Test method for telescopes using a point source at a finite distance

A test method for telescopes that makes use of a focused ring formed by an annular aperture when using a point source at a finite distance is evaluated theoretically and experimentally. The results show that the concept can be applied to near-normal, as well as grazing incidence. It is particularly suited for X-ray telescopes because of their intrinsically narrow annular apertures, and because of the largely reduced diffraction effects

Test plane uniformity analysis for the MSFC solar simulator lamp array

A preliminary analysis was made on the solar simulator lamp array. It is an array of 405 tungsten halogen lamps with Fresnel lenses to achieve the required spectral distribution and collimation. A computer program was developed to analyze lamp array performance at the test plane. Measurements were made on individual lamp lens combinations to obtain data for the computer analysis. The analysis indicated that the performance of the lamp array was about as expected, except for a need to position the test plane within 2.7 m of the lamp array to achieve the desired 7 percent uniformity of illumination tolerance

MSFC solar simulator test plane uniformity measurement

The equipment and procedure used to measure the test plane uniformity produced by the MSFC 405 lamp solar simulator array are described along with details of the computer program used to analyze the measurement data. The results of the first measurement show the uniformity not to be as good as expected. The best uniformity obtained had a standared deviation of 4 percent with peak-to-peak values of + or - 11 percent

Laser furnace technology for zone refining

A carbon dioxide laser experiment facility is constructed to investigate the problems in using a laser beam to zone refine semiconductor and metal crystals. The hardware includes a computer to control scan mirrors and stepper motors to provide a variety of melt zone patterns. The equipment and its operating procedures are described

System for the measurement of ultra-low stray light levels

An apparatus is described for measuring the effectiveness of stray light suppression light shields and baffle arrangements used in optical space experiments and large space telescopes. The light shield and baffle arrangement and a telescope model are contained in a vacuum chamber. A source of short, high-powered light energy illuminates portions of the light shield and baffle arrangement and reflects a portion of same to a photomultiplier tube by virtue of multipath scattering. The resulting signal is transferred to time-channel electronics timed by the firing of the high energy light source allowing time discrimination of the signal thereby enabling the light scattered and suppressed by the model to be distinguished from the walls and holders around the apparatus

Progress on the Development of the UAS C2 Link and Supporting Spectrum - from LOS to BLOS

In order to provide for the safe integration of unmanned aircraft systems (UAS) into the National Airspace System, the control and non-payload communications (CNPC) link connecting the ground-based pilot with the unmanned aircraft must be highly reliable and robust, based upon standards that enable certification. Both line-of-sight (LOS) links using terrestrial-based communications and beyond-line-of-sight (BLOS) links using satellite communications are required to support UAS operations. The development of standards has been undertaken by RTCA Special Committee 228 (SC-228), with supporting technical data developed by NASA under the UAS in the National Airspace (NAS) Project. As a result of this work minimum operational performance standards (MOPS) have been completed and published for the LOS CNPC system. The second phase of work, for both NASA and RTCA involves the BLOS CNPC systems. The development of technical data to support MOPS development for UAS BLOS satellite-based CNPC links has now been initiated by NASA, and RTCA SC-228 has organized itself to begin the MOPS development process. This paper will provide an overview of the work that has been completed to date by the Communications Subproject in support of LOS C2 communications for UAS followed by an update of plans and progress for the BLOS phase of the project, with the focus on the UAS C2 spectrum aspects

A systematic review of naturalistic interventions in refugee populations

Naturalistic interventions with refugee populations examine outcomes following mental health interventions in existing refugee service organisations. The current review aimed to examine outcomes of naturalistic interventions and quality of the naturalistic intervention literature in refugee populations with the view to highlight the strengths and limitations of naturalistic intervention studies. Database search was conducted using the search terms ‘refugee’, ‘asylum seeker’, ‘treatment’, ‘therapy’ and ‘intervention. No date limitations were applied, but searches were limited to articles written in English. Seven studies were identified that assessed the outcome of naturalistic interventions on adult refugees or asylum seekers in a country of resettlement using quantitative outcome measures. Results showed significant variation in the outcomes of naturalistic intervention studies, with a trend towards showing decreased symptomatology at post-intervention. However, conclusions are limited by methodological problems of the studies reviewed, particularly poor documentation of intervention methods and lack of control in the design of naturalistic intervention studies. Further examination of outcomes following naturalistic interventions is needed with studies which focus on increasing the rigour of the outcome assessment process

