Finite element analysis of loaded structures at very high temperatures

At very high temperatures loaded metallic structures undergo creep deformations. The generated creep strains are connected with stress relaxations, stress redistributions and/or progressive deformations.In mainly load controlled situations the behaviour of the material can be described by a nonlinear viscous flow law (Norton power law).A stress-deformation analysis of complex structures can be carried out by finite element codes in which the mentioned constitutive equation is implemented. The code PERMAS-VISCOUS was used to analyse the stress state of a notched tension bar and the deformation behaviour of a tube under external pressure undergoing a creep collapse. The relation to experimental findings is also given.     

Determination of trans fatty acids in cold pressed oils and in dried seeds

The adulteration of cold pressed oils (CPO) by refining or by blending with refined oils leads to an increase in their trans fatty acid (TFA) contents. The regulations of the European Union (EU) lay down strict processing conditions without any steam treatment for native olive oils and provide limits for TFA. However, German regulations allow a “steam washing” for CPO other than native olive oil and do not limit TFA. Thus, the TFA contents of such oils might exceed the limits for native olive oil. Modern capillary GLC serves as a quick tool for the detection of TFA. However, care should be taken to avoid the formation of TFA as artefacts during analysis. We evaluated the TFA contents in several oils labelled as “cold pressed” and the formation of TFA during “steam washing” and deodorization. Analysis of some seeds indicates that preliminary drying of the seeds may also contribute to TFA content.     

Unpopuläre E-Mail-Verschlüsselung – Auflösung des Henne-Ei-Problems

E-Mail-Verschlüsselung könnte längst flächendeckend Verwendung finden. Der Beitrag gibt eine Antwort auf die Frage, warum dies nicht der Fall ist–und macht Vorschläge, was getan werden sollte, um dies zu ändern.     

Vertrauensvolle E-Mail-Kommunikation

Der ?elektronische Brief“ bzw. die elektronische Mail (E-Mail) ist seit über 30 Jahren im privaten wie beruflichen Umfeld im Einsatz. Behörden, Steuerbüros, Krankenhäuser, Finanzinstitute und viele weitere Gruppen versenden und empfangen E-Mails, um Informationen auszutauschen. Innerhalb kurzer Zeit findet eine E-Mail ihren Weg vom Sender in Deutschland zum Empfänger in beispielsweise den USA. Wie funktioniert das? Und was hat es mit E-Mail-Verschlüsselung auf sich? Dieser Artikel betrachtet die grundlegende technische Funktionsweise der E-Mail sowie Hintergründe und Funktionsweise der Verschlüsselung mit S/MIME und PGP.     

Enhancing Virtual Reference: Techniques and Technologies to Engage Users and Enrich Interaction

Virtual reference service has become ubiquitous in academic libraries. The increased adoption of chat technology brings to light some of the challenges of providing high-quality reference service. The lack of a personal connection, increased transaction time, and technical problems are often cited. Techniques, such as conducting a reference interview or using online communication conventions, can make virtual reference as effective as face-to-face reference. Additionally, inclusion of video or Web annotation in the virtual reference session can add an element of personalization that might otherwise be missing. Virtual reference can be an emotionally rich, engaging, and effective form of reference service if these techniques and technologies are adopted.     

Fusion of indigenous knowledge and gamma spectrometry for soil mapping to support knowledge-based extension in Tanzania

Food shortages often threaten central Tanzania. Sustainable action adapted to local environmental conditions is desperately needed. In the framework of the TransSEC project, two food value chains in the Dodoma region of Tanzania were inspected in order to make propositions for improvement , spanning from soil preparation to product consumption. Therefore, soil mapping approaches were required to obtain rapid and reliable information. This would enable local farmers to participate in the development of upgrading strategies and extensionists to develop recommendations that take local soil conditions into account. In this study, a combination of participatory soil mapping and gamma ray spectrometry-assisted transect mapping was applied to establish local soil maps of two villages in the Dodoma region. Participatory mapping included key informant interviews, group discussions and transect walks. Local farmers indicated reference profiles for local soil types. Their gamma radiation signatures delivered base information for further soil exploration and soil unit delineation in the field. Finally, high resolution satellite images were used to establish the village soil maps. This approach allows capture of the major soil differences within a village territory and reduction of the costs of chemical analyses. Challenges were soil unit separation with gamma ray spectrometry due to erosional redistribution processes at the surface, correct translation of specific terms from local tongues as well as variable individual soil knowledge of local participants. Ultimately, the combination of local soil knowledge with innovative scientific mapping yielded quick results with sufficient spatial resolution for extension work.     

Influence of pigment on biodeterioration of acrylic paint films in Southern Brazil

Biodeterioration of paint films leads to loss of durability and increased repainting costs. The influence of pigments on the biodeterioration of architectural paint films in the city of Florianópolis, Brazil, was evaluated using ten differently colored acrylic paint films exposed to the environment for 34 months. Fouling (biofilm formation) on the surfaces was assessed macroscopically, using British Standard BS 3900/1989 G6, and microscopically. After 20 months, major colonizers were bacteria and fungi, with some cyanobacteria and few algae; north-facing suede and peach and south-facing ice colors showed 100% cover at this time. The least affected color at all times was blue, with a maximum of 30% cover on south-facing panels after 34 months. North-facing panels were generally more fouled than South-facing. Blue, red, and ceramic colors always performed best. Resistance to fouling may have been due to copper in blue and acidity from sulfur oxides in ceramic pigments. Pigments may prolong paint film life and reduce the need for biocides.     

采用计量型扫描力显微镜校准微纳米标准样板

为了建立质量保证体系,微米和纳米样板至今仍被广泛地应用于校准微纳米尺度的测量仪器中．介绍了应用由德国联邦物理研究所开发研究的、测量范围为25 mm×25 mm×5 mm的计量型扫描力显微镜(M-LRSFM)的校准方法．上述计量型扫描力显微镜配置有三个零拍的激光干涉仪,可分别测量沿x、y、z三条轴线方向的位移,因而其测量值可直接溯源于“米”定义．此种M-LRSFM能够校准横向的微纳尺度的结构尺寸,诸如阶梯高度、一维和二维光栅、镀层厚度、线宽、微纳尺度的表面粗糙度等．作为实例,介绍了一种横向样板的校准程序及获得的校准结果．研究表明这种方法适合于校验扫描电子显微镜(SEM)的放大倍率．