共查询到20条相似文献，搜索用时 781 毫秒
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通过对基于轴棱锥的贝塞尔谐振腔和贝塞尔-高斯谐振腔的研究,设计了一台腔内倍频Nd:YAG纳秒近似无衍射贝塞尔绿光激光器. 非稳激光器谐振腔由轴棱锥和凸面镜组成. 实验采用单灯脉冲抽运激光增益介质Nd:YAG晶体,倍频晶体选用KTP. 当抽运电压为350 V时,由主动式直接产生纳秒近似零阶贝塞尔绿光,其脉冲宽度为55.1 ns,波长为532 nm,线宽为0.8 nm,近似无衍射零阶贝塞尔绿光的中心光斑直径为192 μm. 利用Fresnel-Kirchhoff 衍射积分和Fox-Li迭代法,通过数值计算得出 相似文献
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提出了一种基于双向Raman放大的Brillouin光时域分析系统(BOTDA).利用双向Raman抽运对信号光进行Raman放大以补偿光纤损耗及Brillouin抽运波的消耗,从而使光纤后端的测量分辨率得到改善,测量分辨率在整段传感光纤趋于一致,同时避免了调制不稳定性引起的频谱扩展,克服了传统BOTDA存在的信号强度指数下降的弊端,使传感精度得到进一步提高.实验实现了50 km传感距离, 温度分辨率达0.6 ℃,空间分辨率为50 m.测量并分析了基于双向Raman放大的BOTDA信噪比和光功率分布特性. 相似文献
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利用蒙特卡罗方法模拟研究405和632 nm波长的高斯光束和均匀光束照射胃正常和肿瘤组织时,光在组织内的传输特性.得到漫反射率和透射率随径向半径r的分布规律和组织内能流率随组织厚度z和径向半径r的二维变化关系及等值线分布.模拟结果表明:632 nm波长光照射时,漫反射率和透射率以及穿透深度均>405 nm波长的值;相同功率和光束半径下,高斯光束的径向传播范围比均匀光束小,中心光场附近光能量集中但衰减较快,穿透深度小于均匀光束;对于632 nm激发光,光在胃正常组织中的穿透深度小于在肿瘤组织中的穿透深度,而对于405 nm激发光,光在胃正常组织中的穿透深度大于在肿瘤组织中的穿透深度. 相似文献
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应用 Von Neumann熵 和 Schmidt number K两种纠缠度量讨论了各向异性光子晶体中二能级原子和自发辐射场间纠缠度的演化性质. 研究发现,原子-光场纠缠度的演化与原子上能级和光子晶体能带带边的相对位置有关,当原子上能级处于光子晶体禁带内,原子-光场纠缠度将保持稳定,当原子上能级处于光子晶体能带中,原子-光场纠缠度先增大后衰减到零. 纠缠度的大小还与原子的初态有关. 可以通过控制原子的初态和原子上能级与带边的相对位置来控制原子-光场纠缠度的演化特性. 相似文献
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点吸收波浪能转换技术是一重要研究方向,其模型试验是该技术的重要基础。文中介绍了一种新型点吸收柔性泵波浪能转换装置,其能量转换主体由振荡浮子和柔性泵组成。建立了该装置的模型水槽试验,分析了波浪要素和柔性泵结构对系统功率转换特性的影响。试验结果表明柔性泵的进出口面积比例和面积大小对模型的转换效率影响较大,柔性泵的进出口面积比值为0.6,出口面积为7.85 cm～2时,装置的平均转换效率较大。该模型试验可以为同类型装置转换效率评估方法提供参考。 相似文献
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斜抽运无机液体激光器的流场热分布 总被引：1，自引：0，他引：1
激光二极管斜抽运的多增益段串接的液体激光器能够明显地提高激光光束质量、获得较高的输出功率.针对斜抽运子增益段工作时所涉及的流动、传热和壁面耦合,建立了计算子增益段流场热分布的流-热-固耦合模型,应用有限单元法完成了其瞬态流场热分布的数值模拟.该方法排除了不精确的换热系数对计算结果的影响,使得换热系数不再是计算的先决条件,而只是计算结果之一;并且为评价流道形状、流速、吸收系数等因素对流场热的影响,以及进一步改进和控制液体激光介质的流场热分布,提供了可靠的分析方法.数值模拟研究表明:换热系数是空间位置的函数; 相似文献
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《Oceanic Engineering, IEEE Journal of》2005,30(3):647-648
The objective of this paper is to theoretically demonstrate how the operational frequency affects the efficiency of a low-speed generator. Due to the varying nature of underwater currents, the voltage from a current power converter has to be rectified first and then digitally reconverted into a stable alternating current. When designing a direct drive generator for water current power conversion, the operational frequency is, thus, a free design parameter and not a fixed value determined by the grid. Finite element method was used to determine the efficiency and weight. A higher frequency means larger frequency-dependent losses, but also a lighter machine. Even at the highest frequency in this study, the frequency-dependent losses were not high enough to overcome the gain of a lighter machine. If a large generator diameter can be allowed, the water current power converter should be designed with as high operational frequency as possible. 相似文献
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An energy conversion system based on deep-sea pressure 总被引：1，自引：0，他引：1
