Control-oriented structures obtained by various strategies for thermal management in electronic devices.

Thermal interface materials (TIMs) with high through-plane thermal conductivity are urgently desired to avoid overheating of high-power density electronics. Introducing and aligning fillers in polymer matrixes via magnetic field is a promising method to improve the thermal conductivity of the polymer. However, either the fillers need to be modified with magnetic particles or a strong magnetic field is needed for good alignment in high filler content. This prevents further improvement of the through-plane thermal conductivity. Herein, mesophase pitch-based carbon fibers (MPCFs) with a content as high as 76 wt.% are aligned vertically in water-soluble polyvinyl alcohol (PVA) under a low magnetic field (∼ 0.4 T), forming a vertically aligned MPCF (VAMPCF)/PVA composite with an extraordinary through-plane thermal conductivity of 86 W/(m·K), which is higher than that of many alloys. In addition, both theoretical and experimental results demonstrate that the critical intensity of the magnetic field needed for good alignment of the fillers depends on their size and magnetic susceptibility. Furthermore, the water solubility of PVA makes it easy to recycle MPCFs. This study offers an inspired venue to develop excellent and eco-friendly TIMs to meet ever increasing demand in heat dissipation for electronics.

A graphene aerogel with different strains meets the opposite demands for battery thermal management in cold and hot environments.

Sentiment analysis has been extensively studied recently for developing methodologies to automatically extract information from online reviews, which is important for manufacturers to improve their products or services. Unfortunately, most of current studies don’t take several key factors (e.g., sentiment strength, background of customer) into account. In this study, after building feature, sentiment, and degree vocabulary from online reviews using part-of-speech and word similarity analysis, a review-feature sentiment word (R-FSW) matrix is developed and classified by a model combining the long short-term memory and gated recurrent unit ensemble. The R-FSV matrix and online rating associated with the review are analyzed by a multivariate linear regression model to derive customer satisfaction. Since the sentiment values for each feature of the product are calculated with consideration of sentiment strength, more accurate sentiment orientation is obtain for each review, which is used to develop a set of rules to identify customer requirements based on the Kano model. By taking into account of both product perspective (e.g., product upgrade) and customer perspective (e.g., background of customers), a multidimensional analysis model is proposed to further analyze customer requirements. This sheds light on the dynamic and diversity of customer satisfaction, which help manufacturers to gain insight on not only how the customer satisfaction correlate with product improvements, but also how to develop products for particular group of customers. The proposed methods is deployed to study the online reviews of mobile phones from one of the main e-commerce companies in China (i.e., JD.com). The results show that our method is capable to identify the change of customer requirements over time and the preferences of different types of users (i.e., iOS or Android). Hence, the proposed method is more effective in extracting information from the online reviews for manufacturer to improve customer satisfaction efficiently.

Polar and nonpolar ZnO thin films were deposited on MgO (001) substrates under different deposition parameters using oxygen plasma-assisted molecular beam epitaxy (MBE). The orientations of ZnO thin films were investigated by in situ reflection high-energy electron diffraction and ex situ X-ray diffraction (XRD). The film roughness measured by atomic force microscopy evolved as a function of substrate temperature and was correlated with the grain sizes determined by XRD. Synchrotron-based X-ray absorption spectroscopy (XAS) was performed to study the conduction band structures of the ZnO films. The fine structures of the XAS spectra, which were consistent with the results of density functional theory calculation, indicated that the polar and nonpolar ZnO films had different electronic structures. Our work suggests that it is possible to vary ZnO film structures from polar to nonpolar using the MBE growth technique and hence tailoring the electronic structures of the ZnO films. PACS: 81; 81.05.Dz; 81.15.Hi.