The diameter of the commuting graph of a finite group with trivial centre

The commuting graph of a finite group with trivial centre is examined. It is shown that the connected components of the commuting graph have diameter at most 10

Translatory shock absorber for attitude sensors

A translatory shock absorber is provided for mounting an attitude sensor thereon for isolating a sensor from translatory vibrations. The translatory shock absorber includes a hollow block structure formed as one piece to form a parallelogram. The absorber block structure includes a movable top plate for supporting the attitude sensor and a fixed base plate with opposed side plates interposed between. At the junctions of the side plates, and the base and top plates, there are provided grooves which act as flexible hinges for attenuating translatory vibrations. A damping material is supported on a pedestal which is carried on the base plate between the side plates thereof. The top of the damping material rests against the bottom surface of the top plate for eliminating the resonant peaks of vibration

THE IMPACT OF EMPLOYMENT EXPANSION ON RURAL COMMUNITY SERVICE EXPENDITURES: A SMALL AREA MODEL

Labor and Human Capital, Public Economics,

Practical quantum key distribution over a 48-km optical fiber network

The secure distribution of the secret random bit sequences known as "key" material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is a new technique for secure key distribution with single-photon transmissions: Heisenberg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non-orthogonal photon states to generate shared key material over multi-kilometer optical fiber paths and over line-of-sight links. In both cases, key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. Here we report the most recent results of our optical fiber experiment in which we have performed quantum key distribution over a 48-km optical fiber network at Los Alamos using photon interference states with the B92 and BB84 quantum key distribution protocols.Comment: 13 pages, 7 figures, .pdf format submitted to Journal of Modern Optic

A PROBIT MODEL ANALYSIS OF FACTORS AFFECTING CONSUMPTION OF FRESH SWEET CORN IN MAJOR U.S. MARKETS

In an effort to more effectively utilize its resources to promote fresh sweet corn, the Fresh Supersweet Corn Council contracted with the Florida Agricultural Market Research Center (FAMRC) of the University of Florida to conduct a comprehensive consumer survey. The consumer survey was designed to investigate consumer preferences, attitudes, and behavior regarding the purchase and consumption of fresh sweet corn. A total of 1,031 consumer telephone interviews were conducted in Dallas, Atlanta, Chicago, Boston and Philadelphia between September 7 and November 3, 2001. Respondents' revealed very limited consumption in the winter, spring, and fall seasons and consumers' perceptions that sweet corn is not available in these seasons. Probit models are estimated to determine effects of seasonalityConsumer/Household Economics,

Simultaneous Estimation of Time Delays and Quasar Structure

We expand our Bayesian Monte Carlo method for analyzing the light curves of gravitationally lensed quasars to simultaneously estimate time delays and quasar structure including their mutual uncertainties. We apply the method to HE1104-1805 and QJ0158-4325, two doubly-imaged quasars with microlensing and intrinsic variability on comparable time scales. For HE1104-1805 the resulting time delay of (Delta t_AB) = t_A - t_B = 162.2 -5.9/+6.3 days and accretion disk size estimate of log(r_s/cm) = 15.7 -0.5/+0.4 at 0.2 micron in the rest frame are consistent with earlier estimates but suggest that existing methods for estimating time delays in the presence of microlensing underestimate the uncertainties. We are unable to measure a time delay for QJ0158-4325, but the accretion disk size is log(r_s/cm) = 14.9 +/- 0.3 at 0.3 micron in the rest frame.Comment: 21 pages, 6 figures, submitted to Ap

Addressing student models of energy loss in quantum tunnelling

We report on a multi-year, multi-institution study to investigate student reasoning about energy in the context of quantum tunnelling. We use ungraded surveys, graded examination questions, individual clinical interviews, and multiple-choice exams to build a picture of the types of responses that students typically give. We find that two descriptions of tunnelling through a square barrier are particularly common. Students often state that tunnelling particles lose energy while tunnelling. When sketching wave functions, students also show a shift in the axis of oscillation, as if the height of the axis of oscillation indicated the energy of the particle. We find inconsistencies between students' conceptual, mathematical, and graphical models of quantum tunnelling. As part of a curriculum in quantum physics, we have developed instructional materials to help students develop a more robust and less inconsistent picture of tunnelling, and present data suggesting that we have succeeded in doing so.Comment: Originally submitted to the European Journal of Physics on 2005 Feb 10. Pages: 14. References: 11. Figures: 9. Tables: 1. Resubmitted May 18 with revisions that include an appendix with the curriculum materials discussed in the paper (4 page small group UW-style tutorial

