High wall-plug efficiency 808-nm laser diodes with a power up to 30.1 W

A very highly efficient InGaAlAs/AlGaAs quantum-well structure was designed for 808 nm emission,and laser diode chips 390-μm-wide aperture and 2-mm-long cavity length were fabricated.Special pretreatment and passivation for the chip facets were performed to achieve improved reliability performance.The laser chips were p-side-down mounted on the AlN submount,and then tested at continuous wave(CW)operation with the heat-sink temperature setting to 25℃using a thermoelectric cooler(TEC).As high as 60.5%of the wall-plug efficiency(WPE)was achieved at the injection current of 11 A.The maximum output power of 30.1 W was obtained at 29.5 A when the TEC temperature was set to 12°C.Accelerated life-time test showed that the laser diodes had lifetimes of over 62111 h operating at rated power of 10 W.

High power-added-efficiency AlGaN/GaN HEMTs fabricated by atomic level controlled etching

An atomic-level controlled etching(ACE)technology is invstigated for the fabrication of recessed gate AlGaN/GaN high-electron-mobility transistors(HEMTs)with high power added efficiency.We compare the recessed gate HEMTs with conventional etching(CE)based chlorine,Cl_(2)-only ACE and BCl^(3)/Cl_(2)ACE,respectively.The mixed radicals of BCl_(3)/Cl_(2)were used as the active reactants in the step of chemical modification.For ensuring precise and controllable etching depth and low etching damage,the kinetic energy of argon ions was accurately controlled.These argon ions were used precisely to remove the chemical modified surface atomic layer.Compared to the HEMTs with CE,the characteristics of devices fabricated by ACE are significantly improved,which benefits from significant reduction of etching damage.For BCl_(3)/Cl_(2)ACE recessed HEMTs,the load pull test at 17 GHz shows a high power added efficiency(PAE)of 59.8%with an output power density of 1.6 W/mm at Vd=10 V,and a peak PAE of 44.8%with an output power density of 3.2 W/mm at Vd=20 V in a continuous-wave mode.

Role of PV-Powered Vehicles in Low-Carbon Society and Some Approaches of High-Efficiency Solar Cell Modules for Cars

Development of highly-efficient photovoltaic (PV) modules and expanding its application fields are significant for the further development of PV technologies and realization of innovative green energy infrastructure based on PV. Especially, development of solar-powered vehicles as a new application is highly desired and very important for this end. This paper presents the impact of PV cell/module conversion efficiency on reduction in CO2 emission and increase in driving range of the electric based vehicles. Our studies show that the utilization of a highly-efficient (higher than 30%) PV module enables the solar-powered vehicle to drive 30 km/day without charging in the case of light weight cars with electric mileage of 17 km/kWh under solar irradiation of 3.7 kWh/m2/day, which means that the majority of the family cars in Japan can run only by the sunlight without supplying fossil fuels. Thus, it is essential to develop high-efficiency as well as low-cost solar cells and modules for automotive applications. The analytical results developed by the authors for conversion efficiency potential of various solar cells for choosing candidates of the PV modules for automotive applications are shown. Then we overview the conversion efficiency potential and recent progress of various Si tandem solar cells, such as III-V/Si, II-VI/Si, chalcopyrite/Si, and perovskite/Si tandem solar cells. The III-V/Si tandem solar cells are expected to have a high potential for various applications because of its high conversion efficiency of larger than 36% for dual-junction and 42% for triple-junction solar cells under 1-sun AM1.5 G illumination, lightweight and low-cost potentials. The analysis shows that III-V based multi-junction and Si based tandem solar cells are considered to be promising candidates for the automotive application. Finally, we report recent results for our 28.2% efficiency and Sharp’s 33% mechanically stacked InGaP/GaAs/Si triple-junction solar cell. In addition, new approaches which are suitable for automotive applications by using III-V triple-junction, and static low concentrator PV modules are also presented.

Fully Integrated High-Voltage Generators with Optimized Power Efficiency

This paper describes how the power efficiency of fully integrated Dickson charge pumps in high- voltage IC technologies can be improved considerably by implementing charge recycling techniques, by replacing the normal PN junction diodes by pulse-driven active diodes, and by choosing an appropriate advanced smart power IC technology. A detailed analysis reveals that the combination of these 3 methods more than doubles the power efficiency compared to traditional Dickson charge pump designs.

