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Postharvest loss in fruit and vegetables accounts for more than one third of the world production. On the other hand, using chemicals has raised food health concerns, and grown the demand for ecofriendly materials. Given the promising results of essential oil use to control and prevent postharvest decay, we conducted this research. In the present study, a twostep statistical method was used to determine and optimize application of essential oils along with parameters of storage conditions. Significant level of essential oils and storage conditions (temperature, ventilation, and relative humidity) were screened by using PBD method and the best concentration were determined by central composite design of response surface method. The results showed that 1000 and 1500 microgram/l (µg/l) of basil essential oils, and 1500 µg/l of peppermint essential oils reduced the lesion diameter in apple fruits infected with Penicillium expansum. All storage conditions had significant effect on postharvest decay. Based on the CCD of RSM method, the best concentration of essential oils and the optimal level of the storage condition were determined. Furthermore, basil and peppermint treatments reduced rate of the ethylene production during 56 days after treatment. The results of this study revealed and confirmed that basil essential oils as a postharvest treatment under optimized storage conditions can be utilized as a lowcost substrate for controlling postharvest decay in apple. [ABSTRACT FROM AUTHOR]

The primary purpose of the paper is to reduce the impact of ambient temperature and internally generated heat on power conversion efficiency in solar cells. To this end, we design a simple layered structure using SiO2, Si3N4, and Si as an optical filter in front of the solar cell. To demonstrate the capability of the proposed structure, the Si and SiC Solar cells are considered and power conversion capabilities for these systems with and without the optical filter are evaluated. Finally, enhancement in power conversion efficiency and other characteristics of the proposed device is studied. It should mention that the Intermediate Band Solar Cells for this study are considered that be suitable cases in this field. In this case, to reduce the internally generated heat, we use a novel method for extracting the hot carrier from different energy levels by using multi-level Energy Selective Contacts. Such contacts promote Efficiency and break the Shockley–Queisser limit. Also, the proposed multilayer structure is used to reduce the effect of the ambient temperature. Using the proposed idea, it is shown that the power conversion efficiency is approximately constant for 300 to 800 °K. [ABSTRACT FROM AUTHOR]

High-energy incoming photons can be absorbed and concluded to generate Hot Carriers. In normal solar cells, these carriers are scattered by electron–electron and electron-lattice mechanisms and rapidly lose extra energy and approach to conduction band energy edge. This event plus other loss mechanisms cause that the efficiency of the solar cells to be limited to 33% theoretically. If one makes the possibility for carriers that can be extracted rapidly, before scattering and releasing extra energy to the lattice, the efficiency of solar cells is enhanced considerably. This type of solar cell is named hot carrier solar cells (HCSCs). To this end and improvement the conversion efficiency, multilevel energy selective contacts (ESCs) as a new concept and new mechanism in solar cells are used. In the other words, several appropriate energy levels as carrier extraction contacts in the conduction band are introduced. Here, we use multilevel ESCs, and based on our simulation it is shown that the maximum efficiency of 75% is achievable for low bandgap materials. For a typical material such as Si, the maximum efficiency is increased to 60% using ten ESCs. [ABSTRACT FROM AUTHOR]

Multi band solar cells provide the possibility to achieve ultra-high power conversion efficiency by absorbing incident infrared wavelengths. In this paper, we provide theoretical evaluation and framework for maximum power conversion efficiency limit for multiband solar cells. In order to achieve this goal, the genetic algorithm (GA) optimization techniques are used. To precise calculation, solar cells with three and four intermediate bands are considered in detail in this paper. Our calculation shows the maximum efficiency of 62.9% and 70.3% for the three and four band solar cells, respectively. The development of this algorithm lets us design and propose a novel and appropriate materials for photovoltaic structures to achieve maximum power conversion efficiency. It should mention that the proposed method can open a new research field in the synthesis of new materials to realize the proposed idea. [ABSTRACT FROM AUTHOR]

