Multi-axis transient vibration testing of space objects: Test philosophy, test facility, and control strategy

IABG has been using various servohydraulic test facilities for many years for the reproduction of service loads and environmental loads on all kinds of test objects. For more than 15 years, a multi-axis vibration test facility has been under service, originally designed for earthquake simulation but being upgraded to the demands of space testing. First tests with the DFS/STM showed good reproduction accuracy and demonstrated the feasibility of transient vibration testing of space objects on a multi-axis hydraulic shaker. An approach to structural qualification is possible by using this test philosophy. It will be outlined and its obvious advantages over the state-of-the-art single-axis test will be demonstrated by example results. The new test technique has some special requirements to the test facility exceeding those of earthquake testing. Most important is the high reproduction accuracy demanded for a sophisticated control system. The state-of-the-art approach of analog closed-loop control circuits for each actuator combined with a static decoupling network and an off-line iterative waveform control is not able to meet all the demands. Therefore, the future over-all control system is implemented as hierarchical full digital closed-loop system on a highly parallel transputer network. The innermost layer is the digital actuator controller, the second one is the MDOF-control of the table movement. The outermost layer would be the off-line iterative waveform control, which is dedicated only to deal with the interaction of test table and test object or non-linear effects. The outline of the system will be presented

Modellierkonzept zur Erfassung wesentlicher Aspekte bei der mobilen Prozessausführung

Das Thema Mobilität ist heutzutage ein immer wichtiger werdender Diskussionspunkt. Dies hängt mit den Möglichkeiten zusammen, welche durch die steigende Zahl an Smartphones und mobilen Endgeräten auf dem Weltmarkt ermöglicht werden. Zudem sinken die Preise aufgrund der zahlreichen Fortschritte und Entwicklungen, die in diesem Bereich erzielt werden. Dadurch wird der Einsatz von Endgeräten in zahlreichen Tätigkeitsfeldern vorangetrieben. Dies spielt daher auch im Bereich des Gesundheitswesens eine immer größere Rolle. Hierbei kommt es häufig vor, dass mobile Einsatzkräfte, Krankenwagen, Notärzte, jedoch auch in den Bergen verschüttete Personen und Unfallopfer lokalisiert werden müssen. Zusätzlich ist Mobilität in Krankenhäusern wichtig, da es einen wesentlichen Vorteil darstellen kann, den Umgang mit personenbezogenen Daten und Patientenakten mobiler zu gestalten, indem eingegebene Daten direkt beim Patienten aufgenommen und zentral abgelegt werden können. Die fehlende Unterstützung im Bereich der Prozessmodellierung, Mobilität grafisch darzustellen, sollte daher schnellstmöglich gefördert werden. Dies ist nötig, da mobile Anwendungen immer häufiger eingesetzt und verwendet werden. Auch die Weiterentwicklung im Bereich der Sensorik ist dabei ausschlaggebend. Beispielsweise zeigt die Lokalisierung von Personen oder Gegenständen durch GPS (global positioning system), wie wichtig es ist, den Bereich von Mobilität zu fördern

Development of a Technical Memorandum Describing Optimal Room Acoustic Parameter Ranges for Musical Performance and Rehearsal Spaces

A working group has been convened by the European Acoustics Association to develop optimum Room Acoustic Parameter (RAP) ranges for musical performance and rehearsal spaces. A Technical Memorandum, outlining the proposals of the working group is in production: the main contents are summarized in this article. The main focus has been to develop optimum parameter ranges for concert halls, as well as for other spaces for music rehearsal and performance, such as chamber music halls and orchestra rehearsal halls. It is widely accepted that room acoustic quality is multi-dimensional: multiple RAPs are therefore required to quantify acoustic quality. The RAPs as currently implemented do not however provide a robust differentiation of acoustic quality - both good and bad sounding halls can fall within the RAP ranges currently proposed in the literature. The Technical Memorandum describes a selection process for RAP ranges, with the aim of setting projects on a good path towards acoustical excellence, and to improve the quantification of the outcome. While the possibility to develop novel parameters was at first discussed, is has been agreed that the RAPs already defined in ISO 3382 Part 1 will be used. The RAPs are physically linked; therefore, the RAP optimum ranges must form an internally consistent set, taking into consideration their variation throughout the space. Other important aspects that must be considered in the definition of optimal RAPs that are often overlooked are the orchestra/ensemble size, music type or genre, room volume available, ideal loudness during loud (forte) passages, variation of parameters with acoustic volume and with distance from the source. It has also been established that measurement protocols should be refined to improve the differentiation between spaces of differing acoustical quality

Surface generation and assessment for peripheral milling

The rotating tool during peripheral milling filters disturbing vibrations between half of the rotation frequency and frequencies assigned to half the time necessary to generate a single cuttermark. This is a relatively large gap in the frequency range being not copied onto the finished surface. Roughness readings returning frequencies in that range are caused by other reasons like secondary fracture effects or the internal structure of the material. Superposition of vibrations at frequencies close to the rotation frequencies may cause interference patterns looking similar to the lines of cuttermarks but without representing the rotating frequency or the frequency of the disturbing vibration. This can also happen for perfectly aligned edges

A Youth-Leader Program in Baltimore City Recreation Centers: Lessons Learned and Applications

