Quantifying Microalgae Growth by the Optical Detection of Glucose in the NIR Waveband.

Microalgae have become a popular area of research over the past few decades due to their enormous benefits to various sectors, such as pharmaceuticals, biofuels, and food and feed. Nevertheless, the benefits of microalgae cannot be fully exploited without the optimization of their upstream production. The growth of microalgae is commonly measured based on the optical density of the sample. However, the presence of debris in the culture and the optical absorption of the intercellular components affect the accuracy of this measurement. As a solution, this paper introduces the direct optical detection of glucose molecules at 940-960 nm to accurately measure the growth of microalgae. In addition, this paper also discusses the effects of the presence of glucose on the absorption of free water molecules in the culture. The potential of the optical detection of glucose as a complement to the commonly used optical density measurement at 680 nm is discussed in this paper. Lastly, a few recommendations for future works are presented to further verify the credibility of glucose detection for the accurate determination of microalgae's growth.

Multi-dimensional optimization of In0.53Ga0.47As thermophotovoltaic cell using real coded genetic algorithm.

The optimization of thermophotovoltaic (TPV) cell efficiency is essential since it leads to a significant increase in the output power. Typically, the optimization of In0.53Ga0.47As TPV cell has been limited to single variable such as the emitter thickness, while the effects of the variation in other design variables are assumed to be negligible. The reported efficiencies of In0.53Ga0.47As TPV cell mostly remain < 15%. Therefore, this work develops a multi-variable or multi-dimensional optimization of In0.53Ga0.47As TPV cell using the real coded genetic algorithm (RCGA) at various radiation temperatures. RCGA was developed using Visual Basic and it was hybridized with Silvaco TCAD for the electrical characteristics simulation. Under radiation temperatures from 800 to 2000 K, the optimized In0.53Ga0.47As TPV cell efficiency increases by an average percentage of 11.86% (from 8.5 to 20.35%) as compared to the non-optimized structure. It was found that the incorporation of a thicker base layer with the back-barrier layers enhances the separation of charge carriers and increases the collection of photo-generated carriers near the band-edge, producing an optimum output power of 0.55 W/cm2 (cell efficiency of 22.06%, without antireflection coating) at 1400 K radiation spectrum. The results of this work demonstrate the great potential to generate electricity sustainably from industrial waste heat and the multi-dimensional optimization methodology can be adopted to optimize semiconductor devices, such as solar cell, TPV cell and photodetectors.

UV-Vis Spectroscopy: A New Approach for Assessing the Color Index of Transformer Insulating Oil.

Monitoring the condition of transformer oil is considered to be one of the preventive maintenance measures and it is very critical in ensuring the safety as well as optimal performance of the equipment. Various oil properties and contents in oil can be monitored such as acidity, furanic compounds and color. The current method is used to determine the color index (CI) of transformer oil produces an error of 0.5 in measurement, has high risk of human handling error, additional expense such as sampling and transportations, and limited samples can be measured per day due to safety and health reasons. Therefore, this work proposes the determination of CI of transformer oil using ultraviolet-to-visible (UV-Vis) spectroscopy. Results show a good correlation between the CI of transformer oil and the absorbance spectral responses of oils from 300 nm to 700 nm. Modeled equations were developed to relate the CI of the oil with the cutoff wavelength and absorbance, and with the area under the curve from 360 nm to 600 nm. These equations were verified with another set of oil samples. The equation that describes the relationship between cutoff wavelength, absorbance and CI of the oil shows higher accuracy with root mean square error (RMSE) of 0.1961.

Enhancing performance of multiwavelength Brillouin-Raman fiber laser by capturing residual pump power.

We demonstrate a simple design to enhance the performance of a multiwavelength Brillouin-Raman fiber laser by capturing the residual Raman pump power (RPP) from the laser cavity using a wavelength-selective coupler. The performance parameters of the laser system are investigated and compared with the conventional design under the same input design parameters. Both laser systems at a RPP of 375 mW can generate up to 33 Stokes lines with an equal channel spacing of 0.08 nm; however, the tunability of the laser without injection of residual RPP is 25% higher than the conventional laser structure. In addition, for a laser system without residual RPP injection, increasing the RPP improves the laser performance and generates up to 42 Stokes lines with a tunability of 24.5 nm, from 1570 to 1594.5 nm, at 475 mW. In contrast, the laser system with a residual RPP has the worst performance as the pump power is increased, and generates only nine Stokes lines with a tuning range of 5 nm at the same RPP of 475 mW.

Characteristics of multiwavelength L-band Brillouin-Raman fiber laser under forward and backward pumped environment.

We experimentally investigate the performance of L-band multiwavelength Brillouin-Raman fiber laser (MBRFL) under forward and backward pumped environments utilizing a linear cavity. A short length of 1.18 km dispersion compensating fiber is used as a nonlinear gain medium for both Brillouin and Raman gain. Experimental results indicate that the gain in the copumped laser configuration is higher than the gain in the counterpumped configuration. A stable and constant number of Brillouin Stokes lines up to 23 Stokes, with channel spacing of 0.08 nm and more than 20 dB of optical signal to noise ratio, can be generated as well as tuning over 20 nm in the L-band region from 1570 to 1590 nm. The laser generating the Brillouin Stokes lines exhibits flat amplitude bandwidth and high average output power of 0.8 and 1.6 dBm for the copropagation and counterpropagation pumps, respectively. Moreover, the tuning range bandwidth of the MBRFL can be predicted from the oscillated Brillouin pump gain profile.

Dual-function remotely-pumped Erbium-doped fiber amplifier: Loss and dispersion compensator.

An efficient Erbium-doped fiber amplifier configured in doublepass amplification scheme with chirped fiber Bragg grating as the reflector is presented in this paper. The proposed amplifier architecture is optimized and designed to work under consideration of low pump powers for remotely-pumped applications. The chirped fiber Bragg grating is used to reflect the amplified signal back to the Erbium-doped fiber and at the same time to compensate the effect of fiber dispersion. The proposed amplifier architecture is able to maintain gain of higher than 20 dB for small signals less than -23 dBm with 10 mW pump power only. The integrated function of loss and dispersion compensator in single black box is an attractive solution to be used as pre-amplifier.