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1.
采用水热-煅烧法制备Cd2SnO4,之后通过超声混合法得到一系列MoS2/Cd2SnO4复合材料。采用X射线衍射、扫描电子显微镜、X射线光电子能谱对Cd2SnO4和一系列MoS2/Cd2SnO4复合材料进行结构和形貌的表征。研究了MoS2掺杂量对于MoS2/Cd2SnO4复合材料的气敏性能影响。实验结果表明,当MoS2与Cd2SnO4的质量比为2.5%,MoS2/Cd2SnO4复合材料制备的气敏元件在170 ℃时对浓度为100 μL·L-1的甲醛气体的灵敏度为40.0,最低检测限为0.1 μL·L-1。  相似文献   
2.
Large amounts of flowback and produced water (FPW) have been generated from hydraulic fracturing process for the production of unconventional gas such as shale gas. Complex organic pollutants are abundantly present in FPW with revealed toxicity to aquatic organisms and these contaminants may transfer into surrounding aquatic environment. Characterization and determination of complicated organic pollutants in FPW remains a challenge due to its complex composition and high salinity matrix. This review article covers the progress of recent 5 years regarding the sample preparation and instrumental analysis methods and thus summarizes the advantages and disadvantages of these methods for critical analysis of organic contaminants in FPW samples. Furthermore, the natural distribution of detected organic compounds and their transformation were reviewed and discussed to enhance the understanding of spatial and temporal behaviors of these organic pollutants in natural environment, paving the way for future development of pollution control policies and strategies. Enlightened by the studies of FPW contamination in the US, the investigations of FPW contamination in China continued to grow due to rapidly growing production of shale gas in China and resulted pollution.  相似文献   
3.
Jie Miao 《中国物理 B》2022,31(8):80306-080306
We demonstrate that dual dark magnetic-optical-traps (MOTs) have great importance in the two-species 87Rb and 40K mixture compared with dual bright MOTs. The dark MOT has a little improvement in the trapping of single-species 87Rb or 40K gases compared with bright MOT. For the case of loading two-species 87Rb and 40K simultaneously, the improvement of 40K in the dual dark MOTs is mainly from the reduction of light-assisted collision losses. The dual dark MOTs employ a pair of conical lenses to produce the hollow beam for repump laser with high efficiency. The number and density of 87Rb and 40K atoms after evaporative cooling in the hybrid magnetic trap with dark MOT loading are compared with those in bright MOT. The atoms with large number and high density make it easier to realize the quantum degenerate of Bose-Fermi mixture.  相似文献   
4.
甲氧基多溴联苯醚(methoxypolybrominated diphenyl ethers, MeO-PBDEs)广泛存在于生物体和海洋环境。以象山海域的生物体和沉积物为样本,采用固相萃取净化-气相色谱-负化学源质谱法,检测了6种MeO-PBDEs,结果显示,当目标分析物浓度为0.1~20.0 μg?L-1时,线性关系良好(R2>0.999),检出限为0.13~0.22 μg?kg-1,定量限为0.42~0.72 μg?kg-1,实际样品的平均回收率为71.2%~116.2%。MeO-PBDEs的分布状况调查结果显示,藻类样品中仅检出6-MeO-BDE-47,且浓度较低,其他生物体中检出3种MeO-PBDEs,检出率为31.3%,浓度为0.21~2.72 μg?kg-1。沉积物中无MeO-PBDEs被检出。  相似文献   
5.
采用基于Compass力场的分子动力学(MD)方法,研究了惰性气体氙(Xe)和氪(Kr)在塑料闪烁体(聚乙烯基对甲苯)的平整和粗糙表面的吸附和扩散行为.由惰性气体吸附曲线的均方根位移(MSD),得到了Xe/Kr气体在聚乙烯基对甲苯表面的扩散系数.研究结果表明,Kr/Xe气体均被稳定地吸附在塑料闪烁体表面,其稳定性随着温度的升高而增加,Xe分子的吸附性强于Kr分子. Kr/Xe气体在聚乙烯基对甲苯表面具有较强的扩散性能,扩散深度随着温度与厚度的增加而增加,最大为22.865?,Kr分子扩散能力强于Xe分子.基底粗糙表面增加了两种惰性气体分子的吸附和扩散.  相似文献   
6.
As a representative of traditionally fermented Chinese medicine, Massa Medicata Fermentata (MMF) shows the functions of invigorating the spleen and stomach and promoting digestion, which plays an important role in the treatment of gastrointestinal diseases. The fermentation mechanism and the key factors that affect the quality of MMF have not been revealed yet, which has become an urgent issue that limits its clinical application. This article aims to systematically and comprehensively reveal the transformation of physical properties and the dynamic trend of chemical components including substrate components, volatile components, and lactic acid as anaerobic fermentation product during MMF fermentation. Along with obvious hyphae growth observed for MMF, the weight of MMF decreased, and the moisture and temperature increased. Through the quantified 14 components from substrate, ferulic acid increased from 45.53 ± 6.94 to 141.89 ± 78.40 μg/g, while glycosides and phenolic acids declined except caffeic acid. Also, within the 66 volatile components analyzed, alcohols and acids increased, while aldehydes and ketones decreased. Lactic acid was not detected in the fermentation substrate, but an apparent increase in lactic acid content was observed along with the increased fermentation days, resulting in 2.54 ± 0.15 mg/g on day 8. Based on the tested components, the fermentation process of MMF was discriminated into three distinct stages by principal component analysis, and an optimal fermentation time of four days was proposed. The results of this study will be of great significance to clarify the characteristics of fermentation and conduce to improving quality standards of MMF.  相似文献   
7.
