Temperature-Independent Strain Sensor Based on a Hi-Bi Photonic Crystal Fiber Loop Mirror

This work presents an optical sensor based on a highly birefringent photonic crystal fiber (Hi-Bi PCF) loop mirror. The length of the sensing head is 380 mm and its corresponding wavelength spacing between two interferometer minima is 8 nm. The optical sensor was characterized in strain and in temperature with an uncoated Hi-Bi PCF and with an acrylate coated Hi-Bi PCF. Different results for strain and temperature sensitivity were obtained. Relatively to the strain measurement, the sensor with the uncoated Hi-Bi PCF presents slightly less sensitivity (1.11 ) when compared with coated Hi-Bi PCF (1.21 ). For the temperature measurement and with the uncoated Hi-Bi PCF, the optical sensor is insensitive to temperature (0.29 pm/K).     

On the design and development of a new BTA tool to increase productivity and workpiece accuracy in deep hole machining

This paper presents the design and method of development of a new three-pad BTA tool. The advantages of this cutting tool over a conventional two-pad BTA tool are brought out using a probabilistic approach in both the static and dynamic case. Experiments were conducted with the new three-pad tool, and it confirmed the theoretical prediction that the three-pad tool is more stable than the conventional BTA tool. Also, the cause of grooves observed on the workpiece produced by the two-pad tool has been explained. Further, it is observed that the third pad stiffens the tool thereby improving the chip breaking effect which improves the quality of the holes produced at high feeds. Thus this new development increases the productivity and improves workpiece accuracy in deep hole machining.     

Radio-Frequency Self-Referencing Technique With Enhanced Sensitivity for Coarse WDM Fiber Optic Intensity Sensors

A self-referenced passive optical network (PON) with coarse wavelength division multiplexing (CWDM) is reported for remotely addressing optical intensity sensors with enhanced sensitivity. The self-referencing remote configuration is described as a finite-impulse-response (FIR) filter in reflective operation using two fiber Bragg gratings (FBG) and a fiber delay line. The antisymmetrical phase response of the configuration permits to achieve a self-referencing measurement parameter two times more sensitive than reported previously. To enhance the power budget of the network, CWDM devices with low insertion losses are used for spectral splitting of a radio-frequency (RF) modulated broadband light source (BLS). The network topology and the sensor's interrogation technique are theoretically analyzed and experimental results validating the models are reported.     

Development of vegetable extracts by microencapsulation

The microencapsulation of essential oils offers protection against oxidation and evaporation, and allows the concurrent utilization of several vegetable extracts. Complex coacervation methods have been described for essential oils. Even though microencapsulation involves wrapping the essential oils in shells, some difficulties arise in the process of stabilizing the essential oils: oil may be lost by evaporation and partial dissolution in the water-gelatin phase and this will vary with the type of essential oil being encapsulated. In order to investigate the efficacy of the gelatin-polyphosphate methods we analysed their essential oil microcapsules peppermint and rosemary, in particular their granulometric size distribution, oil content (%) and encapsulation yield (%). In addition the essential oils were analysed by GC before and after microencapsulation so as to investigate the loss of their components during the process.     

Optimal Placement of Phasor Measurement Units Using a Modified Canonical Genetic Algorithm for Observability Analysis

This paper proposes a method for optimal placement of synchronized PMUs （phasor measurement units） in electrical power systems using a MCGA （modified canonical genetic algorithm）, which the goal is to determine the minimum number of PMUs, as well as the optimal location of these units to ensure the complete topological observability of the system. In case of more than one solution, a strategy of analysis of the design matrix rank is applied to determine the solution with the lower number of critical measurements. In the proposed method of placement, modifications are made in the crossover and mutation genetic operators, as well as in the formation of the subpopulation, and are considered restrictive hypotheses in the search space to improve the performance in solving the optimization problem. Simulations are performed using the IEEE 14-bus, IEEE 30-bus and New England 39-bus test systems. The proposed method is applied on the IEEE 118-bus test system considering the presence of observable zones formed by conventional measurements.     

Sampled fibre Bragg grating sensors for simultaneous strain andtemperature measurement

A new scheme is presented for simultaneous measurement of strain and temperature using a sampled fibre Bragg grating based on a long period structure written using the electric arc technique. The temperature and strain measurement resolutions are estimated to be ±0.50°C/√Hz and ±3.38 μϵ/√Hz, respectively     

Strain and Temperature Discrimination Using Concatenated High-Birefringence Fiber Loop Mirrors

In this letter, a new configuration for simultaneous strain and temperature discrimination is presented using two concatenated high-birefringence (Hi-Bi) fiber loop mirrors. The first loop mirror includes a Hi-Bi photonic crystal fiber, while the second one contains a length of internal elliptical cladding fiber. It is shown that by monitoring the wavelength and optical power of one of the peaks of the system spectral transfer function, it is possible to obtain information that permits the simultaneous measurement of strain and temperature.     

Frequency Modulated Continuous Wave System for Optical Fiber Intensity Sensors With Optical Amplification

We report on the use of erbium doped fiber (EDF) amplification to enhance a frequency modulated continuous wave (FMCW) technique for referencing optical intensity sensors located between two Bragg grating structures. The experiment combines the concept of FMCW with the spectrally selective mirror properties of Bragg gratings to interrogate with referencing properties intensity based sensors. The interrogation system without amplification yields a sensor resolution of around 0.078 dB. When the EDF amplifier is introduced into the experimental set up, the sensor sensitivity does not change, but the signal-to-noise ratio is improved, resulting into an enhanced resolution of 0.025 dB. We also obtain a remote sensing operation at a location of 50 km, showing the feasibility of this configuration to be used as a remote sensing application.     

An investigation into the influence of helix angle on the torque-thrust coupling effect in twist drills

This paper presents an experimental investigation into the torque-thrust coupling effect in twist drills. A set of cross-coupling stiffness coefficients (K_ft and K_tf) are defined. The influence of helix angle on torsional and the cross-coupling stiffnesses is studied. The coupling interaction (as measured by K_ft and K_tf) is strongly influenced by the helix angle and has a distinct maxima around 28°. Also, the magnitudes of the coefficients increase parabolically with drill diameter. The pure torsional stiffness also has a maxima around the same helix angle. Under axial restraint, the torsional stiffness increases by 10 to 25% owing to the coupling effect. The larger the torque-thrust interaction, the larger is this increase in torsional stiffness. The findings of this investigation is proposed as a probable basis for the traditional popularity of a 28 to 30° helix angle for drills.