Infrared thin layer drying of saffron (Crocus sativus L.) stigmas: Mass transfer parameters and quality assessment

Saffron is the most precious and expensive agricultural product. A dehydration treatment is necessary to convert Crocus sativus L. stigmas into saffron spice. To the best of our knowledge, no information on mass transfer parameters of saffron stigmas is available in the literature. This study aimed at investigating the moisture transfer parameters and quality attributes of saffron stigmas under infrared treatment at different temperatures(60,70, …, 110 °C). It was observed that the dehydration process of the samples occurred in a short accelerating rate period at the start followed by a falling rate period. The effective moisture diffusivity and convective mass transfer coefficient were determined by using the Dincer and Dost model. The diffusivity values varied from1.1103 × 10~(-10)m~2·s~(-1)to 4.1397 × 10~(-10)m~2·s~(-1) and mass transfer coefficient varied in the range of 2.6433 × 10~(-7)–8.7203 × 10~(-7)m·s~(-1). The activation energy was obtained to be 27.86 k J·mol~(-1). The quality assessment results showed that the total crocin content increased, when the temperature increased up to90 °C but, in higher temperatures, the amount of crocin decreased slightly. The total safranal content of the samples decreased slightly when drying temperature increased from 60 °C to 70 °C and then continuously increased up to 110 °C. Also, the amount of picrocrocin increased from 83.1 to 93.3 as the drying temperature increased from 60 °C to 100 °C.     

Analysis of polymer foil heaters as infrared radiation sources

Infrared radiation as a heat source is used in many fields. In particular, the positive effect of far-infrared radiation on living organisms has been observed. This paper presents two technological solutions for infrared heater production using polymer-silver and polymer-carbon pastes screenprinted on foil substrates. The purpose of this work was the identification of polymer layers as a specific frequency range IR radiation sources. The characterization of the heaters was determined mainly by measurement of the surface temperature distribution using a thermovision camera and the spectral characteristics were determined using a special measuring system. Basic parameters obtained for both, polymer silver and polymer carbon heaters were similar and were as follows: power rating of 10–12 W/dm², continuous working surface temperature of 80–90 °C, temperature coefficient of resistance (TCR) about +900 ppm/K for polymer-carbon heater and about +2000 ppm/K for polymer-silver, maximum radiation intensity in the wavelength range of 6–14 μm with top intensity at 8.5 μm and heating time about 20 min. For comparison purposes, commercial panel heater was tested. The results show that the characteristics of infrared polymer heaters are similar to the characteristics of the commercial heater, so they can be taken into consideration as the alternative infrared radiation sources.     

Determining the infrared reflectance of specular surfaces by using thermographic analysis

Specular surfaces as glass, mirrors and metals are commonly used in solar devices and in building facades. Determining the temperature distribution of such kind of surfaces allows estimating their thermal losses and detecting hot spots and temperature gradients that provokes material stress and rupture. In this sense, thermography is a non-contact measurement technique that is capable to quickly scan and record these surface temperature distributions, but when specular materials are inspected the infrared reflectance becomes a crucial parameter. This work describes a methodology to measure the reflectance of specular materials for different incidence angles in the infrared range 8 μm–14 μm, by using a thermographic camera and an infrared radiation source. The methodology includes the analysis of errors in the estimation of the reflectance and how to select the temperature of the source that minimizes these errors. The method is applied to different specular surfaces commonly used in building facades and solar devices, whose infrared specular reflectances are estimated for different incidence angles. The obtained results are analyzed in order to provide valuable information for in-situ thermographic measurements of specular surfaces.     

Feature extraction and classification for detecting the thermal faults in electrical installations

This paper proposed an effort to investigate the suitability of input features and classifier for identifying thermal faults within electrical installations. The features are extracted from the thermal images of electrical equipment and classified using a multilayered perceptron (MLP) artificial neural network and support vector machine (SVM). In the experiments, the classification performances from various input features are evaluated. The commonly used classification performance indices, including sensitivity, specificity, accuracy, area under curve (AUC), receiver operating characteristic (ROC) and F-score are employed to identify the most suitable input feature as well as the best configuration of classifiers. The experimental results demonstrate that the combination of features set T_max, T_delta and DT_bg produce the best input feature for thermal fault detection. In addition, the implementation of SVM using radial basis kernel function (RBF) produces slightly better performance than the MLP artificial neural network.     

Dynamic foreground detection based on improved Codebook model

Foreground detection method based on improved Codebook algorithm is discussed in this paper: first of all, transform RGB colour space into YCbCr colour space to make chromaticity convergent, and cope with illumination changing. Second, search for the CodeWords matching with the pixel values of the YCbCr to update the algorithm, so as to ensure the foreground detection effect. Then apply random abandon value method to delete the CodeWords that have not been accessed for a long time, reduce memory consumption and improve processing speed. Finally, conduct experiments on the infrared imagery and the colour image, respectively, to make foreground detection. The results demonstrate that the model and algorithm presented in this paper can make better foreground detection and reduce memory consumption. Meanwhile, compare this method with other algorithms to prove its advantages.     

