提高声光调Q光纤激光器输出功率的关键因素分析

声光调Q光纤激光器具有所需驱动调制电压很低，容易实现对连续激光调Q获得高重复频率脉冲输出的特点。介绍丁声光调Q光纤激光器的原理，并对影响它性能的几个重要因素如自发辐射的放大、泵浦功率和速率、光纤的选择、声光Q开关的重复频率等主要因素做理论分析，提出了优化这些因素的方法。     

Collaborative study of the oil stability index analysis

The Oil Stability Index Analysis method was subjected to a fifteen-laboratory collaborative study in which the participants used currently available commercial and home-built instruments to provide data to support the approval process as an Official Method of the American Oil Chemists’ Society. The overall average coefficient of variation was 11.3% for samples from 7 to 80 h of stability testing at 110°C.     

An Acousto-Optic Vibrometer for Measurement of Vibration in Ultra-Precision Machine Tools

Measurement of vibration is a vital factor that limits the precision and accuracy of machining of micro and macro components. In this paper, a novel technique for measurement of vibration is proposed using an acousto-optic modulator, which highlights an improved approach in measuring vibration in the subnanometre range. An experimental comparison was made with a laser Doppler vibrometer. This novel concept is proposed for application to a precision machine tool to measure the vibration on the machine bed induced during the machining process and by the external environment, which can be compensated for by in-process techniques. This novel measurement technique can also be applied for the precision measurement of the stage movement in ultra-precision machines to a subnanometre resolution.     

UV-induced photochemical heterogeneity of dissolved and attached organic matter associated with cyanobacterial blooms in a eutrophic freshwater lake

Cyanobacterial blooms represent a significant ecological and human health problem worldwide. In aquatic environments, cyanobacterial blooms are actually surrounded by dissolved organic matter (DOM) and attached organic matter (AOM) that bind with algal cells. In this study, DOM and AOM fractionated from blooming cyanobacteria in a eutrophic freshwater lake (Lake Taihu, China) were irradiated with a polychromatic UV lamp, and the photochemical heterogeneity was investigated using fluorescence excitation–emission matrix (EEM)-parallel factor (PARAFAC) analysis and synchronous fluorescence (SF)-two dimensional correlation spectroscopy (2DCOS). It was shown that a 6-day UV irradiation caused more pronounced mineralization for DOM than AOM (59.7% vs. 41.9%). The EEM-PARAFAC analysis identified one tyrosine-, one humic-, and two tryptophan-like components in both DOM and AOM, and high component photodegradation rates were observed for DOM versus AOM (k > 0.554 vs. <0.519). Moreover, SF-2DCOS found that the photodegradation of organic matters followed the sequence of tyrosine-like > humic-like > tryptophan-like substances. Humic-like substances promoted the indirect photochemical reactions, and were responsible for the higher photochemical rate for DOM. The lower photodegradation of AOM benefited the integrality of cells in cyanobacterial blooms against the negative impact of UV irradiation. Therefore, the photochemical behavior of organic matter was related to the adaptation of enhanced-duration cyanobacterial blooms in aquatic environments.     

The impact of differing cell and algogenic organic matter (AOM) characteristics on the coagulation and flotation of algae

The aim of this study was to compare the coagulation and flotation of different algae species with varying morphology and algogenic organic matter (AOM) composition in order to link physical and chemical algae characteristics to treatment. Microcystis aeruginosa (cyanobacteria), Chlorella vulgaris (green algae), Asterionella formosa and Melosira sp. (diatoms) were treated by coagulation with aluminium sulphate and flotation. The AOM was extracted and treated separately. Analyses included cell counts, dissolved organic carbon, aluminium residual and zeta potential. Removal efficiencies in the range 94-99% were obtained for each species. Cells, AOM and aluminium were concurrently removed at a coagulant dose that was related on a log-log basis to both cell surface area and total charge density, although the relationship was much stronger for the latter. This was attributed to a significant proportion of the coagulant demand being generated by the AOM. The implications of such findings are that relatively simple charge measurements can be used to understand and control coagulation and flotation of algae.     

