Biomimetic smart nanochannels for power harvesting

With the increasing requirements of reliable and environmentally friendly energy resources, porous materials for sustainable energy conversion technologies have attracted intensive interest in the past decades. As an important block of porous materials, biomimetic smart nanochannels (BSN) have been developed rapidly into an attractive field for their well-tunable geometry and chemistry. With inspiration from nature, many works have been reported to utilize BSN to harvest clean energy. In this review, we summarize recent progress in the BSN for power harvesting from four parts of brief introduction of BSN, biological prototypes for power harvesting, BSN-based energy conversion, and conclusion and outlook. Overall, by learning from nature, exploiting new avenues and improving the performance of BSN, a number of exciting developments in the near future may be anticipated.

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Bad-scenario-set robust scheduling for a job shop to hedge against processing time uncertainty

This paper proposed two robust scheduling formulations in real manufacturing systems based on the concept of bad scenario set to hedge against processing time uncertainty, which is described by discrete scenarios. Two proposed robust scheduling formulations are applied to an uncertain job-shop scheduling problem with the makespan as the performance criterion. The united-scenario neighbourhood (UN) structure is constructed based on bad scenario set for the scenario job-shop scheduling problem. A tabu search (TS) algorithm with the UN structure is developed to solve the proposed robust scheduling problem. An extensive experiment was conducted. The computational results show that the first robust scheduling formulation could be preferred to the second one for the discussed problem. It is also verified that the obtained robust solutions could hedge against the processing time uncertainty through decreasing the number of bad scenarios and the degree of performance degradation on bad scenarios. Moreover, the computational results demonstrate that the developed TS algorithm is competitive for the proposed robust scheduling formulations.     

Green synthesis of silver nanoparticles using biopolymers,carboxymethylated-curdlan and fucoidan

There is a growing need in developing a reliable and eco-friendly methodology for the synthesis of metallic nanoparticles, which may be applied for many nanotechnological applications. Natural compounds such as biopolymers are one of the resources which could be used for this purpose. The present study involves the development of a simple, ecological and user-friendly method in synthesizing silver nanoparticles by using carboxymethylated-curdlan or fucoidan as reducing and stabilizing agents. Reduction of silver ions by these biopolymers occurred when heating at 100 °C, led to the formation of silver nanoparticles in the range of 40–80 nm in dimensions. The silver nanoparticles were formed readily within 10–15 min. Morphological observation and characterization of the silver nanoparticles were performed by using dynamic light scattering (DLS), high-resolution transmission electron microscopy (HRTEM), and UV–vis absorption spectrophotometer. The size of silver nanoparticles can be controlled by using different concentrations of carboxymethylated-curdlan, fucoidan or silver nitrate. This way of silver nanoparticles preparation is easy, fast, user-friendly and suitable for large-scale production.     

Silk nanofibers as high efficient and lightweight air filter

Silk is a widely available, edible, biocompatible, and environmentally sustainable natural material. Particulate matter (PM) pollution has drawn considerable attention because it is a serious threat to public health. Herein, we report a human-friendly silk nanofiber air filter, which exhibits superior filtration efficiency for both PM_2.5 and submicron particles with obviously low pressure drop and low basis weight compared to typical commercial microfiber air filters. Additionally, other functions such as antibacterial activity could be easily integrated into the silk nanofiber air filters, enabling the fabrication of multifunctional air filters. All the above characteristics, combined with the natural abundance and biocompatibility of silk, suggest a great potential for the use of silk nanofibers as air filters, especially as comfortable and personal air purifiers.

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Fatigue Failure Process Characterization for Carbon Fiber Sheet Reinforced Steel Rods Using the Acoustic Emission Technique

Acoustic emission (AE) technique is a widely used CM technique. In this paper, AE technique was used to characterize the fatigue failure process for carbon fiber sheet (CFS) reinforced steel rod. The AE signals at the frequency band of 50–400 kHz are detected by using AE sensors mounted on the steel rod and analyzed by both parameter analysis and spectrum analysis in order to investigate the feasibility of using the AE technique to identify various failure modes during fatigue failure process for CFS reinforced steel rods. Tension-tension fatigue experiments were carried out on both CFS reinforced and unreinforced steel rods. Based on AE energy parameter analysis using wavelet decomposition method, failure process was initially divided into three stages for unreinforced specimen and seven stages for CFS reinforced specimen. The frequency contents within the frequency band of 50–400 kHz for various failure modes in each stage including crack initiation, developing, final rupture in steel rod and matrix crack, debonding in CFS were revealed by fast Fourier transform (FFT) method. Further wavelet transform (WT) analysis was performed to illustrate the sequences of the failure modes and main failure mode in each stage by the occurrence time and longest duration time, respectively. This work indicates that the proposed method is promising for distinguishing failure stages qualitatively and identifying failure modes quantitatively in CFS reinforced steel rods.     

