Abstract

Abstract
In recent years the need to monitor different parameters has led to the development of several architectures able to make real time, un-attended measurements. Particularly in regard to environmental issues, it is very important that the equipment and measuring systems be small and light to avoid maximum interference of the ecosystems Studied. In this context, optical fibre sensors have become extremely attractive for use in natural environments to monitor different parameters of biological interest, due to their intrinsic small weight and size and low reactivity to chemical and biological parameters. In this paper we present an innovative and technologically advanced system for the simultaneous measurement of temperature and salinity based on optical fibre Bragg grating sensors and on an optical sensing cable especially designed for large-scale and distributed or quasi-distributed measurements. A prototype of this optical cable was installed in the Mira Channel at Ria de Aveiro, Portugal. Temperature variation during three weeks from 4 to 23 June 2002 is investigated and presented here.

Abstract
An intensity-referenced temperature-independent curvature-measurement technique that uses a smart composite that comprises two chirped fiber Bragg gratings is demonstrated. The two gratings are embedded on opposite sides of the composite laminate and act simultaneously as curvature sensors and as wavelength discriminators, enabling a temperature-independent intensity-based scheme to measure radius of curvature. Also, the system's performance is independent of arbitrary power losses that are induced in the lead fibers to the sensing head. It is demonstrated that the measurement range depends on the relative positions of the chirped fiber Bragg gratings and on their spectral bandwidths. By using two chirped fiber Bragg gratings with bandwidths W-1 = 2.8 nm and W-2 = 3.7 nm and with central wavelengths at lambda(01) = 1560.3 nm and lambda(02) - 1563.7 nm, we obtained a resolution of 1.6 mm/(1)Hz for the measurement of the radius of curvature (similar to R = 350 mm) over the measurement range 190 mm < R < infinity. (c) 2005 Optical Society of America.

Abstract
BM_virtual enterprise (BM_VE) is a virtual enterprise (VE) in a total or partial conformance with the BM_virtual enterprise architecture reference model (BM_VEARM). BM_VE is a kind of VE characterized as a dynamically reconfigurable network integrated over the global domain, satisfying the requirements for integrability, distributivity, agility, and virtuality as competitiveness factors. BM_VE uses three main mechanisms, or tools: market of resources, broker, and virtuality. This chapter presents the three fundamental mechanisms for the VE reconfiguration dynamics and virtuality; introduces the basic concept of the BM_VEARM, which serves as the conceptual and formal base for building BM_VE instances; shows the formal specification and theory of the structural aspects of the BM_VE as well as some aspects of the BM_VE reconfiguration dynamics; presents the BM_VE as an agile/virtual enterprise (A/VE); and finally, describes some important consequences of virtuality in BM_VE, i.e., that the BM_VE structure is hierarchical, a new definition of the VE (in which the network as the VE characteristic is irrelevant from the operational unit's point of view), and the process of a "traditional" enterprise virtualization. © 2005, Idea Group Inc.

Abstract
This paper addresses objectification, a formal specification technique which inspects the potential for object-orientation of a declarative model and brings the 'implicit objects' explicit. Criteria for such objectification are formalized and implemented in a runnable prototype tool which embeds VDM-SL into VDM++. The paper also includes a quick presentation of a (coinductive) calculus of such generated objects, framed as generalised Moore machines.

Abstract
In optical coherence tomography (OCT). it is often assumed that the signal-to-noise ratio is limited by shot noise. However, a high data acquisition rate and a low target reflectivity require operation under high optical power. Balance detection is used with the aim to bring the noise close to shot noise regime, but this is not all the time achievable in practice. If the balance detection is ideal, the limiting factor is the beat noise. This is proportional to the stray reflectance in the object arm and inverse proportional to the effective noise bandwidth. It was often noticed that the limiting theoretical value for the S/N ratio for a given stray reflectance and optical source bandwidth could not be experimentally achieved. In the present study, we develop a new model where we address this issue by taking into account the limited spectral response of fiber based balanced detection receivers. We show that due to mismatches in the balanced receiver, excess photon noise has a larger contribution than normally expected. with important implications in the maximum achievable SNR. The theoretical model developed leads to a redefinition of the effective noise bandwidth to take into account the non-flat response of the directional coupler used in the balanced stage. The model is capable to explain the limitation of SNR observed in practice when stray reflectances within the interferometer are brought to infinitesimal values. The model guides optimization of parameters in order to maximize system performance. for a given optical source power and directional coupler characteristics. In this paper we present experimental results to validate the theoretical model. Such S/N analysis is paramount in the modem OCT technology. which makes use of wide bandwidth sources in the quest for high-depth resolution.