It is well-known that near-infrared (NIR) light sources are appropriate to ablate benign tumor irreversibly using heat treatment even in deep tissues. The laser light penetration into the skin in these wavelengths is deep (3–5 mm). Applying new stable materials for emitting NIR wavelengths in tumor positions can help cancer treatment. In this paper, synthesis of the conjugated core-multishell Ag/SiO2/Ag and Au/SiO2/Au quantum dots (QDs) with indocyanine green (ICG) is done and their theoretical and experimental absorptions and emissions in the NIR region are investigated. Thus, heat generation (high-resolution medical imaging capabilities) and emission enhancement are explained and described based on the FRET model for the proposed core-multishell QDs and it is shown that Ag/SiO2/Ag with ICG presents 4 times higher emission rate versus ICG alone in NIR region. Also, because of the plasmon hybridization and also resonance light penetration enhancement, the temperature in tissues increases that is useful for photothermal therapy and NIR high-resolution medical imaging for deep tissues. As an alternative application, these nanoparticles with amazing features are used as a heat source in cancer treatment for shallow and deep tissues. Finally, it is shown that Ag/SiO2/Ag QDs are the best solution for this purpose. [ABSTRACT FROM AUTHOR]

A photoconductive fractal antenna significantly improves the performance of photomixing-based continuous wave (CW) terahertz (THz) systems. An analysis has been carried out for the generation of CW-THz radiation by photomixer photoconductive antenna technique. To increase the active area for generation and hence the THz radiation power we used interdigitated electrodes that are coupled with a fractal tree antenna. In this paper, both semiconductor and electromagnetic problems are considered. Here, photomixer devices with Thue-Morse fractal tree antennas in two configurations (narrow and wide) are discussed. This new approach gives better performance, especially in the increasing of THz output power of photomixer devices, when compared with the conventional structures. In addition, applying the interdigitated electrodes improved THz photocurrent, considerably. It produces THz radiation power several times higher than the photomixers with simple gap. [ABSTRACT FROM AUTHOR]

In the present study, we report a simple and solution-processed visible blind metal-insulator-semiconductor (MIS) ultraviolet (UV) detector based on core-shell Si/SiO nanocrystals that are fabricated on interdigitated electrodes. The fabricated photo detector shows high photosensitivity in the UV-B and UV-C wavelength ranges. The absorption spectra of the nano-structured materials used in this work is simulated by the density functional theory (DFT) method and analyzed based on the electronic structure. It is then compared with the experimental results. The synthesized nano materials show very low density of structural defects based on the measured photoluminescence spectra, which results in a fast response time for the fabricated photodetector. Compared to the previously reported similar Si/SiO-based photo-detectors, the fabricated detector shows very good photo responsivity. [ABSTRACT FROM AUTHOR]

In this paper, we propose a compact and integrated optical spectrum analyzer (OSA) based on ring resonator. In this design thermo-optic, electro-optic, acousto-optic and nonlinear optic effects can be used as control signal to sweep the output frequency. The applied control signal changes the index of refraction and therefore the resonance frequency and the trapped optical intensity are changed corresponds to the input signal contents. Also, the proposed idea can easily be integrated on optical single chips. The presented design idea is simple for realization and implementation using optical integrated circuits, has high accuracy (less than 4 pm) and compact. This new proposed OSA is suitable for wavelength-division-multiplexing performance monitoring that requires high speed and high wavelength measurement. [ABSTRACT FROM AUTHOR]

An interesting topology with easy integration capability (from mask designing aspect) for optical filters using Fibonacci-class (FC(J,n)) ring-resonators is introduced. For some special cases, analytical transfer function (Transmission Coefficient Hm(n)) is obtained and corresponding simulated result is illustrated. In this work, optical multi-band filter design and analysis using Fibonacci-class ring resonators is considered. With suitable selection of system parameters and FC(J,n), we report multi-band characteristic for this structure. Also, dominant factors effects on multi-band operation are shown. We show that the coupling coefficients, effectively affects (e.g. generation or annihilation of additional band) the multi-band properties obtained in proposed structure. Also, the bandwidth and position of additional band can be controlled using Fibonacci-class basic elements (A, B) parameters such as rings diameters. Also, proposed system is easier than general multistage rings coupled to main waveguide from implementation point of view. [ABSTRACT FROM AUTHOR]

Basic units for realization of all-pole and all-zero transfer functions in all-optical systems using ring resonators and electromagnetic-induced transparency (EIT) are introduced. Using the basic blocks for generation of pole and zero proposed Any type and any degree of optical filters and optical processing systems can be implemented. In this paper, z transform is used for design and synthesize of low-pass, bandpass, and high-pass Butterworth optical filters as an example. The stability of optical systems designed by the proposed structures is investigated. In addition, EIT is used for the control of pole and zero position. [ABSTRACT FROM PUBLISHER]