Study on Hyperspectral Estimation Model of Chlorophyll Content in Grape Leaves

In view of the shortage of using traditional methods to monitor chlorophyll content, hyperspectral technology was used to estimate the chlorophyll content of grape leaves rapidly, accurately and non-destructively. Based on the data of hyperspectral reflectivity and SPAD value of grape leaves collected from Wanjishan grape planting base in Tai an, the correlations of SPAD value with the original spectral reflectivity of grape leaves and its first derivative were analyzed to select sensitive bands, and an estimation model of chlorophyll content in grape leaves based on hyperspectral reflectivity was established. The best model was SPAD = 59.352＋ 44 836.313 R 601 .

Observation of parity-time symmetry in microwave photonics

Symmetry plays a crucial role in explorations of the laws of nature.Parity-time(PT)symmetry phenomena can lead to entirely real spectra in non-Hermitian systems,which attracts considerable attention in the fields of optics and electronics because these phenomena provide a new tool for the manipulation of oscillation modes and nonreciprocal signal transmission.A potential new field of application is microwave photonics,an interdisciplinary field in which the interaction between microwaves and optical signals is exploited.In this article,we report the experimental use of PT symmetry in an optoelectronic oscillator(OEO),a key microwave photonics system that can generate singlefrequency sinusoidal signals with high spectral purity.PT symmetry is theoretically analyzed and experimentally observed in an OEO with two mutually coupled active oscillation cavities via a precise manipulation of the interplay between gain and loss in the two oscillation cavities.Stable single-frequency microwave oscillation is achieved without using any optical/electrical filters for oscillation mode selection,which is an indispensable requirement in traditional OEOs.This observation opens new avenues for signal generation and processing based on the PT symmetry principle in microwave photonics.

Recent advances in optoelectronic oscillators

An optoelectronic oscillator(OEO)is a microwave photonic system that produces microwave signals with ultralow phase noise using a high-quality-factor optical energy storage element.This type of oscillator is desired in various practical applications,such as communication links,signal processing,radar,metrology,radio astronomy,and reference clock distribution.Recently,new mode control and selection methods based on Fourier domain mode-locking and parity-time symmetry have been proposed and experimentally demonstrated in OEOs,which overcomes the long-existing mode building time and mode selection problems in a traditional OEO.Due to these mode control and selection methods,continuously chirped microwave waveforms can be generated directly from the OEO cavity and single-mode operation can be achieved without the need of ultranarrowband filters,which are not possible in a traditional OEO.Integrated OEOs with a compact size and low power consumption have also been demonstrated,which are key steps toward a new generation of compact and versatile OEOs for demanding applications.We review recent progress in the field of OEOs,with particular attention to new mode control and selection methods,as well as chip-scale integration of OEOs.

Optimized production of a novel bioflocculant M-C11 by Klebsiella sp. and its application in sludge dewatering

The optimized production of a novel bioflocculant M-C11 produced by Klebsiella sp. and its application in sludge dewatering were investigated. The optimal medium carbon source,nitrogen source, metal ion, initial pH and culture temperature for the bioflocculant production were glucose, NaNO3, MgSO4, and pH 7.0 and 25°C, respectively. A compositional analysis indicated that the purified M-C11 consisted of 91.2% sugar, 4.6% protein and 3.9% nucleic acids（m/m）. A Fourier transform infrared spectrum confirmed the presence of carboxyl, hydroxyl,methoxyl and amino groups. The microbial flocculant exhibited excellent pH and thermal stability in a kaolin suspension over a pH range of 4.0 to 8.0 and a temperature range of 20 to 60°C.The optimum bioflocculating activity was observed as 92.37% for 2.56 mL M-C11 and 0.37 g/L CaCl2 dosages using response surface methodology. The sludge resistance in filtration（SRF）decreased from 11.6 × 1012 to 4.7 × 1012m/kg, which indicated that the sludge dewaterability was remarkably enhanced by the bioflocculant conditioning. The sludge dewatering performance conditioned by M-C11 was more efficient than that of inorganic flocculating reagents,such as aluminum sulfate and polymeric aluminum chloride. The bioflocculant has advantages over traditional sludge conditioners due to its lower cost, benign biodegradability and negligible secondary pollution. In addition, the bioflocculant was favorably adapted to the specific sludge pH and salinity.