Novel method for the determination of five carbamate pesticides in water samples by dispersive liquid-liquid microextraction combined with high performance liquid chromatography

A novel method for the determination of five carbamate pesticides （metolcarb, carbofuran, carbaryl, isoprocard and diethofencard） in water samples was developed by dispersive liquid-liquid microextraction （DLLME） coupled with high performance liquid chromatography-diode array detector （HPLC-DAD）. Some experimental parameters that influence the extraction efficiency were studied and optimized to obtain the best extraction results. Under the optimum conditions for the method, the calibration curve was linear in the concentration range from 5 to 1000 ng mL^-1 for all the five carbamate pesticides, with the correlation coefficients （r^2） varying from 0.9984 to 0.9994. Good enrichment factors were achieved ranging from 80 to 177- fold, depending on the compound. The limits of detection （LODs） （S/N = 3） were ranged from 0.1 to 0.5 ng mL^-1. The method has been successfully applied to the analysis of the pesticide residues in environmental water samples.

Neutron Diffraction of Large-Volume Samples at High Pressure Using Compact Opposed-Anvil Cells

Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China＇s Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30°, Φ4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi（Ⅰ–Ⅱ 2.55 GPa, Ⅱ–V 7.7 GPa） are observed at 100 and 300 kN, respectively, by resistance measurements.The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth.As a result, pressures up to about 7.7 GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9 mm^3.

A New High-throughput Real-time PCR Assay for the Screening of Multiple Antimicrobial Resistance Genes in Broiler Fecal Samples from China

Objective Antimicrobial resistance(AMR)has become a global concern and is especially severe in China.To effectively and reliably provide AMR data,we developed a new high-throughput real-time PCR assay based on microfluidic dynamic technology,and screened multiple AMR genes in broiler fecal samples.Methods A high-throughput real-time PCR system with an new designed integrated fluidic circuit assay were performed AMR gene detection.A total of 273 broiler fecal samples collected from two geographically separated farms were screened AMR genes.Results The new assay with limits of detection ranging from 40.9 to 8,000 copies/reaction.The sensitivity rate,specificity rate,positive predictive value,negative predictive value and correct indices were 99.30%,98.08%,95.31%,99.79%,and 0.9755,respectively.Utilizing this assay,we demonstrate that AMR genes are widely spread,with positive detection rates ranging from 0 to 97.07%in 273 broiler fecal samples.bla CTX-M,bla TEM,mcr-1,fex A,cfr,optr A,and int I1 showed over 80%prevalence.The dissemination of AMR genes was distinct between the two farms.Conclusions We successfully established a new high-throughput real-time PCR assay applicable to AMR gene surveillance from fecal samples.The widespread existence of AMR genes detected in broiler farms highlights the current and severe problem of AMR.

The determination of 52 elements in marine geological samples by an inductively coupled plasma optical emission spectrometry and an inductively coupled plasma mass spectrometry with a high-pressure closed digestion method

An improved analytical method to determine the content of 52 major, minor and trace elements in marine geological samples, using a HF-HCl-HNO_3 acid system with a high-pressure closed digestion method（HPCD）, is studied by an inductively coupled plasma optical emission spectrometry（ICP-OES） and an inductively coupled plasma mass spectrometry（ICP-MS）. The operating parameters of the instruments are optimized, and the optimal analytical parameters are determined. The influences of optical spectrum and mass spectrum interferences, digestion methods and acid systems on the analytical results are investigated. The optimal spectral lines and isotopes are chosen, and internal standard element of rhodium is selected to compensate for matrix effects and analytical signals drifting. Compared with the methods of an electric heating plate digestion and a microwave digestion, a high-pressure closed digestion method is optimized with less acid, complete digestion,less damage for digestion process. The marine geological samples are dissolved completely by a HF-HCl-HNO_3 system, the relative error（RE） for the analytical results are all less than 6.0%. The method detection limits are 2–40μg/g by the ICP-OES, and 6–80 ng/g by ICP-MS. The methods are used to determine the marine sediment reference materials（GBW07309, GBW07311, GBW07313）, rock reference materials（GBW07103, GBW07104,GBW07105）, and cobalt-rich crust reference materials（GBW07337, GBW07338, GBW07339）, the obtained analytical results are in agreement with the certified values, and both of the relative standard deviation（RSD） and the relative error（RE） are less than 6.0%. The analytical method meets the requirements for determining 52 elements contents of bulk marine geological samples.

