High efficiency of graded index photonic crystal as an input coupler

Cataloged from PDF version of article.A graded index photonic crystal (GRIN PC) configuration was placed at the input side of a photonic crystal waveguide (PCW) in order to efficiently couple the light waves into the waveguide. We compared the transmission efficiencies of light in the absence and presence of the GRIN PC structure. We report a significant improvement in coupling when the GRIN PC is incorporated with the PCW. The intensity profiles were obtained by carrying out the experiments at microwave frequencies. Finite difference time domain based simulations were found to be in good agreement with our experimental results

The focusing effect of graded index photonic crystals

Cataloged from PDF version of article.We describe an approach to implement graded index (GRIN) structures using two- dimensional photonic crystals (PCs). The lattice spacing along the transverse direction to propagation is altered and we show, both theoretically and experimentally, that such a spatial perturbation is an effective way to obtain GRIN PC. The response of the structure to spatially wide incident beams is investigated and strong focusing behavior is observed. The large spot size conversion ratio can be attainable and is mainly limited by the finite size of the structure. The designed GRIN PC shows promise for use in optical systems that require compact and powerful focusing elements compared to the traditional bulky lenses. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3009965

Frequency dependent steering with backward leaky waves via photonic crystal interface layer

Cataloged from PDF version of article.A Photonic Crystal (PC) with a surface defect layer (made of dimers) is studied in the microwave regime. The dispersion diagram is obtained with the Plane Wave Expansion Method. The dispersion diagram reveals that the dimer-layer supports a surface mode with negative slope. Two facts are noted: First, a guided (bounded) wave is present, propagating along the surface of the dimer-layer. Second, above the light line, the fast traveling mode couple to the propagating spectra and as a result a directive (narrow beam) radiation with backward characteristics is observed and measured. In this leaky mode regime, symmetrical radiation patterns with respect to the normal to the PC surface are attained. Beam steering is observed and measured in a 70 degrees angular range when frequency ranges in the 11.88-13.69GHz interval. Thus, a PC based surface wave structure that acts as a frequency dependent leaky wave antenna is presented. Angular radiation pattern measurements are in agreement with those obtained via numerical simulations that employ the Finite Difference Time Domain Method (FDTD). Finally, the backward radiation characteristics that in turn suggest the existence of a backward leaky mode in the dimer-layer are experimentally verified using a halved dimer-layer structure. (C) 2009 Optical Society of Americ

Coupling effect between two adjacent chiral structure layers

Cataloged from PDF version of article.A pair of mutually twisted metallic cross-wires can produce giant optical activity. When this single chiral layer is stacked layer by layer in order to build a thick chiral metamaterial, strong coupling effects are found between the two adjacent chiral layers. We studied these coupling effects numerically and experimentally. The results show that the existing coupling between chiral layers can make the chiral properties of a two-layered chiral metamaterial different from the constituting single chiral layers. It is explained qualitatively that the coupling effects are generated from the coupling of metallic cross-wires belonging to different chiral layers. Our experimental results are in good agreement with the simulation results. ©2010 Optical Society of Americ

Solar flare prediction using advanced feature extraction, machine learning and feature selection

YesNovel machine-learning and feature-selection algorithms have been developed to study: (i) the flare prediction capability of magnetic feature (MF) properties generated by the recently developed Solar Monitor Active Region Tracker (SMART); (ii) SMART's MF properties that are most significantly related to flare occurrence. Spatio-temporal association algorithms are developed to associate MFs with flares from April 1996 to December 2010 in order to differentiate flaring and non-flaring MFs and enable the application of machine learning and feature selection algorithms. A machine-learning algorithm is applied to the associated datasets to determine the flare prediction capability of all 21 SMART MF properties. The prediction performance is assessed using standard forecast verification measures and compared with the prediction measures of one of the industry's standard technologies for flare prediction that is also based on machine learning - Automated Solar Activity Prediction (ASAP). The comparison shows that the combination of SMART MFs with machine learning has the potential to achieve more accurate flare prediction than ASAP. Feature selection algorithms are then applied to determine the MF properties that are most related to flare occurrence. It is found that a reduced set of 6 MF properties can achieve a similar degree of prediction accuracy as the full set of 21 SMART MF properties

The influence of temperature, light, pH and salinity on germination and growth of Cutandia memphitica (Spreng.) Benth

