Online Testing of MEMS Based on Encoded Stimulus Superposition

This article presents a technique that enables online testing of sensors through the superposition of the test stimulus onto the measurand. Perturbations due to the surrounding environment can very often introduce fluctuations in the test output creating a major concern for this type of sensor testing. In this paper, a signal processing technique is proposed where the test stimulus is encoded by a pseudo-random sequence in order to reduce the test output fluctuations. The trade-off between the level of rejection of a perturbation and the overall test time is studied. In the case of the MEMS accelerometer considered in this paper, it is theoretically demonstrated that the rejection is more than 20 dB for a test time of 2.55 s. Furthermore, excessively strong perturbations can be monitored so that the test status is updated only if the accuracy of the test signal permits so. The technique has been implemented on a demonstration board and validated on a vibration platform.

Broad-band second-harmonic generation in holey optical fibers

Holey fibers are shown to have an ideal geometry for efficient parametric processes due to their tailorable modal properties. These fibers can have the additional advantage of single-mode operation at all the interacting wavelengths. We demonstrate theoretically that by appropriate choice of holey fiber geometry, these fibers can be up to four orders of magnitude more efficient for second harmonic generation than conventional poled fibers     

The Future of Web Services

Much of the Web's success can be attributed to its simplicity. It offers a straightforward means by which static information could be published and interconnected on a global basis. The Web Services initiative effectively adds computational objects to the static information of yesterday's Web and as such offers a distributed services capability over a network. Web Services have the potential to create new paradigms for both the delivery of software capabilities and the models by which networked enterprises will trade. Today's Web Services technology, useful though it is, will be enhanced over the next 2-5 years by the harnessing of Semantic Web technology to deliver a step change in capability. Web Services provide an easy way to make existing (or indeed new) components available to applications via the Internet. However, currently, Web Services are essentially described using semi-structured natural language mechanisms, which means that considerable human intervention is needed to find and combine Web Services into an end application. The Semantic Web will enable the accessing of Web resources by semantic content rather than just by keywords. Resources (in this case Web Services) are defined in such a way that they can be automatically ‘understood’ and processed by machine. This will enable the realisation of Semantic Web Services, involving the automation of service discovery, acquisition, composition and monitoring. Software agents will be able automatically to create new services from already published services, with potentially huge implications for models of eBusiness. Having identified limitations in current Web Services technology, this paper will survey existing research in Semantic Web Services, most notably USA's DAML-S initiative and the European WSMF work, and describe BT's research into creating a set of tools to support next-generation Semantic Web Services. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fibre Bragg grating compression-tuned over 110 nm

A fibre Bragg grating with a tuning range covering beyond the C- and L-bands has been realised, which represents the broadest tuning range reported of any Bragg grating. The device exhibits constant spectral response and polarisation mode dispersion within these bands.     

Self-starting, passively mode-locked Fabry-Perot fiber solitonlaser using nonlinear polarization evolution

The authors demonstrate pure self-starting mode-locked operation in a fiber Fabry-Perot cavity. The laser produces 1.6 ps transform-limited soliton pulses by means of nonlinear polarization evolution in conjunction with an intracavity fiber polarizer. This laser system can be used for the generation and study of soliton pulses in the picosecond regime. With a careful choice of the fiber dispersion and fiber length, the system should also be able to operate in the femtosecond regime. The advantage of the system over existing self-starting fiber soliton lasers is that an optical isolator (an expensive component) is not required. The replacement of the two mirrors with fiber reflection gratings would make this configuration a truly all-fiber device     

Rotary injection reaction injection molding (RI-RIM). Part II: Interfacial segregation of release systems

This paper describes the shear imposed interfacial segregation of release systems for the facilitated attenuation of polyurethane (PU) adhesion to metal coun-terfaces using a RI-RIM system. It is shown that the migration rate of the dispersed release additives due to a shear imposed stress in the resin fluid is much greater than that arising from Fickian diffusion, thereby removing a vital constraint from conventional practice. The novel rotary injection RIM system is presented to simulate the on-line injection and shear induced interfacial segregation in model PU/abherent systems. A wide range of recipes comprising single (liquids or solids) and multicomponent (liquid-liquid and solid-liquid) release materials were injected into the polymerizing resin mixture to provide cohesively weak and friable “particle” boundary layer assemblies at the PU/metal interface. An instrumented Blister Test was employed to evaluate the quality of the molded interfaces in terms of adhesion and the concentration distribution of the injected species in the final cured moldings was determined through high pressure liquid chromatography (HPLC). A comparison of the results on the shear modified and the compounded interfaces confirm an accentuated lateral migration of the additives to the interface resulting in an appreciable diminution in the adhesion of the system. Finally, transport models are suggested to account for the observed augmented transport.     

