Computer design of a compact cyclotron

Here we present results of the computer design of the structural elements of a compact cyclotron by the example of HITFiL cyclotron selected as the driving accelerator that is under construction at the Institute of Modern Physics (Lanzhou, China). In the article a complex approach to modeling of the compact cyclotron, including calculation of electromagnetic fields of the structural elements and beam dynamics calculations, is described. The existing design data on the axial injection, magnetic, acceleration and extraction systems of the cyclotron are used as a starting point in the simulation. Some of the upgrades of the cyclotron structural elements were proposed, which led to substantial improvement of the beam quality and transmission.     

Integrated optical devices based on broadband epsilon-near-zero meta-atoms

We verify the feasibility of the proposed theoretical strategy for designing the broadband near-zero permittivity (ENZ) metamaterial at optical frequency range with numerical simulations. In addition, the designed broadband ENZ stack is used as meta-atoms to build functional nanophotonic devices with extraordinary properties, including an ultranarrow electromagnetic energy tunneling channel and an ENZ concave focusing lens.     

增压输送过程中卧式贮罐液氢温度分层研究

分析了大型卧式液氢贮罐增压输出过程中低温介质传热数学模型,揭示了贮罐内液氢温度分布规律,说明了液氢温度分层形成的原因及过程,给出了输出液氢品质保障方法。研究表明:大型卧式液氢贮罐输出过程中液氢温度分布可用修正后的半无限大平板非稳态导热方程描述;在增压压力一定情况下,热液层厚度随着输送时间的增加而增大,且热液层厚度及其温度分布受卧式贮罐截面形状影响;液氢贮罐输出品质与贮罐内热液层厚度密切相关,可通过计算热液层厚度从而确定贮罐留底余量的方法,保证贮罐输出品质。     

基于Lissajous图技术的波长移相标定方法

波长移相干涉仪可应用于大口径光学元件的检测。研究了基于Lissajous图技术的波长移相标定方法,实现了干涉图间移相量的计算,解决了在不同干涉腔长下进行测试时移相量需控制成为一个特定值的问题。首先通过模拟仿真,验证了方法的正确性;然后编写程序对已知移相量的实际干涉图进行计算。结果表明,在干涉图对比度较好以及对计算的两点选择恰当的情况下,计算出的相对误差在4%范围内。     

Enhanced mechanism of catalytic ozonation by ultrasound with orthogonal dual frequencies for the degradation of nitrobenzene in aqueous solution

The experiments have been performed with a semi-continuous batch reactor to investigate the degradation efficiency of nitrobenzene in aqueous solution by ultrasound with the different orthogonal dual frequencies catalytic ozonation. The introduction of ultrasound can enhance the degradation efficiency of nitrobenzene compared to the results obtained from the processes of ozonation alone and ultrasound alone. The degradation of nitrobenzene is found to be zero-order in the two systems of ultrasound alone, and the reactions follow the pseudo-first-order kinetic model in the processes of ozone alone and ozone/ultrasound. The investigation confirms that the degradation of nitrobenzene follows the mechanism of hydroxyl radical (^•OH) oxidation, and the enhancement function is even more pronounced in the presence of ultrasound with the greater difference between the orthogonal dual frequencies due to the obvious synergetic effect between ozone and ultrasound, which increases the utilization efficiency of ozone, and accelerates the initiation of ^•OH and the formation of H₂O₂, resulting in the rapid formation of an increasing diversity of byproducts and the advancement degree of mineralization of total organic carbon (TOC). The oxidative byproducts have been, respectively identified in the different processes selected, including o, p, m-nitrophenols, phenol, malonic acid, 4-nitrocatechol, nitrate ion, maleic acid, oxalic acid, hydroquinone, p-quinone, 1,2,3-trihydroxy-5-nitrobenzene and acetic acid.     

Characterization of different-Al-content AlGaN/GaN heterostructures on sapphire

Al x Ga 1-x N/GaN high-electron-mobility transistor (HEMT) structures with Al composition ranging from x = 0.13 to 0.36 are grown on sapphire substrates by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The effects of Al content on crystal quality, surface morphology, optical and electrical characteristics of the AlGaN/GaN heterostructures have been analyzed. Although high Al-content (36%) heterostructure exhibits a distinguished photoluminescence peak related to recombination between the two-dimensional electron gas and photoexcited holes (2DEG-h), its crystal quality and rough surface morphology are poor. 2DEG mobility increases with the Al content up to 26% and then it apparently decreases for high Al-content (36%) AlGaN/GaN heterostructure. The increase of sheet carrier density with the increase of Al content has been observed. A high mobility at room temperature of 2105 cm 2 /V s with a sheet carrier density of n s = 1.10 × 10 13 cm -2 , for a 26% Al-content AlGaN/GaN heterostructure has been obtained, which is approaching state-of-the-art for HEMT grown on SiC. Sheet resistance as low as 274 Ω/□ has also been achieved.     

Exact solutions to a coupled modified KdV equations with non-uniformity terms

The bilinear form of a coupled modified KdV equations with non-uniformity terms is given and a few soliton solutions are obtained. Furthermore, the multisoliton of the coupled system is expressed by Pfaffian.     

化学沉淀法制备硒化铅薄膜

采用化学沉淀的方法沉淀PbSe薄膜,分别加入缓冲剂联氨(方法A)和碘化钾(方法B)。对反应原理进行了分析,对制备过程进行了优化,分别制备出了高质量的PbSe薄膜。采用XRD、SEM、EDS以及红外光谱测试对所制备样品进行了分析。结果表明,两种方法制备均为PbSe多晶薄膜,方法A制备薄膜结晶质量更好,择优生长方向明显;薄膜颗粒度、表面粗糙度都小于方法B;两种薄膜的Pb元素与Se元素比例接近化学计量比,方法B含有少量I元素;两种方法制备样品的吸收边相对带边跃迁都发生蓝移。     

6.17-W continuous wave operation of a 2132-nm c-cut Tm,Ho:YAP pumped by a laser diode of 794.3 nm

Continuous wave (CW) operation of a c-cut Tm (5 at %), Ho (0.3 at %):YAP laser at 2132 nm wavelength were reported in this paper. In the temperature of 77 K, the Tm,Ho:YAP crystal was double end-pumped by a 21.4 W fiber-coupled laser diode (LD) at the center wavelength of 794.3 nm. Different resonator lengths and output couplers for the total pump power were tried. The resonator length was 205 mm, and the maximum CW output power of 6.17 W was acquired, corresponding to an optical-optical conversion efficiency of 28.8% and a slope efficiency of 35.6%.     

燃煤锅炉粉煤灰中痕量元素赋存形态研究

本文运用改进的Tessier法对某燃煤电厂静电除尘器收集的三个电场的粉煤灰进行分级提取(SEE)实验研究.SEE实验将粉煤灰中的重金属分为五个存在形态进行分级提取:水溶态(pH=7),酸溶态(pH=5),氧化物结合态,难还原态及残渣态.试验结果表明,残渣态在ESP除尘器所收集的飞灰中含量占据绝大部分;在容易迁移的离子可交换态和酸溶态中,所研究的痕量重金属元素均呈现出FA1相似文献