Showing papers by "Nanchang University published in 2019"

Engineering bunched Pt-Ni alloy nanocages for efficient oxygen reduction in practical fuel cells

Abstract: Development of efficient and robust electrocatalysts is critical for practical fuel cells. We report one-dimensional bunched platinum-nickel (Pt-Ni) alloy nanocages with a Pt-skin structure for the oxygen reduction reaction that display high mass activity (3.52 amperes per milligram platinum) and specific activity (5.16 milliamperes per square centimeter platinum), or nearly 17 and 14 times higher as compared with a commercial platinum on carbon (Pt/C) catalyst. The catalyst exhibits high stability with negligible activity decay after 50,000 cycles. Both the experimental results and theoretical calculations reveal the existence of fewer strongly bonded platinum-oxygen (Pt-O) sites induced by the strain and ligand effects. Moreover, the fuel cell assembled by this catalyst delivers a current density of 1.5 amperes per square centimeter at 0.6 volts and can operate steadily for at least 180 hours.

A molecular perovskite solid solution with piezoelectricity stronger than lead zirconate titanate.

Abstract: Piezoelectric materials produce electricity when strained, making them ideal for different types of sensing applications. The most effective piezoelectric materials are ceramic solid solutions in which the piezoelectric effect is optimized at what are termed morphotropic phase boundaries (MPBs). Ceramics are not ideal for a variety of applications owing to some of their mechanical properties. We synthesized piezoelectric materials from a molecular perovskite (TMFM)x(TMCM)1–xCdCl3 solid solution (TMFM, trimethylfluoromethyl ammonium; TMCM, trimethylchloromethyl ammonium, 0 ≤ x ≤ 1), in which the MPB exists between monoclinic and hexagonal phases. We found a composition for which the piezoelectric coefficient d33 is ~1540 picocoulombs per newton, comparable to high-performance piezoelectric ceramics. The material has potential applications for wearable piezoelectric devices.

Resilient Event-Triggered Controller Synthesis of Networked Control Systems Under Periodic DoS Jamming Attacks

Abstract: In this paper, the event-based controller synthesis problem for networked control systems under the resilient event-triggering communication scheme (RETCS) and periodic denial-of-service (DoS) jamming attacks is studied. First, a new periodic RETCS is designed under the assumption that the DoS attacks imposed by power-constrained pulsewidth-modulated jammers are partially identified, that is, the period of the jammer and a uniform lower bound on the jammer’s sleeping periods are known. Second, a new state error-dependent switched system model is constructed, including the impacts of the RETCS and DoS attacks. According to this new model, the exponential stability criteria are derived by using the piecewise Lyapunov functional. In these criteria, the relationship among DoS parameters, the triggering parameters, the sampling period, and the decay rate is quantitatively characterized. Then, a criterion is also proposed to obtain the explicit expressions of the triggering parameter and event-based state feedback controller gain simultaneously. Finally, the obtained theoretical results are verified by a satellite yaw-angles control system.

Mussel-Inspired Surface Engineering for Water-Remediation Materials

Abstract: Mussel-inspired chemistry, as a powerful tool to manipulate material properties, has been widely studied and implemented in surface engineering of a variety of materials for multipurpose functionalization. With the rapid development of this field, more flexible and efficient modification strategies for surface engineering and application modes have been developed recently. It is therefore critical to update the broader scientific community on the important advances in this interdisciplinary field. Here, we summarize recent progress in mussel-inspired chemistry and its emerging applications in water remediation. The reaction and adhesion mechanisms of polydopamine, as well as its chemical and physical properties, are discussed. The functionalization strategies are categorized into post-functionalization, co-deposition, and pre-modification, and the roles of mussel-inspired surface coatings are highlighted in filtration, adsorbing, and catalytic materials as well as the burgeoning area of photothermal distillation materials.

