Aerodynamic penalties of heavy rain on a landing aircraft

The aerodynamic penalties of very heavy rain on landing aircraft were investigated. Based on severity and frequency of occurrence, the rainfall rates of 100 mm/hr, 500 mm/hr, and 2000 mm/hr were designated, respectively, as heavy, severe, and incredible. The overall and local collection efficiencies of an aircraft encountering these rains were calculated. The analysis was based on raindrop trajectories in potential flow about an aircraft. All raindrops impinging on the aircraft are assumed to take on its speed. The momentum loss from the rain impact was later used in a landing simulation program. The local collection efficiency was used in estimating the aerodynamic roughness of an aircraft in heavy rain. The drag increase from this roughness was calculated. A number of landing simulations under a fixed stick assumption were done. Serious landing shortfalls were found for either momentum or drag penalties and especially large shortfalls for the combination of both. The latter shortfalls are comparable to those found for severe wind shear conditions

Ultrashort-Pulse Matter Interactions Using Compact Fiber CPA Technology.

Chirped pulse amplification (CPA) was a breakthrough that allowed for high energy ultrashort pulses, leading to many technological and scientific discoveries. Many CPA systems relied on bulky, alignment-sensitive diffraction-grating based pulse stretchers and compressors, making them impractical for industrial applications. Chirped Bragg gratings (CBGs) have recently been demonstrated as compact, monolithic, and robust pulse stretchers and compressors, and so they are more practical for industrial applications. This thesis explores two key properties of CBGs: reciprocity and thermal loading. The CBG would appear to be reciprocal by nature, where one configuration would stretch a bandwidth-limited pulse and the reverse configuration would recompress the pulse back to the bandwidth-limited duration. However, this reciprocity property is not absolute, and under certain conditions recompressed pulses acquire significant temporal distortions. We explored and defined proper CBG design requirements to minimize these temporal distortions. Furthermore, we explored the performance of chirped volume Bragg gratings (CVBGs) in a high average power CPA system. We found that absorbed incident power induces a volumetric thermal gradient in CVBGs that led to significant chromatic aberrations at approximately 1 kW average power; however, we also found that thermally induced warping of the CVBG can introduce significant beam distortions in the form of spatial chirp at an average power one order of magnitude lower, although this can be controlled by proper mechanical mounting conditions or by proper CVBG fabrication. CVBG-based fiber CPA lasers can enable practical high average power systems with a variety of material science and biomedical applications. We built a 50 W, 10 μJ CVBG-based CPA system with variable repetition rate to explore select potential applications of the system, namely the formation of high spatial frequency laser-induced periodic surface structures on Si as well as subsurface laser surgery in the sclera. The scattering properties of the tissue limit the precision with which the surgery could be performed, but we developed a model using naturally-occurring second harmonic generation in ex vivo porcine sclera that can be used as a non-invasive probe to measure scattering properties and predict the pulse energy needed for subsurface incisions in the sclera.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120656/1/mkhaines_1.pd

Peculiar Velocities of Nonlinear Structure: Voids in McVittie Spacetime

As a study of peculiar velocities of nonlinear structure, we analyze the model of a relativistic thin-shell void in the expanding universe. (1) Adopting McVittie (MV) spacetime as a background universe, we investigate the dynamics of an uncompensated void with negative MV mass. Although the motion itself is quite different from that of a compensated void, as shown by Haines & Harris (1993), the present peculiar velocities are not affected by MV mass. (2) We discuss how precisely the formula in the linear perturbation theory applies to nonlinear relativistic voids, using the results in (1) as well as the previous results for the homogeneous background (Sakai, Maeda, & Sato 1993). (3) We re-examine the effect of the cosmic microwave background radiation. Contrary to the results of Pim & Lake (1986, 1988), we find that the effect is negligible. We show that their results are due to inappropriate initial conditions. Our results (1)-(3) suggest that the formula in the linear perturbation theory is approximately valid even for nonlinear voids.Comment: 12 pages, aastex, 4 ps figures separate, Fig.2 added, to appear in Ap

The Ursinus Weekly, January 17, 1944

Students hear Senator Ball speak at forum • War loan campaign to be sponsored by Student Council and Weekly: $15,000 goal will permit Ursinus to buy plane • A. J. Cronin\u27s drama Jupiter Laughs marks new undertaking for club • Y handbooks distributed • Churchmen to speak at Y conferences • Hobson girls take amateur night prize • Dr. C. G. Haines addresses students at open meeting • Cabinet room of Y open to faculty members • Y\u27s to stage country fair • Women students see movies about Navy WAVE training • Pastor urges happy spirit in Sunday vespers talk • Daughter born to athlete • Club holds vocabulary bee • Tau Sigs to hold treasure hunt • Physical Education Club hears Tadley • Thespians learn make-up • Russia and Poland • Support bond drive • The judges write • Protect east campus • Wake up and live! • Among our alumni • Girls meet Garnet sextette in first clash of season • Bears drop games to Owls and F. & M. • Wrestlers stop F. & M. streak with hard earned 19-13 win • Marines stopped by Bears, 43-37 • Civilians, Carney pace intra basketball league • Shope leads volleyballhttps://digitalcommons.ursinus.edu/weekly/3107/thumbnail.jp