Traveling Reaction Zone Method for Preparation of Textured Ceramic Superconductor Thick Films

Textured thick films of superconducting YBa₂Cu₃O_7−x (YBCO) have been prepared on ceramic substrates using a traveling reaction zone method. The technique utilizes the rapid reaction between Y₂Cu₂O₅ and BaCuO₂ to form YBCO as the film passes through a steep temperature gradient furnance. The films consist of a single continuous superconducting phase with strong c -axis orientation normal to the translation direction of the film.     

Development of Agrometeorological Crop Model Inputs from Remotely Sensed Information

The goal of developing agrometeorological crop model inputs from remotely sensed information (AgRISTARS Early Warning/Crop Condition Assessment Project Subtask 5 within the U. S. Department of Agriculture (USDA)) provided a focus and a mission for crop spectral investigations that would have been lacking otherwise. Because the task had never been attempted before, much effort has gone into developing measurement and interpretation skill, convincing the Scientific community of the validity and information content of the spectral measurements, and providing new understanding of the crop scenes viewed as affected by bidirectional, atmospheric, and soil background variations. Nonetheless, experiments conducted demonstrate that spectral vegetation indices (VI) a) are an excellent measure of the amount of green photosynthetically active tissue present in plant stands at any time during the season, and b) can reliably estimate leaf area index (LAI) and intercepted photosynthetically active radiation (IPAR)-two of the inputs needed in agrometeorological models. Progress was also made on using VI to quantify the effects of yield-detracting stresses on crop canopy development. In a historical perspective, these are significant accomplishments in a short time span. Spectral observations of fields from aircraft and satellite make direct checks on LAI and IPAR predicted by the agrometeorological models feasible and help extend the models to large areas. However, newness of the spectral interpretations, plus continual revisions in agrometeorological models and lack of feedback capability in them, have prevented the benefits of spectral inputs to agrometeorological models from being fully realized.     

Effect of cetylpyridinium chloride on pathogenic fungi and Nocardia asteroides in sputum

The effect of cetylpyridinium chloride (CPC) on pathogenic fungi and Nocardia asteroides was studied. Sputa seeded with each of 11 organisms (Aspergillus flavus; Aspergillus fumigatus, Blastomyces dermatitidis, Candida albicans, Coccidioides immitis, Cryptococcus neoformans, Geotrichum candidum, Histoplasma capsulatum; Nocardia asteroides, Paracoccidioides brasiliensis, and Sporothrix schenckii) were treated with CPC and kept for 2, 5 and 9 days. The CPC reagent used (0.5% CPC and 0.5% sodium chloride) is one the Mycobacteriolgoy Branch at the Center for Disease Control added to sputa before shipping them to laboratories for recovery of mycobacteria. None of the organisms tested survived this treatment, and none was recovered on mycological or mycobacteriological media. Seeded sputa containing these organisms were also tested with a second CPC reagent (0.02% CPC and 0.5% sodium chloride) and held for 2, 5 and 9 days. A few colonies of A. flavus, A. fumigatus, and N. asteroides were recovered from these samples. Neither the morphology of the fungi nor their stainability by the fluorescent antibody method was affected by treatment with the reagent containing 0.5% CPC. However, the background material in smears from the 0.5% CPC-treated samples retained the conjugate, and this made weakly fluorescing organisms more difficult to detect. The 0.5% CPC treatment did not alter the morphology of N. asteroides or its ability to be stained with Kinyoun acid-fast stain.     

Psychomotor and intellectual development after deep hypothermia and circulatory arrest in early infancy

Somatic, psychomotor, and intellectual development were studied in 11 patients who had total correction of congenital cardiac malformation in early infancy by the method of surface-induced deep hypothermia and circulatory arrest up to 43 minutes. Time between operation and re-evaluation ranged from 3 to 11 years (average 7 years). Somatic development was normal in all children. Psychomotor and intellectual behavior, measured by a battery of specially adapted test methods, failed to show a statistically significant difference when compared between the study group, a matched control group, and the normal population. Normal scores in psychomotor tests and normal intelligence quotients (I.Q.) were present in 8 patients; mental retardation was found in 2 patients: and unstable behavior, evident from different tests, was present in one. Except for the last case, in none of the patients was the method was found to be the primary cause of the abnormal behavior. Deep hypothermia and circulatory arrest in early infancy does not appear to have a negative influence on somatic, psychomotor, or intellectual development.