Yet Another Graph Partitioning Problem is NP-Hard

Recently a large number of graph separator problems have been proven to be \textsc{NP-Hard}. Amazingly we have found that $\alpha$-Subgraph-Balanced-Vertex-Separator, an important variant, has been overlooked. In this work ``Yet Another Graph Partitioning Problem is NP-Hard" we present the surprising result that $\alpha$-Subgraph-Balanced-Vertex-Separator is $NP$-Hard. This is despite the fact that the constraints of our new problem are harder to satisfy than the original problem

The influence of laser hardening on wear in the valve and valve seat contact

In internal combustion engines it is important to manage the wear in the valve and valve seat contact in order to minimise emissions and maximise economy. Traditionally wear in this contact has been controlled by the use of a valve seat insert and the careful selection of materials for both the valve and the insert. More recently, due to the increasing demands for both performance and cost, alternative methods of controlling the wear, and the resulting valve recession, have been sought. Using the heating effect of a laser to induce localised phase transformations, to increase hardness and wear resistance, in materials has been used since the 1970s, however it is only in recent years that it has been able to compete with more established surface treatment techniques, particularly in terms of cost, as new laser hardware has been developed. In this work, a laser has been used to treat the valve seat area of a cast iron cylinder head. In order to optimise the laser parameters for use on the head, preliminary tests were carried out to investigate the fundamental wear characteristics of untreated cast iron and also cast iron with a range of laser treatments. Previous work has identified the predominant wear mechanism in the valve and valve seat contact as impact on valve closure. Two bespoke test machines, one for testing basic specimens and one for testing components, were used to identify the laser parameters most likely to yield acceptable results when applied to a cylinder head to be used in a fired dynamometer test. © 2009 Elsevier B.V. All rights reserved

Effect of solid propellant rocket exhaust impingement on spacecraft materials Final report, 18 Mar. 1966 - 21 Feb. 1969

Solid propellant rocket exhaust impingement effect on spacecraft material

An Image Based Feature Space and Mapping for Linking Regions and Words

We propose an image based feature space and define a mapping of both image regions and textual labels into that space. We believe the embedding of both image regions and labels into the same space in this way is novel, and makes object recognition more straightforward. Each dimension of the space corresponds to an image from the database. The coordinates of an image segment(region) are calculated based on its distance to the closest segment within each of the images, while the coordinates of a label are generated based on their association with the images. As a result, similar image segments associated with the same objects are clustered together in this feature space, and should also be close to the labels representing the object. The link between image regions and words can be discovered from their separation in the feature space. The algorithm is applied to an image collection and preliminary results are encouraging

Human safety in the lunar environment

Any attempt to establish a continuously staffed base or permanent settlement on the Moon must safely meet the challenges posed by the Moon's surface environment. This environment is drastically different from the Earth's, and radiation and meteoroids are significant hazards to human safety. These dangers may be mitigated through the use of underground habitats, the piling up of lunar materials as shielding, and the use of teleoperated devices for surface operations. The lunar environment is detailed along with concepts for survival

Bacteriology of select aquatic hosts utilized in lunar sample exposure studies Final report

Procedures and immunofluorescent techniques for screening Apollo aquatic test animals for bacterial pathogens after lunar sample exposur

Aerospace engineers: We're tomorrow-minded people

Brief job-related autobiographical sketches of engineers working on NASA aerospace projects are presented. Career and educational guidance is offered to students thinking about entering the aerospace field