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In this study, heat and polarization treatments were applied to poly(vinylidenefluoride-co-trifluoroethylene (PVDF-TrFE) films to improve their crystallinity and piezoelectric effect. Carbon-based nanomaterials (CBNs) of multiple dimensions (i.e., modified zero-dimensional (0D) carbon black (OCB), one-dimensional (1D) modified carbon nanotubes (CNT&ndash, COOH) and two-dimensional (2D) graphene oxide (GO)) were added to the copolymer to study the effects of different CBN dimensions on the crystallinity and piezoelectric effect of PVDF-TrFE films. Additionally, amphiphilic polymeric dispersants were added to improve the dispersibility of CBNs, the dispersant was synthesized by the amidation, and imidization reactions of styrene-maleic anhydride copolymer (SMAz) and polyoxyalkylene amine (M1000). Polymer solutions with different ratios of CBN to dispersant (z = 10:1, 5:1, 1:1, 1:5, 1:10) were prepared. The enhanced dispersibility enabled the fluorine atoms in the PVDF-TrFE molecular chain to more efficiently form hydrogen bonds with the &ndash, COOH group in the CBN, thereby increasing the content of the &beta, crystal phase (the origin of the piezoelectric effect) of the film. Therefore, the resulting film exhibited a higher output voltage on the application side and better sensitivity on the sensing element. The addition of CNT&ndash, COOH and polymeric dispersants increased the &beta, phase content in PVDF-TrFE from 73.6% to 86.4%, which in turn raised the piezoelectric coefficient from 19.8 &plusmn, 1.0 to 26.4 &plusmn, 1.3 pC/N. The composite film-based pressure sensor also exhibited a high degree of sensitivity, which is expected to have commercial potential in the future.

When wind flows over a human body, it may cause flow separation on the body surface and a wake region is formed behind the body. The main source of drag is the difference between the pressure before and after the body and it is called the pressure drag. The aim of this study is to achieve drag reduction by changing the surface roughness of the full-scale cyclist model in dropped position. Different roughness patterns that were placed on a full-scale cyclist model and cycling jerseys were tested in wind tunnel experiment to realize the impact on drag reduction. Comparing the Cd values of the reference case without roughness patterns and a number of cycling jerseys under the same Reynolds number shows that the best drag reduction of about 7.5% in the cycling jersey experiment. This finding evidences the drag crisis occurred in the case of the cyclist model with jerseys.

Environmental issues have received increasing attention recently. Compared to solvent borne polyurethane (PU), waterborne PU requires relatively little solvent dosage. Therefore, waterborne PU is used to replace traditional solvent borne PU to satisfy environmental and economic requirements. Chitosan is a material that has been discussed widely in recent years because of its exceptional antimicrobial performance, biocompatibility, bioactivity, and biodegradability. This study primarily uses a prepolymer mixing process to synthesize m-TMXDI based waterborne PU with different ratios of aqueous chitosan and chain extenders (ethylenediamine; EDA). Modification reactions are conducted and waterborne PU modified by aqueous chitosan is synthesized. Through this experimental method, emulsions modified by different compositional proportions of aqueous chitosan to EDA were tested. For material determination, FTIR, NMR, and XPS were used to conduct chemical structure determination and GPC molecular weight tests. Regarding membrane properties, a contact angle meter analyzed the hydrophility of the membrane and the antimicrobial performance of the prepared waterborne PU membrane against Staphylococcus aureus and Escherichia coli. The test results showed the following characteristics: (1) The terminal NCO group of the waterborne PU (WPU) was bonded with the terminal amino group(-NH2) of chitosan, and (2) as the proportion of aqueous chitosan added increased, improvements were observed regarding molecular weight, hydrophility, and antimicrobial performance.