光声光谱技术在层状物质的逐层分析研究中的应用——Ⅰ.光声相位精细谱技术

本文提出光声相位精细谱法(PAPFS)。通过对层状物初始态光声相位扫描和对由此产生的PAPFS曲线的解析,可获取各层与光学热学和空间坐标相关的有价值的信息。本文用该法对彩色相纸作了逐层分析,并将结果与电镜作了比较。与PAPFS相关的层状物光声理论将在本文第Ⅱ部分中涉及。     

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.     

Simulation of growing GaN in vertical HVPE reactor

The paper reports the setting up of a model of fluid dynamic for GaN HVPE system and the simulation. It is found that when the direction of gravity is opposite to the direction of GaCl flow inlet,there exits a distance at which the uniformity of the deposition is optimal. Here the good uniformity of the deposition is obtained when the distance between the substrate and GaCl inlet is 5 cm. The parameters of gas flow used in growing GaN are also optimized. In addition, the influence of gravity and buoyancy on...     

直接酸提取电感耦合等离子体发射光谱法测定煤中主要成灰 …

本文提出了一种全新的以酸直接提取煤中的矿物元素、ＩＣＰ－ＡＥＳ测定其含量的方法。考察了最佳酸配比、酸用量、最佳提取时间、仪器最佳操作参数以及元素间的干扰等诸多因素。与其灰分含量相比,煤中矿物质的提取率在９５％以上,各元素加标回收率为９６％～１０４％,九次测定相对标准偏差小于４％。方法准确、快速、适合于不同煤样中矿物元素的分析测定。     

Improving the precision of fluorescence lifetime measurement using a streak camera

Streak camera has high temporal resolution and high sensitivity, and is a powerful tool in biomedical study to measure fluorescence lifetime and perform fluorescence lifetime imaging. However, nonuniformity of the gain in the streak tube and nonlinearity of the sweeping speed limit the precision of fluorescence lifetime measurement, particularly when fluorescence lifetimes are short. We have constructed a two-photon excitation fluorescence lifetime measurement system that is based on a synchroscan streak camera and have developed accordingly a method to correct the effect of gain nonuniformity and nonlinearity of sweeping speed on the measurement precision. A continuous-wave laser of high stability is used to calibrate the gain of the streak camera, and a Fabry-Perot etalon is used to calibrate the nonlinearity of the sweeping speed. Fitting algorithms are used to correct the gain of the streak camera and nonlinearity of the sweeping speed respectively, which significantly improves the measurement precision of the system, as characterized through the fluorescence lifetime of the short-lived fluorescence dye, Rose Bengal. Experimental results show that the measurement fluctuation of the lifetime has been improved from more than 10% to 2% after correcting the effects of gain nonuniformity and sweeping speed nonlinearity.     

Photolyses of mammalian carboxy-hemoglobin studied by photoacoustic calorimetry

The enthalpy and conformational volume changes in the photolyses of carboxy-hemoglobin (HbCO) of human, bovine, pig, horse and rabbit are investigated by photoacoustic calorimetry. Considering the time scales of the exciting laser pulse and the receiving ultrasound transducers (PVDF films and PZT ceramics), as well as the reaction lifetimes in the photolysis processes of HbCO, the measured results are related to the geminate recombination and tertiary relaxation in photolyses of HbCO. Moreover, the quantum yields of the five mammals are also measured by laser pump-probe technique. The results show that the dynamic parameters, such as enthalpy and conformational volume changes, differ between the processes of the geminate recombination and tertiary relaxation. Also, the dynamic parameters differ among the five mammals although some of them may be consistent with each other.     

铁电移相器优值研究

基于双周期性电容加载共面波导传输线的移相器结构,系统研究了温度变化对铁电薄膜移相器移相能力、传输损耗的影响.调整温度可以在一定的范围内实现对移相器性能指标的微调.给出了加载因子对移相能力的示意曲线图,并在实验上,借助氩离子刻蚀技术,改变加载因子的大小,使得移相器的优值从原来的13degree/dB提升到23degree/dB.     

Experimental implementation of a fixed-point duality quantum search algorithm in the nuclear magnetic resonance quantum system

In this work, we demonstrated a fixed-point quantum search algorithm in the nuclear magnetic resonance (NMR) system. We constructed the pulse sequences for the pivotal operations in the quantum search protocol. The experimental results agree well with the theoretical predictions. The generalization of the scheme to the arbitrary number of qubits has also been given.     

Investigation into the rotational bands of ~(185)Pt with the particle-rotor model

Theoretical calculations have been performed for the ν9/2+[624](i13/2) and ν7/2-[503](f7/2) bands of 185Pt in the framework of particle-rotor model. The band properties of signature splitting and configuration mixing have been analyzed. The level energy and signature splitting before the band crossing can be well interpreted by introducing triaxiality. The positive-parity yrast band is pro posed to be dominated by the ν9/2+[624](i13/2) component, while the negative-parity band shows strong mixing of ν7/2-[5...     

Effects of initial crystal size of diamond powder on surface residual stress and morphology in polycrystalline diamond (PCD) layer

Polycrystalline diamond compacts (PDC) were synthesized using diamond powder of average crystal size 3-20 μm by the Ni 70 Mn 25 Co 5 alloy infiltration technique at high temperature and high pressure (HPHT).The surface residual stress of polycrystalline diamond (PCD) layer was measured using micro-Raman spectroscopy with hydrostatic stress model and X-ray diffraction (XRD).Measurements of the stress levels of PCDs show that the residual compressive stresses range from 0.12 to 0.22 GPa,which increase with th...