Investigation of Fiber Splitting in Side-by-side Bicomponent Meltblown Nonwoven Webs through Post Treatment

Finer fibers are increasingly desirable in the nonwoven industry in many applications due to increased specific surface area, increased surface adsorption ability, and improved filtration efficiency. Splitting bicomponent (Bico) fibers to produce finer fibrous nonwoven webs has become one of the hot topics in nonwoven industries. Investigation of Bico fiber splitting mechanism and hence finding proper ways to achieve fiber splitting in S/S Bico MB nonwoven webs are the key issues in this research. Based on the fiber splitting mechanism, incompatible polymer pairs were chosen and appropriate post-treating methods as well as the post-treating agents were selected to facilitate fiber splitting in S/S Bico MB nonwoven webs. Several post treatments were used to split side-by-side meltblown nonwoven fibers in this research, including hydroentanglement, heat-stretching, NaOH and benzoic acid treatment. In each post treatment method, fiber splitting was examined with SEM and/or laser-source microscope. Fiber diameter, web structure and web properties were examined before and after the fiber splitting inducing treatment. Hydoentanglement has been applied to S/S Bico MB nonwoven webs with Bico pairs of PA6/PE. PA6/PP and PA6/PET. Fiber diameter, web structure and webproperties were examined based on the corresponding test standards. Fiber splitting phenomenon and web morphology were observed with SEM, and web structure was evaluated using WebPro technology. Heat-stretching post treatment was applied to S/S Bico MB nonwoven webs with Bico pairs of PA6/PE and PA6/PP. The fiber splitting phenomenon was observed using SEM; fiber diameter and web properties in MD and CD were examined, especially the change in flexural rigidity and elasticity of the heat-stretched webs. The S/S Bico MB nonwoven webs of 25PE/75PET, and 50PBT/50PP were treated with sodium hydroxide at a bath ratio of 1/20 and temperature of 100C using different concentrations of NaOH at different treating times. The fiber splitting phenomenon was investigated using SEM in this research. Benzoic acid (BA) has been employed to split S/S Bico MB webs composed of 50PET/50PA6 and 50PP/50PA6. The degree of fiber splitting was evaluated using both fiber splitting ratio and initial dye adsorption ration (initial dyeing ration) in this research. Web properties were examined to characterize the change after benzoic acid treatment. The fiber splitting mechanism during BA treatment was discussed as well, and it was concluded that the BA method could be an efficient way to split S/S Bico MB fibers, compared to the foresaid three methods

Unique continuation property with partial information for two-dimensional anisotropic elasticity systems

In this paper, we establish a novel unique continuation property for two-dimensional anisotropic elasticity systems with partial information. More precisely, given a homogeneous elasticity system in a domain, we investigate the unique continuation by assuming only the vanishing of one component of the solution in a subdomain. Using the corresponding Riemann function, we prove that the solution vanishes in the whole domain provided that the other component vanishes at one point up to its second derivatives. Further, we construct several examples showing the possibility of further reducing the additional information of the other component. This result possesses remarkable significance in both theoretical and practical aspects because the required data is almost halved for the unique determination of the whole solution.Comment: 14 pages, 1 figur

Geodynamic setting of Late Cretaceous Sn–W mineralization in southeastern Yunnan and northeastern Vietnam

The Sn–W mineralization in SE Yunnan Province, China and NE Vietnam shares many similarities. Through comparing the geological and geochronological data, we suggest the Sn–W deposits and the associate igneous rocks in the region represent one regional magmatic-mineralization event. To explore the geodynamic setting of these mineralization and magmatic activities, a geochronological dataset in the regions has been presented, containing data of this study and previously published. The dataset shows that the Late Cretaceous magmatic–mineralization–metamorphic activities widely distribute along the eastern Asian continental margin. Existing studies support that this is the product of the subduction of the Palaeo-Pacific Plate beneath the Eurasian continent, which probably formed under an Andean-type active continental margin setting. According to the exhibited data, we preliminarily conclude that the late Cretaceous magmatic and Sn–W mineralization activities in the southeast Yunnan and northeast Vietnam region is one part of this subduction activities and should have formed under the same geodynamic setting

How does tourism industry dependence affect economic growth in western China? --Based on the inspection and interpretation of the Resource Curse transmission mechanism

The relationship between tourism industry dependence and economic growth is still controversial, and there are few quantitative studies on its transmission mechanism. Based on the Resource Curse hypothesis, the panel data of 46 excellent tourism cities in the western region from 2000 to 2017 was used to examine the existence and transmission mechanism of the Resource Curse. The results show that: tourism industry dependence in the western region of China appears as a curse rather than a gospel for economic growth, and the transmission route of the curse effect is mainly that the tourism industry has a negative impact on the regional economy by squeezing out the manufacturing industry. The findings of the paper provide a theoretical proof for the existence and transmission mechanism of the tourism resource curse in western China, and have certain enlightenment for similar regions to avoid falling into the tourism resources curse trap

A META-ANALYTIC REVIEW OF SOCIAL MEDIA STUDIES

Social media such as social networking sites, blogs, micro-blogs, Wikis, are increasingly and widely used in our daily lives. In the information system (IS) discipline, social media have become a hot research area and draw the attention of many scholars. The paper systematically reviewed social media studies published in Association for Information Systems (AIS) listed top 20 journals from 2009 to 2013. The publication time, journal preferences, research objects and research topics are discussed. Generally, the current social media studies including four areas, namely user, management, technology and information. Each area has distinct focuses and topics. By thoroughly analyzing the research topics, the authors formulate our projections and recommendations for future social media studies

Robust Inference with Stochastic Local Unit Root Regressors in Predictive Regressions

This paper explores predictive regression models with stochastic unit root (STUR) components and robust inference procedures that encompass a wide class of persistent and time-varying stochastically nonstationary regressors. The paper extends the mechanism of endogenously generated instrumentation known as IVX, showing that these methods remain valid for short and long-horizon predictive regressions in which the predictors have STUR and local STUR (LSTUR) generating mechanisms. Both mean regression and quantile regression methods are considered. The asymptotic distributions of the IVX estimators are new and require some new methods in their derivation. The distributions are compared to previous results and, as in earlier work, lead to pivotal limit distributions for Wald testing procedures that remain robust for both single and multiple regressors with various degrees of persistence and stochastic and fixed local departures from unit roots. Numerical experiments corroborate the asymptotic theory, and IVX testing shows good power and size control. The IVX methods are illustrated in an empirical application to evaluate the predictive capability of economic fundamentals in forecasting S\&P 500 excess returns