Characteristics analysis on high density spatial sampling seismic data

China＇s continental deposition basins are characterized by complex geological structures and various reservoir lithologies. Therefore, high precision exploration methods are needed. High density spatial sampling is a new technology to increase the accuracy of seismic exploration. We briefly discuss point source and receiver technology, analyze the high density spatial sampling in situ method, introduce the symmetric sampling principles presented by Gijs J. O. Vermeer, and discuss high density spatial sampling technology from the point of view of wave field continuity. We emphasize the analysis of the high density spatial sampling characteristics, including the high density first break advantages for investigation of near surface structure, improving static correction precision, the use of dense receiver spacing at short offsets to increase the effective coverage at shallow depth, and the accuracy of reflection imaging. Coherent noise is not aliased and the noise analysis precision and suppression increases as a result. High density spatial sampling enhances wave field continuity and the accuracy of various mathematical transforms, which benefits wave field separation. Finally, we point out that the difficult part of high density spatial sampling technology is the data processing. More research needs to be done on the methods of analyzing and processing huge amounts of seismic data.

Distribution and Migration of Heavy Metals in Undisturbed Forest Soils:A High Resolution Sampling Method

The vertical distribution and migration of Cu,Zn,Pb,and Cd in two forest soil profiles near an industrial emission source were investigated using a high resolution sampling method together with reference element Ti.One-meter soil profile was sectioned horizontally at 2 cm intervals in the first 40 cm,5 cm intervals in the next 40 cm,and 10 cm intervals in the last 20 cm.The migration distance and rate of heavy metals in the soil profiles were calculated according to their relative concentrations in the profiles,as calibrated by the reference element Ti.The enrichment of heavy metals appeared in the uppermost layer of the forest soil,and the soil heavy metal concentrations decreased down the profile until reaching their background values.The calculated average migration rates of Cd,Cu,Pb,and Zn were 0.70,0.33,0.37,and 0.76 cm year-1,respectively,which were comparable to other methods.A simulation model was proposed,which could well describe the distribution of Cu,Zn,Pb,and Cd in natural forest soils.

DESIGN OF NOVEL HIGH PRESSURE-RESISTANT HYDROTHERMAL FLUID SAMPLE VALVE

Sampling study is an effective exploration method, but the most extreme environments of hydrothermal vents pose considerable engineering challenges for sampling hydrothermal fluids. Moreover, traditional sampler systems with sample valves have difficulty in maintaining samples in situ pressure. However, decompression changes have effect on microorganisms sensitive to such stresses. To address the technical difficulty of collecting samples from hydrothermal vents, a new bidirectional high pressure-resistant sample valve with balanced poppet was designed. The sample valve utilizes a soft high performance plastic ＂PEEK＂ as poppet. The poppet with inapposite dimension is prone to occur to plastic deformation or rupture for high working pressure in experiments. To address this issue, based on the fmite element model, simulated results on stress distribution of the poppet with different structure parameters and preload spring force were obtained. The static axial deformations on top of the poppet were experimented. The simulated results agree with the experimental results. The new sample valve seals well and it can withstand high working pressure.

Rapid determination of atrazine in environmental water samples by a novel liquid phase microextraction

A novel method was described for the rapid determination of atrazine using dispersive liquid phase microextraction in combination with high performance liquid chromatography （HPLC）. Possible impact parameters such as sample pH, extraction and disperser solvents, salting-out effect, and extraction time were investigated. The experimental results indicated that proposed method possessed an excellent analytical performance, The linear range, detection limit, and precision （R.S.D.） were 0.1- 50 ng mL- 1 （R2 = 0.9955）, 0.601 ng mL- 1 and 6,4%, respectively. The proposed method was validated with the real water samples, and the spiked recoveries were in the range of 69.9-89.8%, respectively. These results indicated that the established method with high enrichment factor, short extraction time was an excellent alternative for the routine analysis of atrazine in environmental samples. 2007 Qing Xiang Zhou. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Silicon PIN photodiode applied to acquire high-frequency sampling XAFS spectra