The First 2D Homochiral Lead Iodide Perovskite Ferroelectrics: [R- and S-1-(4-Chlorophenyl)ethylammonium] 2 PbI 4

Abstract: 2D organic-inorganic lead iodide perovskites have recently received tremendous attention as promising light absorbers for solar cells, due to their excellent optoelectronic properties, structural tunability, and environmental stability. However, although great efforts have been made, no 2D lead iodide perovskites have been discovered as ferroelectrics, in which the ferroelectricity may improve the photovoltaic performance. Here, by incorporating homochiral cations, 2D lead iodide perovskite ferroelectrics [R-1-(4-chlorophenyl)ethylammonium]2 PbI4 and [S-1-(4-chlorophenyl)ethylammonium]2 PbI4 are successfully obtained. The vibrational circular dichroism spectra and crystal structural analysis reveal their homochirality. They both crystalize in a polar space group P1 at room temperature, and undergo a 422F1 type ferroelectric phase transition with transition temperature as high as 483 and 473.2 K, respectively, showing a multiaxial ferroelectric nature. They also possess semiconductor characteristics with a direct bandgap of 2.34 eV. Nevertheless, their racemic analogue adopts a centrosymmetric space group P21 /c at room temperature, exhibiting no high-temperature phase transition. The homochirality in 2D lead iodide perovskites facilitates crystallization in polar space groups. This finding indicates an effective way to design high-performance 2D lead iodide perovskite ferroelectrics with great application prospects.

Toward the Targeted Design of Molecular Ferroelectrics: Modifying Molecular Symmetries and Homochirality

Abstract: ConspectusAlthough the first ferroelectric discovered in 1920 is Rochelle salt, a typical molecular ferroelectric, the front-runners that have been extensively studied and widely used in diverse ap...

UAV-Enabled Cooperative Jamming for Improving Secrecy of Ground Wiretap Channel

Abstract: This letter proposes a novel unmanned aerial vehicle (UAV)-enabled mobile jamming scheme to improve the secrecy rate of ground wiretap channel. Specifically, a UAV is employed to transmit jamming signals to combat against eavesdropping. Such a mobile jamming scheme is particularly appealing since the UAV-enabled jammer can fly close to the eavesdropper and opportunistically jam it by leveraging the UAV’s mobility. We aim to maximize the average secrecy rate by jointly optimizing the UAV’s trajectory and jamming power over a given flight period. To make the problem more tractable, we drive a closed-form lower bound for the achievable secrecy rate, based on which the UAV’s trajectory and transmit power are optimized alternately by an efficient iterative algorithm applying the block coordinate descent and successive convex optimization techniques. Simulation results demonstrate that the proposed joint design can significantly enhance the secrecy rate of the considered wiretap system as compared to benchmark schemes.

Integrated process of lignocellulosic biomass torrefaction and pyrolysis for upgrading bio-oil production: A state-of-the-art review

Abstract: Renewable fuels or chemicals from lignocellulosic biomass have the potential to be a substitute for fossil fuels, thereby reducing greenhouse gas emissions and diversifying energy supplies. Integrating torrefaction and pyrolysis is a feasible and promising technology that converts biomass into fuels or chemicals. Understanding of the relevant process designs and mechanisms is favorable to the cohesion and optimization of these two processes and the innovation of reactors for commercial-scale biorefineries. First, biomass properties and their corresponding pyrolysis behaviors have been discussed in consideration of the challenge presented by complex biomass structures that limit the in-depth research on torrefaction or pyrolysis. Second, torrefaction fundamentals are illustrated in detail, and many kinetic models with comprehensive mechanism schemes, such as pseudo-mechanistic model and one-, two-, or multi-step models, are summarized. The effect of torrefaction on biomass characteristics and subsequent pyrolysis is reviewed to further elucidate the integrated process. The novel integration of torrefaction and up-to-date pyrolysis techniques is also outlined to improve product quality. Finally, future directions and technological challenges associated with the integrated process are proposed and its economic potential is also evaluated.

Platelet integrin αIIbβ3: signal transduction, regulation, and its therapeutic targeting

Abstract: Integrins are a family of transmembrane glycoprotein signaling receptors that can transmit bioinformation bidirectionally across the plasma membrane. Integrin αIIbβ3 is expressed at a high level in platelets and their progenitors, where it plays a central role in platelet functions, hemostasis, and arterial thrombosis. Integrin αIIbβ3 also participates in cancer progression, such as tumor cell proliferation and metastasis. In resting platelets, integrin αIIbβ3 adopts an inactive conformation. Upon agonist stimulation, the transduction of inside-out signals leads integrin αIIbβ3 to switch from a low- to high-affinity state for fibrinogen and other ligands. Ligand binding causes integrin clustering and subsequently promotes outside-in signaling, which initiates and amplifies a range of cellular events to drive essential platelet functions such as spreading, aggregation, clot retraction, and thrombus consolidation. Regulation of the bidirectional signaling of integrin αIIbβ3 requires the involvement of numerous interacting proteins, which associate with the cytoplasmic tails of αIIbβ3 in particular. Integrin αIIbβ3 and its signaling pathways are considered promising targets for antithrombotic therapy. This review describes the bidirectional signal transduction of integrin αIIbβ3 in platelets, as well as the proteins responsible for its regulation and therapeutic agents that target integrin αIIbβ3 and its signaling pathways.

