Physical mechanism of silicon ablation with long nanosecond laser pulses at 1064 nm through time-resolved observation

Nanosecond (ns) laser ablation can provide a competitive solution for silicon micromachining in many applications. However, most of the previous studies focus on ns lasers at visible or ultraviolet (UV) wavelengths. The research is very limited for ns lasers at infrared (e.g., 1064 nm) wavelengths (which often have the advantage of much lower cost per unit average output power), and the research is even less if the ns laser also has a long pulse duration on the order of ∼100 ns. In this paper, time-resolved observation using an ICCD (intensified charge-coupled device) camera has been performed to understand the physical mechanism of silicon ablation by 200-ns and 1064-nm laser pulses. This kind of work has been rarely reported in the literature. The research shows that for the studied conditions, material removal in laser silicon ablation is realized through surface vaporization followed by liquid ejection that occurs at a delay time of around 200-300 ns. The propagation speed is on the order of ∼1000 m/s for laser-induced plasma (ionized vapor) front, while it is on the order of ∼100 m/s or smaller for the front of ejected liquid. It has also been found that the liquid ejection is very unlikely due to phase explosion, and its exact underlying physical mechanism requires further investigations.     

光催化甲苯衍生物、环烷烃与无机亚磺酸盐的位点选择性C(sp3)-H砜基化

烃类是最基础的有机分子之一,具有品种丰富、来源广泛、价格低廉等优势,其多样性、选择性转化一直备受合成化学家关注.然而,这些化合物中通常存在多个键能高、极性低、相互间差异性小的C(sp3)-H键,因此,实现高效、选择性C-H官能化极具挑战性.近年来,可见光催化广泛应用于有机合成中,与氢转移催化相结合所发展的可见光氢转移光...     

Simultaneous determination of phthalates and adipates in human serum using gas chromatography–mass spectrometry with solid‐phase extraction

A gas chromatography–mass spectrometry assay was developed and validated for the simultaneous determination of phthalates and adipates in human serum. The phthalates and adipates studied were dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzylbutyl phthalate, di‐2‐ethylhexyl phthalate, di‐n‐octyl phthalate, diethyl adipate, dibutyl adipate, diisobutyl adipate, bis(2‐butoxyethyl) adipate and di‐2‐ethylhexyl adipate, with diisooctyl phthalate as internal standard. The extraction and cleaning up procedure was carried out with solid‐phase extraction cartridges containing dimethyl butylamine groups, which showed extraction efficiencies over 88% for each analyte and the internal standard. The calibration curves obtained were linear with correlation coefficients greater than 0.98. For all analytes, the assay gave CV% values for intra‐day precision from 4.9 to 13.3% and mean accuracy values from 91.4 to 108.4%, while inter‐day precision was 5.2–13.4% and mean accuracy 91.0–110.2%. The limits of detection for the assay of phthalates and adipates were in the range 0.7–4.5 ng/mL. The method is simple, sensitive and accurate, and allows for simultaneous determination of nanogram levels of phthalates and adipates in human serum. It was successfully applied to an investigation on the level of phthalates and adipates in a non‐occupationally exposed population.     

光学非球面面形拟合方法研究

作者在研制一台高精度检测非球面仪器的过程中,探讨了二次和高次非球面面形方程参数的拟合方法。计算实例表明,线性化拟合法和非线性拟合法较圆满地达到了各种非球面面形拟合精度和实时处理的要求。     

多圆柱域上带间断系数的边值问题

本文研究多个复变数解析函数在多圆柱区域上带间断系数的Ｒｉｅｍａｎｎ－Ｈｉｌｂｅｒｔ边值问题。文中给出了这个问题适定的变态提法，首先证明了相应变态问题解的存在唯一性。然后给出原边值问题可解的充要条件及解的积分表达式。     

Gas chromatographic/mass spectrometric measurement of deuterium-labelled valine,leucine, isoleucine and phenylalanine in the human body

N-Trifluoroacetyl-n-butyl ester derivatives of deuterium-labelled valine, leucine, isoleucine and phenylulanine were analysed by the isotope dilution technique and gas chromatography/mass spectrometry (GC/MS). Selected ion retrieval and peak-area integration were applied. The conditions adopted gave good separations with a short experimental time and high intensity. Ratios of the total isotopic abundance and metabolic kinetic curves were obtained. The regression coefficient of the standard dilution curve was 0.99 and the relative standard deviation was 0.3%. The stabilities of the amino acid derivatives were also tested.     

DISTORTION OF CRYSTAL LATTICE IN NANOCRYSTALLINE Fe_2O_3

ＤＩＳＴＯＲＴＩＯＮＯＦＣＲＹＳＴＡＬＬＡＴＴＩＣＥＩＮＮＡＮＯＣＲＹＳＴＡＬＬＩＮＥＦｅ２Ｏ３ＹｅＸｉｓｈｅｎｇＳｈａＪｉａｎＪｉａｏＺｈｅｎｇｋｕａｎＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓ，ＺｈｅｊｉａｎｇＵｎｉｖｅｒｓｉｔｙＨａｎｇｚｈｏｕ３...     

实Clifford分析中六类拟Bochner-Martinelli型高阶奇异积分的几个问题

本文借助于Ｈａｄａｍａｒｄ关于高阶奇异积分有限部分的思想,研究关于实 Ｃｌｉｆｆｏｒｄ分析中六个类型(含一个奇点或二个奇点的)拟Ｂｏｃｈｎｅｒ－Ｍａｒｔｉｎｅｌｌｉ型高阶奇异积分的归纳定义、Ｈａｄａｍａｒｄ主值的存在性、递推公式、计算公式、微分公式、Ｐｏｉｎｃａｒｅ－Ｂｅｒｔｒａｎｄ置换公式以及拟Ｂ－Ｍ型高阶奇异积分的Ｈｏｌｄｅｒ连续性等问题．这些问题是研究单、多元复分析的学者们在研究奇异积分时,通常要涉及到的几个问题．