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排序方式: 共有3421条查询结果,搜索用时 15 毫秒
791.
Sijie Wan Shaoli Fang Lei Jiang Qunfeng Cheng Ray H. Baughman 《Advanced materials (Deerfield Beach, Fla.)》2018,30(36)
The goal of this work is to develop an inexpensive low‐temperature process that provides polymer‐free, high‐strength, high‐toughness, electrically conducting sheets of reduced graphene oxide (rGO). To develop this process, we have evaluated the mechanical and electrical properties resulting from the application of an ionic bonding agent (Cr3+), a π–π bonding agent comprising pyrene end groups, and their combinations for enhancing the performance of rGO sheets. When only one bonding agent was used, the π–π bonding agent is much more effective than the ionic bonding agent for improving both the mechanical and electrical properties of rGO sheets. However, the successive application of ionic bonding and π–π bonding agents maximizes tensile strength, toughness, long‐term electrical stability in various corrosive solutions, and resistance to mechanical abuse and ultrasonic dissolution. Using a combination of ionic bonding and π–π bonding agents, high tensile strength (821 MPa), high toughness (20 MJ m?3), and electrical conductivity (416 S cm?1) were obtained, as well as remarkable retention of mechanical and electrical properties during ultrasonication and mechanical cycling by both sheet stretch and sheet folding, suggesting high potential for applications in aerospace and flexible electronics. 相似文献
792.
Hyperporous Sponge Interconnected by Hierarchical Carbon Nanotubes as a High‐Performance Potassium‐Ion Battery Anode 下载免费PDF全文
Yunsong Wang Zhipeng Wang Yijun Chen Hui Zhang Muhammad Yousaf Huaisheng Wu Mingchu Zou Anyuan Cao Ray P. S. Han 《Advanced materials (Deerfield Beach, Fla.)》2018,30(32)
Recently, commercial graphite and other carbon‐based materials have shown promising properties as the anode for potassium‐ion batteries. A fundamental problem related to those carbon electrodes, significant volume expansion, and structural instability/collapsing caused by cyclic K‐ion intercalation, remains unsolved and severely limits further development and applications of K‐ion batteries. Here, a multiwalled hierarchical carbon nanotube (HCNT) is reported to address the issue, and a reversible specific capacity of 232 mAh g?1, excellent rate capability, and cycling stability for 500 cycles are achieved. The key structure of the HCNTs consists of an inner CNT with dense‐stacked graphitic walls and a loose‐stacked outer CNT with more disordered walls, and individual HCNTs are further interconnected into a hyperporous bulk sponge with huge macropore volume, high conductivity, and tunable modulus. It is discovered that the inner dense‐CNT serves as a robust skeleton, and collectively, the outer loose‐CNT is beneficial for K‐ion accommodation; meanwhile the hyperporous sponge facilitates reaction kinetics and offers stable surface capacitive behavior. The hierarchical carbon nanotube structure has great potential in developing high‐performance and stable‐structure electrodes for next generation K and other metal‐ion batteries. 相似文献
793.
Strong,Twist‐Stable Carbon Nanotube Yarns and Muscles by Tension Annealing at Extreme Temperatures 下载免费PDF全文
794.
Sai Sidhardh M. C. Ray 《International Journal of Mechanics and Materials in Design》2018,14(2):297-311
The paper is concerned with the development of finite element model for the static analysis of smart nanobeams integrated with a flexoelectric layer on its top surface, using nonlocal elastic theory. The flexoelectric layer acts as a distributed actuator of the nanobeam. A layerwise displacement theory has been used to derive the element stiffness matrices from variational principles incorporating nonlocal effects. The finite element model for nonlocal response of the beams has been validated with the exact solution for the case of a simply supported standalone flexoelectric layer. Also, the finite element model of the simply supported smart beam has been validated with exact solutions and numerical models for the local elastic case. The performance of the flexoelectric actuator has been compared for different values of nonlocal parameters and different combinations of nonlocal and local elastic substrate and flexoelectric layer. Further, the model developed has been utlized for investigating the performance of the active flexoelectric layer in case of cantilever beam, for which the exact solutions are not available. 相似文献
795.
Attacks on computer systems are now attracting increased attention. While the current trends in software vulnerability discovery indicate that the number of newly discovered vulnerabilities continues to be significant, the time between the public disclosure of vulnerabilities and the release of an automated exploit is shrinking. Thus, assessing the vulnerability exploitability risk is critical because this allows decision-makers to prioritize among vulnerabilities, allocate resources to patch and protect systems from these vulnerabilities, and choose between alternatives. Common vulnerability scoring system (CVSS) metrics have become the de facto standard for assessing the severity of vulnerabilities. However, the CVSS exploitability measures assign subjective values based on the views of experts. Two of the factors in CVSS, Access Vector and Authentication, are the same for almost all vulnerabilities. CVSS does not specify how the third factor, Access Complexity, is measured, and hence it is unknown whether it considers software properties as a factor. In this work, we introduce a novel measure, Structural Severity, which is based on software properties, namely attack entry points, vulnerability location, the presence of the dangerous system calls, and reachability analysis. These properties represent metrics that can be objectively derived from attack surface analysis, vulnerability analysis, and exploitation analysis. To illustrate the proposed approach, 25 reported vulnerabilities of Apache HTTP server and 86 reported vulnerabilities of Linux Kernel have been examined at the source code level. The results show that the proposed approach, which uses more detailed information, can objectively measure the risk of vulnerability exploitability and results can be different from the CVSS base scores. 相似文献
796.
