Cavity-length optimization for high energy pulse generation in a long cavity passively mode-locked all-fiber ring laser

In order to achieve higher pulse energy in a passively mode-locked fiber ring laser, a long cavity length is commonly implemented. However, a long cavity operating in the anomalous dispersion regime also leads to pulse broadening, which reduces the average pulse power. In this paper, the trade-off between cavity length and average pulse power is investigated with the aim of optimizing the cavity length to achieve maximum pulse energy. Numerical simulation results, presented here, indicate that there exists an optimum cavity length for which the pulse energy is maximum and the optimum length shifts as the pump power changes. The simulation results for a pump power of 500 mW are verified by measurements carried out on a long cavity nonlinear polarization rotation mode-locked all-fiber ring laser operating in the anomalous dispersion regime. With a repetition rate of 266 kHz for the dissipative solitons, we achieve a pulse energy of 139.1 nJ for a cavity length of 700 m. Higher pulse energy can be expected by using a pump laser diode with higher pump power.     

折衍混合系统实现长焦深方法研究

通过对传统能量守恒法设计长焦深元件进行介绍与分析,根据衍射元件设计灵活的特性,提出了改进的能量守恒设计方法,利用折衍混合系统实现长焦深元件,并建立了优化的评价函数分两步对设计结果进行优化。     

Delamination‐Free Multifunctional Separator for Long‐Term Stability of Lithium‐Ion Batteries

Next‐generation lithium‐ion batteries (LIBs) that satisfy the requirements for an electric vehicle energy source should demonstrate high reliability and safety for long‐term high‐energy‐density operation. This inevitably calls for a novel approach to advance major components such as the separator. Herein, a separator is designed and fabricated via application of multilayer functional coating on both sides of a polyethylene separator. The multilayer‐coated separator (MCS) has a porous structure that does not interfere with lithium ion diffusion and exhibits superior heat resistance, high electrolyte uptake, and persistent adhesion with the electrode. More importantly, it enables high capacity retention and reduced impedance build up during cycling when used in a coin or pouch cell. These imply its promising application in energy sources requiring long‐term stability. Fabrication of the MCS without the use of organic solvents is not only environmentally beneficial but also effective at cost reduction. This approach paves the way for the separator, which has long been considered an inactive major component of LIBs, to become an active contributor to the energy density toward achieving longer cycle stability.     

耗能型辅助墩抗震性能数值研究

耗能型辅助墩可以有效地实现大跨度斜拉桥的地震损伤控制。刚度和强度是耗能型辅助墩的关键设计参数,因此,该文对安装剪切型连梁和屈曲约束支撑两种耗能构件的双柱墩进行理论分析,推导了耗能型辅助墩的刚度和强度的简化计算公式,能够快速准确地估算其弹性刚度和屈服强度。通过有限元模型,仿真分析了其滞回性能,可以准确地模拟耗能型辅助墩的非线性行为,为大跨度斜拉桥的整体弹塑性分析提供了可靠的依据。与试验结果对比,验证了简化公式和有限元模型的准确性。对比研究了安装耗能构件的双柱墩试件和拆除耗能构件的裸双柱墩试件的性能差异,结果表明耗能构件能够显著提高辅助墩的抗震能力。最后,对安装屈曲约束支撑的辅助墩抗震性能进行了参数分析。     

Gibbs free-energy barrier against irreversible magnetic flux entry into a superconductor

We have calculated the Gibbs free-energy barrier against irreversible magnetic flux entry into a superconductor for a long cylinder with elliptical cross section which approximates a long, flat strip. Our model is simplified to the two-dimensional case by assuming magnetic flux to enter in the form of a long, narrow, normal domain parallel to the axis of the cylinder. The following four contributions to the Gibbs free energy have been taken into account: (1) loss of condensation energy and gain of magnetic field energy inside the superconductor, (2) magnetic field energy outside the superconductor, (3) energy of interaction of the domain with an applied magnetic field, and (4) energy of interaction with an applied electrical transport current. Because of the Gibbs free-energy barrier, the critical magnetic field for entry of magnetic flux can be enhanced considerably above that calculated using Silsbee's rule. This enhancement is found to be proportional to the square root of the width of the superconducting cylinder. Important consequences of this are the enhancement of the critical current in a superconducting strip in zero magnetic field at which electrical resistance starts to appear and a corresponding modification of Silsbee's rule. We have demonstrated these effects experimentally through measurements of the onset of the current-induced resistive state in a series of superconducting indium strips of different widths and thicknesses. The experimental results confirm the theoretical predictions. The Gibbs free-energy-barrier effect described here can be interpreted as a novel flux-pinning mechanism, which might be called edge pinning.Work performed in part in the Ames Laboratory and in part in the Argonne National Laboratory of the U.S. Atomic Energy Commission.     

