Defence Science and Technology Organisation

About: Defence Science and Technology Organisation is a nonprofit organization based out in Canberra, Australian Capital Territory, Australia. It is known for research contribution in the topics: Radar & Clutter. The organization has 2465 authors who have published 3856 publications receiving 90614 citations.

Durable, Self-Healing Superhydrophobic and Superoleophobic Surfaces from Fluorinated-Decyl Polyhedral Oligomeric Silsesquioxane and Hydrolyzed Fluorinated Alkyl Silane

Abstract: Super-liquid-repellent surfaces have attracted much attention in both scientific and industrial areas. They are often deemed superhydrophobic or superoleophobic depending on the liquid to be repelled. Superhydrophobic surfaces have a water contact angle greater than 1508. They have interesting nonsticking, self-cleaning, and anti-contamination functions. The emerging applications include separation of oil from water, energy conversion, protection of electronic devices, adjusting cell/substrate adhesion in the biomedical area, and reducing fluid resistance for aquaculture and microfluidic devices. In contrast, superoleophobic surfaces can be rather complicated, but they have great potential applications in antifouling from hazard chemicals and biological contaminants. Although any solid surface can be characterized as superoleophobic as long as its contact angle with an oily fluid is greater than 1508, the surface properties revealed from the contact angle measurement using different contacting oils could be considerably different. For example, a surface that is superoleophobic to certain oily fluids may have lower repellency or even be wettable by other oily fluids of a lower surface tension. It is normally easy to make a surface super-repellent to oils of a high surface tension, but difficult to prepare superoleophobic surfaces against oily fluids that have a surface tension below 35 mNm . Most super-liquid-repellent surfaces have poor durability. Chemical oxidation from exposure to air, a special chemical environment, strong light, or physical rubbing could cause the surfaces to lose their super-repellency permanently. It is imperative to improve the durability for practical applications. Recently, great progress has been made to develop mechanically robust superhydrophobic surfaces and laundering-durable superhydrophobic fabrics. On the other hand, the bioinspired self-healing ability has been proposed to be a promising solution to improve the durability of synthetic superhydrophobic surfaces. Recently, Li et al. reported a self-healing superhydrophobic coating that was prepared by chemical vapor deposition (CVD) of a fluoroalkyl silane on a layer-by-layer assembled porous surface, and self-healing was derived from the reacted fluoroalkyl silane embedded in the rigidly flexible coating layer. Wang et al. also reported the formation of a self-healing superamphiphobic surface on anodized alumina by filling the intrinsic pores with a lowsurface energy liquid. In the recent study, we have also found that fabrics coated with a hydrolysis product from fluorinated-decyl polyhedral oligomeric silsesquioxane (FD–POSS) and a fluorinated alkyl silane (FAS) have a self-healing superhydrophobic and superoleophobic surface and the coating shows excellent durability to acid, UV light, machine wash, and abrasion. Herein, we first report on its novel multiple self-healing ability and durable performance. The chemical structures of FD-POSS and FAS are shown in Figure 1 a. The coating solution was prepared by dissolving FD-POSS in five times its weight of FAS, and the resulting viscous solution was then dispersed in ethanol. After ultrasonication for 30 min, a homogeneous dispersion was obtained. Figure 1b shows the appearance of an FD–POSS/ FAS dispersion in ethanol. Such a suspension was stable at

Mining e-mail content for author identification forensics

Abstract: We describe an investigation into e-mail content mining for author identification, or authorship attribution, for the purpose of forensic investigation. We focus our discussion on the ability to discriminate between authors for the case of both aggregated e-mail topics as well as across different e-mail topics. An extended set of e-mail document features including structural characteristics and linguistic patterns were derived and, together with a Support Vector Machine learning algorithm, were used for mining the e-mail content. Experiments using a number of e-mail documents generated by different authors on a set of topics gave promising results for both aggregated and multi-topic author categorisation.

Qualitative Case Study Guidelines

Abstract: Although widely used, the qualitative case study method is not well understood. Due to conflicting epistemological presuppositions and the complexity inherent in qualitative case-based studies, scientific rigor can be difficult to demonstrate, and any resulting findings can be difficult to justify. For that reason, this paper discusses methodological problems associated with qualitative case-based research and offers guidelines for overcoming them. Due to its nearly universal acceptance, Yin’s six-stage case study process is adopted and elaborated on. Moreover, additional principles from the wider methodological literature are integrated and explained. Finally, some modifications to the dependencies between the six case study stages are suggested. It is expected that following the guidelines presented in this paper may facilitate the collection of the most relevant data in the most efficient and effective manner, simplify the subsequent analysis, as well as enhance the validity of the resulting findings. The paper should be of interest to students (honour, masters, doctoral), academics, and practitioners involved with conducting and reviewing qualitative case-based studies.

A review of the effect of stitching on the in-plane mechanical properties of fibre-reinforced polymer composites

Abstract: This paper reviews over fifty studies into the effect of through-the-thickness stitching on the in-plane mechanical properties of fibre-reinforced polymer composites. Reviewed are the in-plane tensile, compressive, flexure, interlaminar shear, creep, fracture and fatigue properties, although little work has been undertaken on the last three properties. When comparing studies it is apparent that many contradictions exist: some studies reveal that stitching does not affect or may improve slightly the in-plane properties while others find that the properties are degraded. In reviewing these studies it is demonstrated that predicting the influence of stitching on the in-plane properties is difficult because it is governed by a variety of factors, including the type of composite (eg. type of fibre, resin, lay-up configuration), the stitching conditions (eg. type of thread, stitch pattern, stitch density, stitch tension, thread diameter), and the loading condition. The implications of these findings for the use of stitching in lightweight engineering structures are discussed.