南海北部Site 3A站位沉积物地球化学特征及其对甲烷渗漏的指示*

南海北部陆坡具有较好的水合物成藏潜力,而甲烷渗漏区的地球化学特征和沉积环境以及自生矿物的关系对天然气水合物的勘探和开采有重要指示意义。选取南海北部陆坡Site 3A站位柱状沉积物作为研究对象,通过对其主微量元素、五种形态的磷、不同形态的铁、铬还原硫（CRS）、硫同位素以及有机碳值等数据进行地球化学特征分析。结果表明,南海北部Site 3A站位柱状沉积物主要以200 cmbsf深度作为分界线,分成以有机质硫酸盐还原作用为主的上部和以甲烷厌氧氧化（AOM）作用为主的下部,对比上部,下部可指示黄铁矿含量的CRS含量增加,说明该站位存在AOM作用,200 cmbsf深度以下为硫酸盐-甲烷过渡带（SMTZ）。δCe在200 cmbsf深度以下呈现先增大后减小的趋势,说明200 cmbsf深度以下为偏碱性的还原环境。沉积物中的锰、自生磷灰石态磷（P_CFA）、铁结合磷（P_Fe）、可还原性铁（Fe_ox）、磁铁矿铁（Fe_mag）和碳酸盐铁（Fe_cab）的含量变化均受到了AOM作用的影响,下部沉积物中指示富镁方解石含量的Mg/Ca值较高,指示文石含量的Sr/Ca值无明显变化;同时,δ³⁴S并未出现明显的正偏现象,而200 cmbsf深度以下CRS和总硫（TS）的含量只是略有增加,说明该地区主要以低渗漏或甲烷扩散为主。     

用于半导体激光器冷却囚禁原子的声光晶体驱动器及其性能测量

为满足半导体激光器应用于激光冷却囚禁原子的需要,本文设计了输出功率和频率可由外部信号控制的声光晶体驱动器,其输出功率可由0W变至2W,频率由54MHz变至120MHz.提出了F-P腔和声光晶体双通过装置联用来测量其频率动态特性的一种方法,对驱动器的频率和功率动态性能进行了测量.     

干涉条纹相位锁定系统

干涉曝光系统中干涉条纹的相位漂移会导致曝光对比度降低,为了有效抑制相位漂移,利用声光调制器对干涉光频率进行实时调制。分析了条纹漂移的特点,指出了主要干扰源是0~5 Hz的空气扰动。应用数值分析法得到了条纹漂移量与曝光对比度的关系曲线,并以此为依据提出了条纹锁定精度的目标值。针对所要达到的锁定精度,给出了系统硬件的选型方法,搭建了基于RTX的干涉条纹相位锁定系统。利用闭环辨识的方法得到了系统的参数模型,完成了反馈控制器的设计,最终实现了实时锁定条纹相位的功能。实验结果表明,在400Hz的控制频率下,干涉锁定系统能够有效抑制0~5Hz的低频扰动,干涉条纹相位漂移的3σ值可以控制在±0.04个条纹周期内,满足干涉光刻的曝光对比度要求。     

一种新的儿茶素类食用植物油抗氧化剂

以大豆色拉油和精炼菜籽色拉油为实验油，采用活性氧法(AOM)研究了儿茶素EGCG的长链脂肪酸酯EGCG单棕榈酸酯的抗氧化活性，并与合成抗氧化剂特丁基-4-羟基茴香醚(BHA)、2，6-二特丁基对甲酚(B肿)、叔丁基对苯二酚(TBHQ)的抗氧化活性进行了比较，结果表明脂溶性的EGCG单棕榈酸酯的抗氧活性与TBHQ相当，而比BHA、BHT有更强的活性，是食用植物油很好的抗氧化剂。     

双级时变圆柱齿轮系统的扭转振动特性研究

在考虑二级齿轮传动系统时变啮合刚度的情况下,建立了其动力学方程,它是一个具有周期性时变系数的线性动力学系统。将时变啮合刚度用Fourier级数展开后,用AOM推导出了系统的近似解析解。在系统的响应中,含有基频、倍频和组合频率成分,因此,AOM比谐波平衡法具有更高的精度;与其他数值方法相比,具有更快的计算速度;当响应频率等于派生系统的固有频率时,将会出现主共振、超谐共振和组合共振现象;时变啮合刚度还导致了较大的动载荷;如果忽略时变啮合刚度三次以上谐波分量,在特定的系统参数下,系统的响应无明显变化。