Colour shift and mechanism investigation on the PMMA diffuser used in LED-based luminaires

PMMA material is widely used in LED-based luminaires due to several advantages such as excellent optical transparency, durability against radiation, surface hardness (scratch free), rigidity and strength and can be completely recycled. However, few studies have been reported on the colour shift and failure mechanisms caused by this type of material. This paper experimentally investigated PMMA materials with different aging conditions. The following conclusions could be drawn. (1) Discolouration was not observed for any sample subjected to aging of 85 °C for 5000 h, or with additional blue light irradiation for 5000 h, or with additional humidity of 85%RH for 5000 h, or even with aging of 100 °C for 3000 h. (2) The specimen subjected to aging of 150 °C for 360 h has a surface discoloration and has a significant wavelength dependent degradation in the transmission spectrum caused by oxidation. The specimen with aging of 100 °C for 3000 h has a less oxidation, although no significant transmission spectrum reduction was observed. (3) Using such aged specimen as a diffuser mounted on a LED-based luminaire, the radiant flux peak intensity in the blue light area has a more severe reduction than that in the yellow light area, which results in a reduction of the radiant flux intensity ratio of blue light to yellow light and hence induces the colour shift to yellow. The colour shift investigated is 0.005, very close to the general failure criterion of 0.007, while the lumen decay is 10.2%, far less than the failure criterion of 30%.     

Room temperature synthesis and characterization of polythiophene thin films by chemical bath deposition (CBD) method

Polythiophene thin films were deposited successfully on glass substrate by chemical bath deposition method using FeCl₃ as an oxidant and chloroform as solvent. The effect of oxidant concentration on the properties of polythiophene thin films was studied. The surface morphology was influenced by oxidant concentration and deposition time. The oxidation concentration also strongly affects the optical properties of the polythiophene thin films. The transmittance decreases while the absorption, band gap and refractive index increases due to increase in oxidant concentration.     

Compositional design,structure stability,and microwave dielectric properties in Ca3MgBGe3O12 (B = Zr,Sn) garnet ceramics with tetravalent cations on B-site

Two garnet-structured Ca₃MgBGe₃O₁₂ (B = Zr, Sn) ceramics with tetravalent cations at B-site were prepared by conventional solid state reaction. The crystal structure, microstructure evolution, and microwave dielectric performance were investigated using X-ray powder diffraction, Rietveld refinement, scanning electron microscopy, Raman spectroscopy, and infrared spectroscopy techniques. Dense Ca₃MgZrGe₃O₁₂ and Ca₃MgSnGe₃O₁₂ ceramics were obtained at sintering temperatures of 1420 and 1400 °C, respectively. The dielectric constant, unloaded quality factor, and temperature coefficient of resonance frequency of Ca₃MgZrGe₃O₁₂ were 10.80 ± 0.2; 79,600 ± 1000 GHz (f = 12.61 GHz); and ?66.8 ± 1 ppm/°C, respectively, and the corresponding values for Ca₃MgSnGe₃O₁₂ were 9.68 ± 0.2; 83,400 ± 1000 GHz (f = 14.19 GHz); and ?57.9 ± 1 ppm/°C, respectively. The dielectric performances of the two ceramics were compared by analyzing the ionic polarizability, packing fraction, and bond valence. The intrinsic dielectric properties were predicted by fitting the infrared reflectivity spectra.     

A new model to predict soil pressure acting on deep burial jacked pipes

Soil pressure is a critical factor to pipe jacking projects both during and after the jacking. Current practices are based on modifications of one of Terzaghi arching model, e.g. Japan Microtunnelling Association, German standard ATV A 161, UK ‘Pipe Jacking Association’, ASCE 27, and Chinese standard GB 50332. In these practices, it is assumed that shearing bands arise from the outside of tunnel cross sections and extend to the ground surface. However, the shearing bands may desist below the ground surface (This scenario is called deep burial). If these practices are still applied, the calculations will result in underestimations. In this paper, a new calculation model, modified from the other Terzaghi arching model was proposed to specifically predict the soil pressure acting on the deep burial jacked pipes. Values of crucial parameters of the height of the shearing bands, friction angle, friction coefficient, soil pressure ratio, silo width and soil cohesion were analyzed based on published tunnel research results and trap-door experiments. The correctness of the new model was verified by in-situ measured soil pressure in Gongbei Tunnel project in Zhuhai city. In comparison to the in-situ measured soil pressure, the new model provided more logical estimations, while the current practices were found to underestimate the soil pressure.     

Crystallization and infrared radiation properties of iron ion doped cordierite glass-ceramics

Heterogeneous ion solution is an important method to improve the wanted property of polycrystalline materials. In this paper, for the purpose of infrared radiation property modification, different contents Fe₂O₃ were doped in MgO-Al₂O₃-SiO₂ system glasses. The effects of Fe₂O₃ doping on nucleation mechanism, crystallization behaviors and especially infrared radiation properties of this cordierite-crystalline based glass-ceramics were systematically investigated by means of differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results show that, the doping of iron ion can promote the phase separation of this magnesium aluminosilicate glass, and therefore change the crystallization mechanism of this glass from surface crystallization to bulk crystallization. The iron ion incorporates into the crystal structure of cordierite by mean of substituting Mg²⁺ in M site. The substitution of Fe³⁺ to Mg²⁺ can form the vacant site of Mg²⁺ cations. For the effects of lattice distortion, impurity and vacancy defects which caused by the incorporation of iron ion, the infrared radiation performance of cordierite based glass-ceramics can be improved effectively.