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.

Modeling the Parking Pricing of Multiple Parking Facilities under Different Operation Regimes

To explore the parking pricing of multiple parking facilities, this paper proposes a bi-level programming model, in which the interactions between parking operators and travelers are explicitly considered. The upper-level sub-model simulates the price decision-making behaviors of the parking operators whose objectives may vary under different operation regimes, such as monopoly market, oligopoly competition, and social optimum. The lower level represents a network equilibrium model that simulates how travelers choose modes, routes, and parking facilities. The proposed model is solved by a sensitivity based algorithm, and applied to a numerical experiment, in which three types of parking facilities are studied, i.e., the off-road parking lot, the curb parking lot, and the parking-and-ride (P&R) facility. The results show in oligopoly market that the level of parking price reaches the lowest point, nonetheless the social welfare decreases to the lowest simultaneously;and the share of P&R mode goes to the highest value, however the total network costs rise also to the highest. While the monopoly market and the social optimum regimes result in solutions of which P&R facilities suffer negative profits and have to be subsidized.

Compact solid-state waveguide lasers operating in the pulsed regime:a review[Invited]

Over the last years, there has been tremendous progress with compact pulsed lasers based on various solid-state gain media, such as crystals and glasses doped with laser-active ions. With the integration of increasingly diverse saturable absorber materials, these small sources are capable of delivering stable pulses with durations as short as femtoseconds and repetition rates exceeding 10 GHz. These promising sources are known as solid-state waveguide lasers, which have become synonymous with miniaturization, integration, and functionality.This article overviews the progress in the development of passively Q-switched and mode-locked solid-state waveguide lasers employing diverse saturable absorbers. The most commonly used laser configurations,state-of-the-art waveguide fabrication techniques, and experimental demonstrations of pulsed waveguide lasers are summarized and reviewed. Selected well-noted topics, which may shape the future directions in this field, are also presented.

Determination of optimum operating conditions for production of polyhydroxybutyrate by activated sludge submitted to dynamic feeding regime

Polyhydroxybutyrate (PHB) was produced by activated sludge in a two-stage process. In the first stage,the sludge with high storage potential was enriched in a sequencing batch reactor (SBR) operated by a dynamic feeding regime. The biosynthesis of PHB was sequentially accomplished in a batch reactor in the second stage. This article focused on the optimization of PHB content by evaluating the effects of three critical factors: Dissolved oxygen,pH and food-to-microorganism (F/M) ratio in the batch reactor. The results showed that the rate of substrate uptake,as well as the yield and content of PHB increased with the increase of dissolved oxygen concentration. The control of pH was not necessary under the weak alkaline condition for improvement of PHB content,except for the case in which the pH value was out of rang of 7.0 to 10.0. The enhanced F/M ratio favored PHB accumulation in the range of 1.0 to 4.5 C-mmol/C-mmol and the highest PHB content,64%,was achieved at 4.5 C-mmol/C-mmol. When F/M ratio was enhanced to 6.0 C-mmol/C-mmol,the phenomenon of utilizing simultaneously intracellular PHB and external substrate by sludge was observed,which resulted in a sharp decrease of PHB con-tent. The microscopic observation clearly confirmed that dynamic feeding regime was effective for selecting and enriching the sludge with a high storage potential.

Analyzing environmental flow supply in the semi-arid area through integrating drought analysis and optimal operation of reservoir

This study proposes a novel form of environmental reservoir operation through integrating environmental flow supply,drought analysis,and evolutionary optimization.This study demonstrates that simultaneous supply of downstream environmental flow of reservoir as well as water demand is challenging in the semi-arid area especially in dry years.In this study,water supply and environmental flow supply were 40%and 30%in the droughts,respectively.Moreover,mean errors of supplying water demand as well as environmental flow in dry years were 6 and 9 m3/s,respectively.Hence,these results highlight that ecological stresses of the downstream aquatic habitats as well as water supply loss are considerably escalated in dry years,which implies even using environmental optimal operation is not able to protect downstream aquatic habitats properly in the severe droughts.Moreover,available storage in reservoir will be remarkably reduced(averagely more than 30×106 m3 compared with optimal storage equal to 70×106 m3),which implies strategic storage of reservoir might be threatened.Among used evolutionary algorithms,particle swarm optimization(PSO)was selected as the best algorithm for solving the novel proposed objective function.The significance of this study is to propose a novel objective function to optimize reservoir operation in which environmental flow supply is directly addressed and integrated with drought analysis.This novel form of optimization system can overcome uncertainties of the conventional objective function due to considering environmental flow in the objective function as well as drought analysis in the context of reservoir operation especially applicable in semi-arid areas.The results indicate that using either other water resources for water supply or reducing water demand is the only solution for managing downstream ecological impacts of the river ecosystem.In other words,the results highlighted that replanning of water resources in the study area is necessary.Replacing the conventional optimization system for reservoir operation in the semi-arid area with proposed optimization system is recommendable to minimize the negotiations between stakeholders and environmental managers.

