燃烧蜡烛水中悬浮现象的研究

对燃烧蜡烛在水中悬浮的机理进行了理论与实验探究.通过建立近似垂直井结构模型,从辐射能流的角度对蜡烛的整个燃烧过程进行了理论分析.并且从实验上探究了蜡烛长度、蜡烛半径、以及配重对于蜡烛悬浮过程的影响.最后还对其振动模式进行了分析.     

密立根油滴实验人为操作引起的误差探析

针对密立根油滴实验由于人为操作引起的误差进行了探究与分析,重点分析了下落时间t、平衡电压U、下降距离L三种操作引起的误差.结合相应的图示,对不同误差组进行了分析,最后给出了与理论分析一致的结论.     

基于FTIR指纹光谱的牛肉产地溯源技术研究

在中国牛肉4个产区吉林省榆树市,贵州省安顺市、宁夏自治区同心县、河北省张北县屠宰场采集了58个肉牛牛肉样品,进行脱脂、干燥、粉碎.利用近红外光谱分析技术,对牛肉样品的近红外光谱进行主成分分析、聚类分析、判别分析,建立了判别牛肉产地来源的傅里叶变换红外光谱定性分析模型.分析结果显示4个产区的牛肉的平均近红外光谱存在有差异,牛肉样品的主成分空间分布也位于不同的区域.根据光谱距离,对样品进行聚类分析,初步判定了牛肉的产区,其中贵州的牛肉光谱比较复杂,与河北牛肉样品的光谱距离很近,存在一定交叉.利用来源于4个产区的18个独立样品对模型进行了验证,正确识别率为100%.说明应用近红外光谱分析技术可准确、快速、低廉地追溯牛肉的产地来源.     

煤粉再燃燃烧含氮组分转化机理的敏感性分析

本文以GRI 3.0数据库为基础,结合CHEMKIN模块软件中敏感性分析的方法对煤粉再燃燃烧过程进行了数值模拟研究.通过对整个全模型反应方程进行分析,可以把整个反应机理模型主要分为碳氢组分转化反应机理和含氮组分转化反应机理两大类.本文重点对含氮组分转化反应机理进行了分析.在模拟的基础上,对含氮组分HCN、HNCO、NHt、NCO等转化反应进行了分类,系统地讨论了燃烧过程中含氮组分转化反应对NO的敏感性分析,清晰地揭示了含氮组分生成与还原NO的途径以及作用大小,为实际超细煤粉再燃燃烧技术提供了一定的理论依据.     

新型发蓝光材料的合成和光谱表征及光致和电致发光性能的研究

合成了能发射蓝光的锌的配合物.对配合物进行了元素分析、激发光谱、发射光谱、红外光谱进行了研究.利用配合物制成发光二极管的发光层,对其光致和电致发光性能进行了探讨.它能发射蓝光,波长为455 nm,亮度为37.20 cd·m-2 .     

人参总皂甙近红外光谱及定标建模分析

采用近红外光谱分析技术对人参进行了光谱及定量分析.对人参的原始漫反射吸收光谱采用二阶导数、散射校正、相关分析等多种光谱解析手段,研究了人参中的主要成分总皂甙的光谱吸收特性,并结合偏最小二乘回归法对人参总皂甙进行了定标建模分析.分析结果精度高,定标标准差(RMSEC)为0.154%,相关系数为0.982 8.     

CO2跨临界循环中膨胀过程的对比与分析

本文对于CO2超临界流体的等熵膨胀和等焓膨胀过程进行了热力学分析、计算和对比,发现等熵膨胀过程与等焓膨胀相比,增大了有效制冷量,增大的数值略大于所回收的膨胀功.而且对于减小节流损失的回热循环和膨胀机循环进行了分析和对比,对于选用原则给出了具体的判定方法.本文还进行了膨胀机中膨胀过程的热力学分析,分别得出了超临界区和两相区的膨胀功来源,及变化规律.经分析,本文作者认为可以采用"闪蒸破碎模型"简化汽液两相流绝热膨胀基本特性方程.最后,本文对膨胀机实际工作的不可逆因素进行了分析.     