A C-band 55% PAE high gain two-stage power amplifier based on AlGaN/GaN HEMT

A C-band high efficiency and high gain two-stage power amplifier based on A1GaN/GaN high electron mobility transistor （HEMT） is designed and measured in this paper. The input and output impedances for the optimum power-added efficiency （PAE） are determined at the fundamental and 2nd harmonic frequency （f0 and 2f0）. The harmonic manipulation networks are designed both in the driver stage and the power stage which manipulate the second harmonic to a very low level within the operating frequency band. Then the inter-stage matching network and the output power combining network are calculated to achieve a low insertion loss. So the PAE and the power gain is greatly improved. In an operation frequency range of 5,4 GHz-5.8 GHz in CW mode, the amplifier delivers a maximum output power of 18.62 W, with a PAE of 55.15 % and an associated power gain of 28.7 dB, which is an outstanding performance.

High-efficiency S-band harmonic tuning GaN amplifier

In this paper, we present a high-efficiency S-band gallium nitride （GaN） power amplifier （PA）. This amplifier is fabri- cated based on a self-developed GaN high-electron-mobility transistor （HEMT） with 10 mm gate width on SiC substrate. Harmonic manipulation circuits are presented in the amplifier. The matching networks consist of microstrip lines and discrete components. Open-circuited stub lines in both input and output are used to tune the 2rid harmonic wave and match the GaN HEMT to the highest efficiency condition. The developed amplifier delivers an output power of 48.5 dBm （70 W） with a power-added efficiency （PAE） of 72.2% at 2 GHz in pulse condition. When operating at 1.8-2.2 GHz （20% relative bandwidth）, the amplifier provides an output power higher than 48 dBm （,-~ 65 W）, with a PAE over 70% and a power gain above 15 dB. When operating in continuous-wave （CW） operating conditions, the amplifier gives an output power over 46 dBm （40 W） with PAE beyond 60% over the whole operation frequency range.

Highly Efficient Power Conversion from Salinity Gradients with Ion-Selective Polymeric Nanopores

A polymeric nanopore membrane with selective ionic transport has been proposed as a potential device to convert the chemical potential energy in salinity gradients to electrical power. However, its energy conversion efficiency and power density are often limited due to the challenge in reliably controlling the size of the nanopores with the conventional chemical etching method. Here we report that without chemical etching, polyimide （PI） membranes irradiated with GeV heavy ions have negatively charged nanopores, showing nearly perfect selectivity for cations over anions, and they can generate electrical power from salinity gradients. We further demonstrate that the power generation efficiency of the PI membrane approaches the theoretical limit, and the maximum power density reaches 130m W/m2 with a modified etching method, outperforming the previous energy conversion device that was made of polymeric nanopore membranes.

Architecture of Intra Prediction for High Efficiency Video Coding

This paper explains intra prediction method for High Efficiency Video Coding(HEVC).Intra prediction removes correlation of adjacent samples in spatial domain.Intra predictor requires reference images which are stored in external memory.Memory access is required frequently in process of intra prediction.The proposed architecture can reduce external memory access by optimized internal buffer.

High-repetition-rate and high-power efficient picosecond thin-disk regenerative amplifier

We present an effective approach to realize a highly efficient,high-power and chirped pulse amplification-free ultrafast ytterbium-doped yttrium aluminum garnet thin-disk regenerative amplifier pumped by a zero-phonon line 969 nm laser diode.The amplifier delivers an output power exceeding 154 W at a pulse repetition rate of 1 MHz with custom-designed 48 pump passes.The exceptional thermal management on the thin disk through high-quality bonding,efficient heat dissipation and a fully locked spectrum collectively contributes to achieving a remarkable optical-to-optical efficiency of 61%and a near-diffraction-limit beam quality with an M2 factor of 1.06.To the best of our knowledge,this represents the highest conversion efficiency reported in ultrafast thin-disk regenerative amplifiers.Furthermore,the amplifier operates at room temperature and exhibits exceptional stability,with root mean square stability of less than 0.33%.This study significantly represents advances in the field of laser amplification systems,particularly in terms of efficiency and average power.This advantageous combination of high efficiency and diffraction limitation positions the thin-disk regenerative amplifier as a promising solution for a wide range of scientific and industrial applications.

Improving thermal efficiency and stability of laser welding process for magnesium alloy by combining power modulation and subatmospheric pressure environment

The laser welding(LW)process of highly reflective materials presents low thermal efficiency and poor stability.To solve the problem,the effects of subatmospheric environment on LW process,technological parameters in subatmospheric environment on weld formation and welding with sinusoidal modulation of laser power on the stability of LW process in subatmospheric environment were explored.The AZ31magnesium(Mg)alloy was used as the test materials.The test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal pressure.After the keyhole depth greatly rises,significantly periodic local bulge is observed on the backwall surface of the keyhole and the position of the bulge shifts along the direction of the keyhole depth.Eventually,the hump-shaped surface morphology of the welded seam is formed;moreover,the weld width in local zones in the lower part of the welded seam remarkably grows.During LW in subatmospheric environment,the weld penetration can be further greatly increased through power modulation.Besides,power modulation can inhibit the occurrence of bulges in local zones on the backwall of the keyhole during LW in subatmospheric environment,thus further curbing the significant growth of the weld widths of hump-shaped welding beads and local zones in the lower part of welded seams.Finally,the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was illustrated.This was conducted according to theoretical analysis of recoil pressure and observation results of dynamic behaviors of laser induced plasma clouds and keyholes in the molten pool through high speed photography.