A novel seawater pressure energy conversion system that utilizes seawater pressure to generate electricity has been studied in this paper. The energy conversion system utilizes the pressure difference between the pressurized seawater and the empty pressure container to drive hydraulic motor and the coaxially coupled generator to generate electric power. The output electric energy is recorded by the data logger throughout the process. In the current study, technical analysis is performed with the emphasis on conversion efficiency between seawater pressure energy and output electric energy. The analysis is conducted at various pressure differences through the throttle valve so as to obtain maximum conversion efficiency. Research shows that the optimum pressure difference through the throttle valve and the maximum conversion efficiency can be theoretically calculated when the properties of the conversion system are given. Simulation results have demonstrated the influence of pressure difference on conversion efficiency. The test apparatus has been designed, built and tested in 2004. It successfully generated electric energy of approximately 0.85 kW h at the depth of 2400 m with empty pressure container's holding capacity of 200 L in the voyage “DY105-16” in South China Sea on June 12, 2004. The actual conversion efficiency from seawater pressure energy to electric energy reaches as high as 63.8% which is attractive for underwater equipments. The success of the experiment has tested the feasibility of utilizing seawater pressure energy and brings a new power supply way for long-term in-situ underwater equipments. 相似文献
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随着海洋波浪能发电技术的发展和成熟,其在海洋观测领域的应用受到关注和研究。自主设计并研制了一种集波浪能发电、海表/海底同步观测、实时4G 通信传输、远程无线控制于一体的海洋立体观测系统,于2021 年7 月在珠江口万山岛海域通过锚泊系留方式布放,开展海上波浪能供电和观测应用试验。海试期间连续获取了海底原位观测视频数据,以及海表波浪变化和波浪能发电参数等监测数据,并对波浪能发电电流、电压和功率进行了统计分析,讨论了波浪能发电水平受波浪变化的影响,分析了两者之间的相关性。试验结果表明：利用波浪能供电的海洋观测系统具备连续、长周期、全天候观测的优势和潜力,源源不断的波浪能可保障海洋观测系统的稳定观测和数据可靠传输,实现了海洋观测系统长期独立运行所需的绿色高效供能,验证了波浪能在海洋观测领域应用的可行性和先进性。 相似文献
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In the Maidao Ecological Laboratory of the Huanghai Sea Fisheries Research Institute in 1998 ~ 2000, the continuous flow-through method was adopted to determine the energy budget components and models of Schlegel＇ s black rockfish under different ecological and environmental factors, such as temperature, food species, body mass and feeding level, etc. The body mass of test fish ranged from 21.2 to 224.5 g. The specific growth rate tended to invert ＂U＂ change with temperature increase. The ecological conversion efficiency showed the same trend as temperature and feeding level rise. Only the specific growth rate tended to decelerate the increment with the rise of feeding level. From the above quantitative relationships, the maximum and optimal growth temper- atures could be obtained as 17.5 and 16.2 ℃, and the maintenance feeding rate and optimum feeding rate as 0.8% and 4. 