单轴应变硅N沟道金属氧化物半导体场效应晶体管电容特性模型

电容特性模型是单轴应变硅金属氧化物半导体场效应晶体管(Si MOSFET)和电路进行瞬态分析、交流小信号分析、噪声分析等的重要基础. 本文首先建立了单轴应变Si NMOSFET 的16 个微分电容模型, 并将微分电容的仿真结果与实验结果进行了比较, 验证了所建模型的正确性. 同时对其中的关键性栅电容C_gg 与应力强度、偏置电压、沟道长度、栅极掺杂浓度等的关系进行了分析研究. 结果表明, 与体硅器件相比, 应变的引入使得单轴应变Si NMOSFET器件的栅电容增大, 随偏置电压、沟道长度、栅极掺杂浓度的变化趋势保持不变.     

ICP-AES测定铜合金中的铜及10种杂质元素

建立了ICP-AES同时测定铜合金中铜及杂质元素磷、硅、锰、铁、镍、钴、锌、铅、铝、锡11种元素的分析方法,通过对样品溶解方法、元素分析谱线的选择和仪器分析参数进行试验比较,确定了实验条件,并对铜合金标准样品进行了精密度和回收率实验.结果表明,相对标准偏差小于3.0％,回收率在90％-110％之间.该方法快速简便,准确度高,可以满足日常检验的分析要求.     

关于分数阶RL_α-C_β并联谐振品质因数Q的讨论

根据电路理论求得分数阶RL_α-C_β并联电路的导纳,以α=β、CR~2/L1为条件,求得电路谐振频率的简易表达式.在此基础上推导出了RL_α-C_β并联谐振电路品质因数的简易表达式,并对其进行了分析讨论.用MATLAB软件进行了仿真分析,理论分析和仿真分析基本吻合,从而找到了品质因数Q随元件参数及分数阶次数变化的规律.     

Monitoring of persistent organic pollutants in the ambient air as an element of implementation of the Stockholm Convention on persistent organic pollutants

The results of monitoring of persistent organic pollutants (POPs) in the atmosphere of the Russian Arctic are presented. The concentrations of POPs in different regions of the Russian and foreign Arctic are compared. It was revealed that the concentrations of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) are higher in the Northern Chukotka (Valkarkai) as compared to that at the other Russian stations (Amderma and Dunay) and foreign global POPs monitoring stations. The composition of PCB congeners in the air of the Arctic Chukotka turned out to be different from that observed at the other monitoring stations, being similar to commercial PCBs mixtures. In contrast to observations at most of the global POPs monitoring stations, monitoring in the Far East Russian Arctic has revealed increased levels of PCBs in the air for the last 6?C8 years. The levels of DDT in the past 6?C8 years have remained virtually unchanged, whereas those hexachlorocyclohexane have decreased somewhat. It was shown that polybrominated diphenyl ethers (PBDEs) are ubiquitous and are found in significant quantities in the air in both the central cities (Moscow, Obninsk) and remote locations (Arkhangelsk, Amderma, Valkarkai). The gas phase contains largely more volatile low-brominated DEs, while atmospheric aerosols contain predominantly highly brominated congeners. The indoor air at all sampling locations contained substantially higher concentrations of PBDEs as compared to the atmospheric air. Priorities for the establishment of a national system for monitoring of POPs within the framework of the Stockholm Convention on POPs control are proposed.     

Insights into the elimination mechanisms employed for the degradation of different hexachlorocyclohexane isomers using kinetic isotope effects and docking studies

Modern DFT functional as well as the continuum solvation model have been applied in order to theoretically predict carbon, chlorine and hydrogen kinetic isotope effects (KIEs) during aerobic degradation of four hexachlorocyclohexane isomers (α, β, δ and γ). A small model of the hexachlorocyclohexane dehydrochlorinase (LinA) active site comprising its catalytic dyad has been constructed based on the receptor–ligand complexes suggested by docking studies and compared to the respective reaction modeled in aqueous solution. In‐depth analysis of chlorine and hydrogen KIEs patterns clearly indicates different transition states in aqueous solution and in the model mimicking the protein active site. Although all isomers seem to undergo a concerted E2 mechanism, the contribution of proton transfer and carbon–chlorine leaving group bond stretch in the transition states differs for the different isomers giving rise to totally different magnitudes of predicted isotope effects. Copyright © 2013 John Wiley & Sons, Ltd.     

