Supercontinuum generation and carrier envelope offset frequency measurement in a tapered single-mode fiber

We report supercontinuum generation by launching femtosecond Yb fiber laser pulses into a tapered single-mode fiber of 3 um core diameter. A spectrum of more than one octave, from 550 to 1400 nm, has been obtained with an output power of 1.3 W at a repetition rate of 250 MHz, corresponding to a coupling efficiency of up to 60%. By using a typical f-2f interferometer, the carrier envelope offset frequency was measured and found to have a signal-to-noise ratio of nearly 30 dB.Comment: 10 pages, accepted by Appl Phys

Determination of Optimal Opening Scheme for Electromagnetic Loop Networks Based on Fuzzy Analytic Hierarchy Process

Studying optimization and decision for opening electromagnetic loop networks plays an important role in planning and operation of power grids. First, the basic principle of fuzzy analytic hierarchy process (FAHP) is introduced, and then an improved FAHP-based scheme evaluation method is proposed for decoupling electromagnetic loop networks based on a set of indicators reflecting the performance of the candidate schemes. The proposed method combines the advantages of analytic hierarchy process (AHP) and fuzzy comprehensive evaluation. On the one hand, AHP effectively combines qualitative and quantitative analysis to ensure the rationality of the evaluation model; on the other hand, the judgment matrix and qualitative indicators are expressed with trapezoidal fuzzy numbers to make decision-making more realistic. The effectiveness of the proposed method is validated by the application results on the real power system of Liaoning province of China

Multi-dimensional value evaluation for power-to-hydrogen technology based on fuzzy analytic hierarchy process

At present, the large-scale development of renewable energy is restricted by the absorption problem. The electric-hydrogen technology becomes a new flexible resource for coupling electric energy, heat energy and other kinds of energy by absorbing abandoned electricity. The lack of flexibility in a power system with high proportion of intermittent renewables can lead to issues like large-scale curtailment of wind and solar, uneconomic energy system operation; even endanger the security of energy supply. As a new flexible resource, power-to-hydrogen technology has received widespread attention and also requires a comprehensive assessment. The electricity-to-hydrogen technology has become a new flexible resource for coupling electric energy, thermal energy and other energy sources by absorbing and discarding electricity. To this end, this paper proposes a multi-dimensional system value evaluation method for the power-to-hydrogen (P2H) technology, the collaborative planning of large-scale electric-hydrogen resources in the new power system is an important issue in this study. The method, based a fuzzy analytic hierarchy process, delivers a multi-dimensional index that involves a P2H’s flexibility, ability to consume intermittent renewables, economy and environmental value. The system value of P2H and the effectiveness of the proposed algorithm are demonstrated by a use case study. The effects caused by P2H capacity variation are quantified, and an optimal capacity of P2H was found

Research on the optimal planning method of hydrogen-storage units in wind–hydrogen energy system considering hydrogen energy source

Utilizing wind power (WP) for hydrogen production can alleviate wind curtailment and improve wind energy utilization. The optimal planning of hydrogen-storage units(HSUs) in wind–hydrogen energy system(W-HES) will affect its economic operation. This paper proposes a W-HES model comprising WP, HSUs, and loads. We then utilize clustering algorithm-based WP and power load scenario division method. And taking the minimum investment, operation, and maintenance cost of W-HES as the objective function, use the particle swarm optimization(PSO) algorithm to optimize the planning of HSUs of W-HES. Finally, we investigate the impact of diverse hydrogen energy sources and daily hydrogen load variations on the optimal planning outcomes of HSUs. It will provide a valuable insights for the planning and configuration of HSUs in W-HES

A Comprehensive Strategy for Accurate Reactive Power Distribution, Stability Improvement, and Harmonic Suppression of Multi-Inverter-Based Micro-Grid

Among the issues of accurate power distribution, stability improvement, and harmonic suppression in micro-grid, each has been well studied as an individual, and most of the strategies about these issues aim at one inverter-based micro-grid, hence there is a need to establish a model to achieve these functions as a whole, aiming at a multi-inverter-based micro-grid. This paper proposes a comprehensive strategy which achieves this goal successfully; since the output voltage and frequency of micro-grid all consist of fundamental and harmonic components, the strategy contains two parts accordingly. On one hand, a fundamental control strategy is proposed upon the conventional droop control. The virtual impedance is introduced to solve the problem of accurate allocation of reactive power between inverters. Meanwhile, a secondary power balance controller is added to improve the stability of voltage and frequency while considering the aggravating problem of stability because of introducing virtual impedance. On the other hand, the fractional frequency harmonic control strategy is proposed. It can solve the influence of nonlinear loads, micro-grid inverters, and the distribution network on output voltage of inverters, which is focused on eliminating specific harmonics caused by the nonlinear loads, micro-grid converters, and the distribution network so that the power quality of micro-grid can be improved effectively. Finally, small signal analysis is used to analyze the stability of the multi-converter parallel system after introducing the whole control strategy. The simulation results show that the strategy proposed in this paper has a great performance on distributing reactive power, regulating and stabilizing output voltage of inverters and frequency, eliminating harmonic components, and improving the power quality of multi-inverter-based micro-grid

Dye-Sensitized Core/Active Shell Upconversion Nanoparticles for Optogenetics and Bioimaging Applications

Near-infrared (NIR) dye-sensitized upconversion nanoparticles (UCNPs) can broaden the absorption range and boost upconversion efficiency of UCNPs. Here, we achieved significantly enhanced upconversion luminescence in dye-sensitized core/active shell UCNPs <i>via</i> the doping of ytterbium ions (Yb³⁺) in the UCNP shell, which bridged the energy transfer from the dye to the UCNP core. As a result, we synergized the two most practical upconversion booster effectors (dye-sensitizing and core/shell enhancement) to amplify upconversion efficiency. We demonstrated two biomedical applications using these UCNPs. By using dye-sensitized core/active shell UCNP embedded poly­(methyl methacrylate) polymer implantable systems, we successfully shifted the optogenetic neuron excitation window to a biocompatible and deep tissue penetrable 800 nm wavelength. Furthermore, UCNPs were water-solubilized with Pluronic F127 with high upconversion efficiency and can be imaged in a mouse model