Fiber-optic miniature sensor for in situ temperature monitoring of curing composite material

This study proposes a fiber-optic temperature sensor with a single-mode fiber tip covered with a thermo-sensitive polymer resin. The temperature is sensed by measuring the Fresnel reflection from the optical fiber/polymer interface. Because the thermo-optic coefficients differ between the optical fiber and the polymer, the in situ temperature can be measured even in curing composite materials. In initial experiments, the proposed sensor successfully measured and recovered the temperature information. The measured sensor data were linearly correlated, with an R² exceeding 0.99. The standard deviation in the long-term measurements of constant temperature was 2.6%. The durability and stability of the sensor head material in long-term operation was validated by Fourier transform infrared spectroscopy and X-ray diffraction analysis. In further experiments, the suggested miniature temperature sensor obtained the internal temperatures of curing composite material over a wide range (30–110 °C).     

BCP ceramic microspheres as drug delivery carriers: synthesis,characterisation and doxycycline release

Resorbable ceramics such as biphasic calcium phosphates (BCP) are ideal candidates as drug delivery systems. The BCP ceramic is based on the optimum balance of the most stable hydroxyapatite (HA) phase and more soluble tricalcium phosphate phase (TCP). Doxycycline is a broad-spectrum antibiotic used for the local treatment of periodontitis. The development of BCP microspheres and its release kinetics with doxycycline have been studied. The BCP ceramic powder were prepared by microwave processing and characterised by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) methods. The BCP microspheres were formed by liquid immiscibility effect using gelatin and paraffin oil. Difference in the morphology of the microspheres as a function of gelatin content has been observed. Scanning electron microscope indicated spherical and porous morphology of the microspheres. Drug incorporation was studied at varying pH and the pH 7 was found to be optimal for drug loading. Release pattern tend to depend on the morphology of BCP microspheres. An optimum release of 80% drug has been observed for BCP microsphere with HA:TCP = 65:35 ratio. The surface area measurement results also correlate with drug release obtained.     

Study of viscoelastic effect on the frequency shift of microcantilever chemical sensors

Microcantilevers coated with a chemically sensitive layer are increasingly being used in chemical detection systems. The sensitive coating, often a polymer, absorbs specific molecules, which can be detected by monitoring the shift in the mechanical resonant frequency. Usually, the frequency shift resulting from molecular absorption is interpreted as a mass loading effect. However, mass loading is not the only effect that has an impact on the frequency shift; the viscoelastic properties of the sensitive coating also are affected by the sorption process. Sorption-induced modulus changes are typically difficult to characterize. However, it is known that the sorption of analyte molecules in a polymer coating results in the plasticization of the coating. In most cases, the polymer becomes more rubbery with increasing concentration of analyte molecules, i.e., the coating becomes softer with increasing loss modulus, and the storage modulus decreases. Using a new analytical model developed for the resonant frequency expression of a hybrid microcantilever (elastic base and viscoelastic layer), the effects of the modification of the storage and loss moduli of the sensitive layer on the resonant frequency are examined. The main conclusion of this analytical study is that, even if the sensitive coating moduli are small compared to the base cantilever's Young's modulus, the effect of the change in the viscoelastic coating properties could contribute significantly to the overall frequency shift (8-23% in the simulations depending on the coating thickness, with even higher contributions for other sets of problem parameters).     

Influence of quenching methods on martensitic transformation and mechanical properties of P/M processed Cu–Al–Ni–Ti shape memory alloys

The effect of quenching conditions on phase transformation characteristics and microstructural features of Cu–Al–Ni–Ti shape memory alloys (SMAs) have been studied. The alloys were synthesised via conventional powder metallurgy process using elemental metal powders. Four different quenching techniques, such as (a) two-step quenching, first to 100°C and then to 0°C; (b) two-step quenching, initially to 40°C and later to 0°C; (c) direct quenching to 40°C and (d) direct quenching to 0°C, were used. The microstructural features and phase transformations that the alloys had undergone were studied using FE-SEM and XRD techniques. The martensitic phase transformation analyses were carried out by differential scanning calorimeter while the mechanical properties were studied by microhardness and flexural bending tests. The results obtained clearly indicate that the quenching routes followed have a remarkable influence on the properties of Cu-based SMAs.     

Erosion studies on duplex and graded ceramic overlay coatings

The solid-particle erosion resistance of ceramic thermal barrier coatings (TBCs) is of considerable economic and industrial significance. Of additional significance to the service performance of these coatings is the effort to minimize the differences in coefficients of thermal expansion between the metallic substrate and the overlay TBC. A new design strategy toward this effort is the introduction of functionally graded interlayers between the metallic and ceramic layers. This research examines the role of interlayer grading, microstructure, and thermal cycling on the solid-particle erosion behavior of partially stabilized zirconia and alumina coatings at ambient and elevated temperatures. The results point to beneficial effects of grading and processing on the elevated temperature erosion response of these deposits.     

Relating aviation service difficulty reports to accident data for safety trend prediction

Commercial aviation fatalities are predicted (Fulwood et al., ‘Relating aviation service difficulty reports to accident data for safety trend prediction’, BNL Tech. Rpt 63018, March 1996) using linear superposition of the time-dependent spectra of key aircraft systems difficulties reporting in FAA's Service Difficulty Reports (SDR (DOT, FAA, ‘Flight standards service difficulty program’, Order 8010.2, Feb. 22, 1978, reissued 4:5/14/81)) data base. The fitting coefficients are found by a linear regression model (referred to as ‘the model’) to FAA's Accident Incident Data System (AIDS (DOT/FAA, ‘Aviation standards accident/incident data system—AIDS’, Users Guide VS ASAS-D-335, July 1982)) covering 5.5 years beginning January 1990. The model was tested by dividing the data approximately in half, using the first half to calibrate the model for prediction of the second half. A second test did the opposite. A third test used the first 60 months of data to predict the following 6 months. These tests (Fig. 5) showed good agreement between the model and AIDS data.The deficiency frequency of ATA (Aircraft Transportation Association) systems is reported (Table 2). Third-order fitting of the AIDS data was also used for prediction. All methods are compared in Fig. 4. The model was deemed superior because it reflects inspections and may be updated with SDR data from the Internet. The magnitude of the model's fitting coefficients indicate systems importances to the results.     

Robust controller design for temperature tracking problems in jacketed batch reactors

There is an increasing trend to employ advanced instrumentation and control strategies for batch processes where expensive products are being manufactured. In this paper, a robust nonlinear control strategy is developed for temperature tracking problems in batch reactors in the presence of parametric uncertainty. The controller has a multi-loop feedback configuration. An inner loop is designed for approximate input–output linearization of a nominal plant. The outer loop is designed for stability and robust performance by utilizing results from structured singular values (μ-synthesis). It is shown via simulation of a temperature tracking problem in batch synthesis that the controller provides excellent tracking despite parametric uncertainty.     

Nonlinear Gravitational and Radiation Aspects in Nanoliquid with Exponential Space Dependent Heat Source and Variable Viscosity

The nonlinear convective flow of kerosene-Alumina nanoliquid subjected to an exponential space dependent heat source and temperature dependent viscosity is investigated here. This study is focuses on augmentation of heat transport rate in liquid propellant rocket engine. The kerosene-Alumina nanoliquid is considered as the regenerative coolant. Aspects of radiation and viscous dissipation are also covered. Relevant nonlinear system is solved numerically via RK based shooting scheme. Diverse flow fields are computed and examined for distinct governing variables. We figured out that the nanoliquid’s temperature increased due to space dependent heat source and radiation aspects. The heat transfer rate is higher in case of changeable viscosity than constant viscosity.