沸水浸提-电感耦合等离子体发射光谱法测定土壤中的有效硼

土壤中有效硼测定对评价土壤有效硼供应水平具有重要意义,土壤中有效硼含量的高低直接影响植物的生长过程,因此如何提取和测定有效硼的含量至关重要。然而传统的沸水浸提-姜黄素比色法和沸水浸提-亚甲胺比色法前处理部分流程长、速度慢和使用试剂较多且不易操作,检测结果容易造成较大的误差,随着土地质量地球化学调查、生态地球化学调查和农业地质调查项目工作的开展,该方法已经不能满足大批量及快速测定土壤样品的要求。采用沸水浸提土壤中的有效硼,浸提液采用电感耦合等离子体发射光谱测定,主要是从密闭和敞开环境浸提、最佳浸提时间、测定过程中谱线的干扰和不同的土壤类型进行实验的对比研究,优选出适合分析土壤中有效硼的实验条件。结果表明：不同类型的土壤中有效硼在敞开环境条件下,沸水浸提10 min中,测量值与标准物质推荐值最接近,在测定过程中,由于沸水浸提出的铁的含量较低,对测定有效硼的含量基本无影响。该方法的检出限为0.004 9 μg·g-1,测定结果的相对标准偏差（RSD,n=12）均小于9%,准确度经12个国家一级土壤有效态成分分析标准物质验证,测定结果与推荐值相符。沸水浸提-电感耦合等离子体发射光谱法前处理操作简单、流程短、检测快速,分析结果准确可靠,避免样品处理过程中的硼污染,且一次可浸提几十个土壤样品,大大提高了分析效率,适合于土壤中有效硼含量的测定。     

土壤中无机砷测定的三种前处理方法比较

对土壤无机砷分析的样品前处理技术-微波辅助提取、超声波提取、水浴提取进行了对比研究.结合氢化物发生-原子荧光光谱(HG-AFS)测定技术比较了3种方法对国家土壤标准物质中无机砷的提取效果,并对溶剂类型、提取时间和提取剂用量等影响因素进行了考察.与超声波提取法和水浴提取法相比,微波辅助提取法具有快速、高效的优势.     

铝粉-空气混合物爆燃转爆轰过程及爆轰波结构

 在长为32.4 m、内径为0.199 m的大型长直水平管道中,对铝粉-空气两相流的燃烧转爆轰（DDT）过程及爆轰波结构进行了实验研究。对铝粉-空气混合物弱点火条件下DDT过程不同阶段的特征进行了分析,实验结果显示混合物经历了缓慢反应压缩阶段、压缩波加速冲击波形成阶段、冲击反应过渡阶段、冲击反应向过压爆轰过渡阶段和爆轰阶段,得到了混合物各阶段的DDT参数,由此进一步分析了DDT浓度的上、下限。在1.4 m爆轰测试段的4个截面的环向上各均匀安装8个传感器,对爆轰波结果进行测试,并对铝粉-空气混合物爆轰波的单头结构进行了分析。     

气相DDT中过爆轰现象产生条件的实验研究

针对目前国际上关于气相过爆轰产生条件的3种不同观点,利用压力传感器,实验研究了氢氧混合物的爆燃转爆轰(DDT)全过程。获得了比较完整的、能反映气相DDT从爆燃成长为过爆轰再衰减为稳定爆轰的全过程压力变化曲线。分析实验结果表明,氢氧混合物的DDT过程中,过爆轰的产生需要一定条件;在初始压力一定的情况下,氢氧混合物DDT过程的转变时间或距离随氢气浓度的增加,先减小后增大,过爆轰的压力峰值约为稳定爆轰压力的1.5～2倍。     

Spontaneous transition of turbulent flames to detonations in unconfined media

A deflagration-to-detonation transition (DDT) can occur in environments ranging from experimental and industrial systems to astrophysical thermonuclear (type Ia) supernovae explosions. Substantial progress has been made in explaining the nature of DDT in confined systems with walls, internal obstacles, or preexisting shocks. It remains unclear, however, whether DDT can occur in unconfined media. Here we use direct numerical simulations (DNS) to show that for high enough turbulent intensities unconfined, subsonic, premixed, turbulent flames are inherently unstable to DDT. The associated mechanism, based on the nonsteady evolution of flames faster than the Chapman-Jouguet deflagrations, is qualitatively different from the traditionally suggested spontaneous reaction-wave model. Critical turbulent flame speeds, predicted by this mechanism for the onset of DDT, are in agreement with DNS results.     