Background: There are many weed species that affect yield and quality in date palm orchards. Cutandia memphitica (Spreng.) Benth. is one of the weeds that is common in date palm orchards in Iraq. However, there is not enough information about C. memphitica in the literature. In order to provide information about the effect of key environmental factors (temperature, light, pH, and salt) on the seed biology of this weed species, this study was conducted.Methods: Within 2020, seeds were collected from agricultural regions in southern Iraq, and trials were done at Erciyes University Faculty of Agriculture labs in Kayseri Türkiye. All experiments were carried out with 30 seeds in the sterile 90 mm (90×15) petri dishes containing two layers of sterile filter paper.Results: The results of this investigation revealed that the seeds of this species germinated by 72.49% in three days when incubated at 25°C, and by 96.66% in 14 days when incubated at 15°C. The results also indicated that even during the longest incubation time examined, which was 28 days, the seeds of this species never germinated at 30 degrees or above. They can germinate during this period if kept at 5°C. The study also revealed that 90% of the seeds of this species germinated in complete darkness, whereas only 11.66% germinated in light. However, light has a significant impact on studied growth parameters (plant height and seedling fresh and dry weight). The results also demonstrate that the pH levels examined, which varied from 4 to 10, had no effect on the seed germination and growth parameters of seedling.Conclusion: The results showed that the seeds of this species germinated at the highest salinity levels (250 mM NaCl) by 10.83%. Meanwhile, the best germination was recorded at 25 mM salinity level of 89.16%, but without significant differences with salinity level at 50 mM and control. Also, the growth indicators were reduced significantly at the salinity level of 250 mM compared to the control.Keywords: Light; Salinity; Seed Germination; Temperature; Weed; Date Palm 

Cultivation of Agaricus bisporus on wheat straw and waste tea leaves based composts and locally available casing materials Part III: Dry matter, protein, and carbohydrate contents of Agaricus bisporus

This study was performed to determine the effects of composts and casing materials on dry matter, protein, and carbohydrate contents of the fruit bodies of Agaricus bisporus. Results showed that Agaricus bisporus cultivated on group I and group II casing soil groups showed remarkably higher dry matter and carbohydrate contents compared to other casing groups. No significant differences were found among casing soil groups in terms of protein content of Agaricus bisporus cultivated on wheatstraw. But, there were significant differences between casing soil groups in terms of protein content of Agaricus bisporus cultivated on waste tea leaves

Yield response of mushroom (Agaricus bisporus) on wheat straw and waste tea leaves based composts using supplements of some locally available peats and their mixture with some secondary casing materials

The study was conducted to investigate yields of mushroom (Agaricus bisporus) on wheat straw and waste tea leaves based composts. Mixtures (50:50, v/v) of some locally available peats including peat ofBolu (PB), peat of Agacbasi (PA), peat of Caykara (PC) and their mixture (80:20; v/v) with which piece of mosaic and sand were used. Also, some activator materials such as wheat bran, wheat chaff, chickenmanure, pigeon manure, and poplar leaves were used for A. bisporus cultivation. The results on wheat straw based composts provided the highest mushroom yield (23.01%) that was obtained on wheat strawand pigeon manure based compost using a mixture of PA with PC (50+50; v/v) as casing material. For waste tea leaves based composts, the highest mushroom yield (24.90%) were recorded on wheat straw and pigeon manure based compost using a mixture of PC with sand (80+20; v/v) as casing material

Cultivation of Agaricus bisporus on wheat straw and waste tea leaves based compost formulas using wheat chaff as activator material

This study was designed to determine the pin head formation time and yield values of Agaricus bisporus on some casing materials. Composts were prepared basically from wheat straw and waste tea leaves by using wheat chaff as activator substance. Temperatures of the compost formulas were measured during composting at various depths in order to determine the compostability level. Results showed that in both compost types, maximum temperature values were recorded in the second turning stage. Composting was completed in 21 days for both composts. While the fastest pin head formation (12.50 days) was obtained on wheat straw based compost using peat of Bolu (PB) and peat of Agacbasi (PA) (50+50; in volume); waste tea leaves based compost using peat of Caykara (PC) and forest soil (FS) mixture (50+50; in volume) as casing material gave the fastest pin head formation (13.25 days). In terms of yield, a mixture of peat of Bolu and peat of Agacbasi (PA) (50+50; in volume) gave the highest yieldfor wheat straw based compost, a mixture of peat of Agacbasi and perlite (P) (80+20; involume) had the highest yield for waste tea leaves based compost

Cultivation of Agaricus bisporus on some compost formulas and locally available casing materials. Part II: Waste tea leaves based compost formulas and locally available casing materials

Three compost formulas (formula I, formula II, and formula III) based waste tea leaves and using some activator materials such as wheat bran, chicken manure and pigeon manure were studied for Agaricusbisporus cultivation. Some locally available peats such as peat of Bolu, peat of Agacbasi, peat of Caykara and theirs mixture (80:20; volume : volume) with perlite were used. Temperature values of allcompost formulas during composting process were measured to determine the compostability level. According to results, compost temparature steadily increased until the 8th, 9th, and 9th day ofcomposting for formula I, formula II, and formula III, respectively. The maximum compost temperature values were measured for all compost formulas at the second turning stage of composting process.The highest compost temperature values were measured prepared from a mixture of waste tea leaves and wheat bran (formula I). The best mushroom yield was obtained by a mixture of waste tea leaves andpigeon manure with the peat of Caykara and perlite mixture as casing material. Peat of Caykara gave higher mushroom yield than those of other peats