Strain Measurement Using Embedded Fiber Bragg Grating Sensors Inside an Anchored Carbon Fiber Polymer Reinforcement Prestressing Rod for Structural Monitoring

Results are reported from a study carried out using a series of Bragg grating-based optical fiber sensors written into a very short length (60 mm) optical fiber network and integrated into carbon fiber polymer reinforcement (CFPR) rod. Such rods are used as reinforcements in concrete structures and in tests were subjected to strain through a series of cycles of pulling tests, with applied forces of up to 30 kN. The results show that effective strain measurements can be obtained from the different sensors mounted along the rod. Additionally, the tests show that close agreement with the results obtained from the calibrated force applied by the pulling machine and from a conventional resistive strain gauge mounted on the rod itself is obtained. Calculations from strain to shear stress show a relatively uniform stress distribution along the bar anchor used. The results give confidence to results from various methods of in situ monitoring of strains on such CFRP rods when used in different engineering structures.     

Full vectorial finite-element-based imaginary distance beampropagation solution of complex modes in optical waveguides

In this paper, we address accurate computation of complex propagation constants and field distributions of different modes, in general, lossless and lossy optical dielectric waveguides. Using the vector finite-element formulation of the beam propagation method combined with the imaginary distance propagation technique, sequence of both the guided and leaky modes can be accurately calculated. To show the versatility and numerical precision of the proposed technique, we compute the modes of three different three-dimensional (3-D) waveguide structures and compare the results against those of other, different, vector formulations. Further, we present the design of a higher order mode filtering device, based on a 3-D leaky mode optical waveguide     

Speech recognition for the disabled

A simple and inexpensive system for telephone communication that includes a modular speech recognition device developed for use by a disabled person is presented. User considerations are reviewed, and hardware details are given. The complete automatic speech recognition (ASR) system consists of five main blocks: a TCM29C18 codec (analog interface for the digital signal processor), an SRS-1 speech recognizer, an LED display, a dual-tone multifrequency generator, and tone enable plus data input circuitry. Results of a semiqualitative assessment in terms of recognition success for the limited vocabulary of numbers and commands from the user are reported. The results are described in chronological order, beginning with testing of the SRS-1 and the codec working as a stand-alone recognizer system, and leading to the testing of the recognition system combined with the tone generator. Finally, results were obtained when the whole ASR system was interfaced to the telephone line. Some further work is suggested.     

Full vectorial finite-element solution of nonlinear bistable optical waveguides

The accurate computation of the propagation constants and field distributions of different modes in nonlinear optical dielectric waveguides is addressed in this paper. Using the vector finite-element formulation of the beam propagation method, combined with the imaginary distance propagation technique, both linear and nonlinear modes can be accurately calculated. The proposed technique is applied to obtain the fundamental TE nonlinear mode of a strip-loaded waveguide, and the excellent agreement seen with published results shows its high numerical precision.     

Stray light correction for diode-array-based spectrometers using a monochromator

Photodiode-array-based spectrometers are increasingly being used in a wide variety of applications. However, the signal measured by this type of instrument often is not what is anticipated by the user and is often subject to contamination from stray light. This paper describes an efficient and low-cost stray light correction approach based on a relatively simple system using a monochromator-based source. The paper further discusses the limitations of using a monochromator instead of a laser, as used by previous researchers, and its impact on the quality of the stray light correction. The reliability and robustness of the stray light correction matrix generated have been studied and are also reported.     

Temperature and nonlinearity corrections for a photodiode array spectrometer used in the field

Temperature and nonlinearity effects are two important factors that limit the use of photodiode array spectrometers. Usually the spectrometer is calibrated at a known temperature against a reference source of a particular spectral radiance, and then it is used at different temperatures to measure sources of different spectral radiances. These factors are expected to be problematic for nontemperature-stabilized instruments used for in-the-field experiments, where the radiant power of the site changes continuously with the sun tilt. This paper describes the effect of ambient temperature on a nontemperature-stabilized linear photodiode array spectrometer over the temperature range from 5?°C to 40?°C. The nonlinearity effects on both signal amplification and different levels of radiant power have also been studied and are presented in this paper.     