基于Dinkelbach-Quadratic算法的高速铁路通信能效优化功率分配研究

为了提高高速铁路通信能量效率,提出一种基于Dinkelbach-Quadratic变换的迭代算法来解决高速铁路通信下行链路的功率分配问题。通过在小区内部署远程天线单元构建高速铁路通信分布式天线系统模型,基于完美信道状态信息(CSI)和列车内接入点反馈的最小速率要求建立能效优化模型;基于所建立的非凸优化模型,采用Dinkelbach变换将分数形式的非线性规划问题转换为求差形式;利用Quadratic变换特性对目标函数进一步展开;采用交替迭代的方法完成能效最优的功率分配。仿真结果表明:所提算法在满足最小传输速率和最大发射功率的同时,可以兼顾系统能量效率和频谱效率;随着发射天线数量和接收中继数量的增加,系统性能也有明显提升,相比传统算法系统的能效和频谱效率至少提升5%。

不同参数高效超超临界机组经济性分析及建议

本文根据目前大量已投运二次再热机组运行经验,结合某660MW项目高效一次再热和二次再热不同的高效超超临界参数,结合对应的汽机热平衡图参数,通过对THA、80%THA、60%THA三个运行负荷进行了相关的机组经济性参数的计算和对比,通过分析提出了在选择一次再热或二次再热参数上的一些建议和结论。

用于微波无线输能的高增益柔性天线研究

为克服传统有线供能方式的接入不便问题,提出了一种用于5.8 GHz微波无线输能(MWPT)高增益柔性天线。天线以聚酰亚胺(PI)为基底,采用广义迭代设计方法得到3层圆环结构,并选用共面波导(CPW)方式馈电。此外,为提高天线增益,在天线背面加载空气层和柔性反射板,并对天线性能进行了测试。测量结果显示:该天线在频率5.8 GHz处的峰值增益为9.51 dBi;当天线弯曲在曲率半径为85,60,45 mm时,增益始终保持在8.89 dBi以上,S_(11)幅值始终小于-10 dB。最后,通过微波无线输能实验测得该天线最大能量捕获效率可达71.3%,在弯曲状态下也能保持59%以上的捕获效率。该天线的高增益、高能量捕获效率以及稳定性证明了其在微波无线输能中具有潜在的应用价值。

兆瓦级高效紧凑型核动力系统运行特性研究

为研究兆瓦级高效紧凑型核动力系统的运行特性,使用自主开发的热管堆瞬态分析程序TAPIRS(Transient Analysis code for heat Pipe and AMTEC power conversion space Reactor power System)和超临界二氧化碳布雷顿循环的瞬态分析程序SCTRAN/CO_(2)(Super Critical reactors Transient Analysis code/Carbon Dioxide)的耦合程序对其反应性、负荷、冷却水温度和流量等扰动进行了开环动态响应分析,并据此进行了控制系统设计。在此基础上,对线性变负荷、阶梯式变负荷以及甩负荷这三种变负荷运行工况进行了计算分析。结果表明:该核动力系统的转速对扰动的变化较为敏感,需要加以控制;低负荷下旁通会使压缩机流量上升,需对压缩机流量加以控制;系统在控制方案下能以6%FP(Full Power)·min^(−1)的速度实现0%~100%的负荷变动,且可以在任意负荷水平下运行;甩负荷下系统的波动时间变长,但是仍可达到新的稳态进行工作,且各参数处于安全范围内。本研究可为新型核动力系统的概念设计提供参考。

综采面坚硬顶板超深孔预裂爆破远场解危控制技术

工程实践表明,顶板事故在煤矿各类事故中占首要位置,已严重制约了我国现代化矿井安全高效开采。为了实现煤矿综采面坚硬顶板的安全治理,亟需形成综采面坚硬顶板超深孔预裂爆破远场解危控制技术以有效解决因工作面大空间坚硬顶板垮落而影响安全生产的重大难题。基于此,通过自主创新和联合攻关,面向深部矿井坚硬顶板,开展了综采面坚硬顶板超深孔预裂爆破远场解危技术研究;研发了高威力三级煤矿许用水胶炸药、填塞材料等技术与装备,形成了成熟的深孔爆破工艺,突破了厚硬顶板爆破中煤矿许用炸药威力与安全度的矛盾,解决了超深孔爆破中炸药可靠起爆等技术瓶颈问题;通过构建大空间采场覆岩-支架-围岩系统力学模型,揭示了采场大小周期来压及强矿压作用机理,提出了大空间采场厚硬覆岩多层位精准定位爆破弱化控制原理和基于爆破损伤的综采工作面厚硬顶板深孔爆破参数设计方法,形成了综采工作面厚硬顶板超前深孔卸压控制技术。研究成果在全国近百个综采面进行工程应用,未发生一起顶板事故,避免了综采面厚硬顶板发生压架、形成飓风、矿震等重大安全事故的风险,保障了综采面的安全高效生产,为综采面坚硬顶板远场解危的设计提供了理论依据并为现场施工提供了指导作用。

