The Star Formation Histories and Efficiencies of Two Giant HII Regions in M33

$UBV$ photometry is used to re-identify the OB associations which power the two most luminous HII regions in M33, NGC 604 and NGC 595. There is a significant difference (2-3 Myr) in the ages of the most recent star formation episode in these two regions, while NGC 595 also has undergone a prior episode of star formation (10-15 Myr ago). These data, combined with the presence of molecular clouds in the heart of NGC 604, suggest that molecular clouds may survive at least one intense episode of massive star formation. The star formation efficiencies (mass of stars per mass of gas) of these two HII regions are up to a factor of 3 larger than the average efficiency in the inner disk of M33 or in Galactic molecular clouds, but are still only 2-5\%.Comment: 26 pages including 2 figures, uuencoded compressed postscript file (Figure 1 not available electronically). Accepted to Ap

The electrical response matrix of a regular 2n-gon

Consider a unit-resistive plate in the shape of a regular polygon with 2n sides, in which even-numbered sides are wired to electrodes and odd-numbered sides are insulated. The response matrix, or Dirichlet-to-Neumann map, allows one to compute the currents flowing through the electrodes when they are held at specified voltages. We show that the entries of the response matrix of the regular 2n-gon are given by the differences of cotangents of evenly spaced angles, and we describe some connections with the limiting distributions of certain random spanning forests.Comment: 10 pages, 4 figures; v2 adds more background informatio

Behavior of composite bolted joints at elevated temperature

Experimental results from an investigation which examines the combined effects of temperature, joint geometry and out-of-plane constraint upon the response of mechanically fastened composite joints are presented. Data are presented for simulated mechanically fastened joint conditions in two laminate configurations fabricated from Hercules AS/3501-6 graphite-epoxy. Strength and failure mode results are presented for the test temperatures of 21 C, 121 C and 177 C and for a range of the geometric parameters W/D and e/D from 3.71 to 7.43 and 1.85 to 3.69, respectively. A hole diameter, D of 5.16 mm was utilized for all tests. Pin bearing tests with out-of-plane constraint were conducted at room temperature only. All elevated temperature data were generated for pin bearing conditions. Ultrasonic C scan inspection of the failed specimens was employed to assess the damage region and to determine failure mode. Comparative data are presented for pin bearing and out-of-plane constraint conditions for the above mentioned joint configurations. The joint under pin loading was modeled by two dimensional finite element methods. Predicted net section strain concentrations were compared with experimental results

Influence of constituent properties and geometric form on behavior of woven fabric reinforced composites

Th potential for woven fabric composite forms to increase the interlaminar strength and toughness properties of laminated composite septems is studied. Experimental and analytical studies were performed on a z-axis fabric

Methods of resistance estimation in permanent magnet synchronous motors for real-time thermal management

Real-time thermal management of electrical ma- chines relies on sufficiently accurate indicators of internal tem- perature. One indicator of temperature in a permanent-magnet synchronous motor (PMSM) is the stator winding resistance. Detection of PMSM winding resistance in the literature has been made on machines with relatively high resistances, where the resistive voltage vector is significant under load. This paper describes two techniques which can be applied to detect the winding resistance, through ‘Fixed Angle’ and ‘Fixed Mag- nitude’ current injection. Two further methods are described which discriminate injected current and voltages from motoring currents and voltages: ‘Unipolar’ and ‘Bipolar’ separation. These enable the resistance to be determined, and hence the winding temperature in permanent-magnet machines. These methods can be applied under load, and in a manner that does not disturb motor torque or speed. The method distinguishes between changes in the electro-motive force (EMF) constant and the resistive voltage. This paper introduces the techniques, whilst a companion paper covers the application of one of the methods to a PMSM drive system

Induced scattering of short radio pulses

Effect of the induced Compton and Raman scattering on short, bright radio pulses is investigated. It is shown that when a single pulse propagates through the scattering medium, the effective optical depth is determined by the duration of the pulse but not by the scale of the medium. The induced scattering could hinder propagation of the radio pulse only if close enough to the source a dense enough plasma is presented. The induced scattering within the relativistically moving source places lower limits on the Lorentz factor of the source. The results are applied to the recently discovered short extragalactic radio pulse.Comment: submitted to Ap