Novel nanocomposite concept based on cross-linking of hyperbranched polymers in reactive cellulose nanopaper templates

Cellulosic fibers offer interesting possibilities for good interfacial adhesion due to the high density of hydroxyl groups at the surface. In the present study, the potential of a new nanocomposite concept is investigated, where a porous cellulose nanofiber network is impregnated with a solution of reactive hyperbranched polyester. The polymer is chemically cross-linked to form a solid matrix. The resulting nanocomposite structure is unique. The matrix surrounds a tough nanopaper structure consisting of approximately 20 nm diameter nanofibers with an average interfiber distance of only about 6 nm. The cross-linked polymer matrix shows strongly altered characteristics when it is cross-linked in the confined space within the nanofiber network, including dramatically increased T_g, and this must be due to covalent matrix-nanofiber linkages.     

Referate

Ohne Zusammenfassung     

Speisefette und Speisefettzubereitungen

Ohne Zusammenfassung     

Second Order Taylor Polyphase Reconstruction of Periodic-Nonuniform Samples in Time-Interleaved ADCs

This paper focuses on a filter bank approach for reconstructing periodic-nonuniform samples using second order Taylor polyphase decomposition for a four-channel time-interleaved ADC (TIADC). The proposed method is based on a parametric linear least squares approach to find the coefficients of synthesis filters used for signal reconstruction of periodic-nonuniform samples. The coefficients of synthesis filters found by linear least squares approach satisfy the general condition for an alias-free filter bank.     

等离子弧焊熔敷Ti-6Al-4V合金原位拉伸过程中显微组织及应变响应的电子背散射衍射表征

航天级钛合金的新型叠层制造技术（ALM）的优势体现在较低的制造成本等方面,并可替代传统加工成型工艺。由等离子弧焊熔敷叠层制造技术制备Ti-6Al-4V合金的显微组织由定向凝固生长的β柱状晶及在其晶内生长的细小的α片层组织构成。在原位拉伸过程中结合应用高速离线电子背散射衍射表征（Offline EBSD）可快速获取试样显微组织和形变特征之间的关系。揭示出不均匀变形的发生取决于柱状晶界间的应变响应。柱状滑移和基面滑移系统被激活进而导致最后出现形变滑移线,即在某些柱状晶中滑移扩展至整个晶粒;而在另一些晶粒中表现为存在应变梯度和应力集中的地方发生形变失配。形变的扩展习性受制于定向凝固生长的柱状晶生长方向及其之间的界面取向关系。在垂直于柱状晶方向的拉伸试验揭示存在剧烈的变形局域化。基于原位拉伸观测及高速的离线电子背散射衍射表征结果,本文作者提出从微观到宏观形变扩展的控制机制。     

Participation as a matter of concern in participatory design

This article starts from the paradox that, although participation is a defining trait of participatory design (PD), there are few explicit discussions in the PD literature of what constitutes participation. Thus, from a point of departure in Actor-Network Theory (ANT), this article develops an analytical understanding of participation. It is argued that participation is a matter of concern, something inherently unsettled, to be investigated and explicated in every design project. Specifically, it is argued that (1) participation is an act overtaken by numerous others, rather than carried out by individuals and (2) that participation partially exists in all elements of a project. These traits are explicated in a design project called ‘Teledialogue’, where the participants are unfolded as networks of reports, government institutions, boyfriends, social workers and so on. The argument is synthesised as three challenges for PD: (1) participants are network configurations, (2) participation is an aspect of all project activities and (3) there is no gold standard for participation.