Experimental techniques based on SR facilities have emerged with the development of synchrotron radiation(SR)sources.Accordingly,detector miniaturization has become significant for the development of SR experimental techniques.In this study,the miniaturization of a detector was achieved by coupling a commercial silicon PIN photodiode(SPPD)into a beamstop,aiming for it not only to acquire X-ray absorption fine structure(XAFS)spectra,but also to protect the subsequent two-dimensional detector from high-brilliance X-ray radiation damage in certain combination techniques.This mini SPPD detector coupled to a beamstop was used as the rear detector in both the conventional sampling scheme and novel high-frequency(HF)sampling scheme to collect the transmission XAFS spectra.Traditional ion chambers were also used to collect the transmission XAFS spectra,which were used as the reference.These XAFS spectra were quantitatively analyzed and compared;the results demonstrated that the XAFS spectra collected by this SPPD in both the conventional sampling scheme and HF sampling scheme are feasible.This study provides a new detector-selection scheme for the acquisition of the quick-scanning XAFS(QXAFS)and HF sampling XAFS spectra.The SPPD detector presented in this study can partially meet the requirements of detector miniaturization.

高压密闭酸溶-电感耦合等离子体发射光谱法测定硼矿石中的硼

应用电感耦合等离子体发射光谱法(ICP-OES)分析硼矿石中的硼含量,样品分解方法多采用酸溶法和熔融法,硼酸在浓酸溶液中加热蒸发时形成易挥发的BF_(3)或BCl_(3),造成硼的损失。熔融法可分解难溶于酸的硅硼钙石、电气石等样品,但将大量钠盐引入了样品中,基体较大,检出限高。本文建立了高压密闭酸溶、ICP-OES测定硼矿石中硼含量的方法。样品经硝酸和氢氟酸在高压密闭溶样罐中分解完全、定容稀释后,样品溶液用配备耐氢氟酸进样系统的ICP-OES测定。在ICP-OES中,硼有三条常用分析谱线,选取249.677nm为硼的分析谱线,标准曲线的线性相关系数大于0.9995。采用本方法对硼镁矿、锰方硼石和盐湖型固体硼矿三种类型5个不同含量范围的实际样品进行测定,相对标准偏差(RSD,n=11)为0.39%~2.66%,方法检出限为1.76μg/g,硼含量定量范围为5.87μg/g~10.8%。经标准物质验证,硼含量测定值与标准值一致,与容量法和微波消解法测定结果吻合。本方法试剂用量少,无需蒸干样品溶液,有效地避免了硼酸易挥发和试剂用量大的问题。

基于动态阈值和差异性检验的自训练算法

针对自训练算法在迭代训练分类器的过程中存在难以有效选取高置信度样本以及误标记样本错误累积的问题,本文提出了基于动态阈值和差异性检验的自训练算法。引入样本的局部离群因子,据此剔除有标签样本中的离群点以及分类标注无标签样本,依据标注分批次处理无标签样本,以使模型更易选取到高置信度的无标签样本;根据新增伪标签样本的数量和对比隶属度的变化,设计一种动态隶属度阈值函数,提升高置信度样本的质量;定义密集距离度量样本间的差异性,分别计算伪标签样本与同类和不同类样本之间的密集距离之和,从而找出不确定度高的伪标签样本,并将此类样本并入下轮训练的无标签样本集中,缓解误标记样本错误累积的问题。实验结果表明,该算法在12个UCI基准数据集上均取得理想效果。