耦合水文情势及鱼类繁殖的江垭水库生态调度需求研究

为了修复河流水文情势、维持河流生态系统健康,通过环境DNA采样、IHA水文指标变动分析和文献资料总结等方法,开展了江垭水库坝下水文情势及鱼类繁殖需求关系研究,提出了水库生态调度需求与建议。结果显示,2021年9月在溇水干支流综合调查获得鱼类55种,与20世纪90年代相比,流水性种类在干流江段显著减少了51.35%;按照生态调度优先等级评估原则,确定江垭水库生态调度的主要目标物种为产漂流性卵的银鲴(Xenocypris argentea)、银鮈(Squalidus argentatus)、贝氏䱗(Hemiculter bleekeri)和产粘沉性卵的鲤(Cyprinus carpio)、鲫(Carassius auratus);江垭建坝前后下游水文情势变化较大,发生高度改变且对鱼类洄游产卵及鱼卵发育有重要作用的水文指标包括年最大1日、3日平均流量指标、年出现高流量脉冲事件的次数和持续时间以及连续日流量上涨率。研究表明,以促进坝下不同产卵类型的鱼类繁殖为目标,生态调度需要一定的高流量脉冲次数和历时,还需要控制下游水位的日降幅,通过泄放合理的生态流量来维持下游鱼类的生物多样性。

Characterization of x-shaped nanoaperture antenna arrays operating in mid-infrared regime

The characterization of x-shaped antenna arrays operating in the mid-infrared is proposed. An equivalent circuit model for the resonant characteristic of the x-shaped nanoaperture antenna arrays is also included. In order to understand the resonance behavior of the structure, a detailed study of the field-enhancement capabilities and light transmission characteristics of the structure is proposed. In the experimental stud- ies, the transmission characteristics of the periodic x-apertures are analyzed by varying the geometrical dimensions. Consequently, it is observed that the periodic subwavelength x-apertures show extremely high near-field optical resolution and enhanced transmission compared with the other nm-sized apertures.

新型配电网多虚拟电厂分布式资源聚合与聚合体优化运行方法

随着新型电力系统建设的不断推进,配电网侧分布式资源聚合与聚合体优化运行成为支撑电网平衡能力提升的关键技术之一。为快速准确表征分布式资源聚合体的功率调节能力,首先通过顶点枚举法求解考虑电源出力不确定性的虚拟电厂可行域;进一步为解决配电网多虚拟电厂经济优化运行问题,设计了计及有功-无功的二元一致性算法,并证明所提算法的收敛性;通过基于可行域边界与二元一致性变量修正方程的修正法则,以满足功率与电压约束;最终得到多虚拟电厂分布式资源聚合与聚合体优化运行的算法流程。通过算例分析与对比,验证了所提资源聚合与聚合体优化运行的框架可行性,以及其相较于传统一致性算法的优势。通过对分布式资源有功-无功调节能力的充分利用,提升了分布式资源参与电网运行的灵活性。

基于工况序列寻优的列车节能操纵策略优化

传统“三阶段”“四阶段”工况序列的列车操纵模式难以满足城市轨道交通复杂线路条件下的列车节能运行需求,本文提出一种基于工况序列寻优的列车节能操纵策略优化方法。将物理区间离散为多个等距离子区间,建立工况序列与子区间之间的映射关系,以区间总牵引能耗和运行时间最小化为目标构建列车节能操纵策略多目标优化模型。为提高模型求解效率,改进非支配排序遗传算法的交叉算子和距离算子,通过离散仿真求解列车节能操纵策略集。以福州地铁1号线的两个典型区间为对象进行案例分析,结果表明,相比传统操纵模式,优化后列车牵引能耗平均降低约19%。本文方法通过合理选择算法参数能够有效构建适应不同线路条件的运行工况序列,生成秒级运行时间划分下的列车节能操纵策略集。

