 ceramics that large piezoelectricity can develop at poling fields far below the measured coercive field. Using in situ transmission electron microscopy, such an unusual behavior, is interpreted with the polarization alignment of polar nanodomains in the non-ergodic relaxor phase

Understanding WeChat User’s Intention to Use Various Functions: from Social Cognitive Perspective

Based upon social cognitive theory, this study explores the effect of personal and environment factors on Wechat user’s continuous intention to use various functions. Online survey is used to collect data from the WeChat users. The results confirms that some personal factors (relationship benefit and performance benefit) have a positive effect on intention to use, while image does not have significant effect. Besides, three social environmental factors, the popularity of WeChat, subjective norm and company guarantee, all have significant impacts. Furthermore, we find that environmental factors’ effects are stronger than personal factors. Finally, we propose our theoretical and practical implications according to the findings of this study

Optimization Rotor Hole to Reduce Force in Cold Pressing Rotor into Crankshaft

Assembling rotor with crankshaft of a hermetic reciprocating compressor is, normally, heating of the rotor and then putting it into crankshaft. This assembly method allows larger magnitude of interference between rotor and crankshaft. Tolerance band of crankshaft could be relaxed and facilitate the process, however, the process requires heating equipment and higher energy consumption, obviously, this will increase the manufacturing cost of the compressor. In this situation, using cold pressing rotor into crankshaft can avoid the disadvantage mentioned above effectively, moreover, easily mount the rotor at the accurate location. Using of the original design of the rotor and crankshaft cold press will lead large force which may damage the crankshaft. This article presents an analysis about a geometric proposal for the rotor hole that guarantees to withstand sufficient torque, while cold press force is under the crankshaft yield strength