The 30-cm ion thruster power processor

A power processor unit for powering and controlling the 30 cm Mercury Electron-Bombardment Ion Thruster was designed, fabricated, and tested. The unit uses a unique and highly efficient transistor bridge inverter power stage in its implementation. The system operated from a 200 to 400 V dc input power bus, provides 12 independently controllable and closely regulated dc power outputs, and has an overall power conditioning capacity of 3.5 kW. Protective circuitry was incorporated as an integral part of the design to assure failure-free operation during transient and steady-state load faults. The implemented unit demonstrated an electrical efficiency between 91.5 and 91.9 at its nominal rated load over the 200 to 400 V dc input bus range

Limiter Control of a Chaotic RF Transistor Oscillator

We report experimental control of chaos in an electronic circuit at 43.9 MHz, which is the fastest chaos control reported in the literature to date. Limiter control is used to stabilize a periodic orbit in a tuned collector transistor oscillator modified to exhibit simply folded band chaos. The limiter is implemented using a transistor to enable monitoring the relative magnitude of the control perturbation. A plot of the relative control magnitude vs. limiter level shows a local minimum at period-1 control, thereby providing strong evidence that the controlled state is an unstable periodic orbit (UPO) of the uncontrolled system

Memento Of A Region

The car sped down the highway. Many familiar hills and houses appeared on either side. The car gained speed as it headed down the hill. At the bottom, the highway leveled of!\u27 across the bridge spanning the deep ravine. The noise of the automobile took on a new, hollow sound as it rolled upon the bridge. I looked over the valley spreading out to the left. How warm and green the valley was! How blue the sky was! How familiar it all was

Annual Survey of Virginia Law: Civil Practice and Procedure

Virginia courts and the General Assembly have effected several changes in civil practice and procedure during the past year. This article focuses on some significant developments and interests to the general litigation attorney

Annual Survey of Virginia Law: Civil Practice and Procedure

Virginia courts and the General Assembly have effected a number of changes in civil practice and procedure during the past year. This article focuses on some significant developments of interest to the general litigation attorney. Matters affecting real property, juveniles, and construction laws are treated elsewhere in this volume

Benefits Of Inmate Employment Programs: Evidence From The Prison Industry Enhancement Certification Program

The United States is experiencing a persistent increase in its prison population and, consequently, a steady increase in public spending on incarceration. A possible systemic change to mitigate these trends is a return to historically cost effective inmate labor programs. Government savings and business revenues from these programs have been documented. Additional benefits have been hypothesized from an associated reduction in recidivism. This paper examines if this recidivism effect occurs following inmate participation in the Prison Industry Enhancement Certification Program (PIECP). Inmate characteristics and PIECP participation variables are identified as potential predictors of recidivism. Logit regression procedures, including a two-stage instrumental variable procedure to address endogeneity, are used to capture the predictive value of the independent variables and quantify the reduction in the odds of inmate recidivism attributable to PIECP participation. The results indicate that employment in a PIECP program contributes to a statistically significant reduction in the odds of inmate recidivism

Ownership Structure, Property Performance, Multifamily Properties and REITs

This research extends literature that empirically evaluates the impact of ownership and management structure on property level performance. The results show that multifamily properties owned and managed by real estate investment trusts (REITs) generate higher effective rents at the property level than non-REIT-owned properties. After controlling for positive operating scale and brand effects, REIT property level performance is better than non-REIT property level performance in the market studied. The REIT structure represents diversified scale operators with property management skills. The results imply that the structure of property ownership can impact property performance.

Extremely asymmetrical scattering in gratings with varying mean structural parameters

Extremely asymmetrical scattering (EAS) is an unusual type of Bragg scattering in slanted periodic gratings with the scattered wave (the +1 diffracted order) propagating parallel to the grating boundaries. Here, a unique and strong sensitivity of EAS to small stepwise variations of mean structural parameters at the grating boundaries is predicted theoretically (by means of approximate and rigorous analyses) for bulk TE electromagnetic waves and slab optical modes of arbitrary polarization in holographic (for bulk waves) and corrugation (for slab modes) gratings. The predicted effects are explained using one of the main physical reasons for EAS--the diffractional divergence of the scattered wave (similar to divergence of a laser beam). The approximate method of analysis is based on this understanding of the role of the divergence of the scattered wave, while the rigorous analysis uses the enhanced T-matrix algorithm. The effect of small and large stepwise variations of the mean permittivity at the grating boundaries is analysed. Two distinctly different and unusual patterns of EAS are predicted in the cases of wide and narrow (compared to a critical width) gratings. Comparison between the approximate and rigorous theories is carried out.Comment: 16 pages, 5 figure

Eucalyptus virginea and E. relicta (Myrtaceae), two new rare forest trees from south-western Australia allied to E. lane-poolei, and a new phantom hybrid

Hopper, S.D. & Wardell-Johnson, G. Eucalyptus virginea and E. relicta (Myrtaceae), two new rareforest trees from south-western Australia allied to E. lane-poolei, and a new phantom hybrid. Nuytsia 15(2): 227-240 (2004). Eucalyptus virginea and E. relicta are described from Mt Lindesay National Park and from the Whicher Range south-east of Busselton respectively. Both species, together with E. lane-poolei, are in the earliest branching clade of E. ser. Curviptera, which contains many horticulturally attractive large-flowered mallees from semi-arid and desert regions such as E. macrocarpa and E. youngiana. The discovery and description of these two rare relictual forest trees so recently highlights the need for ongoing botanical survey of south-western Australia's forests. A phantom hybrid, Eucalyptus lane-poolei x relicta, is also described for the first time. It occurs close to populations of E. relicta in the Whicher Range but 150 km south of the nearest recorded E. lane-poolei

Status of Tree Snails (Gastropoda: Partulidae) on Guam, with a Resurvey of Sites Studied by H. E. Campton in 1920

Tree snails of the family Partulidae have declined on Guam since World War II. One species, indigenous to the western Pacific, Partula radiolata, is still locally common along stream courses in southern areas of the island. The Mariana Island endemic Samoana fragilis is present but not found in abundance anywhere on Guam. Partula gibba, another Mariana endemic, is currently known only from one isolated coastal valley along the northwestern coast, and appears to be in a state of decline. The Guam endemic Partula salifana was not found in areas where it had been previously collected by earlier researchers, and is thus believed to be extinct. The decline and extinction of these snails are related to human activities. The single most important factor is likely predation by snails that were introduced as biological control agents for the giant African snail, Achatina fulica. The current, most serious threat is probably the introduced flatworm Platydemus manokwari. This flatworm is also the likely cause of extinctions of other native and introduced gastropods on Guam and may be the most important threat to the Mariana Partulidae