Controlling micro‐ and nanofibrillar morphology of polymer blends in low‐speed melt spinning process. Part III: Fibrillation mechanism of PLA/PVA blends along the spinline

The effects of spinning conditions on the fibrillation process of poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVA) polymer blends in an elongational flow within the fiber formation zone are systematically and thoroughly investigated. By considering the relationship between the changes in filament parameters with the focus on the maximum axial strain rate (ASR) and tensile stress at maximum ASR and the morphological evolution of the dispersed PLA phase along the spinline, the fibrillation process from rod‐like to nanofibrillar structures of the dispersed PLA phase in a binary blend with PVA matrix is elucidated. The final morphology of the dispersed PLA phase in PLA/PVA blends is controlled by the changes in the spinning conditions. The lengths and diameters of the PLA fibrils are caused not only by the deformation of their initial sizes but also by the combination of the deformation, coalescence, and break‐up process. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44259.     

Computer security

A strong factor in the early development of computers was security – the computations that motivated their development, such as decrypting intercepted messages, generating gunnery tables, and developing weapons, had military applications. But the computers themselves were so big and so few that they were relatively easy to protect simply by limiting physical access to them to their programmers and operators. Today, computers have shrunk so that a web server can be hidden in a matchbox and have become so common that few people can give an accurate count of the number they have in their homes and automobiles, much less the number they use in the course of a day. Computers constantly communicate with one another; an isolated computer is crippled. The meaning and implications of “computer security” have changed over the years as well. This paper reviews major concepts and principles of computer security as it stands today. It strives not to delve deeply into specific technical areas such as operating system security, access control, network security, intrusion detection, and so on, but to paint the topic with a broad brush. Published online: 27 July 2001     

Does open source improve system security?

The current climate of functionality and performance-driven markets has created enormous code bases, which have helped drive growth in the US gross domestic product. However, these code bases have also created an information infrastructure whose vulnerabilities are so striking as to endanger national and economic security. Distributed denial of service attacks have demonstrated that such vulnerabilities can degrade the Internet's aggregate performance, and recurrent virus outbreaks have inflicted substantial repair and recovery costs on businesses worldwide. An attacker could examine public source code to find flaws in a system. So, is source code access a net gain or loss for security? The authors consider this question from several perspectives and tentatively conclude that having source code available should work in favor of system security     

Processing of ZrC–Mo Cermets for High Temperature Applications, Part II: Pressureless Sintering and Mechanical Properties

Pressureless sintering of ZrC–Mo cermets was investigated in a He/H₂ atmosphere and under vacuum. A large density increase was observed for specimens with >20 vol% Mo after heating at 2150°C for 60 min in a He/H₂ atmosphere. The increase in density was attributed to the formation of Mo₂C during heating and its subsequent eutectic reaction with Mo, which produced rounded ZrC grains in a Mo–Mo₂C matrix. Sintering in vacuum did not produce the same increase in density, due to the lack of Mo₂C formation and subsequent lack of liquid formation, which resulted in a microstructure with irregular ZrC grains with isolated areas of Mo. Mechanical properties testing showed a decrease in Young's modulus with increasing Mo content that was consistent with the models presented. Flexure strength of ZrC–Mo cermets sintered in He/H₂ atmosphere materials increased with increasing Mo content from 320 MPa at 20 vol% Mo to 410 MPa at 40 vol% Mo. Strength was predicted by adapting theories developed previously for WC–Co cermets.