A Growing Self-Organizing Network for Reconstructing Curves and Surfaces

Self-organizing networks such as Neural Gas, Growing Neural Gas and many others have been adopted in actual applications for both dimensionality reduction and manifold learning. Typically, in these applications, the structure of the adapted network yields a good estimate of the topology of the unknown subspace from where the input data points are sampled. The approach presented here takes a different perspective, namely by assuming that the input space is a manifold of known dimension. In return, the new type of growing self-organizing network presented gains the ability to adapt itself in way that may guarantee the effective and stable recovery of the exact topological structure of the input manifold

Explicit excluded volume of cylindrically symmetric convex bodies

We represent explicitly the excluded volume Ve{B1,B2} of two generic cylindrically symmetric, convex rigid bodies, B1 and B2, in terms of a family of shape functionals evaluated separately on B1 and B2. We show that Ve{B1,B2} fails systematically to feature a dipolar component, thus making illusory the assignment of any shape dipole to a tapered body in this class. The method proposed here is applied to cones and validated by a shape-reconstruction algorithm. It is further applied to spheroids (ellipsoids of revolution), for which it shows how some analytic estimates already regarded as classics should indeed be emended

Retraction with face saving: Modelling conversational interaction through dynamic hypermedia

This paper describes RWFS (Retraction With Face Saving), a hypermedia application which models an interview between a lawyer and his client ‐ a lorry driver ‐ facing court charges of reckless driving. At one level RWFS takes the form of a sophisticated game in which different outcomes to the interview are possible according to the learner's degree of skill. At another level, RWFS is designed to encourage the language learner's awareness and understanding of the pragmatic features of conversation. RWFS runs on HyperContext, a hybrid hypertextlexpert system developed in Pavia by two of the authors, Marco Piastra and Roberto Bolognesi, and which supports dynamic hypermedia units. HyperContext's dynamic linking capacity plays a vital role in simulating significant conversational features such as the conditioning of a current move in the conversation by information acquired much earlier in the course of the interview. In this connection, the paper discusses the contribution of RMCI (Re‐usable Model of Conversational Interaction), a re‐usable application‐independent applied model of interaction on which the game is based, and which links a tactical level (the conversation) to a metalevel which provides a move‐by‐move commentary on interactional theory. In its turn, RMCFs metalevel is linked to a strategic level which interprets the structure of the conversation in terms of a pyramid‐like hierarchy of increasingly abstract theoretical concepts

Some Further Evidence about Magnification and Shape in Neural Gas

Neural gas (NG) is a robust vector quantization algorithm with a well-known mathematical model. According to this, the neural gas samples the underlying data distribution following a power law with a magnification exponent that depends on data dimensionality only. The effects of shape in the input data distribution, however, are not entirely covered by the NG model above, due to the technical difficulties involved. The experimental work described here shows that shape is indeed relevant in determining the overall NG behavior; in particular, some experiments reveal richer and complex behaviors induced by shape that cannot be explained by the power law alone. Although a more comprehensive analytical model remains to be defined, the evidence collected in these experiments suggests that the NG algorithm has an interesting potential for detecting complex shapes in noisy datasets

Cosmogenic activation of xenon and copper

Rare event search experiments using liquid xenon as target and detection medium require ultra-low background levels to fully exploit their physics potential. Cosmic ray induced activation of the detector components and, even more importantly, of the xenon itself during production, transportation and storage at the Earth's surface, might result in the production of radioactive isotopes with long half-lives, with a possible impact on the expected background. We present the first dedicated study on the cosmogenic activation of xenon after 345 days of exposure to cosmic rays at the Jungfraujoch research station at 3470m above sea level, complemented by a study of copper which has been activated simultaneously. We have directly observed the production of 7Be, 101Rh, 125Sb, 126I and 127Xe in xenon, out of which only 125Sb could potentially lead to background for a multi-ton scale dark matter search. The production rates for five out of eight studied radioactive isotopes in copper are in agreement with the only existing dedicated activation measurement, while we observe lower rates for the remaining ones. The specific saturation activities for both samples are also compared to predictions obtained with commonly used software packages, where we observe some underpredictions, especially for xenon activation.Comment: 9 pages, 11 figure

Italians in the ‘Old Shanghai’: a Preliminary Contribution

Besides other Western nationalities, ‘Old Shanghai’ also hosted an Italian community, which experienced, throughout the years, a slight development, particularly after the establishment there of the consulate of the Kingdom of Sardinia in 1860 (later kept by the new Kingdom of Italy), and the signing, in 1866, of a Sino-Italian Treaty (ratified in Shanghai in 1867). It was a small group, if compared with the English, the Americans or the French (from some dozens to some hundreds between the 19th and the 20th centuries), but it had distinctive spatial and socio-economic urban patterns: in ‘Old Shanghai’, there were specific areas with a high concentration of Italian economic activities (in the International Settlement: Kiukiang Road; Kiangse Road; crossroads between Nanking Road and Szechuen Road; Bubbling Well Road), areas with Italian residences (French Concession), other suburban areas with Italians (Zikawei; in this case, they were priests). Moreover, Italians were involved in specific economic sectors (primarily, silk): as the textile sector was developed mainly in Lombardy at that time, most of the expatriate Italian managers and supervisors in Shanghai mills came from this Italian region. The migration flow from Italy to ‘Old Shanghai’, involving highly educated or highly skilled people mainly from Northern Italy, represented an exception in the general context of the migrations from Italy between the 19th and 20th centuries, which was mostly based, as in the case of the flow of people directed to the USA in that period, on poor and poorly educated people, originally involved in the primary sector, from the Southern regions of Italy