Escape of the German Army Across the Westerscheldt, September 1944

The writing of this article was made possible by Mr. K. Schacht (Steinkirchen), former officer of the Bundesmarine, who gave me the unpublished script of Mr. F. Roher. Mr. Roher belonged to the Kriegsmarine and took part in operations in the Dutch waters in 1944. He put together a captivating document. Some additional research had to be done to put it in a clear and complete perspective. The fact that a specially formed unit of the Kriegsmarine was able, in 15 days, to ferry across the Westerscheldt 100,000 men, 6,000 vehicles, 6,000 horse-drawn wagons and 750 pieces of artillery, undoubtedly lengthened the war and the occupation of a large part of the Netherlands. The evacuation across the Wester-Scheldt surely can be found in literature. The role of the Kriegsmarine, however, forms a forgotten chapter, even more so because the event was overshadowed by the long battle for the mouth of the Scheldt. Now, 50 years after the event, through examination of the facts gathered by Mr. Roher, we will have to admit this was a remarkable logistical operation that was perfectly executed under the most difficult conditions

E-Books: Cognitive and Visual Effects

Sight is incredibly important to daily life. One critical use of this sense is reading, which allows people to communicate and learn new things if the reader is able to effectively comprehend what he or she has read. The proliferation of technology has resulted in much of our reading today being done through digital media. Information-presenting screens are found nearly everywhere, including within the education system. While E-books can offer some advantages, their purpose would not be served if they hindered understanding. Additionally, excessive use of technological devices can bring about symptoms of eyestrain. It was hypothesized that E-books are in fact neither helpful nor harmful in reading comprehension but may increase reading time. In the present study, 40 students at Butler University read a short story either on paper or on a laptop screen. They then took a quiz over the plot events of the short story, either in a physical or digital format. Lastly, they completed a short survey regarding their use of E-books and how their technological interactions affect their vision. It was found that the only factor that affected quiz scores was the testing medium. It is important, then, to ensure that online exams are user-friendly

The Development of a Fiber Optic Raman Temperature Measurement System for Rocket Flows

A fiberoptic Raman diagnostic system for H2/O2 rocket flows is currently under development. This system is designed for measurement of temperature and major species concentration in the combustion chamber and part of the nozzle of a 100 Newton thrust rocket currently undergoing testing. This paper describes a measurement system based on the spontaneous Raman scattering phenomenon. An analysis of the principles behind the technique is given. Software is developed to measure temperature and major species concentrations by comparing theoretical Raman scattering spectra with experimentally obtained spectra. Equipment selection and experimental approach are summarized. This experimental program is part of a program, which is in progress, to evaluate Navier-Stokes based analyses for this class of rocket

Ka-band (32 GHz) allocations for deep space

At the 1979 World Administrative Conference, two new bands were allocated for deep space telecommunications: 31.8 to 32.3 GHz, space-to-Earth, and 34.2 to 34.7 GHz, Earth-to-space. These bands provide opportunity for further development of the Deep Space Network and its support of deep space research. The history of the process by which JPL/NASA developed the rationale, technical background, and statement of requirement for the bands are discussed. Based on this work, United States proposals to the conference included the bands, and subsequent U.S. and NASA participation in the conference led to successful allocations for deep space telecommunications in the 30 GHz region of the spectrum. A detailed description of the allocations is included

Frequency sharing between passive sensors and aeronautical radionavigation systems employing ground transponders in the band 4.2 - 4.4 GHz

The 4.2 to 4.4 GHz band is reserved for radio altimeters aboard aircraft and for associated transponders on the ground. A radar altimeter system which utilizes associated ground transponders is described and the feasibility of co-channel operation of such a system with a typical passive sensor is analyzed

A stabilization theorem for dynamics of continuous opinions

A stabilization theorem for processes of opinion dynamics is presented. The theorem is applicable to a wide class of models of continuous opinion dynamics based on averaging (like the models of Hegselmann-Krause and Weisbuch-Deffuant). The analysis detects self-confidence as a driving force of stabilization.Comment: 7 pages, no figures, first time presented at First Bonzenfreies Colloquium on Market Dynamics and Quantitative Economics, Sep 9/10 200

Laser Doppler Velocimetry for Joint Measurements of Acoustic and Mean Flow Velocities : LMS-based Algorithm and CRB Calculation

This paper presents a least mean square (LMS) algorithm for the joint estimation of acoustic and mean flow velocities from laser doppler velocimetry (LDV) measurements. The usual algorithms used for measuring with LDV purely acoustic velocity or mean flow velocity may not be used when the acoustic field is disturbed by a mean flow component. The LMS-based algorithm allows accurate estimations of both acoustic and mean flow velocities. The Cram\'er-Rao bound (CRB) of the associated problem is determined. The variance of the estimators of both acoustic and mean flow velocities is also given. Simulation results of this algorithm are compared with the CRB and the comparison leads to validate this estimator

Laser Rayleigh and Raman Diagnostics for Small Hydrogen/oxygen Rockets

Localized velocity, temperature, and species concentration measurements in rocket flow fields are needed to evaluate predictive computational fluid dynamics (CFD) codes and identify causes of poor rocket performance. Velocity, temperature, and total number density information have been successfully extracted from spectrally resolved Rayleigh scattering in the plume of small hydrogen/oxygen rockets. Light from a narrow band laser is scattered from the moving molecules with a Doppler shifted frequency. Two components of the velocity can be extracted by observing the scattered light from two directions. Thermal broadening of the scattered light provides a measure of the temperature, while the integrated scattering intensity is proportional to the number density. Spontaneous Raman scattering has been used to measure temperature and species concentration in similar plumes. Light from a dye laser is scattered by molecules in the rocket plume. Raman spectra scattered from major species are resolved by observing the inelastically scattered light with linear array mounted to a spectrometer. Temperature and oxygen concentrations have been extracted by fitting a model function to the measured Raman spectrum. Results of measurements on small rockets mounted inside a high altitude chamber using both diagnostic techniques are reported

Species and temperature measurement in H2/O2 rocket flow fields by means of Raman scattering diagnostics

Validation of Computational Fluid Dynamics (CFD) codes developed for prediction and evaluation of rocket performance is hampered by a lack of experimental data. Non-intrusive laser based diagnostics are needed to provide spatially and temporally resolved gas dynamic and fluid dynamic measurements. This paper reports the first non-intrusive temperature and species measurements in the plume of a 110 N gaseous hydrogen/oxygen thruster at and below ambient pressures, obtained with spontaneous Raman spectroscopy. Measurements at 10 mm downstream of the exit plane are compared with predictions from a numerical solution of the axisymmetric Navier-Stokes and species transport equations with chemical kinetics, which fully model the combustor-nozzle-plume flowfield. The experimentally determined oxygen number density at the centerline at 10 mm downstream of the exit plane is four times that predicted by the model. The experimental number density data fall between those numerically predicted for the exit and 10 mm downstream planes in both magnitude and radial gradient. The predicted temperature levels are within 10 to 15 percent of measured values. Some of the discrepancies between experimental data and predictions result from not modeling the three dimensional core flow injection mixing process, facility back pressure effects, and possible diffuser-thruster interactions