面向产黏性卵鱼类繁殖需求的水风光生态协同调度

黏性卵黏附于砾石表面或砾石间隙中、近岸浅坑中发育孵化,对产卵场水文条件有特定需求。水风光互补运行下水电调峰造成日内下泄流量变化率增大,易导致黏性鱼卵暴露于空气中干燥死亡。已有生态流量缺乏日内流量变化率的量化研究,水风光协同调度缺乏鱼类繁殖适宜流量过程的考虑。提出通过计算不同流量工况下鱼类繁殖适宜生境面积的重叠率,以评估不同基准流量下生态适宜的流量变化率。同时,综合考虑水电调峰对新能源消纳及其对水文情势的改变,提出一种面向鱼类繁殖需求的水风光生态协同调度模型。以羊曲坝下河段为例,结果表明,为满足产黏沉性卵鱼类繁殖需求,最大流量增率不宜超过120 m^(3)/(s·h);生态权衡调度方案相比调峰效益最大解,平水和枯水时期分别减少7%和6%的新能源消纳量,减少2%和6%的水电出力,但水文情势的改变量相比降低了15%和21%。研究成果可为鱼类产卵期水电站生态调度优化运行提供技术支撑,促进水电可持续发展。

拉萨河流域梯级电站水光互补调度对水文情势的影响分析

梯级电站水光互补调度能提高光伏消纳能力和系统总发电量,但也要求调整梯级电站的调度规则,进而会加剧梯级电站下游的水文情势改变。为定量评价水光互补调度对水文情势的影响,以系统总发电量和总保证出力最大为目标,构建了拉萨河流域梯级电站水光互补优化调度模型,提出了基于水光互补的梯级电站优化调度方案,分析评价了不同优化调度方案的水文情势改变度。结果表明:梯级电站的水光互补优化调度能有效提升电力系统的总发电量和总保证出力;水光互补后拉萨河水文情势的综合改变度略大于水光互补之前,处于轻度至中度改变的临界值附近。研究成果可为拉萨河的水光互补调度及流域综合管理提供科学方法和依据。

Linear OPF-based Robust Dynamic Operating Envelopes with Uncertainties in Unbalanced Distribution Networks

Dynamic operating envelopes(DOEs),as key enablers to facilitate distributed energy resource(DER)integration,have attracted increasing attention in the past years.However,uncertainties,which may come from load forecasting errors or inaccurate network parameters,have been rarely discussed in DOE calculation,leading to compromised quality of the hosting capacity allocation strategy.This letter studies how to calculate DOEs that are immune to such uncertainties based on a linearised unbalanced three-phase optimal power flow(UTOPF)model.With uncertain parameters constrained by norm balls,formulations for calculating robust DOEs(RDOEs)are presented along with discussions on their tractability.Two cases,including a 2-bus illustrative network and a representative Australian network,are tested to demonstrate the effectiveness and efficiency of the proposed approach.

新情势下黄河小浪底水库调水调沙策略及效果评价

在当前黄河来沙量减少、小浪底水库累计淤积量增多以及下游河道冲刷效率下降的背景下,调水调沙初期制定的尽可能多塑造洪峰冲刷下游河道的策略需要调整,有必要对新情势下黄河调水调沙策略进行创新。根据不同需求,拟定维持现状、长期保持水库拦沙库容、最大化利用水资源、根据水沙丰枯变化灵活运用4种调水调沙策略,并制定相应的小浪底水库运用方式。采用2000年以来实测水沙系列循环3次作为计算条件,通过一维水沙动力学模型和基于人工神经网络法的模糊优选评价模型从减淤、兴利、生态3个方面计算并评价了不同策略下小浪底水库综合利用效益,结果表明:根据水沙丰枯变化灵活运用的策略最优,与维持现状策略相比,水库淤积量减少11%,发电量增加2%,不满足下游供水天数减少5%,出库含沙量大于80 kg/m3天数减少65%,减淤、兴利、生态效益均有所提升。

一种万向节阀门电动操作工具在水力发电中的可行性研究

水电站检修期间,设备运行和检修状态的互转,涉及到阀门全关或全开操作。其中,会出现阀门圈数多、卡涩,多人轮换开关单个阀的问题,造成工作时间长、效率低、人力成本高等现象。通过从万向节和电动扳手获得灵感,研发一种辅助操作工具,针对阀门开关的问题进行研究和分析,制定方案且研究其可行性。

