30,837 research outputs found

### Investigation of Mechanical Properties of Cryogenically Treated Music Wire

It has been reported that treating music wire (high carbon steel wire) by
cooling to cryogenic temperatures can enhance its mechanical properties with
particular reference to those properties important for musical performance. We
use such wire for suspending many of the optics in Advanced LIGO, the upgrade
to LIGO - the Laser Interferometric Gravitational-Wave Observatory. Two
properties that particularly interest us are mechanical loss and breaking
strength. A decrease in mechanical loss would directly reduce the thermal noise
associated with the suspension, thus enhancing the noise performance of mirror
suspensions within the detector. An increase in strength could allow thinner
wire to be safely used, which would enhance the dilution factor of the
suspension, again leading to lower suspension thermal noise. In this article we
describe the results of an investigation into some of the mechanical properties
of music wire, comparing untreated wire with the same wire which has been
cryogenically treated. For the samples we studied we conclude that there is no
significant difference in the properties of interest for application in
gravitational wave detectors

### Span programs and quantum algorithms for st-connectivity and claw detection

We introduce a span program that decides st-connectivity, and generalize the
span program to develop quantum algorithms for several graph problems. First,
we give an algorithm for st-connectivity that uses O(n d^{1/2}) quantum queries
to the n x n adjacency matrix to decide if vertices s and t are connected,
under the promise that they either are connected by a path of length at most d,
or are disconnected. We also show that if T is a path, a star with two
subdivided legs, or a subdivision of a claw, its presence as a subgraph in the
input graph G can be detected with O(n) quantum queries to the adjacency
matrix. Under the promise that G either contains T as a subgraph or does not
contain T as a minor, we give O(n)-query quantum algorithms for detecting T
either a triangle or a subdivision of a star. All these algorithms can be
implemented time efficiently and, except for the triangle-detection algorithm,
in logarithmic space. One of the main techniques is to modify the
st-connectivity span program to drop along the way "breadcrumbs," which must be
retrieved before the path from s is allowed to enter t.Comment: 18 pages, 4 figure

### Evaluation of live human-computer music-making: Quantitative and qualitative approaches

NOTICE: this is the author’s version of a work that was accepted for publication in International Journal of Human-Computer Studies. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in International Journal of Human-Computer Studies, [VOL 67,ISS 11(2009)] DOI: 10.1016/j.ijhcs.2009.05.00

### Synchronizing Sequencing Software to a Live Drummer

Copyright 2013 Massachusetts Institute of Technology. MIT allows authors to archive published versions of their articles after an embargo period. The article is available at

### On the pathwidth of almost semicomplete digraphs

We call a digraph {\em $h$-semicomplete} if each vertex of the digraph has at
most $h$ non-neighbors, where a non-neighbor of a vertex $v$ is a vertex $u
\neq v$ such that there is no edge between $u$ and $v$ in either direction.
This notion generalizes that of semicomplete digraphs which are
$0$-semicomplete and tournaments which are semicomplete and have no
anti-parallel pairs of edges. Our results in this paper are as follows. (1) We
give an algorithm which, given an $h$-semicomplete digraph $G$ on $n$ vertices
and a positive integer $k$, in $(h + 2k + 1)^{2k} n^{O(1)}$ time either
constructs a path-decomposition of $G$ of width at most $k$ or concludes
correctly that the pathwidth of $G$ is larger than $k$. (2) We show that there
is a function $f(k, h)$ such that every $h$-semicomplete digraph of pathwidth
at least $f(k, h)$ has a semicomplete subgraph of pathwidth at least $k$.
One consequence of these results is that the problem of deciding if a fixed
digraph $H$ is topologically contained in a given $h$-semicomplete digraph $G$
admits a polynomial-time algorithm for fixed $h$.Comment: 33pages, a shorter version to appear in ESA 201

