[1] The Photochemistry Experiment during BERLIOZ (PHOEBE) was conducted in July and August 1998 at a rural site located near the small village of Pabstthum, about 50 km northwest of downtown Berlin. In this paper, spectroscopic measurements of hydroxyl (OH) and peroxy radicals (HO 2 and RO 2 ) are discussed for two intensive days (20 and 21 July) of the campaign. On both days peak values of the radical concentrations were similar, reaching 6-8 Â 10 6 cm À3 for OH and 20-30 ppt for RO 2 and HO 2 . Fairly high OH concentrations were observed during the morning hours in the presence of high-NO x mixing ratios (>20ppb). The ''master chemical mechanism'' (MCM) was used to calculate OH, HO 2 , and RO 2 concentrations from the simultaneously measured data comprising a comprehensive set of speciated hydrocarbons and carbonyl compounds, O 3 , CO, NO, NO 2 , HONO, PAN, J(NO 2 ), J(O 1 D), and meteorological parameters. The calculated OH concentrations are in excellent agreement with the measurements during the morning hours at high-NO x (>10 ppb). However, at low NO x conditions the model overestimates OH by a factor 1.6. The modeled concentrations of HO 2 and RO 2 are in reasonable agreement with the measurements on 20 July. On the next day, when isoprene from nearby sources was the dominant VOC, the model overpredicted HO 2 and RO 2 in addition to OH. Radical budgets solely calculated from measured data show that a missing sink for OH must be responsible for the overestimation by MCM. Missing VOC reactivity is unlikely, unless these VOC would not lead to RO 2 production upon reaction with OH. The measured RO 2 /HO 2 ratio of about one is well reproduced by the MCM, whereas a simple model without recycling of RO 2 from decomposition and isomerisation of alkoxy radicals underpredicts the measured ratio by about a factor of two. This finding highlights the importance of RO 2 recycling in the chemical mechanism. The ozone production rate P(O 3 ), calculated from the peroxy radical concentrations and NO, had a maximum of 8 ppb/hr at 0.5 ppb NO, which is in good agreement with results from previous campaigns at Tenerife and Schauinsland.

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For an optimal preparation of mechanical engineering students for their future work life, the use of problem-based methods in design teaching is investigated. Therefore an intelligent tutoring system for computer aided design education will be developed, which can automatically evaluate computer aided design models of design students. A knowledge-based engineering system will be used to assistance the design students in the execution of design tasks. Using a practice-oriented example, the application and the advantages for teaching will be verified and discussed.

In times of increasing digitalization, universities are turning to digital media to promote effective learning. In addition to comprehensive learning platforms, on which learning materials and communication options are offered, interactive and adaptive learning programs are also being developed in many subject areas. These so-called intelligent tutoring systems are used as a lecture-accompanying tool to make lessons more varied and thus more efficient. This paper reports on the use of an intelligent tutoring system that was embedded as a formative assessment tool in computer-aided design education. The system was used by over a hundred-second semester mechanical engineering students to prepare for a design course. The obtained system data is evaluated and then discussed. As a result, it is shown that an intelligent tutoring system within the framework of formative assessment can help students complete open design tasks and lead them to a valid solution through supportive feedback. Furthermore, this paper presents the use of the system data to improve the course by detecting and evaluating knowledge gaps and misconceptions of the students.

The present work deals with the numerical crack simulation of fiber-matrix debonding in single fiber pull-out tests. For this purpose, two models are used: a finite element model (FE model) with the cohesive zone approach and a peridynamic model. For calibration a reference experiment is applied. In addition analytical equations are used for reference values. The influence of the model parameters and the material parameters of the cohesive zone model on the force-displacement curve is investigated. Besides the free fiber length, the critical interface strength, the critical energy release rate as well as the initial interface stiffness have a great influence on the force-displacement curve of the pull-out test. From the crack simulation it can be seen that Mode I has an influence on the crack initiation, but further crack growth after initiation is dominated by Mode II. The FE model can be calibrated in a way that the crack initiation point and the maximum force correspond to the reference experiment. The peridynamic model depicts a comparable crack formation process.

To develop problem-solving skills during engineering studies, students must be given the opportunity to act independently and to apply their expertise in professional application situations with feedback that promotes learning. Although practical projects in university teaching deal with real-world problems, individual support and promotion of the students is often difficult due to a lack of personnel and time.Asynchronous learning methods such as e-learning platforms, on which exercises can be made directly available to students, offer a supplement to this. Since the problems of design theory do not contain a unique correct solution but allow a multitude of valid results, the simple true/false question formats of most platforms are unsuitable for the evaluation of design tasks. In this paper a system architecture is presented which provides students with asynchronous design tasks, automatically evaluates solution variants and thus supports the solution process individually by direct feedback. The functionality of the described system was verified and tested by several students, which allowed to demonstrate the usability of the system in the context of education. A subsequent evaluation presents the strengths and weaknesses of the task and the feedback generated by the system.

For the economic use of repair in the spare parts business, additive repair by Laser Powder Bed Fusion (LPBF) is a promising technology. As material can only be applied to a flat surface in LPBF, prior machining is required. The selection of the section plane requires expert knowledge, though. To provide that knowledge and recommend a suitable section plane, an expert system can be used. In this paper, a concept for such an expert system is presented and its functionality is evaluated by an example.