太阳能LED照明系统研究

太阳能作为一种新型的绿色可再生能源,具有储量大、利用经济、清洁环保等优点。太阳能的利用越来越受到人们的重视。发光二极管（LED）具有高效、节能、寿命长、环保等优点。基于LED和太阳能电池的优点,本文围绕太阳能电池和LED的照明系统开展了相应研究。     

Simulation of ultrarelativistic beam dynamics in the plasma wake-field accelerator

With two-dimensional hybrid code LCODE, the long-term dynamics of two drivers in plasma is studied. The bunch train is shown to produce a well-controlled wake-field good for particle acceleration. In this wake-field, a narrow witness bunch can be accelerated with a small energy spread (several percent), a high energy gain (exceeding the initial driver energy), and the driver-witness efficiency about 20%. The shaped long bunch is unusable for particle acceleration, since it is rapidly destroyed by the transverse two-stream instability.     

Stress intensity factors for cylindrical cracks in long cylinders

Stress intensity factors for a long cylindrical crack in a long cylinder have been calculated using the energy release rate approach. The investigated loading cases include centrifugal forces (Mode I), radial surface forces (Mode I), forces parallel to the axis (Mode II), and twisting moments (Mode III).     

低时延能耗均衡的水声传感器网络簇间路由算法

针对水声传感器网络的簇间路由选择问题,提出了一种基于前向网关的低时延能耗均衡路由算法,该算法采用最优方向角原则和能耗均衡原则选择中继簇头和中继网关,以减小长延迟和高能耗对水声通信的影响。仿真结果表明该算法在网络平均能耗、端到端时延和网络生命周期等方面具有较好的性能。     

Magnetostatic energy of paramagnetic particles in magnetic separators

A series expansion is obtained for the magnetostatic interaction energy of an infinitely long cylinder of arbitrary cross section, uniformly magnetized in a direction perpendicular to its long axis, and a spherical paramagnetic particle, in powers of the radius of the paramagnetic particle. For a cylinder of elliptic cross section magnetized in an arbitrary direction, the first three terms in this series are evaluated explicitly.     

Energy and long term hygrothermal performance of building enclosures based on dynamic environmental simulation test

Dynamic environmental testing is an effective means to study the energy and long-term hygrothermal performance of building enclosures. Southeast University is designing and building a large-scale dynamic environment simulation testing facility. It can simultaneously and dynamically simulate temperature, relatively humidity, infrared solar radiation, UV radiation, and precipitation. A transformation is needed to predict the energy and long-term hygrothermal performance of building enclosures under real service conditions using data obtained from accel-erated tests.     

浅析离子辅助光学薄膜镀膜机的特性

真空镀膜产品的质量问题，一直是应用镀膜技术人员探索的课题。人们经过长期探索，采用离子束辅助沉积镀膜技术，改善了镀膜层牢固性，提高了反射率。本技术在通讯技术、太阳能应用、汽车、装潢等领域应用十分广泛。本文介绍了真空离子束辅助沉积镀膜设备特性。     

Rational design of nitrogen doped hierarchical porous carbon for optimized zinc-ion hybrid supercapacitors

Nano Research - Aqueous rechargeable zinc-ion hybrid supercapacitors are considered to be a promising candidate for large-scale energy storage devices owing to their high safety, long life, and low...     

A method for scaling ballistic penetration phenomena

There are several established formulae for projectile penetration into semi-infinite concrete targets. Most of them include a term which indicates that regular scaling does not hold in this situation. Most of these formulae were derived using curve-fitting procedures, so that these terms do not represent any physical meaning. Non-scaling is also found in long rod penetrations, which cannot be attributed to strain rate effects. It is suggested here to differentiate the energy spent by the projectile during the penetration process into two parts, one—the energy expended for surface effects and the other—the energy expended for volume effects. By doing so, it is possible to derive expressions which account for the irregularity in scaling. These expressions are derived from the global, energy balance point of view, so they do not require the detailed characterization of the materials involved. They only require strict adherence to replica scaling procedures.

