Equilibrium mode distribution and steady-state distribution in 100-400 μm core step-index silica optical fibers

Using the power flow equation, the state of mode coupling in 100-400 μm core step-index silica optical fibers is investigated in this article. Results show the coupling length L(c) at which the equilibrium mode distribution is achieved and the length z(s) of the fiber required for achieving the steady-state mode distribution. Functional dependences of these lengths on the core radius and wavelength are also given. Results agree well with those obtained using a long-established calculation method. Since large core silica optical fibers are used at short distances (usually at lengths of up to 10 m), the light they transmit is at the stage of coupling that is far from the equilibrium and steady-state mode distributions.     

Characterizing the structure of pharmaceutical granules obtained by wet granulation with varying amounts of water via Raman chemical imaging

A pharmaceutical formulation containing metformin hydrochloride (MET), hydroxypropyl cellulose (HPC), and microcrystalline cellulose (MCC) was wet granulated with varying amounts of water and the structure of the obtained granules was characterized by Raman chemical mapping. Univariate Raman mapping was found to be satisfactory for producing the images of the two components of interest (HPC and MCC). In addition to the images, the average Raman spectra from the maps as well as the micro-Raman spectra from the hot pixels were analyzed. HPC is found to strongly respond to the addition of water, with its domain dissipating and Raman bands becoming weaker as the water addition increases. MCC is also responsive to water, reacting similarly to HPC but to a much smaller extent and only for the largest amounts of water. Granules made with increasing water content also have improved tabletting properties and flow.     

Assessment of DNA damage in coal open-cast mining workers using the cytokinesis-blocked micronucleus test and the comet assay

Coal mining is one of the most important causes of environmental pollution, as large quantities of coal dust particles are emitted. Colombia-South America has large natural coal reserves and “El Cerrejón” is the world's largest open-cast mine located in the northern department of Guajira. The aim of the present study was to evaluate genotoxic effects in a population exposed to coal residues from the open-cast mine “El Cerrejón”. 100 exposed workers and 100 non-exposed control individuals were included in this study. The exposed group was divided according to different mining area activities: (i). Transport of extracted coal, (ii). Equipment field maintenance, (iii). Coal stripping and, (iv). Coal embarking. Blood samples were taken to investigate biomarkers of genotoxicity, specifically, primary DNA damage as damage index (DI), tail length and% of tail DNA using the Comet assay (alkaline version) and chromosome damage as micronucleus (MN) frequency in lymphocytes. Both biomarkers showed statistically significantly higher values in the exposed group compared to the non-exposed control group. No difference was observed between the exposed groups executing different mining activities. These results indicate that exposure to coal mining residues may result in an increased genotoxic exposure in coal mining workers. We did not find a correlation between age, alcohol consumption and service time with the biomarkers of genotoxicity. Our results are the first data of genotoxic effects induced by coal mining exposure in Colombia, and thus, contribute to the exploration of test batteries use for monitoring of exposed populations and may stimulate designing control, hygiene and prevention strategies for occupational health risk assessment in developing countries.     

电工电子实践教学模式改革与实践

本文简要分析了传统实践教学中存在的问题并结合一些实例分别从日常实验教学、课程设计和应用创新层实验三个方面详细地阐述了改革的方式方法。整个改革体系从简单到综合层层递进。通过改革使原有的问题得到了有效解决,使改革取得明显的效果。     

柴油加氢改质装置掺炼催化柴油

为解决中国石油兰州石化公司90万t/a柴油加氢改质装置开工后出现的原料与热量不足的问题,进行了掺炼催化柴油的工业试验。结果表明:当催化柴油掺炼比（质量分数）为10%,裂化反应器第1~第4床层温升依次为7,8,5,6 ℃时,航空煤油收率与柴油转化率最高。与掺炼前相比,掺炼10%催化柴油后,装置能耗由19.48 kg/t（以标准油计）提高至19.96 kg/t;产物中气相、轻重石脑油与航空煤油收率增加;精制柴油收率下降;重石脑油中环烷烃、芳烃质量分数分别提高了2.11,1.67个百分点;航空煤油冰点降低了10 ℃,烟点降低了8.2 mm;精制柴油的质量得到改善。     

Polycyclic aromatic hydrocarbons (PAHs) in two Spanish traditional smoked sausage varieties: "Chorizo gallego" and "Chorizo de cebolla"

The polycyclic aromatic hydrocarbon (PAH) content in two traditional smoked sausages from Spain was determined. Results showed, that total average levels of PAHs found were higher in "Chorizo de cebolla" (101.81 vs. 98.48 μgkg(-1)). Most contents of PAHs found in both sausages were phenanthrene, naphthalene and anthracene. The maximum level for benzo[a]pyrene (BaP) of 5 μgkg(-1) in smoked meat products was not exceeded in any samples. BaP represented a 0.73% and 1.15% with respect to the total sum of the 15 PAHs that were investigated in this study for "Chorizo gallego" and "Chorizo de cebolla", respectively. Correlation statistic analysis (P < 0.01) of the contents from samples analysed, showed that BaP was a good marker for Σ15 PAHs in "Chorizo gallego" samples (R(BaP/Σ15PAHs) = 0.77; P < 0.01) and it was a good marker for 7 U.S. EPA probably carcinogenic PAHs in "Chorizo de cebolla" samples (R(BaP/7EPA) = 0.95) and in "Chorizo gallego" samples (R(BaP/7EPA) = 0.81).     

Effects of loading transition metal(Mn,Cr,Fe,Cu) oxides on oxygen storage/release properties of CeO_2-ZrO_2 solid solution

Cerium zirconium-based(CZ) oxygen storage materials(OSMs) play a crucial role in three-way catalysts(TWCs),while CZ needs to be modified to satisfy more rigorous emission standard.In this study,transition metal(TMs=Mn,Cr,Fe,Cu) oxides modified CZ were prepared by incipient wetness impregnation method to improve the oxygen storage capacity of CZ-based materials.To clearly illustrate the influence of TM oxides,N₂ adsorption-desorption,X-ray diffraction(XRD),oxygen storage capacity(OSC),...     

基于PSO-PSA的光伏系统最大功率点跟踪技术

为弥补恒定电压法实现最大功率点跟踪时忽略外界条件变化的缺陷,提高其跟踪精度和光伏系统的发电效率,本文提出了基于混合粒子群-模式搜索算法(PSO-PSA)的光伏发电最大功率点跟踪方法。对光伏电池模型进行仿真分析,绘制其在外界条件变化的情况下的输出特性曲线,分析环境变化对最大功率点的影响;通过对比PSO-PSA与粒子群算法,对基准测试函数的求解速度、精度与稳定性,验证本文算法的有效性,进而在不同环境条件下将混合算法优化输出结果与模型输出结果进行对比;将PSO-PSA与光伏阵列结合应用到Boost电路,实现模型动态输出结果与理论计算值匹配,从而实现最大功率点的有效跟踪。结果表明:基于PSO-PSA的光伏系统最大功率点跟踪技术合理,跟踪精度较高,弥补了使用固定电压值时无法适应环境改变而造成能源浪费的不足。     

基于DM6446的移动视频监控系统的设计

针对实现移动视频监控系统面临实时性高、运算量大、可用带宽有限的挑战,提出一种新颖的以TI DaVinci技术为支持、TMS320DM6446 Soc为基础的解决方案;完成了相应软硬件设计,并通过GPRS网络实现了移动视频监控的功能.该方案具有实时性高、部署灵活、性能优越、体积小、成本低的特点,随着3G网络的开通和手机处理能力的增强,在移动视频监控领域有着广泛的应用前景.