Raymond Sung

Powder Mn2+ EPR spectra of 5-nm ZnS:Mn quantum dots have been analyzed in detail to account for all the observed fine spectral features. The same spectral features are observed in samples with low doping of Mn2+ (0.003−0.008%), showing 10 weak forbidden transitions between the six-line pattern of the MS = −1/2 to MS = 1/2 transition for the six MI values. Spectral simulations have been performed with the Simfonia program with parameters gxx = 2.0064, gyy = 2.0064, gzz = 2.0066, D = 37.4 × 10-4 cm-1, E = 12.5 × 10-4 cm-1, Axx = 63.9 × 10-4 cm-1, Ayy = 64.0 × 10-4 cm-1, and Azz = 64.4 × 10-4 cm-1, suggesting a lower than Td site symmetry for the doped Mn2+ in the cubic ZnS structure. At higher doping concentration (15.9%), a single broad line is observed with isotropic g and A.

OBJECTIVE: Comparison of the healing process in open osteotomy and closed fracture models that were used to study fracture healing. DESIGN: Randomized, prospective study in experimental animals, with a recovery duration of two and four weeks. SETTING: Unrestricted cage activity with weight bearing as tolerated. ANIMALS: Thirty-four skeletally mature, female New Zealand White rabbits. INTERVENTIONS: Closed fractures and open osteotomies of the tibial diaphysis were reduced and immobilized with four-pin, double-bar external fixators. MAIN OUTCOME MEASUREMENTS: Callus circumference was measured with a tape measure, bridging callus was assessed on biplane radiographs and evaluated histologically, and torsional stiffness and maximum torque were measured. RESULTS: Periosteum damage was more severe and hematoma formation was smaller in the osteotomy model, resulting in a delay in biological healing and restoration of the biomechanical properties. CONCLUSIONS: Investigators should consider the difference between the closed fracture and open osteotomy models when selecting an animal model to investigate fracture healing.

This paper describes a system for the automatic recognition of assembly features and the generation of disassembly sequences. The paper starts by reviewing the nature and use of assembly features. One of the conclusions drawn from this survey is that the majority of assembly features involve sets of spatially adjacent faces. Two principle types of adjacency relationships are identified and an algorithm is presented for identifying assembly features which arise from “spatial” and “contact” face adjacency relationships (known as s-adjacency and c-adjacency respectively). The algorithm uses an octree representation of a B-rep model to support the geometric reasoning required to locate assembly features on disjoint bodies. A pointerless octree representation is generated by recursively sub-dividing the assembly model’s bounding box into octants which are used to locate: 1. Those portions of faces which are c-adjacent (i.e. they effectively touch within the tolerance of the octree). 2. Those portions of faces which are s-adjacent to a nominated face. The resulting system can locate and partition spatially adjacent faces in a wide range of situations and at different resolutions. The assembly features located are recorded as attributes in the B-rep model and are then used to generate a disassembly sequence plan for the assembly. This sequence plan is represented by a transition state tree which incorporates knowledge of the availability of feasible gripping features. By way of illustration, the algorithm is applied to several trial components

This article describes a time-of-flight sensor based on multiple pulsed laser sources which utilizes time-correlated single-photon counting. The sensor has demonstrated good performance at ranges of up to 17 km in daylight conditions. Analysis techniques were developed to examine the returns from targets containing more than one scattering surface.