Assessment of Risk of Musculoskeletal Disorders among Crane Operators in a Steel Plant: A Data Mining–Based Analysis 下载免费PDF全文
Prevalence of musculoskeletal disorders (MSD) among industrial workers is often measured through the Nordic Musculoskeletal Questionnaire (NMQ) survey that captures the MSD complaints across different body parts. The outcomes of such a survey are reported in terms of relative frequency of MSD complaints for the body parts affected and are analyzed through t test, analysis of variance, or logistic regression. The study augments the analysis of NMQ data using relative risk, a statistical measure of prevalence, and classification and regression tree (CART), a data mining–based decision tree. The integrated analysis is done for 76 crane operators of a steel plant in India that considers operators, task, and workplace characteristics as predictors of MSD. The relative risk indices for each of the predictor categories compare the risk of prevalence of MSD. The outcomes of CART‐based analysis are objective importance scores that quantify the contributions of the predictors toward the occurrence and severity of MSD. A risk priority index is computed to prioritize the predictor variables with categories in terms of their contribution. The study shows that the lower back and neck and shoulder are the most affected and account for 78.75% of the MSD complaints. CART shows that crane height contributes the maximum for MSD occurrences of both lower back and neck and shoulder. However, for MSD severity, while crane height contributes the most for neck and shoulder, cabin feature (static or movable) contributes the maximum for the lower back. 相似文献
797.
The capability of ANN to generate synthetic series of river discharge averaged over different time steps with limited data has been investigated in the present study. While an ANN model with certain input parameters can generate a monthly averaged streamflow series efficiently; it fails to generate a series of smaller time steps with the same accuracy. The scope of improving efficiency of ANN in generating synthetic streamflow by using different combinations of input data has been analyzed. The developed models have been assessed through their application in the river Subansiri in India. Efficiency of the ANN models has been evaluated by comparing ANN generated series with the historical series and the series generated by Thomas-Fiering model on the basis of three statistical parameters-periodical mean, periodical standard deviation and skewness of the series. The results reveal that the periodical mean of the series generated by both Thomas–Fiering and ANN models are in good agreement with that of the historical series. However, periodical standard deviation and skewness coefficient of the series generated by Thomas–Fiering model is inferior to that of the series generated by ANN. 相似文献
798.
Oxidation of caffeine by acid‐activated ferrate(VI): Effect of ions and natural organic matter 下载免费PDF全文
Kyriakos Manoli George Nakhla Ajay K. Ray Virender K. Sharma 《American Institute of Chemical Engineers》2017,63(11):4998-5006
Caffeine (CAF) is the most commonly consumed stimulant and frequently detected emerging pollutant in influents and effluents of wastewater treatment plants (WWTP) and surface waters. Acid‐activated ferrate(VI) (FeVI , Fe(VI)) oxidizes CAF in water in seconds to minutes at three times lower molar ratio of Fe(VI) to CAF than oxidative transformation observed in hours by nonactivated Fe(VI) (8.0 vs. 25.0). CAF oxidation by acid‐activated Fe(VI) is not affected by ionic constituents of water. Organic components of natural organic matter (NOM) and secondary effluent wastewater (SE) decrease efficiency of CAF transformation. However, acid‐activated Fe(VI) could mineralize other organics present in both NOM and SE as indicated by the dissolved organic carbon (DOC) removal. Comparatively, no mineralization was seen without activation of Fe(VI). Four oxidized products of CAF were identified by a liquid chromatography high resolution mass spectrometry technique. The reaction pathways of the oxidation of CAF by activated Fe(VI) have been proposed. © 2017 American Institute of Chemical Engineers AIChE J, 2017 相似文献
799.
Flexible Electronics: A Bi‐Sheath Fiber Sensor for Giant Tensile and Torsional Displacements (Adv. Funct. Mater. 35/2017) 下载免费PDF全文
800.
Production of Flexible Transparent Conducting Films of Self‐Fused Nanowires via One‐Step Supersonic Spraying 下载免费PDF全文
Jong‐Gun Lee Do‐Yeon Kim Jong‐Hyuk Lee Suman Sinha‐Ray Alexander L. Yarin Mark T. Swihart Donghwan Kim Sam S. Yoon 《Advanced functional materials》2017,27(1)
Scalable and economical manufacturing of flexible transparent conducting films (TCF) is a key barrier to widespread adoption of low‐cost flexible electronics. Here, a simple, robust, and scalable method of flexible TCF formation using supersonic kinetic spraying is demonstrated. Silver nanowire (AgNW) suspensions are sprayed at supersonic speed to produce self‐sintered films of AgNWs on flexible substrates. These films display remarkably low sheet resistance, <10 Ω sq?1, combined with high transmittance, >90%. These electrically conducting, transparent, and flexible coatings can be deposited over a 100 cm2 area in ≈30 s. Theoretical analysis reveals the underlying physical mechanism behind self‐sintering, showing that self‐sintering is enabled by the high velocity of impact in supersonic spraying. 相似文献