Peer-led interventions may be an effective means of addressing the childhood obesity epidemichowever, few studies have looked at the long-term sustainability of such programs. As part of a multilevel obesity prevention intervention, B'More Healthy Communities for Kids, 16 Baltimore college students were trained as youth-leaders (YLs) to deliver a skill-based nutrition curriculum to low-income African American children (10-14 years old). In April 2015, formative research was used to inform sustainability of the YL program in recreation centers. In-depth interviews were conducted with recreation center directors (n = 4) and the YLs (n = 16). Two focus groups were conducted with YLs (n = 7) and community youth-advocates (n = 10). Barriers to this program included difficulties with transportation, time constraints, and recruiting youth. Lessons learned indicated that improving trainings and incentives to youth were identified as essential strategies to foster continuity of the youth-led program and capacity building. High school students living close to the centers were identified as potential candidates to lead the program. Based on our findings, the initial intervention will be expanded into a sustainable model for implementation, using a train-the-trainer approach to empower community youth to be change agents of the food environment and role models.Johns Hopkins Urban Health InstituteGlobal Obesity Prevention Center at Johns HopkinsEunice Kennedy Shriver National Institute of Child Health and Human DevelopmentOffice of the Director, National Institutes of Health [U54HD070725]646 CNPq [GDE: 249316/2013-7]Johns Hopkins Bloomberg Sch Publ Hlth, Baltimore, MD USAUniv Tennessee, Knoxville, TN USAUniv Fed Sao Paulo, Santos, SP, BrazilDept Recreat & Pk City Baltimore, Baltimore, MD USAUniv Maryland Extens, Ellicott City, MD USAUniv Fed Sao Paulo, Santos, SP, BrazilWeb of Scienc

Honeybee linguistics—a comparative analysis of the waggle dance among species of Apis

All honeybees use the waggle dance to recruit nestmates. Studies on the dance precision of Apis mellifera have shown that the dance is often imprecise. Two hypotheses have been put forward aimed at explaining this imprecision. The first argues that imprecision in the context of foraging is adaptive as it ensures that the dance advertises the same patch size irrespective of distance. The second argues that the bees are constrained in their ability to be more precise, especially when the source is nearby. Recent studies have found support for the latter hypothesis but not for the “tuned-error” hypothesis, as the adaptive hypothesis became known. Here we investigate intra-dance variation among Apis species. We analyse the dance precision of A. florea, A. dorsata, and A. mellifera in the context of foraging and swarming. A. mellifera performs forage dances in the dark, using gravity as point of reference, and in the light when dancing for nest sites, using the sun as point of reference. Both A. dorsata and A. florea are open-nesting species; they do not use a different point of reference depending on context. A. florea differs from both A. mellifera and A. dorsata in that it dances on a horizontal surface and does not use gravity but instead “points” directly toward the goal when indicating direction. Previous work on A. mellifera has suggested that differences in dance orientation and point of reference can affect dance precision. We find that all three species improve dance precision with increasing waggle phase duration, irrespective of differences in dance orientation, and point of reference. When dancing for sources nearby, dances are highly variable. When the distance increases, dance precision converges. The exception is dances performed by A. mellifera on swarms. Here, dance precision decreases as the distance increases. We also show that the size of the patch advertised increases with increasing distance, contrary to what is predicted under the tuned-error hypothesis

The effect of cataract on early stage glaucoma detection using spatial and temporal contrast sensitivity tests

Background: To investigate the effect of cataract on the ability of spatial and temporal contrast sensitivity tests used to detect early glaucoma. Methods: Twenty-seven glaucoma subjects with early cataract (mean age 60 ±10.2 years) which constituted the test group were recruited together with twenty-seven controls (cataract only) matched for age and cataract type from a primary eye care setting. Contrast sensitivity to flickering gratings at 20 Hz and stationary gratings with and without glare, were measured for 0.5, 1.5 and 3 cycles per degree (cpd) in central vision. Perimetry and structural measurements with the Heidelberg Retinal Tomograph (HRT) were also performed. Results: After considering the effect of cataract, contrast sensitivity to stationary gratings was reduced in the test group compared with controls with a statistically significant mean difference of 0.2 log units independent of spatial frequency. The flicker test showed a significant difference between test and control group at 1.5 and 3 cpd (p = 0.019 and p = 0.011 respectively). The percentage of glaucoma patients who could not see the temporal modulation was much higher compared with their cataract only counterparts. A significant correlation was found between the reduction of contrast sensitivity caused by glare and the Glaucoma Probability Score (GPS) as measured with the HRT (p<0.005). Conclusions: These findings indicate that both spatial and temporal contrast sensitivity tests are suitable for distinguishing between vision loss as a consequence of glaucoma and vision loss caused by cataract only. The correlation between glare factor and GPS suggests that there may be an increase in intraocular stray light in glaucoma

Aging and Visual Counting

Much previous work on how normal aging affects visual enumeration has been focused on the response time required to enumerate, with unlimited stimulus duration. There is a fundamental question, not yet addressed, of how many visual items the aging visual system can enumerate in a "single glance", without the confounding influence of eye movements.We recruited 104 observers with normal vision across the age span (age 21-85). They were briefly (200 ms) presented with a number of well- separated black dots against a gray background on a monitor screen, and were asked to judge the number of dots. By limiting the stimulus presentation time, we can determine the maximum number of visual items an observer can correctly enumerate at a criterion level of performance (counting threshold, defined as the number of visual items at which ≈63% correct rate on a psychometric curve), without confounding by eye movements. Our findings reveal a 30% decrease in the mean counting threshold of the oldest group (age 61-85: ∼5 dots) when compared with the youngest groups (age 21-40: 7 dots). Surprisingly, despite decreased counting threshold, on average counting accuracy function (defined as the mean number of dots reported for each number tested) is largely unaffected by age, reflecting that the threshold loss can be primarily attributed to increased random errors. We further expanded this interesting finding to show that both young and old adults tend to over-count small numbers, but older observers over-count more.Here we show that age reduces the ability to correctly enumerate in a glance, but the accuracy (veridicality), on average, remains unchanged with advancing age. Control experiments indicate that the degraded performance cannot be explained by optical, retinal or other perceptual factors, but is cortical in origin