A study of high-lift airfoils at high Reynolds numbers in the Langley low-turbulence pressure tunnel

An experimental study was conducted in the Langley Low Turbulence Pressure Tunnel to determine the effects of Reynolds number and Mach number on the two-dimensional aerodynamic performance of two supercritical type airfoils, one equipped with a conventional flap system and the other with an advanced high lift flap system. The conventional flap system consisted of a leading edge slat and a double slotted, trailing edge flap with a small chord vane and a large chord aft flap. The advanced flap system consisted of a leading edge slat and a double slotted, trailing edge flap with a large chord vane and a small chord aft flap. Both models were tested with all elements nested to form the cruise airfoil and with the leading edge slat and with a single or double slotted, trailing edge flap deflected to form the high lift airfoils. The experimental tests were conducted through a Reynolds number range from 2.8 to 20.9 x 1,000,000 and a Mach number range from 0.10 to 0.35. Lift and pitching moment data were obtained. Summaries of the test results obtained are presented and comparisons are made between the observed aerodynamic performance trends for both models. The results showing the effect of leading edge frost and glaze ice formation is given

Private Health Insurance Provisions of H.R. 3962

[Excerpt] This report summarizes key provisions affecting private health insurance, including provisions to raise revenues, in Division A of H.R. 3962, the Affordable Health Care for America Act, as introduced in the House of Representatives on October 29, 2009. H.R. 3962 is based on H.R. 3200, America’s Affordable Health Choices Act of 2009, which was originally introduced on July 14, 2009, and was reported separately on October 14, 2009, by three House Committees— Education and Labor, Energy and Commerce, and Ways and Means. Division A of H.R. 3962 focuses on reducing the number of uninsured, restructuring the private health insurance market, setting minimum standards for health benefits, and providing financial assistance to certain individuals and, in some cases, small employers. In general, H.R. 3962 would require individuals to maintain health insurance and employers to either provide insurance or pay a payroll assessment, with some exceptions. Several insurance market reforms would be made, such as modified community rating and guaranteed issue and renewal. Both the individual and employer mandates would be linked to acceptable health insurance coverage, which would meet required minimum standards and incorporate the market reforms included in the bill. Acceptable coverage would include (1) coverage under a qualified health benefits plan (QHBP), which could be offered either through the newly created Health Insurance Exchange (the Exchange) or outside the Exchange through new employer plans; (2) grandfathered employment based plans; (3) grandfathered nongroup plans; and (4) other coverage, such as Medicare and Medicaid. The Exchange would offer private plans alongside a public option. Based on income, certain individuals could qualify for subsidies toward their premium costs and cost-sharing (deductibles and copayments); these subsidies would be available only through the Exchange. In the individual market (the nongroup market), a plan could be grandfathered indefinitely, but only if no changes were made to the terms and conditions of that plan, including benefits and cost-sharing, and premiums were only increased as allowed by statute. Most of these provisions would be effective beginning in 2013. The Exchange would not be an insurer; it would provide eligible individuals and small businesses with access to insurers’ plans in a comparable way. The Exchange would consist of a selection of private plans as well as a public option. Individuals wanting to purchase the public option or a private health insurance not through an employer or a grandfathered nongroup plan could only obtain such coverage through the Exchange. They would only be eligible to enroll in an Exchange plan if they were not enrolled in Medicare, Medicaid, and acceptable employer coverage as a full-time employee. The public option would be established by the Secretary of Health and Human Services (HHS), would offer three different cost-sharing options, and would vary premiums geographically. The Secretary would negotiate payment rates for medical providers, and items and services. The bill would also require that the Health Choices Commissioner to establish a Consumer Operated and Oriented Plan (CO-OP) program under which the Commissioner would make grants and loans for the establishment of not-for-profit, member-run health insurance cooperatives. These co-operatives would provide insurance through the Exchange. Only within the Exchange, credits would be available to limit the amount of money certain individuals would pay for premiums and for cost-sharing (deductibles and copayments). (Although Medicaid is beyond the scope of this report, H.R. 3962 would extend Medicaid coverage for most individuals under 150% of poverty; individuals would be ineligible for Exchange coverage if they were eligible for Medicaid.