Optically referenced broadband electronic synthesizer with 15 digits of resolution

Fundamental science, as well as all communications and navigation systems, are heavily reliant on the phase, timing, and synchronization provided by low‐noise and agile frequency sources. Although research into varied photonic and electronic schemes have strived to improve upon the spectral purity of microwave and millimeter‐wave signals, the reliance on conventional electronic synthesis for tuning has resulted in limited progress in broadband sources. Using a digital‐photonic synthesizer architecture that derives its time‐base from a high‐stability optical reference cavity, we generate frequency‐agile and wideband microwave signals with exceptional dynamic range and with a fractional frequency instability of 1 × 10⁻¹⁵ at 1 s. The presented architecture demonstrates digitally controlled, user defined and broadband frequency tuning from RF to 100 GHz with orders‐of‐magnitude improvement in noise performance over room‐temperature electronic wide‐bandwidth synthesis schemes.

     

Frequency comb generation in the green using silicon nitride microresonators

Optical frequency combs enable precision measurements in fundamental physics and have been applied to a growing number of applications, such as molecular spectroscopy, LIDAR and atmospheric trace‐gas sensing. In recent years, the generation of frequency combs has been demonstrated in integrated microresonators. Extending their spectral range to the visible is generally hindered by strong normal material dispersion and scattering losses. In this paper, we report the first realization of a green‐light frequency comb in integrated high‐Q silicon nitride (SiN) ring microresonators. Third‐order optical non‐linearities are utilized to convert a near‐infrared Kerr frequency comb to a broadband green light comb. The 1‐THz frequency spacing infrared comb covers up to 2/3 of an octave, from 144 to 226 THz (or 1327‐2082 nm), and the simultaneously generated green‐light comb is centered around 570‐580 THz (or 517‐526 nm), with comb lines emitted down to 517 THz (or 580 nm) and up to 597 THz (or 502 nm). The green comb power is estimated to be as high as −9.1 dBm in the bus waveguide, with an on‐chip conversion efficiency of −34 dB. The proposed approach substantiates the feasibility of on‐chip optical frequency comb generation expanding to the green spectral region or even shorter wavelengths.

     

Thermal Properties of Oligo(2-ethyl-2-oxazoline) Containing Comb and Graft Copolymers and their Aqueous Solutions

Summary: The cationic ring opening polymerization of 2-ethyl-2-oxazoline (EtOx) was applied for the synthesis of methacrylate end-functionalized well-defined macromonomers that could be polymerized in a controlled manner using reversible addition-fragmentation chain transfer polymerization. The obtained comb polymers revealed lower critical solution temperature behavior in aqueous solution. The cloud points of these solutions could be tuned in a range from 35 °C to 85 °C by the incorporation of hydrophobic methyl methacrylate comonomer in varying amounts into the graft copolymers whereas copolymerization with methacrylic acid rendered temperature and pH sensitive copolymers. Thermo-gravimetric analysis showed a two-step decomposition of the graft copolymers and differential scanning calorimetry revealed glass transition temperatures that are significantly lowered in comparison to linear PEtOx.     

非对称心理压力下的低碳环境友好技术国际转移博弈研究

在全球积极应对和适应气候变化的背景下,研究了心理压力和信息条件因素对低碳环境友好技术(LCEFT)转让企业与受让企业决策行为的影响。通过引入对谈判区间、还价策略和不同心理压力的假设,构造了非对称信息下的LEFCT转移讨价还价博弈模型,深入分析了收益贴现参数、心理压力参数和谈判区间等因素对博弈双方报价策略、还价策略以及成交价格所产生的影响。研究表明,心理压力和信息条件都会直接影响博弈双方的报价策略、还价策略和最终的成交价格,并得出了不同信息条件下受让企业“见好就收”和“对半侃价”的还价策略。本文为受让企业在应对全球气候变化中面对不同的心理压力和信息条件所应采取何种还价策略提供了一定的决策支持。     

一种新型混合非对称多电平逆变器的研究

提出了一种新型混合非对称多电平逆变器,该逆变器的突出优点是在输出相同电平的条件下,电路所需的开关元器件和其他元器件比传统的多电平逆变器要少的多,简化了电路结构和控制,降低了成本。对逆变器主电路的结构和工作原理进行了详细阐述,并采用消谐波脉宽调制（Subharmonic Pulse Width Modulation,简称SHPWM）进行控制。最后给出了仿真结果,验证了理论分析。     

一种新的兼容栅偏源结构AlGaN/GaN HEMT的小信号模型

本文提出了一种新的AlGaN/GaN HEMT小信号模型,此模型可在20GHz以内对栅偏源结构HEMT进行精确模拟。模型中的寄生参数由零偏及截止两种偏置下的S参数来决定,本征部分采用直接提取的方式得出。本模型中的所有参数及比例系数均由器件结构决定,并不涉及任何优化算法,因而保证了模型参数值与物理意义的统一。     

An asymmetrical sensing scheme for 1T1C FRAM to increase the sense margin

A novel asymmetrical current-based sensing scheme for 1T1C FRAM is proposed,in which the two input transistors are not the same size and a feedback NMOS is added at the reference side of the sense amplifier.Compared with the conventional symmetrical scheme in Ref.[8],the proposed scheme increases the sense margin of the readout current by 53.9%and decreases the sensing power consumption by 14.1%,at the cost of an additional 7.89%area of the sensing scheme.An experimental FRAM prototype utilizing the prop...     

基于遗传算法的梳状谱峰值控制方法

针对梳状谱峰值控制问题，采取遗传算法（GA）搜索梳状谱峰值的最小值。通过构造相位集进行编码，采用移民和精英保留使得结果收敛到最优解，实验结果表明此方法比穷举法效果好且耗时短。     

Relaxation effects in the Mössbauer spectra of iron complexes with fatty acids

Six new oxo trinuclear iron(III) complexes of the type [Fe₃O(R–COO)₆(H₂O)₃] X, where X= or Cl^– and R=C₅, C₇, C₈, C₉ were synthesized and investigated by Infra Red, Mössbauer Spectroscopy and magnetic measurements. The data pointed to a high spin state (S=5/2) for iron and for antiferromagnetic interactions. The asymmetrical shape of the Mössbauer doublet and its temperature dependence was treated using the Blume relaxation model. The relaxation process is influenced by both X and R components.     

Hindered rotation of ligands in cis-[PtR2Cl2] complexes

The temperature dependence of the¹H NMR spectra ofcis-[Pt(II)R₂Cl₂] complexes was studied in DMSO at 18–100°C (R is 2-methyl and 2,5-dimethylpyridine). The broadening of the signals from the methyl groups or hydrogen atoms in theortho-positions of heteroaromatic ligands is due to the coexistence of two forms of thecis-complexes in solution. These forms arise from the hindered rotation of asymmetrical ligands around the Pt-N bond.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 424–425, February, 1993.