An image compression and encryption algorithm based on chaotic system and compressive sensing

Abstract: For a linear image encryption system, it is vulnerable to the chosen-plaintext attack. To overcome the weakness and reduce the correlation among pixels of the encryption image, an effective image compression and encryption algorithm based on chaotic system and compressive sensing is proposed. The original image is first permuted by the Arnold transform to reduce the block effect in the compression process, and then the resulting image is compressed and re-encrypted by compressive sensing, simultaneously. Moreover, the bitwise XOR operation based on chaotic system is performed on the measurements to change the pixel values and a pixel scrambling method is employed to disturb the positions of pixels. Besides, the keys used in chaotic systems are related to the plaintext image. Simulation results verify the effectiveness and reliability of the proposed image compression and encryption algorithm with considerable compression and security performance.

An LSTM Short-Term Solar Irradiance Forecasting Under Complicated Weather Conditions

Abstract: Complicated weather conditions lead to intermittent, random and volatility in photovoltaic (PV) systems, which makes PV predictions difficult. A recurrent neural network (RNN) is considered to be an effective tool for time-series data prediction. However, when the weather changes intensely, the long-term sequence of multivariate may cause gradient vanishing (exploding) during the training of RNN, leading the prediction results to local optimum. Long short-term memory (LSTM) network is the deep structure of RNN. Due to its special hidden layer unit structure, it can preserve the trend information contained in the long-term sequence, which is allowed to solve the problems of RNN and improve performance. An LSTM-based approach is applied for short-term predictions in this study based on a timescale that encompasses global horizontal irradiance (GHI) one hour in advance and one day in advance. Inaccurate forecasts usually occur on cloudy days, and the results of ANN and SVR in the literature prove this. To improve prediction accuracy on cloudy days, the clearness-index was introduced as an input data for the LSTM model and to classify the type of weather by k-means during the data processing, where cloudy days are classified as the cloudy and the mixed(partially cloudy). NN models are established to compare the accuracy of different approaches and the cross-regional study is to prove whether the method can be generalizable. From the results of hourly forecast, the R 2 coefficient of LSTM on cloudy days and mixed days is exceeding 0.9, while the R 2 of RNN is only 0.70 and 0.79 in Atlanta and Hawaii. From the results of daily forecast, All R 2 on cloudy days is about 0.85. However, the LSTM is still very effective in improving of RNN and more accurate than other models.

Fish gelatin modifications: A comprehensive review

Abstract: Background Gelatin, one of the most popular biopolymers, is widely used in food, pharmaceutical and cosmetic industries. Mammalian gelatin accounts for the vast majority of commercial gelatin, but due to the socio-cultural and health-related concerns, it has been subjected to constraint and skepticism for many years. Fish gelatin has been considered as an excellent alternative to mammalian gelatin because of similarity of its functional properties with mammalian gelatin. Nevertheless, compared with mammalian gelatin, fish gelatin possesses inferior gelation and rheological properties, which limit its extensive application. Scope and approach This review provides a comprehensive overview of various techniques that have been used to improve gelation properties of fish gelatin underlying their modification mechanisms as well as applications. Finally, a brief discussion on safety and regulatory status, and future potentials of modification fish gelatin is provided. Key findings and conclusions Various approaches have been put forward for improving gelation and rheological properties of fish gelatin. The combination of different modification methods is a novel strategy to overcome the shortcomings of fish gelatin. However, further scientific research studies are still required to better understand the exact mechanism of such modifications and expand their application ranges in food industries.

