Passiv damping on spacecraft sandwich panels

For reusable and expendable launch vehicles as well as for other spacecraft structural vibration loads are safety critical design drivers impacting mass and lifetime. Here, the improvement of reliability and safety, the reduction of mass, the extension of service life, as well as the reduction of cost for manufacturing are desired. Spacecraft structural design in general is a compromise between lightweight design and robustness with regard to dynamic loads. The structural stresses and strains due to displacements caused by dynamic loads can be reduced by mechanical damping based on passive or active measures. Passive damping systems can be relatively simple and yet are capable of suppressing a wide range of mechanical vibrations. Concepts are low priced in development, manufacturing and application as well as maintenancefree. Compared to active damping measures passive elements do not require electronics, control algorithms, power, actuators, sensors as well as complex maintenance. Moreover, a reliable application of active dampers for higher temperatures and short response times (e. g. re-entry environment) is questionable. The physical effect of passive dampers is based on the dissipation of load induced energy. Recent activities performed by OHB have shown the function of a passive friction-damping device for a vertical tail model of the German X-vehicle PHÖNIX but also for general sandwich structures. The present paper shows brand new results from a corresponding ESA-funded activity where passive damping elements are placed between the face sheets of large spacecraft relevant composite sandwich panels to demonstrate dynamic load reduction in vibration experiments on a shaker. Several passive damping measures are investigated and compared

Interimage Effects and the MTF of a Color Reversal Film

Interimage effects have long been recognized as a factor in the reproduction of color. Reversal materials are no exception and exhibit interimage effects which have previously been revealed through techniques using END analysis. This study presents a method for revealing the presence of interimage effects in a reversal film\u27s Modulation Transfer Function. Utilizing filtering techniques, two dyes of a three color transparency are eliminated from the final image by exposure and development. The remaining single dye image at a specified level is then compared to the corresponding layer and image in a colorimetrically specified neutral. The edge gradient analysis method is used to calculate the Modulation Transfer Functions. MTF results indicate the desirability of using colorimetry for the specification of a visual neutral. MTF values are indicative of a significant effect on the Modulation Transfer Function by interimage effects

Geophysical Measurements on Glacial Soils - A Challenge in the Detection, Identification and Reconstruction of Archaeological Targets

The archaeological investigation of Bronze Age features in glacial soils in geophysical data is a great challenge and will be the focus of three distinct chapters of this thesis. Glacial soils are characterised by a high proportion of boulder stones but also by the occurrence of iron oxide concretions and are thus very heterogeneous. One of the challenges is to identify stony archaeological features in the stony environment. The first two chapters deal with the improvement of the detection and identification of archaeological features in radar and magnetic data. Subject of the investigations are burial mounds and their near surroundings. The third chapter attempts to reconstruct the shape and height of an almost eroded burial mound. Extensive geophysical measurement campaigns were carried out over Bronze Age sites in the region of northern Germany, with a strong focus on radar and magnetic measurements. To be able to estimate how much archaeological features are detected in the geophysical data the archaeological documentation was included. Soil analyses were used to estimate soil conditions with the help of numerical modelling. To estimate the height of the former mound geometric shapes, such as bell shape, cone, and spherical section were used. This study demonstrates that the detectability of stony archaeological features can be improved if the measurement campaign is conducted in the wet months, whereas the improved detectability of pit-like features will be improved if one measures in the drier months. The identification of archaeological features can be improved if one combines radar with magnetic data and by the development of a pattern recognition tool by additionally use the signal strength. The minimum height of the former burial mound could be determined, based on the usage of the ditch material from each phase and ranges between 2.1 m and 3.4 m

Artists in All Subjects: Integrating Art Into the Content Areas

The state of Minnesota provides statewide expectations of what students in grades K-12 should know in public schools by the end of the school year. There are standards in all subjects, including art. However, not all schools have an art professional to teach these standards. Fine art programs are often the first programs to be cut from schools due to budget restrictions. This project has two main goals. First, to address the misconception that art is expensive to include in the classroom, whether the general teacher’s classroom or by having an art teacher to lead the instruction. Second, to show that art education can be integrated into all content areas and can make learning for students richer and provide more meaningful connections. This honors project consists of interdisciplinary mini units, meaning across multiple subjects, grounded in the visual arts for students in kindergarten through fifth grade. The mini units also integrate social justice, social emotional learning, collaboration opportunities, and project based learning with the arts being the heart of these lessons. This project shows that art is for the youngest students as well as students in upper elementary and beyond. By having learning that occurs across disciplines, students are more engaged, they participate in higher level thinking, and it shows connections between disciplines to the real world

Default risk and the effective duration of bonds

Basis risk is the risk attributable to uncertain movements in the spread between yields associated with a particular financial instrument or class of instruments, and a reference interest rate over time. There are seven types of basis risk: Yields on 1) Long-term versus short-term financial instruments, 2) Domestic currency versus foreign currencies, 3) Liquid versus illiquid investments, 4) Bonds with higher or lower sensitivity to changes in interest rate volatility, 5) Taxable versus tax-free instruments, 6) Spot versus futures contracts and 7) Default-free versus non-default-free securities. Basis risk makes it difficult for the fixed-income portfolio manager to measure the portfolio's exposure to interest rate risk, heightens the anxiety of traders and arbitrageurs who are hedging their investments, and compounds the financial institution's problem of matching assets and liabilities. Much attention has been paid to the first type of basis risk. In recent years, attention has turned toward understanding the relation between credit risk and duration. The authors focus on that, emphasizing the importance of taking credit risk into account when computing measures of duration. The consensus of all work in this area is that credit risk shortens the effective duration of corporate bonds. The authors estimate how much durations shorten because of credit risk, basing their estimates on observable data and easily estimated bond pricing parameters.Banks&Banking Reform,Payment Systems&Infrastructure,International Terrorism&Counterterrorism,Economic Theory&Research,Insurance&Risk Mitigation,Environmental Economics&Policies,Strategic Debt Management,Economic Theory&Research,Banks&Banking Reform,Insurance&Risk Mitigation

X-chromosome inactivation: the molecular basis of silencing

X-chromosome inactivation occurs randomly for one of the two X chromosomes in female cells during development. Inactivation occurs when RNA transcribed from the Xist gene on the X chromosome from which it is expressed spreads to coat the whole X chromosome. In the first issue of Epigenetics and Chromatin, Nesterova and colleagues investigate the role of the RNA interference pathway enzyme Dicer in DNA methylation of the Xist promoter