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排序方式: 共有849条查询结果,搜索用时 9 毫秒
11.
Wanjun Liu Kelby Thayer Manjusri Misra Lawrence T. Drzal Amar K. Mohanty 《Polymer Engineering and Science》2007,47(7):969-976
Big blue stem grass fiber-reinforced high density polyethylene powder biocomposites were fabricated using two separate processing schemes: (1) by compounding biofiber with the thermoplastic powder in an extruder and subsequently injection molding the extrusion pellets and (2) by combining biofiber and the powder thermoplastic powder using a modified sheet molding compounding (SMC) line and subsequently compression molding the sheet material. The physical properties including storage modulus, heat deflection temperature (HDT), notched Izod impact strength, and morphology were evaluated with dynamic mechanical analysis, Izod impact strength measurement, and microscopy observation. It was found that compression-molded specimens achieved similar modulus values to injection molded specimens for grass-reinforced high density polyethylene (HDPE) composites. The stiffness of the compression-molded specimens is related to the consolidation state of the samples, which depends on compression molding conditions such as temperature, pressure, and mold type. Compression-molded specimens exhibited a higher HDT and notched Izod impact strength compared to injection-molded samples. Grass fiber-reinforced cellulose acetate butyrate (CAB) biocomposites made with SMC processing had similar physical properties with grass fiber-reinforced HDPE composites, which indicates that natural fiber-reinforced CAB biocomposites have the potential to replace polyolefin-based composites for automotive applications. POLYM. ENG. SCI. 47:969–976, 2007. © 2007 Society of Plastics Engineers. 相似文献
12.
R. Polini S. Kumashiro M. J. Jackson M. Amar W. Ahmed H. Sein 《Journal of Materials Engineering and Performance》2006,15(2):218-222
Deposition of diamond films onto various substrates can result in significant technological advantages in terms of functionality
and improved life and performance of components. Diamond is hard, wear resistant, chemically inert, and biocompatible. It
is considered to be the ideal material for surfaces of cutting tools and biomedical components. However, it is well known
that diamond deposition onto technologically important substrates, such as co-cemented carbides and steels, is problematic
due to carbon interaction with the substrate, low nucleation densities, and poor adhesion. Several papers previously published
in the relevant literature have reported the application of interlayer materials such as metal nitrides and carbides to provide
bonding between diamond and hostile substrates. In this study, the chemical vapor deposition (CVD) of polycrystalline diamond
on TiN/SiN
x
nc (nc) interlayers deposited at relatively low temperatures has been investigated for the first time. The nc layers were
deposited at 70 or 400 °C on Si substrates using a dual ion beam deposition system. The results showed that a preliminary
seeding pretreatment with diamond suspension was necessary to achieve large diamond nucleation densities and that diamond
nucleation was larger on nc films than on bare sc-Si subjected to the same pretreatment and CVD process parameters. TiN/SiN
x
layers synthesized at 70 or 400 °C underwent different nanostructure modifications during diamond CVD. The data also showed
that TiN/SiN
x
films obtained at 400 °C are preferable in so far as their use as interlayers between hostile substrates and CVD diamond
is concerned.
This paper was presented at the fourth International Surface Engineering Congress and Exposition held August 1–3, 2005 in
St. Paul, MN. 相似文献
13.
14.
Amar Si Ammour Said Djennoune Woihida Aggoune Maamar Bettayeb 《Asian journal of control》2015,17(5):1946-1954
This paper describes a variable structure control for fractional‐order systems with delay in both the input and state variables. The proposed method includes a fractional‐order state predictor to eliminate the input delay. The resulting state‐delay system is controlled through a sliding mode approach where the controller uses a sliding surface defined by fractional order integral. Then, the proposed control law ensures that the state trajectories reach the sliding surface in finite time. Based on recent results of Lyapunov stability theory for fractional‐order systems, the stability of the closed loop is studied. Finally, an illustrative example is given to show the interest of the proposed approach. 相似文献
15.