高频双频Buck变换器平面集成磁件优化设计

针对目前开关器件和磁性元件性能不足导致双频Buck变换器的效率和功率密度低的问题,研究了一种高效高功率密度的双频Buck变换器。变换器将工作在连续导通(CCM)模式,采用解耦合的平面集成电感器完成系统磁元件的集成,结合磁件的集成方法、有限的PCB层数和变换器的特性给出双频Buck变换器的参数,然后,提出了一种双频Buck变换器平面磁件的设计方法,并完成系统磁元件的优化设计。最后,基于第3代半导体SiC器件以及平面集成磁件,设计了额定功率200 W、开关频率400 kHz的双频Buck变换器。结果表明:该变换器峰值效率将达到96.1%,功率密度为46.1 W/in^(3)(1 in=25.4 mm),验证了双频Buck变换器设计方法的正确性和有效性。

基于谐波控制的Doherty功率放大器设计

功率放大器是无线通信里面重要的射频前端电路。为满足现代无线通信对功率放大器高效率的要求,首先基于谐波控制理论分析,设计了一种新型谐波控制电路,此新型谐波控制电路可对功率管产生的封装寄生参数进行补偿,也可对二次谐波、三次谐波进行谐波控制,提高了Doherty功率放大器效率。随后,针对传统Doherty功率放大器限制带宽的问题,提出了采用后匹配结构的方式设计Doherty功率放大器,提高了Doherty功率放大器的带宽。最后,采用Cree公司的CGH40010F GaN HEMT设计一款Doherty功率放大器并进行测试。在1.85~2.15 GHz工作频带内,Doherty功率放大器输出功率可达到44.3~44.8 dBm,增益为12~15 dB,输出漏极效率(DE)大于75%,6 dB回退效率大于60%。结果表明,提出的Doherty功率放大器在效率方面具有显著优势。

高功率高效率开口波导阵列天线设计与实验

针对研究具有高功率容量、高效率和低剖面特性的阵列天线的应用需求,提出并设计了一种高功率容量高效率开口波导阵列天线。该天线由紧凑型1分16路波导功率分配网络、4×4矩形开口波导单元和陶瓷密封罩组成,通过设计开口波导尺寸、在开口波导表面加载E面金属栅条,使得辐射口面的电场分布更为均匀,提高了单元辐射增益。采用阶梯匹配结构实现了波导功率分配网络输出端口到开口波导单元口面的尺寸变换,同时提高了系统的阻抗带宽。加载在阵面上的陶瓷罩可使天线内部处于真空状态,提高了天线的功率容量。针对X波段高功率阵列天线的应用需求,优化设计了一个中心频率为9.5 GHz的16单元开口波导阵列,仿真结果表明其在9.25~9.65 GHz范围内口径效率均大于90%,反射系数均小于-13.9 dB。对天线进行了加工测试,测试得到的天线反射曲线和中心频率下的辐射方向图与仿真结果吻合良好,中心频率下天线增益为21.7 dBi。天线整体剖面高度为中心频率处波长的2倍,仿真得到的真空中功率容量为40 MW,具有高功率容量、高效率和低剖面的特点。

用于高功率微波系统的全介质透镜阵列天线

为了实现透镜阵列天线所需的移相范围,设计了两种不同的单元结构,通过优化参数,在保证良好的传输幅值的基础上实现相移范围的互补。为了探索在高功率微波系统应用,对两种单元的功率容量也开展了详细研究。在无限周期情况下,随着单元尺寸变化,单元功率容量范围为1.08~19.37 MW;通过研制口径为315 mm×315 mm的透镜天线来构建有限周期条件,并仿真计算得到该天线最大功率容量为226.553 MW,功率密度可以达到2283.23 W/mm^(2),并且该天线在中心频点10 GHz处峰值增益可达到29.37 dBi,口径效率为62.43%,副瓣电平约为-21.54 dBi。结果表明所提出单元的有效性与正确性,也说明设计的透镜阵列天线不仅具有良好的辐射特性,同时具有MW量级的功率容量。