Ranging and tracking system for proximity operations, phase 1

A study task is reported which is directed towards developing a conceptual design of a small, lightweight range and range rate radar sensor system to meet NASA's requirements for accurate short-range and velocity measurements in an orbital environment. Within the context of the requirements, the short range implies system operation at 0 m to 1850 m (6000 ft) and accurate implies a range measurement to within 1 sigma accuracy of 0.20 m (0.67 ft) and a range rate (velocity) measurement to within 1 sigma accuracy of 0.01 m/sec (0.033 ft/sec)

Narrow-band optical filter through phase conjugation by nondegenerate four-wave mixing in sodium vapor

An ultrahigh-Q tunable optical filter with a FWHM bandwidth of 41 MHz is demonstrated. The filtering is produced by nondegenerate phase conjugation through four-wave mixing in atomic-sodium vapor. The filter is observed to have a maximum quantum efficiency of 4 x 10^-3. However, degenerate phase-conjugation experiments in sodium suggest that a quantum efficiency of greater than unity can be attained on a cw basis

A quasi-real-time inertialess microwave holographic imaging system

This thesis records the theoretical analysis and hardware development of a laboratory microwave imaging system which uses holographic principles. The application of an aperture synthesis technique and the electronic commutation of all antennae has resulted in a compact and economic assembly - which requires no moving parts and which, consequently, has a high field mapping speed potential. The relationship of this microwave holographic system to other established techniques is examined theoretically and the performance of the imaging system is demonstrated using conventional optically- and numerically-based reconstruction of the measured holograms. The high mapping speed potential of this system has allowed the exploitation of an imaging mode not usually associated with microwave holography. In particular, a certain antenna array specification leads to a versatile imaging system which corresponds closely in the laboratory scale to the widely used synthetic aperture radar principle. It is envisaged that the microwave holographic implementation of this latter principle be used as laboratory instrumentation in the elucidation of the interaction of hydrodynamic and electromagnetic waves. Some simple demonstrations of this application have been presented, and the concluding chapter also describes a suitable hardware specification. This thesis has also emphasised the hardware details of the imaging system since the development of the microwave and other electronic components represented a substantial part of this research and because the potential applications of the imaging principle have been found to be intimately linked to the tolerances of the various microwave components. Bibliography: pages 122-132

One Strike and You\u27re Out? Constitutional Constraints on Zero Tolerance in Public Education

Notwithstanding the popularity of zero tolerance policies, the resulting denial of public education to massive numbers of children threatens irreparable damage, not only to these individuals but to all of us. This Article assesses the intended and unintended consequences of public school zero tolerance policies and details a number of constitutional infirmities of such policies that could provide an avenue for reform. We begin in Part I with a description of the multifaceted role that zero tolerance has come to play in public schools. Part II examines the rationale and actual impact of zero tolerance as school policy, and Part III explores what we argue are significant constitutional constraints on use of this policy to deny schoolchildren a public education. After assessing the as-yet-unresolved status of educational rights in the federal Constitution, we delineate a number of reasons why expulsions from the public school system may be constitutionally impermissible under both state education provisions and federal and state equal protection clauses

Space Shuttle program communication and tracking systems interface analysis

The Space Shuttle Program Communications and Tracking Systems Interface Analysis began April 18, 1983. During this time, the shuttle communication and tracking systems began flight testing. Two areas of analysis documented were a result of observations made during flight tests. These analyses involved the Ku-band communication system. First, there was a detailed analysis of the interface between the solar max data format and the Ku-band communication system including the TDRSS ground station. The second analysis involving the Ku-band communication system was an analysis of the frequency lock loop of the Gunn oscillator used to generate the transmit frequency. The stability of the frequency lock loop was investigated and changes to the design were reviewed to alleviate the potential loss of data due the loop losing lock and entering the reacquisition mode. Other areas of investigation were the S-band antenna analysis and RF coverage analysis

BCS-BEC Crossover in Atomic Fermi Gases with a Narrow Resonance

We determine the effects on the BCS-BEC crossover of the energy dependence of the effective two-body interaction, which at low energies is determined by the effective range. To describe interactions with an effective range of either sign, we consider a single-channel model with a two-body interaction having an attractive square well and a repulsive square barrier. We investigate the two-body scattering properties of the model, and then solve the Eagles-Leggett equations for the zero temperature crossover, determining the momentum dependent gap and the chemical potential self-consistently. From this we investigate the dependence of the crossover on the effective range of the interaction.Comment: 12 pages, 14 figure

Simultaneous imaging of the near- and far-field intensity distributions of the Ni-like Sn X-ray laser

We report two-dimensional near-field imaging experiments of the 11.9-nm Sn X-ray laser that were performed with a set of novel Mo/Y multilayer mirrors having reflectivities of up to ∼40% at normal and at 45° incidence. Second-moment analysis of the X-ray laser emission was used to determine values of the X-ray beam propagation factor M2 for a range of irradiation parameters. The results reveal a reduction of M2 with increasing prepulse intensity. The spatial size of the output is a factor of ∼2 smaller than previously measured for the 14.7-nm Pd X-ray laser, while the distance of the X-ray emission with respect to the target surface remains roughly the sam

Attention orienting by gaze and facial expressions across development

This article may not exactly replicate the final version published in the APA journal ©. It is not the copy of record. To view the final vesion go to http://psycnet.apa.org/doi/10.1037/a0030463.Processing of facial expressions has been shown to potentiate orienting of attention toward the direction signaled by gaze in adults, an important social-cognitive function. However, little is known about how this social attention skill develops. This study is the first to examine the developmental trajectory of the gaze orienting effect (GOE), its modulations by facial expressions, and its links with theory of mind (ToM) abilities. Dynamic emotional stimuli were presented to 222 participants (7-25 years old) with normal trait anxiety using a gaze-cuing paradigm. The GOE was found as early as 7 years of age and decreased linearly until 12-13 years, at which point adult levels were reached. Both fearful and surprised expressions enhanced the GOE compared with neutral expressions. The GOE for fearful faces was also larger than for joyful and angry expressions. These effects did not interact with age and were not driven by intertrial variance. Importantly, the GOE did not correlate with ToM abilities as assessed by the "Reading the Mind in the Eyes" test. The implication of these findings for clinical and typically developing populations is discussed

Some Remarks on Group Bundles and C*-dynamical systems

We introduce the notion of fibred action of a group bundle on a C(X)-algebra. By using such a notion, a characterization in terms of induced C*-bundles is given for C*-dynamical systems such that the relative commutant of the fixed-point algebra is minimal (i.e., it is generated by the centre of the given C*-algebra and the centre of the fixed-point algebra). A class of examples in the setting of the Cuntz algebra is given, and connections with superselection structures with nontrivial centre are discussed.Comment: 22 pages; to appear on Comm. Math. Phy