三阶段自适应采样和增量克里金辅助的昂贵高维优化算法

代理辅助进化算法已广泛应用于求解代价高昂的多目标优化问题,但大多数由于代理模型的局限性而仅限于解决决策变量低维的问题。为了解决高维的昂贵多目标优化问题,提出了一种基于三阶段自适应采样策略的改进增量克里金辅助的进化算法。该算法使用改进的增量克里金模型来近似每个目标函数,此模型的超参数根据预测的不确定性进行自适应更新,降低计算复杂度的同时保证模型在高维上的准确性;此外,在模型管理方面提出一种三阶段自适应采样的策略,将采样过程分为不同的优化阶段以更有针对性的选择个体,能够首先保证收敛性,提高算法的收敛速度。为了验证算法的有效性,在包含各种特征的两组测试问题DTLZ(deb-thiele-laumanns-zitzler)、MaF(many-objective function)和路径规划实际工程问题上与最新的同类型算法进行实验对比,结果表明该算法在解决决策变量高维的昂贵多目标优化问题上具有较强的竞争力。

磁分散固相萃取-高效液相色谱法检测人体尿样中天麻素

建立了一种磁分散固相萃取技术结合高效液相色谱法,用于快速检测人体尿液样本中的天麻素。采用化学共沉淀法自组装制备磁性活性炭/大孔树脂三元复合材料(Fe_3O_(4)/AC/MR),并将该材料用作吸附剂,实现尿液样本中天麻素的分离富集。在最佳实验条件下,天麻素浓度与峰面积间呈良好线性关系,线性范围为3.0×10^(-2)~10.0μg·mL^(-1),线性相关系数为0.9994,检出限为5.4μg·L^(-1)。以模拟人体尿液作为实际样品进行加标回收验证,加标回收率为94.87%~106.3%,相对标准偏差(RSD)在2.8%-4.2%之间。本研究建立的方法简便、快速、有效,为生物样本中天麻素的分离提纯提供了新方法。

基于高分辨率遥感影像的居民地分类方法研究

随着我国城镇化进程的不断深入,大量乡村居民地已经转化为城镇居民地,为了度量二者实时的转化情况,该文提出一种基于监督分类机制的居民地分类方法,该方法首先采用边缘特征及高斯函数量化影像上的局部特征,然后构建5种城镇及乡村居民地分类规则,其次创建训练样本对各类规则进行学习,最后通过城镇及乡村测试样本验证该文方法的精度。实验表明,该文方法可以对高分辨率遥感影像城镇及乡村居民地进行初级分类,为“城镇化”进程提供一个新的衡量指标。

预制孪晶对AZ31镁合金绝热剪切敏感性的影响

为了分析不同孪晶体积分数对材料绝热剪切敏感性的影响,预制具有不同孪晶体积分数的AZ31镁合金。采用分离式霍普金森压杆在200℃、944 s^(-1)条件下对AZ31镁合金帽状试样进行高速冲击试验,采用电子背散射衍射仪和光学显微镜对试样在高应变速率变形前后的微观组织进行观察,计算了试样发生绝热剪切时的吸收能量,比较了绝热剪切带内外的显微硬度。结果表明:不同孪晶体积分数试样内均产生了绝热剪切带,随着孪晶体积分数的增加,绝热剪切带宽度和吸收能量减小,而绝热剪切敏感性增大。

电感耦合等离子体质谱(ICP-MS)法测定高钨基体样品中稀土元素的含量

准确测定钨矿和钨酸盐晶体等高钨基体样品中稀土元素的含量有助于开展矿床地球化学特征研究及钨酸盐激光晶体材料的制备和性质研究。在采用电感耦合等离子体质谱(ICP-MS)法测定高钨基体样品时,为了考察高钨及高含量阳离子等基体组成对分析结果的影响,针对Na_(2)WO_(4)、CaWO_(4)、NaY(WO_(4))_(2)、MnWO_(4)和(Fe,Mn)WO_(4)等高钨基体样品,采用硝酸和氢氟酸高压密闭消解,加入稀土元素并用2%HNO_(3)溶液稀释定容配制成稀土元素浓度为1 ng/g的基体匹配标准溶液;同时,直接用2%HNO_(3)溶液配制稀土元素浓度相同的非基体匹配标准溶液以对比两种基体溶液中稀土元素的相对灵敏度系数(RSCs)差异。结果显示,基体匹配溶液与2%HNO_(3)溶液中稀土元素的RSCs相对偏差小于15%,表明基体效应的影响可以忽略不计。进而,为了准确测定常见高钨基体样品中稀土元素的含量,建立了基于ICP-MS的高钨基体样品中稀土元素准确定量分析方法,方法线性关系好(R^(2)>0.9997),检出限低(0.5~27.9 pg/g),准确度理想(相对误差-6.2%~10.7%)。用来测定钨酸钙单晶实际样品中稀土元素的含量,并将其与基体匹配法的测定结果进行比对,结果显示,两者大部分元素相对偏差为0.80%~12.8%,说明所建立的分析方法可靠,能用于定量测定高钨基体样品中稀土元素的含量。