Wenjun Yan 《中国物理 B》2022,31(11):110704-110704
Li dendrites and electrolyte leakage are common causes of Li-ion battery failure. H2, generated by Li dendrites, and electrolyte vapors have been regarded as gas markers of the early safety warning of Li-ion batteries. SnO2-based gas sensors, widely used for a variety of applications, are promising for the early safety detection of Li-ion batteries, which are necessary and urgently required for the development of Li-ion battery systems. However, the traditional SnO2 sensor, with a single signal, cannot demonstrate intelligent multi-gas recognition. Here, a single dual-mode (direct and alternating current modes) SnO2 sensor demonstrates clear discrimination of electrolyte vapors and H2, released in different states of Li-ion batteries, together with principal component analysis (PCA) analysis. This work provides insight into the intelligent technology of single gas sensors.  相似文献   
8.
CH4气体的精准检测对防止矿井瓦斯爆炸,确保安全生产至关重要。目前基于可调谐半导体激光吸收光谱技术(TDLAS)存在因温度变化导致气体浓度测量误差较大。探究了基于TDLAS的CH4气体检测系统与温度补偿方法,分析温度对CH4气体吸收谱线的影响,通过算法补偿模型消除环境温度对CH4气体检测的影响。依据TDLAS技术原理及相关理论,对系统发射单元、吸收池、信号接收单元、数据处理单元进行设计,搭建了基于TDLAS技术的CH4气体浓度检测系统,实验检测了不同环境温度(10~50 ℃)时0.04%CH4气体浓度,分析温度变化对CH4气体在波长为1.653 μm处吸收谱线强度和半宽度的影响。为消除温度对CH4气体检测的影响并提高补偿效果,采用粒子群优化算法(PSO)优化BP神经网络(BPNN)的最佳权值和阈值,建立CH4气体的PSO-BP温度补偿模型,克服了BP神经网络收敛速度慢、易陷入局部最优的缺点。结果表明:(1)基于TDLAS的CH4气体检测浓度随环境温度升高而下降,整个实验温度内相对误差范围为4.25%~12.13%,不同环境温度下CH4气体检测浓度与温度之间的关系可用一元三次多项式表示;(2)CH4气体的吸收强度和半宽度随着温度的升高而下降,与温度变化之间的关系为单调递减函数,温度对CH4气体吸收谱线强度的相对变化率大于吸收谱线半宽度的相对变化率,CH4气体吸收谱线的强度更容易受温度变化的影响;(3)BP神经网络和PSO-BP模型测试样本的绝对平均误差(MAE)分别为12.88%和1.81%,平均绝对百分比误差(MAPE)分别为2.3%和0.3%,均方根误差(RMSE)分别为15.96%和2.69%,相关系数R2分别为0.980 6和0.999 6。通过建立PSO-BP温度补偿模型,补偿效果大部分分布在±1.0%的误差范围内,MAE,MAPE,RMSE和R2等评价指标均大幅度提升,对提高TDLAS技术在矿井CH4的精准检测具有一定的参考意义。  相似文献   
9.
We present analytical formulae for the first and second derivatives of the Helmholtz free energy of non-relativistic ideal Fermi gas. Important thermodynamic quantities such as heat capacity, sound velocity, heat capacity ratio, and others are explicitly expressed through the derivatives. We demonstrate correct ideal Boltzmann gas and low-temperature Fermi gas asymptotes and derive corrections to thermodynamic functions for these limiting cases. Numerical computations of thermodynamic properties of ideal Fermi gas can be accurately performed using the developed freely available Python module ifg .  相似文献   
10.
借助高速摄影和图像分析技术对首次发现的附壁气泡的绕圈现象进行了实验研究,重点研究游移气泡的运动轨迹、附壁气泡的布阵过程、气泡的来源以及气泡的振动细节.研究发现游移绕圈气泡的运动轨迹呈现出不稳定、不规则、不光滑的特点.阵列气泡源于游移气泡,而游移气泡变成阵列气泡的方式主要是通过合并增大体积,从而减小所受的Bjerknes力,降低活性的方式实现的.游移气泡源于ALF(acoustic lichtenberg figure)空化云中大量空泡的合并,使以径向振动为主的空泡逐渐过渡到以表面波动为主的气泡.阵列气泡在Bjerknes力的作用下呈现出规则的表面波动,而体积更小受力更大的游移空泡的表面完全失稳,呈现极不规则的形貌,并对附近阵列气泡的表面波动产生影响.阵列气泡呈现出十分规则的排布,相邻阵列气泡之间的振动相位是相反的,表现为相互排斥.  相似文献   
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