Exact Thermodynamics of the Double sinh-Gordon Theory in 1+1-Dimensions

We study the classical thermodynamics of a 1+1-dimensional double-well sinh-Gordon theory. Remarkably, the Schrodinger-like equation resulting from the transfer integral method is quasi-exactly solvable at several temperatures. This allows exact calculation of the partition function and some correlation functions above and below the short-range order (``kink'') transition, in striking agreement with high resolution Langevin simulations. Interesting connections with the Landau-Ginzburg and double sine-Gordon models are also established.Comment: 4 pages, 3 figures (embedded using epsf), uses RevTeX plus macro (included). Minor revision to match journal version, Phys. Rev. Lett. (in press

Noise-Induced Phase Space Transport in Two-Dimensional Hamiltonian Systems

First passage time experiments were used to explore the effects of low amplitude noise as a source of accelerated phase space diffusion in two-dimensional Hamiltonian systems, and these effects were then compared with the effects of periodic driving. The objective was to quantify and understand the manner in which ``sticky'' chaotic orbits that, in the absence of perturbations, are confined near regular islands for very long times, can become ``unstuck'' much more quickly when subjected to even very weak perturbations. For both noise and periodic driving, the typical escape time scales logarithmically with the amplitude of the perturbation. For white noise, the details seem unimportant: Additive and multiplicative noise typically have very similar effects, and the presence or absence of a friction related to the noise by a Fluctuation-Dissipation Theorem is also largely irrelevant. Allowing for colored noise can significantly decrease the efficacy of the perturbation, but only when the autocorrelation time becomes so large that there is little power at frequencies comparable to the natural frequencies of the unperturbed orbit. Similarly, periodic driving is relatively inefficient when the driving frequency is not comparable to these natural frequencies. This suggests strongly that noise-induced extrinsic diffusion, like modulational diffusion associated with periodic driving, is a resonance phenomenon. The logarithmic dependence of the escape time on amplitude reflects the fact that the time required for perturbed and unperturbed orbits to diverge a given distance scales logarithmically in the amplitude of the perturbation.Comment: 15 pages, including 13 Figures and 1 Table, uses Phys. Rev. macro

Explorations, Vol. 4, No. 1

Articles include: Cover: Old Yarmouth Light, 1960, Cape Forchu, Nova Scotia. By and from the collection of Edgar McKay. The Borderlands Concept: a new look at U.S.-Canada relations, by Victor Konrad and Lauren McKensey Fundy Tidal Power Project, by Gregory White Canadian Poet: Ken Norris Native American Life and Art: a celebration, November, 1986, by Lee-Ann Konrad The Montreal Canadiens: a cultural institution, by James J. Herlan U.S. and Canadian Executives: uses of formal and informal plans in top executive decision-making, by Kent Carter Our Cover Artist: bits and pieces of one man\u27s Nova Scotia, by Edgar McKay The Canadian-American Center and the Canadian Collection of the Fogler Library, by Alice Stewart Capitalist Development in the New England-Atlantic Provinces Region, by Robert H. Babcock Atlantic Canadian Members of Parliament as Representatives, by Howard Cody The Rower and the Pyramid: a tribute to Joe Walsh, by Edward D. Ives The Canadian-American Center: exercise in excellence, by Rand Erb Canadian and Maine Potatoes: a bushel of questions, by George K. Griner, Alan S. Kezis, and James D. Leiby After 20: the Future of the Canadian-American Center, by Victor Konra