The aim of this study was to experimentally investigate the effect of repeated low-velocity impacts on tensile strength of fiber metal laminates (FMLs) using instrumented drop weight impact tester. FMLs were fabricated layer by layer intercalating three layers of aluminum 6061 and two layers of glass fiber-reinforced epoxy. The FMLs were subjected to repeated low-velocity impacts (<10?m/s) at the same location on the FML. The degradation of mechanical property due to impact(s) was studied using Zwick UTM at distances of 0, 20, 40, and 60?mm from the impact point. Results indicate that ultimate tensile strength, failure strain, and ductility of all specimens initially decrease, and then remain constant with increase in number of impacts. A closer examination of impacted FML by scanning electron microscope indicates that thinning and shear fracture in aluminum layers, as well as delamination, and fiber failure in composites plies were present. 相似文献
Manganese dioxide electrode shows reversible charge storage capacity, if the charge-discharge process is limited to 0.3e− exchange. Addition of small amount of Bi2O3 to manganese dioxide induces reversibility with an exchange of 2e−/Mn. Nickel hydroxide is known to reversibly exchange 1e−. In spite of isostructural relationship between the cobalt hydroxide, nickel hydroxide and manganese dioxide, cobalt hydroxide does not show any electrochemical activity. Bi2O3 modified cobalt hydroxide electrodes exchanges 0.3-0.5e−/Co during the charge discharge process. The oxidation-reduction process in cobalt hydroxide and Bi2O3 modified cobalt hydroxide electrodes were monitored using the PXRD patterns. 相似文献
Emerging evidence seems to indicate that most systems development organizations are attempting to utilize both agile and traditional approaches. This study aims to understand the reasons organizations feel the need for this unlikely juxtaposition and the organizational challenges in sustaining the opposing cultures. Drawing on the extensive literature in organizational theory and management, we advocate ambidexterity as a viable solution to systems development organizations attempting to harness the benefits of both agile and traditional development. 相似文献
An efficient resource allocation is a fundamental requirement in high performance computing (HPC) systems. Many projects are dedicated to large-scale distributed computing systems that have designed and developed resource allocation mechanisms with a variety of architectures and services. In our study, through analysis, a comprehensive survey for describing resource allocation in various HPCs is reported. The aim of the work is to aggregate under a joint framework, the existing solutions for HPC to provide a thorough analysis and characteristics of the resource management and allocation strategies. Resource allocation mechanisms and strategies play a vital role towards the performance improvement of all the HPCs classifications. Therefore, a comprehensive discussion of widely used resource allocation strategies deployed in HPC environment is required, which is one of the motivations of this survey. Moreover, we have classified the HPC systems into three broad categories, namely: (a) cluster, (b) grid, and (c) cloud systems and define the characteristics of each class by extracting sets of common attributes. All of the aforementioned systems are cataloged into pure software and hybrid/hardware solutions. The system classification is used to identify approaches followed by the implementation of existing resource allocation strategies that are widely presented in the literature. 相似文献
This paper first presents a novel approach for modelling facial features, Local Directional Texture (LDT), which exploits the unique directional information in image textures for the problem of face recognition. A variant of LDT with privacy-preserving temporal strips (TS) is then considered to achieve faceless recognition with a higher degree of privacy while maintaining high accuracy. The TS uses two strips of pixel blocks from the temporal planes, XT and YT, for face recognition. By removing the reliance on spatial context (i.e., XY plane) for this task, the proposed method withholds facial appearance information from public view, where only one-dimensional temporal information that varies across time are extracted for recognition. Thus, privacy is assured, yet without impeding the facial recognition task which is vital for many security applications such as street surveillance and perimeter access control. To validate the reliability of the proposed method, experiments were carried out using the Honda/UCSD, CK+, CAS(ME)2 and CASME II databases. The proposed method achieved a recognition rate of 98.26% in the standard video-based face recognition database, Honda/UCSD. It also offers a 81.92% reduction in the dimension length required for storing the extracted features, in contrast to the conventional LBP-TOP.
This article proposes a hybrid certificateless signcryption scheme that is secure against adaptive chosen ciphertext adversary in the random oracle model. The scheme combines an asymmetric encryption which is one way against chosen plaintext attack and any One-Time secure symmetric encryption scheme, combined using Fujisaki–Okamoto transformation. Uncommon to many Fujisaki–Okamoto based constructions which ensure message integrity alone, this scheme provides entity authentication in addition. By the choice of a hash function that utilizes the advantage of sponge based construction, the scheme enables the user to incorporate any One-Time secure symmetric encryption by re-configuring the input/output parameters. Fujisaki–Okamoto transformation, which is currently a standard in hybrid constructions, guarantees the indistinguishability against adaptive chosen ciphertext attack. The provision for choosing symmetric encryption in the scheme enables it to be implemented in all sort of cryptographic requirements including those in wireless communication.
Doxorubicin increases endothelial permeability, hence increasing cardiomyocytes’ exposure to doxorubicin (DOX) and exposing myocytes to more immediate damage. Reactive oxygen species are major effector molecules of doxorubicin’s activity. Mangiferin (MGN) is a xanthone derivative that consists of C-glucosylxanthone with additional antioxidant properties. This particular study assessed the effects of MGN on DOX-induced cytotoxicity in human umbilical vein endothelial cells’ (HUVECs’) signaling networks. Mechanistically, MGN dramatically elevated Nrf2 expression at both the messenger RNA and protein levels through the upregulation of the PI3K/AKT pathway, leading to an increase in Nrf2-downstream genes. Cell apoptosis was assessed with a caspase-3 activity assay, transferase-mediated dUTP-fluorescein nick end labeling (TUNEL) staining was performed to assess DNA fragmentation, and protein expression was determined by Western blot analysis. DOX markedly increased the generation of reactive oxygen species, PARP, caspase-3, and TUNEL-positive cell numbers, but reduced the expression of Bcl-2 and antioxidants’ intracellular concentrations. These were effectively antagonized with MGN (20 μM), which led to HUVECs being protected against DOX-induced apoptosis, partly through the PI3K/AKT-mediated NRF2/HO-1 signaling pathway, which could theoretically protect the vessels from severe DOX toxicity. 相似文献