小水电区域集中控制和智能运维模式的探索

随着电力市场的快速发展,小水电站群作为电网中的重要组成部分,以区域集中控制和智能运维的管理模式,采取无人值班或关门运行的运维模式成为行业发展的必然趋势。针对小水电的现状、面临的难题等,通过对集中智能运维模式的需求、可行性评估、方案设计、系统部署和数据接入、运行试点、测试评估、完善组织体系、全面推广和应用等8个方面分析,探讨了小水电站集群如何实现集中控制和智能运维模式。

基于BIM技术的高速公路运维管理研究——以兰海高速公路为例

高速公路一直以来是我国基础建设的重要组成部分,其中高速公路的运维管理是运营阶段的基础保障,而基于BIM技术的高速公路运维管理研究,是在我国公路交通行业数字化发展大背景下的新兴技术,是一种高效的项目管理工具。通过分析当前高速公路运维管理阶段的优缺点,结合现有BIM技术的可视化、数字化和模拟化的特点,根据两阶段施工设计图和实地概况,从兰海高速公路临洮至渭源段三维建模应用分析、实现各模块的信息管理、采用BIM技术+智慧图纸的共享应用模式、可视化交通流量动态模拟和深化设计等方面着手研究,进一步优化高速公路全生命周期主线左右幅、附属基础、通道、桥涵、隧道和标志标线的运维管理模式,改善在高速公路运维管理过程中以人工为主的检查、巡视和维护的传统模式,来提高运维管理效率,节约人力物料,也为全国高速公路网的快速发展和运维管理提供参考性的创新和见解。

浮态下营运船舶主机机座换新方案

文章以21万DWT散货船为对象,分析了主机机座裂纹产生的原因,阐述了浮态下营运船舶主机机座换新的流程,制定了专业的换新方案,并验证了该方案的可行性。完成了主机机座换新工程,消除了潜在的安全隐患,为其他船舶的类似工程积累了经验。

基于直流侧储能的新型统一潮流控制器优化设计

首先提出一种新型的考虑有功源(active power,AP)的统一潮流控制器(unified power flow controller,UPFC)UPFC-AP,该有功源从可再生能源发电获取能量,同时使用储能电池组作为储能装置;然后提出了该UPFC-AP的优化设计方案,该优化设计能同时实现两个目标:AP的最优容量和最小化功率传输角。通过优化设计,得到了UPFC-AP的可行工作区域(feasible operating regime,FOR)。使用FOR和经济调度策略,推导得出了上游电源和AP输出功率的最优经济调度策略。在此基础上,提出了最优负荷跟踪机制,同时实现了最经济的上游电源和AP的功率调度,且使功率传输角最小,最后通过仿真实例验证了所提方案的有效性。

黄河上游梯级水库运行的生态影响研究

为科学揭示梯级水库群运行对河流生态的影响,基于黄河上游实测水沙序列,采用IHA(Indicators of Hydrologic Alteration)指标体系,对比分析了不同工程运行时期黄河上游水文情势变化,运用多系列贡献率分割法,量化了不同影响因子对水文情势变化的贡献率。通过输沙率法结合断面淤积形态分析揭示了黄河上游河道冲淤演变。结果表明,黄河上游水库运行对河流径流及河道形态产生了深刻影响,进而影响了河流生态。水库运行后非汛期月均流量上升、汛期月均流量下降、高流量事件发生频率与流量减少,径流趋于平缓,且宁蒙河段泥沙淤积、断面形态趋于宽浅。分析表明水库运行是造成黄河上游兰州水文情势变化的主要原因,以及石嘴山、头道拐水文情势变化的重要原因,高流量事件的减少加剧了河道淤积,使河流生态朝不利方向演化,为维护黄河上游生态健康有必要实施生态调度,提高涨水期和洪水期下泄流量并制造高流量事件。研究为评估梯级水库运行的生态影响、指导梯级水库生态调度提供方向性参考。

丹江口水库对汉江中下游水文情势的影响

以汉江中游的襄阳水文站1946—1995年日均流量资料为研究对象，采用变动范围分析（RVA）法分析了丹江口水库建库前后汉江中下游水文情势特征变化，定量评价了水文情势改变程度．结果表明，丹江口水库对汉江中下游河流水文改变程度为39％，属于中度改变．水文情势的改变，影响了水库下游重要生物资源的生态环境条件，破坏了河流生态系统完整性以及生物多样性，建议尽快改变现有水库调度模式，开展丹江口水库生态调度研究．