Generation of Q-Switched Mode-Locked Erbium-Doped Fiber Laser Operating in Dark Regime

We demonstrate a stable Q-switched mode-locked erbium-doped fiber laser （EDFL） operating in dark regime based on the nonlinear polarization rotation technique. The EDFL produces a pulse train where the Q-switching envelope is formed by multiple dark pulses. The repetition rate of the Q-switched envelope can be increased from 0.96kHz to 3.26kHz, whereas the pulse width reduces from 211 #s to 86#s. The highest pulse of 479nJ is obtained at the pump power of 55 mW. It is also observed that the dark pulses inside the Q-switching envelope consist of two parts： square and trailing dark pulses. The shortest pulse width of the dark square pulse is obtained at 40.5μs when the pump power is fixed at 145mW. The repetition rate of trailing dark pulses can be increased from 27.62kHz to 50kHz as the pump power increases from 55mW to 145mW.

Photo-assisted charging of carbon fiber paper-supported CeO_(2)/MnO_(2) heterojunction and its long-lasting capacitance enhancement in dark

It is important to develop green and sustainable approaches to enhance electrochemical charge storage efficiencies.Herein,a two-step in-situ growth process was developed to fabricate carbon fiber paper-supported CeO_(2)/MnO_(2) composite(CeO_(2)/MnO_(2)–CFP)as a binder-free photoelectrode for the photo-assisted electrochemical charge storage.The formation of CeO_(2)/MnO_(2) type II heterojunction largely enhanced the separation efficiency of photo-generated charge carriers,resulting in a substantially enhanced photo-assisted charging capability of~20%.Furthermore,it retained a large part of its photo-enhanced capacitance(~56%)in dark even after the illumination was off for 12 h,which could be attributed to its slow release of stored photo-generated electrons from its specific band structure to avoid their reaction with O_(2) in dark.This study proposed the design principles for supercapacitors with both the photo-assisted charging capability and its long-lasting retainment in dark,which may be readily applied to other pseudocapacitive materials to better utilize solar energy.

Challenges in developing polymer flocculants to improve bitumen quality in non.aqueous extraction processes:an experimental study

Western Canada’s oil sands hold the third-largest hydrocarbon deposits in the world.Bitumen,a very heavy petroleum,is currently recovered by surface mining with warm water or in situ.Recovery processes that use organic solvents are being developed to reduce water usage and tailings production.While solvent-based methods can effectively extract bitumen,removal of residual fine solids from diluted bitumen product(DBP)to meet the pipeline transport requirement of<0.5 wt%solids and water in DBP remains a major challenge.We propose a novel area of application of polymer flocculants for fine solids removal from DBP.In principle,polymer flocculants can be applied to help remove these residual solids in conjunction with physical separation processes to increase process effectiveness and energy efficiency.Several polymers are selected and screened for flocculation behavior using kaolinite suspended in DBP and toluene,as a model system.Focused beam reflectance measurements and force tensiometer techniques are used to determine flocculation and sedimentation in DBP.The observed flocculation and sedimentation rate enhancements indicate that the polymers tested have only minor effects,providing opportunities for advanced polymer development.These findings exemplify the challenges in identifying polymers that may be effective as flocculants in heavy petroleum media.

Photovoltaic Application Study of Zinc Telluride Thin Films Grown by Chemical Bath Deposition Method

Photovoltaic solar thin films zinc telluride studies on chemically deposited have been carried out to assess its suitability for use in the conversion of solar energy to electrical energy. The configuration of fabricated cell is n-ZnTe| NaOH (0.1M) + S (0.1M) + Na2S (0.1M)|C(graphite). The study shows that ZnTe thin films are n-type conductivity. The junction ideality factor was found to be 2.87. The flat band potential is found to be -0.652 V. The barrier height value was found to be 0.583 eV. The study of the power output characteristic shows open circuit voltage, short circuit current, fill factor and efficiency were found to be 150 mV, 25.6 μA, 24.86% and 0.49%, respectively. The photovoltaic cell characterization of the thin films is carried out by studying current-voltage characteristics in dark, capacitance-voltage in dark, barrier height measurements, power output characteristics.