1% of the body mass. The specific growth rate and ecological conversion coefficient showed a decelerating decrease trend with body mass increment. The small-sized fish food was more advantageous to the feeding level increase in comparison with the small-sized shrimp food, which led to the increase of growth, metabolism and excretion, but had no significant influence on the ecological conversion coefficient. All of temperature, feeding level, body mass and food species can obviously change the energy budget models. The assigning rate of growth energy tended to change along the invert ＂U＂ curve with the increase of temperature and feeding level, and decrease with the body mass increase, but the assigning rates of metabolism energy and excretion energy were quite reverse. These relationships could be quantitatively described as quadratic or power function curve. If the above relationships proved true to other marine fish, the establishment of energy budget model of the same fish under different conditions can be largely simplified. 相似文献
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在多波束测深中,温盐深剖面数据的准确性对测量精度起到非常重要的作用,而在实际测量中,温盐深误差又不可避免地存在。为了分析温盐深变化对波束脚印坐标的影响规律并将其影响值量化,本文在声速剖面间接测量数据的基础上,选择精度较高、适应性较强的声速经验公式推导其误差公式,计算温盐深变化所引起的声速误差值,并且在常梯度声线跟踪模型的基础上推导出声波旅行轨迹的水平位移和垂直位移误差公式,然后结合声速剖面计算出声速误差对波束脚印坐标的影响程度。实验结果表明,温度变化对声速的影响最大,盐度和深度依序次之;温度、盐度、深度3个参量的变化引起波束脚印Z坐标的变化量均大于X、Y坐标,最高可达变化前深度的0.6%。温度和盐度的变化引起的三轴坐标值变化量随入射角的增大而减小,而深度变化引起的三轴坐标值变化量几乎不随入射角的变化而变化。本文研究结果可为温盐深误差对多波束测深精度评估工作提供借鉴作用。 相似文献
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Experimental studies were conducted on a trapezoidal pendulum wave energy converter in regular waves. To obtain the incident wave height, the analytical method (AM) was used to separate the incident and reflected waves propagating in a wave flume by analysing wave records measured at two locations. The response amplitude operator (RAO), primary conversion efficiency and the total conversion efficiency of the wave energy converter were studied; furthermore, the power take-off damping coefficients corresponding to the load resistances in the experiment were also obtained. The findings demonstrate that the natural period for a pendulum wave energy converter is relatively large. A lower load resistance gives rise to a larger damping coefficient. The model shows relatively higher wave energy conversion efficiency in the range of 1.0?1.2 s for the incident wave period. The maximum primary conversion efficiency achieved was 55.5%, and the maximum overall conversion efficiency was 39.4%. 相似文献
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为了解决北极海域海洋观测与通讯导航节点浮标的供电问题,提出利用北极海域冰面上冷空气与冰下海水之间的温差能转换为电能,为冰基浮标供电。根据北极温差的时空分布特性与冰基浮标的应用场景,提出了一种基于有机朗肯循环的冰基浮标温差能发电系统,并对其进行了建模与仿真分析。根据5 种工质的热力循环性能计算结果,确定R124 工质作为系统的循环工质。仿真结果表明：温差能发电系统在北极冬季两个月的总发电量为745 kWh,相当于3.72 t 能量密度为200 Wh/kg 的锂电池。因此,北极海域温差能转换发电系统能输出相当可观的功率与电能,显著提升冰基浮标的供能水平,提高其观测能力,延长其持续工作时间,减少破冰船对其的维护频率,从而打造冰下观测网络的关键节点,支撑北极冰下移动观测网络的构建。 相似文献
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全被动式振荡水翼是振荡水翼式潮流能装置的主要型式之一。对全被动式振荡水翼进行了数值模拟研究,构建了二维数值模型,研究了雷诺数及升沉刚度对全被动式振荡水翼水动力性能的影响。通过流场结构及水动力性能分析研究了典型参量对全被动式振荡水翼获能性能的影响机理,确定了维持其良好水动力性能的参数范围。研究发现,水翼的水动力性能对雷诺数及升沉刚度的变化较为敏感。雷诺数增大,水翼所需升沉刚度随之增加,且水翼可以在更大的参数范围下获得较优的水动力性能。另外,水翼可以在没有升沉刚度的情况下实现周期性运动,其获能甚至优于一些有升沉刚度的情况。最优工况下,平均功率系数和能量转换效率分别为1.07和27.48%。 相似文献