Giant Enhancements of Perpendicular Magnetic Anisotropy and Spin‐Orbit Torque by a MoS2 Layer

2D transition metal dichalcogenides have attracted much attention in the field of spintronics due to their rich spin‐dependent properties. The promise of highly compact and low‐energy‐consumption spin‐orbit torque (SOT) devices motivates the search for structures and materials that can satisfy the requirements of giant perpendicular magnetic anisotropy (PMA) and large SOT simultaneously in SOT‐based magnetic memory. Here, it is demonstrated that PMA and SOT in a heavy metal/transition metal ferromagnet structure, Pt/[Co/Ni]₂, can be greatly enhanced by introducing a molybdenum disulfide (MoS₂) underlayer. According to first‐principles calculation and X‐ray absorption spectroscopy (XAS), the enhancement of the PMA is ascribed to the modification of the orbital hybridization at the interface of Pt/Co due to MoS₂. The enhancement of SOT by the role played by MoS₂ is explained, which is strongly supported by the identical behavior of SOT and PMA as a function of Pt thickness. This work provides new possibilities to integrate 2D materials into promising spintronics devices.     

Band Structure Engineering of Interfacial Semiconductors Based on Atomically Thin Lead Iodide Crystals

To explore new constituents in two‐dimensional (2D) materials and to combine their best in van der Waals heterostructures is in great demand as being a unique platform to discover new physical phenomena and to design novel functionalities in interface‐based devices. Herein, PbI₂ crystals as thin as a few layers are synthesized, particularly through a facile low‐temperature solution approach with crystals of large size, regular shape, different thicknesses, and high yields. As a prototypical demonstration of band engineering of PbI₂‐based interfacial semiconductors, PbI₂ crystals are assembled with several transition metal dichalcogenide monolayers. The photoluminescence of MoS₂ is enhanced in MoS₂/PbI₂ stacks, while a dramatic photoluminescence quenching of WS₂ and WSe₂ is revealed in WS₂/PbI₂ and WSe₂/PbI₂ stacks. This is attributed to the effective heterojunction formation between PbI₂ and these monolayers; type I band alignment in MoS₂/PbI₂ stacks, where fast‐transferred charge carriers accumulate in MoS₂ with high emission efficiency, results in photoluminescence enhancement, and type II in WS₂/PbI₂ and WSe₂/PbI₂ stacks, with separated electrons and holes suitable for light harvesting, results in photoluminescence quenching. The results demonstrate that MoS₂, WS₂, and WSe₂ monolayers with similar electronic structures show completely distinct light–matter interactions when interfacing with PbI₂, providing unprecedented capabilities to engineer the device performance of 2D heterostructures.     

Quasi‐Solid‐State Single‐Atom Transistors

The single‐atom transistor represents a quantum electronic device at room temperature, allowing the switching of an electric current by the controlled and reversible relocation of one single atom within a metallic quantum point contact. So far, the device operates by applying a small voltage to a control electrode or “gate” within the aqueous electrolyte. Here, the operation of the atomic device in the quasi‐solid state is demonstrated. Gelation of pyrogenic silica transforms the electrolyte into the quasi‐solid state, exhibiting the cohesive properties of a solid and the diffusive properties of a liquid, preventing the leakage problem and avoiding the handling of a liquid system. The electrolyte is characterized by cyclic voltammetry, conductivity measurements, and rotation viscometry. Thus, a first demonstration of the single‐atom transistor operating in the quasi‐solid‐state is given. The silver single‐atom and atomic‐scale transistors in the quasi‐solid‐state allow bistable switching between zero and quantized conductance levels, which are integer multiples of the conductance quantum G₀ = 2e²/h. Source–drain currents ranging from 1 to 8 µA are applied in these experiments. Any obvious influence of the gelation of the aqueous electrolyte on the electron transport within the quantum point contact is not observed.     

混凝土结构烟囱爆破拆除的动力响应特征分析

烟囱定向控制爆破倒塌过程中,爆破作用不仅使爆破位置的结构产生破坏,而且爆破产生的应力波对上部结构产生很大的作用,为了探讨其产生的原因,利用运动行波的运动方程,求解不同起爆条件下行波的运动规律,以及不同时刻爆炸应力波在烟囱中产生的应力作用行为和结构质点位移,发现了最大拉应力、结构质点位移可能出现的时刻和位置,并拟合绘制出了最大拉应力、质点位移的分布曲线。对高100m混凝土结构烟囱的爆炸作用进行计算分析,认为烟囱定向控制爆破的起爆宜采用低段别、短延期时差的起爆网路。