大流量高压燃烧加热器振动加速度测试分析

针对不同采样频率下(10、20、50、100、200 kHz)大流量高压燃烧加热器振动加速度差异较大的问题进行了研究,开展了冷吹试验、敲击试验、点火试验。采用时域分析法中的均方根、偏度、峭度,频域分析法中的功率谱密度,时频域分析法中的小波变换,并结合模态参数识别中的多参考最小二乘复频域法重点分析了10 kHz和200 kHz采样频率下的振动数据。获得了传感器的安装谐振频率、安装底座和待测设备组合体的固有频率以及加热器运行的主要频段,与声振频率计算公式的结果偏差小于5%。研究结果表明,采用10 kHz的采样频率能够有效表征加热器的振动情况,该方法可为大型复杂燃烧设备振动测试采样频率的选择提供参考。

高分辨率遥感影像样本库动态构建与智能解译应用

在人工智能时代,遥感影像解译朝着自动化智能化方向发展,高质量的样本数据集是其核心。我国积累了海量优质的时空地理信息基础数据及衍生产品,是深度学习驱动的遥感影像智能解译样本的重要来源。盘活现有数据资源,可推动人工智能与遥感解译的应用深度与广度。本文基于现有数据资源,针对样本数据集区域受限、时效性不强、类型单一等问题,研究了面向深度学习的高分遥感影像智能解译样本库动态构建技术。首先,分析了要素提取、地表覆盖分类、变化检测方面的公开样本数据集的特点,提出业务驱动的样本应需生成-动态构建-智能应用思路;其次,研究了基于历史解译成果的样本自动生成、SAM大模型提示学习引导的样本清洗精化方法及实现过程;再次,设计了具有区域性、时序性、尺度性、多传感器、多类型的样本库,以及顾及空间-时间-地类关系的动态样本数据库架构,研究了样本数据集“量化-检索-组合”动态重构过程,实现时空样本的动态管理与多维检索;最后,开展了地表覆盖分类、要素提取、变化检测等智能解译应用,验证了本文研究思路及方法的可行性,以期推动基于已有基础数据的样本数据集的有效利用,以及样本构建-管理-应用及数据-模型-业务的互联互通,为高分遥感影像智能解译样本库构建与应用提供参考思路。

一种用于常开型智能视觉感算系统的极速高精度模拟减法器

常开型智能视觉感算系统对图像边缘特征提取的精度和实时性要求更高,其硬件能耗也随之暴增。采用模拟减法器代替传统数字处理在模拟域同步实现感知和边缘特征提取,可有效降低感存算一体系统的整体能耗,但与此同时,突破10^(–7)s数量级的长计算时间也成为了模拟减法器设计的瓶颈。该文提出一种新型的模拟减法运算电路结构,由模拟域的信号采样和减法运算两个功能电路组成。信号采样电路进一步由经改进的自举采样开关和采样电容组成;减法运算则由所提出的一种新型开关电容式模拟减法电路执行,可在2次采样时间内实现3次减法运算的高速并行处理。基于TSMC 180 nm/1.8 V CMOS工艺,完成整体模拟减法运算电路的设计。仿真实验结果表明,该减法器能够实现在模拟域中信号采样与计算的同步并行处理,一次并行处理的周期仅为20 ns,具备高速计算能力;减法器的计算取值范围宽至–900~900 mV,相对误差小于1.65%,最低仅为0.1%左右,处理精度高;电路能耗为25~27.8 pJ,处于中等可接受水平。综上,所提模拟减法器具备良好的速度、精度和能耗的性能平衡,可有效适用于高性能常开型智能视觉感知系统。