다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

비만아 부모의 돌봄 경험: q 방법론

A review of shape memory alloy research, applications and opportunities

Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

Dielectric elastomer (DE) is the most promising electroactive polymer material for smart actuators. When a piece of DE film is sandwiched between two compliant electrodes with a high electric field, due to the electrostatic force between the two electrodes, the film expands in-plane and contracts out-of-plane so that its thickness becomes thinner. The thinner thickness results in a higher electric field which inversely squeezes the film again. When the electric field exceeds the critical value, the dielectric field breaks down and the actuator becomes invalid. An elastic strain energy function with two material constants is used to analyze the stability of the dielectric elastomer actuator based on the nonlinear electromechanical field theory. The result shows that the actuator improves its stability as the ratio k of the material constants increases, which can be applied to design of actuators. Finally, this method is extended to study the stability of dielectric elastomers with elastic strain energy functions containing three and more material constants.

Stability analysis of dielectric elastomer film actuator

Carbon fiber reinforced polymer (CFRP) composites with low density, corrosion resistance and excellent mechanical properties are widely applied in the aircraft industry, instead of the traditional metallic material. Their poor electrical conductivity leads to the vulnerability to the lightning strike (LS). In this paper, highly conductive silver modified carbon nanotube film (SMCNF) was developed via the electrophoretic deposition (EPD) method for protecting CFRP structures and components of the aircraft. Lightning strike protection (LSP) efficiency of the SMCNF/CFRP composite was characterized from the micro-scale to the macro-scale, and its possible protective mechanism was discussed. The compressive strength of the SMCNF/CFRP composite after the simulated LS test maintains 91.05% and is higher than that of the Cu mesh/CFRP composite (83.28%). Compared to commercial copper mesh LSP material, it can reduce the weight by 27.4% with the better residual compressive strength ratio. Therefore, highly conductive and lightweight SMCNF as a LSP layer can effectively reduce the damage of the CFRP matrix caused by the LS.

Fabrication of the silver modified carbon nanotube film/carbon fiber reinforced polymer composite for the lightning strike protection application

As a new kind of smart materials, shape memory polymer composites (SMPCs) are being used in large in-space deployable structures. However, the recovery force of pure SMPC laminate is very weak. In order to increase the recovery force of a SMPC laminate, an alloy film was bonded on the surface of the laminate. This paper describes the post bulking behavior of the alloy film reinforced SMPC laminate. The energy term associate with this in-plane post buckling have been given .Based on the theorems of minimum energy, a mathematical model is derived to describe the relation between the strain energy and the material and geometry parameters of the alloy film reinforced SMPC laminate. The finite element model (FEM) is also conducted to demonstrate the validity of the theoretical method. The relation between the recovery force and the material geometry parameters were also investigated. The presented analysis shows great potential in the engineering application such as deployment of space structures.

http://smart.hit.edu.cn/upload/news/1367067057.pdf

Post buckling analysis of the shape memory polymer composite laminate bonded with alloy film

Since the carbon nanotube (CNT) technology was invented in 1991, it has attracted widespread attention from researchers owing to the excellent properties and wide applications. However, the easy agglomeration of CNTs in composite materials severely restricts large-scale applications. The problem of CNT distributing in composites has been solved, since the buckypaper (BP) called ‘carbon nanotube film or carbon nanotube paper’ was first prepared in 1998. Because porous structure of BP is beneficial to impregnation of matrix materials, preparation methods and applications of BP composites have been widely reported. With porous structure, low density, anti-corrosion and excellent properties, BP and its composites could be applied in the electrically conductive fields. This paper is intended to provide a comprehensive review of BPs, including a fundamental understanding of the technology, methods of fabrication, types, related properties of BPs, various BP composites and their potential applications in aeronautics. The first section presents a brief introduction of BPs, then the descriptions of the preparation methods, morphology and related properties of BPs and BP composites are introduced in detail. BP composites, which have been developed for improving related properties of BPs as functional materials, are briefly described. Specially, BP composites are fabricated for conductive applications in aeronautics, such as in deicers, electromagnetic interference (EMI) shielding and lightning striking protection (LSP).

Buckypaper and its Composites for Aeronautic Applications

Shape memory polymers with high glass transition temperature (HSMPs) and HSMP-based deployable structures and devices, which can bear harsh operation conditions for durable applications, have attracted more and more interest in recent years. In this article, colorless and transparent shape memory polyimide (SMCTPI) films were subjected to simulated vacuum thermal cycling, atomic oxygen (AO) and ultraviolet (UV) irradiation environments up to 600 h, 556 h and 600 h for accelerated irradiation. The glass transition temperature (Tg) determined by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) had no obvious changes after being irradiated by varying amounts of thermal cycling, AO and UV irradiation dose. After being irradiated by 50 thermal cycles, 10 × 1021 atoms cm–2 AO irradiation and 3000 ESH UV irradiation, shape recovery behaviors of SMCTPI films also had no obvious damage even if they experienced 30 shape memory cycles, while the surface morphologies and optical properties were seriously destroyed by AO irradiation, as compared with thermal cycling and UV irradiation. The tensile strength could separately maintain 122 MPa, 120 MPa and 70 MPa after 50 thermal cycles, 10 × 1021 atoms cm–2 AO irradiation and 3000 ESH UV irradiation, which shows great potential for use in aerospace structures and devices.

https://iopscience.iop.org/article/10.1088/1361-665X/aa7bd7/pdf

Study on performances of colorless and transparent shape memory polyimide film in space thermal cycling, atomic oxygen and ultraviolet irradiation environments

Yanju Liu

Papers

Stability analysis of dielectric elastomer film actuator

Fabrication of the silver modified carbon nanotube film/carbon fiber reinforced polymer composite for the lightning strike protection application

Post buckling analysis of the shape memory polymer composite laminate bonded with alloy film

Buckypaper and its Composites for Aeronautic Applications

Study on performances of colorless and transparent shape memory polyimide film in space thermal cycling, atomic oxygen and ultraviolet irradiation environments