ICP-AES法与传统FAAS法测定土壤速效钾和钠的数据可转换性研究

近年来兴起的电感耦合等离子体发射光谱法(ICP-AES)测定土壤的速效K和Na采用HCL-H2SO4浸取溶液,而以往大量的土壤速效K和速效Na的数据是用火焰光度法(FAAS)测定的,其溶液用NH4OAc浸取.为了探索两种方法数据的可转换性,使历史数据可用,选择了四种土壤,同时用FlAAS法和ICP-AES法进行测定,对数据进行比较.结果表明,两种方法测定的土壤速效K数据呈显著正相关(0.98,P<0.001),两种方法的数据间可以通过公式换算:y=1.14x+6.53(r2=0.91,n=24,P<0.001).两种方法测定Na的结果可比性比K差,虽然两种方法的数据总体上呈显著正相关(0.51,p<0.05),但壤土和砂壤单独模型的斜率与总模型差距均较大,因此针对不同类型的土壤应用不同的公式进行换算比较合适,即壤土:y=1.23x+10.03;砂壤:y=3.12x-23.03;海砂和河沙归为一类,公式:y=0.60x.     

Tightly bound soil water introduces isotopic memory effects on mobile and extractable soil water pools

Cryogenic vacuum extraction is the well-established method of extracting water from soil for isotopic analyses of waters moving through the soil–plant–atmosphere continuum. We investigate if soils can alter the isotopic composition of water through isotope memory effects, and determined which mechanisms are responsible for it. Soils with differing physicochemical properties were re-wetted with reference water and subsequently extracted by cryogenic water distillation. Results suggest some reference waters bind tightly to the soil and not all of this tightly bound water is removed during cryogenic vacuum extraction. Kinetic isotopic fractionation occurring when reference water binds to the soil is likely responsible for the ¹⁸O-depletion of re-extracted reference water, suggesting an enrichment of the tightly bound soil water pool. Further re-wetting of cryogenically extracted soils indicates an isotopic memory effect of tightly bound soil water on water added to the soil. The data suggest tightly bound soil water can influence the isotopic composition of mobile soil water. Findings show that soils influence the isotope composition of soil water by (i) kinetic fractionation when water is bound to the soil and (ii) equilibrium fractionation between different soil water pools. These findings could be relevant for plant water uptake investigations and complicate ecohydrological and paleohydrological studies.     

Detonation simulations in supersonic flow under circumstances of injection and mixing

The unsteady, reactive Navier-Stokes equations with a detailed chemical mechanism of 11 species and 27 steps were employed to simulate the mixing, flame acceleration and deflagration-to-detonation transition (DDT) triggered by transverse jet obstacles. Results show that multiple transverse jet obstacles ejecting into the chamber can be used to activate DDT. But the occurrence of DDT is tremendously difficult in a non-uniform supersonic mixture so that it required several groups of transverse jets with increasing stagnation pressure. The jets introduce flow turbulence and produce oblique and bow shock waves even in an inhomogeneous supersonic mixture. The DDT is enhanced by multiple explosion points that are generated by the intense shock wave focusing of the leading flame front. It is found that the partial detonation front decouples into shock and flame, which is mainly caused by the fuel deficiency, nevertheless the decoupled shock wave is strong enough to reignite the mixture to detonation conditions. The resulting transverse wave leads to further mixing and burning of the downstream non-equilibrium chemical reaction, resulting in a high combustion temperature and intense flow instabilities. Additionally, the longitudinal and transverse gradients of the non-uniform supersonic mixture induce highly dynamic behaviors with sudden propagation speed increase and detonation front instabilities.