Nonepileptic posttraumatic seizures

BACKGROUND: The aim of this experimental study was to evaluate the risk of tumor recurrence after laparoscopic cecal resection (LCR) of colonic carcinoma in the rat. METHODS: The experimental cancer consisted of one million cells (DHK/K12), incorporated in an extracellular matrix, placed and secured to the cecal serosa in 110 BD9 rats. Four weeks later, all animals were reoperated through a laparotomy to control tumor growth, and animals with diffuse carcinomatosis were excluded. Eligible animals were randomized either to laparoscopic cecal resection (group LCR, n = 10), to open resection (group OCR, n = 13), or to a control group without resection (group C, n = 13). Resection was always considered as macrocopically complete. All animals were killed 4 weeks after the resection to determine the tumor recurrence and quantify carcinomatosis. RESULTS: We noted diffuse carcinomatosis in 70% of rats in groups C and LCR versus 23% in group OCR (p = 0.038). For tumors noted as S- (not extending outside the serosa), diffuse carcinomatosis was observed in all animals of group C (3 of 3), in 6 of 8 in group LCR, and 0 of 6 in group OCR (p = 0.004). The rate of port site or incisional metastases was not significantly different between groups. CONCLUSIONS: These preliminary results demonstrated the deleterious impact of the laparoscopy for resection of large bowel malignancy. LCR increased significantly the incidence of a diffuse carcinomatosis even when performed for locally noninvasive tumors (S-).     

Distinctive forms of partial retrograde amnesia after asymmetric temporal lobe lesions: possible role of the occipitotemporal gyri in memory

We tested the hypothesis that partial forms of retrograde amnesia were associated with highly asymmetric lesions to the inferior and anterior-medial temporal lobe. Postencephalitic subjects EK and DR were both impaired on standardized retrograde memory tests, but showed strikingly different profiles in cognitive tasks of name stem completion, name:face matching, temporal ordering, forced choice recognition, and occupational judgments of famous names and faces from the past 3 decades. EK sustained left inferior and anterior-medial temporal lobe lesion with a small right temporal polar lesion, and showed near-complete loss of retrieval, knowledge, and familiarity associated with famous names but minimal deficiencies with famous faces. DR sustained right inferior and anterior-medial temporal lobe lesion and showed a milder retrograde loss limited to utilizing famous face prompts in name stem completion, name:face matching, occupational judgments, and forced choice recognition. These impairments were also different from the memory retrieval deficit, but intact recognition shown by a case of ruptured anterior communicating artery aneurysm with presumed basal forebrain damage. We hypothesize that EK's extensive loss of famous name knowledge was related to left inferior temporal lobe damage, particularly in the lateral and medial occipitotemporal gyri. This region in the left temporal lobe may serve as a critical processing area for retrograde memory that permits activation of established semantic, temporal, and visual (i.e., facial) associations biographically dependent on the category of proper names. On the basis of connectional anatomy patterns in the nonhuman primate, this region receives extensive hippocampal output and is interconnected with the temporal polar region and cortical association areas, which have been implicated in retrieval and storage aspects of retrograde memory. In the right hemisphere, the occipitotemporal gyri may serve an important role in famous face processing as part of a bilateral neural network.     

A novel electronically scanned white-light interferometer using aMach-Zehnder approach

A theoretical analysis and experimental evaluation of a novel Mach-Zehnder interferometer (MZI), used as a recovery interferometer in an electronically scanned white-light interferometer is reported. This modified version of a MZI has the advantages of being very simple and compact, with high stability and does not introduce any spatial “misoverlapping” of the beams. In addition, since only one beamsplitter is employed in the interferometer (instead of the usual two used in a conventional MZI), the system is relatively easy to implement and at low cost. Furthermore, this configuration can be simply set to cover a wide range of optical path difference values by simply changing the angle and position of one of the mirrors. This gives the interferometer the advantage of being easily adapted far a range of different measurement applications     

Instantaneous fringe-order identification using dual broadband sources with widely spaced wavelengths

A new fringe-order identification technique for interferometric optical fibre sensors is described using dual broadband optical sources coupled with white-light interferometry. Compared with previous work, this technique enables the central (zero-order) fringe to be directly identified through its dominant amplitude, and does not require digitisation and its associated computing power. Therefore, it is suitable for coherence multiplexed quasidistributed sensors and for monitoring quickly varying measurands.<>