The ultrasonic attenuation due to phonon–phonon interaction, thermoelastic relaxation and dislocation damping mechanisms has been investigated in cerium monopnictides CeX (X: N, P, As, Sb and Bi) for longitudinal and shear waves along \({\langle }100{\rangle }\), \({\langle }110{\rangle }\) and \({\langle }111{\rangle }\) directions. The second- and third-order elastic constants of CeX have also been computed in the temperature range 0 K to 500 K using Coulomb and Born–Mayer potential upto second nearest neighbours. The computed values of these elastic constants have been applied to find out Young’s moduli, bulk moduli, Breazeale’s non-linearity parameters, Zener anisotropy, ultrasonic velocity, ultrasonic Grüneisen parameter, thermal relaxation time, acoustic coupling constants and ultrasonic attenuation. The fracture/toughness ratio is less than 1.75, which shows that the chosen materials are brittle in nature as found for other monopnictides. The drag coefficient acting on the motion of screw and edge dislocations due to shear and compressional phonon viscosities of the lattice have also been evaluated for both the longitudinal and shear waves. The thermoelastic loss and dislocation damping loss are negligible in comparison to loss due to Akhieser damping (phonon–phonon interaction). The obtained results for CeX are in qualitative agreement with other semi-metallic monopnictides. 相似文献
16.
Amar R. Marathe Jason S. Metcalfe Brent J. Lance Jamie R. Lukos David Jangraw Kuan-Ting Lai 《Theoretical Issues in Ergonomics Science》2018,19(3):283-320
ABSTRACTA primary goal for human-autonomy integration (HAI) is to balance the strengths of human and autonomy in order to achieve performance objectives more efficiently and robustly than either the human or autonomous agents would independently. This paper proposes the Privileged Sensing Framework (PSF) as a novel approach to HAI. This approach is based on the concept of dynamically ‘privileging’ information during the process of integration by dynamically bestowing special rights based on the characteristics of each individual agent, the task context, and the performance goals. The proposed framework is tested through a series of simulation experiments that provide a clear demonstration of increased accuracy and throughput of human-autonomy performance. These proof-of-concept simulations provide initial evidence of the utility of the PSF. Continued development of this approach has the potential to revolutionise capabilities of multi-agent cooperative teams across a broad range of applications. 相似文献
17.
The 24-H Knowledge Factory facilitates collaboration between geographically and temporally distributed teams. The teams themselves
form a strategic partnership whose joint efforts contribute to the completion of a project. Project-related tasks are likewise
distributed, allowing tasks to be completed on a continuous basis, regardless of the constraints of any one team’s working
hours. However, distributing a single task between multiple teams necessitates a handoff process, where one team’s development
efforts and task planning are communicated from one team ending their shift to the next that will continue the effort. Data
management is, therefore, critical to the success of this business model. Efficiency in data management is achieved through
a strategic leveraging of key tools, models, and concepts. 相似文献
18.
Maher El��Arbi Mohamed Koubaa Maha Charfeddine Chokri Ben Amar 《Multimedia Tools and Applications》2011,55(3):579-600
In this paper, we propose a video watermarking algorithm which embeds different parts of a single watermark into different shots of a video under the wavelet domain. Based on a Motion Activity Analysis, different regions of the original video are separated into perceptually distinct categories according to motion information and region complexity. Thus, the localizations of the watermark are adjusted adaptively in accordance with the human visual system and signal characteristics, which makes them perceptually invisible and less vulnerable to automated removal. In addition, contrary to traditional methods where the watermark remains at a fixed position on the screen, the watermark moves along with moving objects and thus motion artefacts can be avoid. The multi-frame based extraction strategy ensures that the watermark can be correctly recovered from a very short segment of video. Individual frames extracted from the video also contain watermark information. Experimental results show that the inserted watermark is not only less perceptible but also robust against common video processing attacks. 相似文献
19.
Chaabouni Souad Benois-pineau Jenny Tison François Ben Amar Chokri Zemmari Akka 《Multimedia Tools and Applications》2017,76(21):22527-22546
Multimedia Tools and Applications - Studies of visual attention of patients with Dementia such as Parkinson’s Disease Dementia and Alzheimer Disease is a promising way for non-invasive... 相似文献
20.
Rigaud V. Coste-Maniere E. Aldon M.J. Probert P. Perrier M. Rives P. Simon D. Lang D. Kiener J. Casal A. Amar J. Dauchez P. Chantler M. 《Robotics & Automation Magazine, IEEE》1998,5(1):25-35
The main goal of the UNION ESPRIT Basic Research Action is to develop methods for increasing the autonomy and intelligence of underwater remotely operated vehicles (ROVs). The project focuses mainly on the development of coordinated control and sensing strategies for combined manipulator and vehicle systems. Both fundamental theories and methods for the design of these heterogeneous systems are investigated. A complex canonical mission in the field of offshore inspection maintenance and repair tasks was chosen as an integration guideline of all the results 相似文献