### Entrepreneurs'' attitude towards the computer and its effect on e-business adoption

This paper presents research exploring further the concept that many SMEs do not adopt computer based technologies due to decision maker's negative attitudes towards computers generally. Importantly, by assessing the entrepreneur's belief structure, we provide quantitative evidence how SMEs, particularly micros, are affected. Earlier research that addresses technology acceptance model (TAM) suggests that TAM parameters are particularly influential factors of e-commerce adoption, as perceived by top managers of SMEs. The model we develop is tested using a sample of 655 enterprises. The information was gathered, via a telephone survey of UK SMEs, from decisions makers in the enterprise. Technically, the paper uses k-means cluster analysis to segment respondents using the TAM perceptions, ease of use, usefulness and enjoyment. Based on two determined segments we look at the differential rate of adoption of internet, and the potential adoption of new e-collaborative technologies like video conferencing and electronic whiteboards. The diffusion of internet for low IT utility (LIT) segments was considerably slower than in the high utility segment (HIT). Similarly, the anticipated adoption of e-collaboration technologies was much lower for LIT than HIT. Interestingly, we find that LIT is populated by more micro SMEs than HIT. The results we present are limited however as our sample is considerably underweight in micro SMEs, suggesting that the problem may be much larger in the economy than our model predicts. For policy makers, this research confirms the value of knowledge transfer programs to SMEs in the form of technology support. Our research shows that organisations which have dedicated IT support will tend to be more advanced technologically than those that do not. The implication for entrepreneurs is if they can be persuaded that a technological route is beneficial to them, and that suitable support can be provided via KT, then operational efficiency gains could be made. This paper contributes to knowle

### The search for innovators and early adopters of e-collaborative technologies within small and medium sized enterprises in the UK

New product diffusion theory predicts that innovators and early adopters are critical to the success of new innovations. The rate at which enterprises adopt e-Science technologies must therefore rely upon reliable market intelligence so that the critical early stages of adoption are successfully navigated by developers and planners. Failure to understand attitudes towards new technologies can lead to even useful technologies being under-adopted. This paper applies a survey based methodology to develop estimates of demand for web based virtual Collaborative technologies. We show that approximately 76% of the 1029 firms that we interviewed are technologically ready to deploy these technologies. We also show that 10% of all firms are ready look at these technologies as solutions to collaborative problem solving

### Passive and active seismic isolation for gravitational radiation detectors and other instruments

Some new passive and active methods for reducing the effects of seismic disturbances on suspended masses are described, with special reference to gravitational radiation detectors in which differential horizontal motions of two or more suspended test masses are monitored. In these methods it is important to be able to determine horizontal seismic accelerations independent of tilts of the ground. Measurement of changes in inclination of the suspension wire of a test mass, relative to a direction defined by a reference arm of long period of oscillation, makes it possible to carry this out over the frequency range of interest for earth-based gravitational radiation detectors. The signal obtained can then be used to compensate for the effects of seismic disturbances on the test mass if necessary. Alternatively the signal corresponding to horizontal acceleration can be used to move the point from which the test mass is suspended in such a way as to reduce the effect of the seismic disturbance and also damp pendulum motions of the suspended test mass. Experimental work with an active anti-seismic system of this type is described

### Maximum Edge-Disjoint Paths in $k$-sums of Graphs

We consider the approximability of the maximum edge-disjoint paths problem
(MEDP) in undirected graphs, and in particular, the integrality gap of the
natural multicommodity flow based relaxation for it. The integrality gap is
known to be $\Omega(\sqrt{n})$ even for planar graphs due to a simple
topological obstruction and a major focus, following earlier work, has been
understanding the gap if some constant congestion is allowed.
In this context, it is natural to ask for which classes of graphs does a
constant-factor constant-congestion property hold. It is easy to deduce that
for given constant bounds on the approximation and congestion, the class of
"nice" graphs is nor-closed. Is the converse true? Does every proper
minor-closed family of graphs exhibit a constant factor, constant congestion
bound relative to the LP relaxation? We conjecture that the answer is yes.
One stumbling block has been that such bounds were not known for bounded
treewidth graphs (or even treewidth 3). In this paper we give a polytime
algorithm which takes a fractional routing solution in a graph of bounded
treewidth and is able to integrally route a constant fraction of the LP
solution's value. Note that we do not incur any edge congestion. Previously
this was not known even for series parallel graphs which have treewidth 2. The
algorithm is based on a more general argument that applies to $k$-sums of
graphs in some graph family, as long as the graph family has a constant factor,
constant congestion bound. We then use this to show that such bounds hold for
the class of $k$-sums of bounded genus graphs

### Evidence for extended IR emission in NGC2798 and NGC6240

Extended emission at 10 and 20 microns can be used to distinguish starbursts from monsters as the underlying energy source driving the luminous infrared emission in the central regions of galaxies. The spatial extent of the mid infrared emission in the interacting galaxy NCG 2798 and the merger NGC 6240 were investigated. The 10 and 20 micron profiles of the IR source in NGC 2798 are significantly wider than beam profiles measured on a standard star, supporting a starburst interpretation of its IR luminosity. For NGC 6240 there is marginal evidence for an extended 10 micron source, suggesting that a significant fraction of its IR luminosity could be produced by a burst of star formation

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