A similar approach is used to account for strain rate effects, but in that case, the results are not as general and can be applied only to a narrow span of configurations. Examples are cited from tests with concrete penetration and long rod penetration into different targets.     

Dynamic energy release rate and fracture heat in polymethylmethacrylate (PMMA) and a high-strength steel

The energy release rate G is a measure of the elastic energy causing crack propagation whereas the fracture heat Q indicates the amount of energy dissipated in the fracture zone. As long as any change in structure and energy losts by elastic waves can be neglected, the fracture heat represents the energy consumption of the crack and should be equivalent with G. If this can be proven one could use Q-measurements as an alternative method for investigating running cracks and dynamic fracture criteria, which in some cases may be a more appropriate measurement of the dynamic energy release rate G^dyn or the dynamic stress intensity factor K^dyn.     

Germanium enhanced large-grain growth by pulse mode rapid thermal crystallization process

The large-grain crystallization for silicon film was implemented by doping germanium in silicon film and using a rapid thermal process with near-infrared illumination. Germanium atoms acted as nuclei for crystallization of the amorphous silicon film. Because the germanium embedded in silicon film could absorb infrared photonic energy and convert it into thermal energy. Due to the low thermal conductivity of germanium, the absorbed energy remained in the germanium-doped film for a long time and helped the grain growth. With the amount of germanium in silicon film increased, a large grain will be obtained readily. A grain size of 3.92 μm was achieved in germanium-doped film.     

风电项目中的土木工程问题及有关研究的思考和发展展望

从配套工程建设、风况数据的搜集、整理及分析、预测等角度,探讨了促进我国风电事业的发展方式;指出关注风电建设中的土木工程问题,编制有关规范或指导手册等文件,做好风资源的普查、评估和风电场发电量预测,并在这些技术领域做到专业化、规范化,形成可靠的、成熟的、具有自主知识产权的技术体系对我国的风电发展至关重要。最后探讨了需要进行研究的方向,并结合中国国情对风电的发展做了展望。     

二元合金自由能的统计理论

为了处理二元合金中多种相的相平衡和相变总是根据准化学近似法和熵的统计理论,提出了二元合金自由能统计理论的一般处理模式,推导了自由能与成分和有序参数关系的表达式,由此对Ｆｅ－Ｃｏ、Ｐｔ－Ｃｏ和Ｒ－Ｃｏ合金的相平衡和相变问题进行了处理,获得了理想的结果。     

脉冲宽度对偏转电场法内表面等离子体浸没离子注入的影响

近年来 ,采用等离子体浸没离子注入 (PIII)对零部件内表面进行改性处理引起了各国研究工作者的广泛关注 .研究表明 ,提出的偏转电场法是进行内表面注入处理的有效方法 ,可以极大提高内表面注入的注入剂量和注入能量 .研究了采用偏转电场法注入时注入电压脉冲宽度对注入效果的影响 .结果表明 ,长注入脉宽可以提高内表面注入能量 ,但对注入剂量影响不大 ;脉冲宽度对注入峰值深度和注入剂量的分布有很大影响 ,长注入脉宽使注入峰值深度和注入剂量的最大值向筒内部移动 ;采用适当的不同宽度脉冲进行注入 ,可以改善注入均匀性 .     

Challenges and future perspectives on sodium and potassium ion batteries for grid-scale energy storage

The energy crisis and environmental pollution require the advancement of large-scale energy storage techniques. Among the various commercialized technologies, batteries have attracted enormous attention due to their relatively high energy density and long cycle life. Nevertheless, the limited supply and uneven distribution of lithium minerals, as well as their high cost, has greatly hindered the application of lithium-ion batteries in large-scale energy storage. Therefore, building next-generation alternative rechargeable batteries that feature low cost, long service life, and high safety is of the utmost importance. Over the past several years, we have witnessed many successful research outcomes for sodium and potassium ion batteries (SIBs and PIBs) in regard to electrode and electrolyte materials. In this Perspective, we summarize the current developments on SIBs/PIBs and their challenges when facing practical applications, including their cost, energy density, ion diffusivity in solids/electrolytes/interphases, cycle life, and safety concerns. Furthermore, we provide an overview of strategies to overcome the remaining challenges for achieving better electrochemical performance. Finally, we outline several possible directions for the future development of these two battery chemistries, with the hope of aiding the transition from the laboratory to next-generation practical applications for SIBs/PIBs batteries in grid-scale energy storage.