Decoupled freshwater transport and meridional overturning in the South Atlantic

Freshwater transports (F_ov) by the Atlantic Meridional Overturning Circulation (AMOC) are sensitive to salinity distributions and may determine AMOC stability. However, climate models show large salinity biases, distorting the relation between F_ov and the AMOC. Using free-running models and ocean reanalyses with realistic salinities but quite different AMOCs, we show that the fresh Antarctic Intermediate Water (AAIW) layer eliminates salinity differences across the AMOC branches at ~1200 m, ∆S_1200m, which decouples F_ov from the AMOC south of ~10˚N. As AAIW disappears north of ~10˚N, a large ∆S_1200m allows the AMOC to drive substantial southward F_ov in the North Atlantic. In the South Atlantic the 0-300 m zonal salinity contrasts control the gyre freshwater transports F_gyre, which also determine the total freshwater transports. This decoupling makes the southern F_ov unlikely to play any role in AMOC stability, leaving indirect F_gyre feedbacks or F_ov in the north, as more relevant factors

The link between the Barents Sea and ENSO events simulated by NEMO model

An analysis of observational data in the Barents Sea along a meridian at 33°30' E between 70°30' and 72°30' N has reported a negative correlation between El Niño/La Niña Southern Oscillation (ENSO) events and water temperature in the top 200 m: the temperature drops about 0.5 °C during warm ENSO events while during cold ENSO events the top 200 m layer of the Barents Sea is warmer. Results from 1 and 1/4-degree global NEMO models show a similar response for the whole Barents Sea. During the strong warm ENSO event in 1997–1998 an anomalous anticyclonic atmospheric circulation over the Barents Sea enhances heat loses, as well as substantially influencing the Barents Sea inflow from the North Atlantic, via changes in ocean currents. Under normal conditions along the Scandinavian peninsula there is a warm current entering the Barents Sea from the North Atlantic, however after the 1997–1998 event this current is weakened. During 1997–1998 the model annual mean temperature in the Barents Sea is decreased by about 0.8 °C, also resulting in a higher sea ice volume. In contrast during the cold ENSO events in 1999–2000 and 2007–2008, the model shows a lower sea ice volume, and higher annual mean temperatures in the upper layer of the Barents Sea of about 0.7 °C. An analysis of model data shows that the strength of the Atlantic inflow in the Barents Sea is the main cause of heat content variability, and is forced by changing pressure and winds in the North Atlantic. However, surface heat-exchange with the atmosphere provides the means by which the Barents sea heat budget relaxes to normal in the subsequent year after the ENSO events

Assessment of the dimensionality of the Wijma delivery expectancy/experience questionnaire using factor analysis and Rasch analysis

Background: Fear of childbirth has negative consequences for a woman's physical and emotional wellbeing. The most commonly used measurement tool for childbirth fear is the Wijma Delivery Expectancy Questionnaire (WDEQ-A). Although originally conceptualized as unidimensional, subsequent investigations have suggested it is multidimensional. This study aimed to undertake a detailed psychometric assessment of the WDEQ-A; exploring the dimensionality and identifying possible subscales that may have clinical and research utility. Methods: WDEQ-A was administered to a sample of 1410 Australian women in mid-pregnancy. The dimensionality of WDEQ-A was explored using exploratory (EFA) and confirmatory factor analysis (CFA), and Rasch analysis. Results: EFA identified a four factor solution. CFA failed to support the unidimensional structure of the original WDEQ-A, but confirmed the four factor solution identified by EFA. Rasch analysis was used to refine the four subscales (Negative emotions: five items; Lack of positive emotions: five items; Social isolation: four items; Moment of birth: three items). Each WDEQ-A Revised subscale showed good fit to the Rasch model and adequate internal consistency reliability. The correlation between Negative emotions and Lack of positive emotions was strong, however Moment of birth and Social isolation showed much lower intercorrelations, suggesting they should not be added to create a total score. Conclusion: This study supports the findings of other investigations that suggest the WDEQ-A is multidimensional and should not be used in its original form. The WDEQ-A Revised may provide researchers with a more refined, psychometrically sound tool to explore the differential impact of aspects of childbirth fear.Full Tex

Embedding the concept of ecosystems services:The utilisation of ecological knowledge in different policy venues

The concept of ecosystem services is increasingly being promoted by academics and policy makers as a means to protect ecological systems through more informed decision making. A basic premise of this approach is that strengthening the ecological knowledge base will significantly enhance ecosystem health through more sensitive decision making. However, the existing literature on knowledge utilisation, and many previous attempts to improve decision making through better knowledge integration, suggest that producing ‘more knowledge’ is only ever a necessary but insufficient condition for greater policy success. We begin this paper by reviewing what is already known about the relationship between ecological knowledge development and utilisation, before introducing a set of theme issue papers that examine—for the very first time—how this politically and scientifically salient relationship plays out across a number of vital policy venues such as land-use planning, policy-level impact assessment, and cost–benefit analysis. Following a detailed synthesis of the key findings of all the papers, this paper identifies and explores new research and policy challenges in this important and dynamic area of environmental governance