Circular RNA circFGFR1 promotes progression and anti-PD-1 resistance by sponging miR-381-3p in non-small cell lung cancer cells

Abstract: Immune system evasion, distance tumor metastases, and increased cell proliferation are the main reasons for the progression of non-small cell lung cancer (NSCLC) and the death of NSCLC patients. Dysregulation of circular RNAs plays a critical role in the progression of NSCLC; therefore, further understanding the biological mechanisms of abnormally expressed circRNAs is critical to discovering novel, promising therapeutic targets for NSCLC treatment. The expression of circular RNA fibroblast growth factor receptor 1 (circFGFR1) in NSCLC tissues, paired nontumor tissues, and cell lines was detected by RT-qPCR. The role of circFGFR1 in NSCLC progression was assessed both in vitro by CCK-8, clonal formation, wound healing, and Matrigel Transwell assays and in vivo by a subcutaneous tumor mouse assay. In vivo circRNA precipitation, RNA immunoprecipitation, and luciferase reporter assays were performed to explore the interaction between circFGFR1 and miR-381-3p. Here, we report that circFGFR1 is upregulated in NSCLC tissues, and circFGFR1 expression is associated with deleterious clinicopathological characteristics and poor prognoses for NSCLC patients. Forced circFGFR1 expression promoted the migration, invasion, proliferation, and immune evasion of NSCLC cells. Mechanistically, circFGFR1 could directly interact with miR-381-3p and subsequently act as a miRNA sponge to upregulate the expression of the miR-381-3p target gene C-X-C motif chemokine receptor 4 (CXCR4), which promoted NSCLC progression and resistance to anti-programmed cell death 1 (PD-1)- based therapy. Taken together, our results suggest the critical role of circFGFR1 in the proliferation, migration, invasion, and immune evasion abilities of NSCLC cells and provide a new perspective on circRNAs during NSCLC progression.

Advances in ultra-precision machining of micro-structured functional surfaces and their typical applications

Abstract: Micro-structured functional surfaces have achieved widespread applications in various advanced scientific, technological, industrial, and engineered fields due to their excellent performances, which are vitally limited by their feasible fabrication. Currently, ultra-precision machining, typically including ultra-precision diamond turning, ultra-precision diamond milling, ultra-precision diamond scratching, ultra-precision grinding, and ultra-precision polishing, is developed as a very-promising solution for the micro-structured functional surface fabrication with high quality, high efficiency, high flexibility, and low cost. Therefore, this paper aims to briefly review the current state of the art in the investigation into ultra-precision machining characteristics of micro-structured functional surfaces with a focus on their typical advanced applications as the significant achievements of their ultra-precision machining fabrication, discuss the key challenges, and further provide new insights into ultra-precision machining of micro-structured functional surfaces for the future research and their further advanced applications.

Symmetry-protected bound states in the continuum supported by all-dielectric metasurfaces

Abstract: Symmetry-protected bound states in the continuum (BICs) are nonradiative states with infinite lifetime and perfect confinement of energy even though lying in the radiation continuum due to the symmetry incompatibility. Herein, we study the symmetry-protected BIC supported by metasurfaces composed of silicon nanodisks. Through adding or removing parts of the nanodisks from the edge, a sharp Fano resonance emerges and demonstrates the excitation of quasi-BIC. Their $Q$ factors exhibit the same dependence on the asymmetry degree with these two opposite operations. Furthermore, from both qualitative and quantitative perspectives, analysis on far-field contributions from multipole moments along different directions combining with near-field distributions explains the evolution from BIC to quasi-BIC. The dominant contributor to the quasi-BIC is illustrated to be the electric quadrupole in the $x\ensuremath{-}y$ plane. Finally, the topological charge carried by the BIC is calculated to be $\ensuremath{-}1$, demonstrating the topological characteristics of our design. Such metasurfaces are robust in nanofabrication. Our results may provide a route for resonators with better performance applied in sensing, switching, nonlinear optics, and so on.

A Catalase-Like Metal-Organic Framework Nanohybrid for O 2 -Evolving Synergistic Chemoradiotherapy.

Abstract: Tumor hypoxia, the "Achilles' heel" of current cancer therapies, is indispensable to drug resistance and poor therapeutic outcomes especially for radiotherapy. Here we propose an in situ catalytic oxygenation strategy in tumor using porphyrinic metal-organic framework (MOF)-gold nanoparticles (AuNPs) nanohybrid as a therapeutic platform to achieve O2 -evolving chemoradiotherapy. The AuNPs decorated on the surface of MOF effectively stabilize the nanocomposite and serve as radiosensitizers, whereas the MOF scaffold acts as a container to encapsulate chemotherapeutic drug doxorubicin. In vitro and in vivo studies verify that the catalase-like nanohybrid significantly enhances the radiotherapy effect, alleviating tumor hypoxia and achieving synergistic anticancer efficacy. This hybrid nanomaterial remarkably suppresses the tumor growth with minimized systemic toxicity, opening new horizons for the next generation of theranostic nanomedicines.