Assembly operator training and process planning via virtual systems

In this paper, we present an integrated intuitive system for assembly operators training and assembly process planning by combining virtual reality with motion-tracking technologies. The developed conceptual prototype for assembly planning and training enables individuals to interact with a virtual environment in real time. It extends the new technologies of motion tracking and integrates them with virtual environment technologies to create real-time virtual work cell simulations in which assembly operators may be immersed with hands-on experiences. In addition to operators training, the experimental results to date are presented to demonstrate the potential contributions of human skills in achieving effective assembly planning including disassembly operations. It is expected that this approach will lead to environment-friendly and sustainable operations by conserving energy and cost that are first tested in a human-emerged virtual system.     

浏阳河长沙段CODMn、NH3-N和TP综合降解系数研究

采用现场水团追踪法,研究了浏阳河长沙段COD_Mn、NH₃-N和TP的综合降解系数与河段水流流速之间的相关关系,并通过河段历史水文和水质监测数据对所建立的相关方程进行了验证.结果表明,浏阳河长沙段COD_Mn、NH₃-N和TP的综合降解系数与流速之间呈明显的线性相关关系,相关方程形式分别为K（COD_Mn）=0.037+0.635v、K（NH₃-N）=0.059+0.315v和K（TP）=0.004+0.140v.所建立的线性相关方程对研究河段COD_Mn、NH₃-N和TP浓度预测结果的决定系数均大于0.90、相对均方根误差均小于0.10.受风浪作用、紊动水流和弯道环流的影响,当流速小于0.35m/s时,顺直河段的污染物综合降解系数均大于弯曲河段的污染物综合降解系数;当流速大于0.46m/s时,弯曲河段污染物综合降解系数均大于顺直河段的污染物综合降解系数.研究成果对浏阳河长沙段水质管理与水环境保护具有重要的参考价值.     

Influence of particle size on the aggregation behavior of nanoparticles: Role of structural hydration layer

More and more attention has been paid to the aggregation behavior of nanoparticles, but little research has been done on the effect of particle size. Therefore, this study systematically evaluated the aggregation behavior of nano-silica particles with diameter 130–480 nm at different initial particle concentration, pH, ionic strength, and ionic valence of electrolytes. The modified Smoluchowski theory failed to describe the aggregation kinetics for nano-silica particles with diameters less than 190 nm. Besides, ionic strength, cation species and pH all affected fast aggregation rate coefficients of 130 nm nanoparticles. Through incorporating structural hydration force into the modified Smoluchowski theory, it is found that the reason for all the anomalous aggregation behavior was the different structural hydration layer thickness of nanoparticles with various sizes. The thickness decreased with increasing of particle size, and remained basically unchanged for particles larger than 190 nm. Only when the distance at primary minimum was twice the thickness of structural hydration layer, the structural hydration force dominated, leading to the higher stability of nanoparticles. This study clearly clarified the unique aggregation mechanism of nanoparticles with smaller size, which provided reference for predicting transport and fate of nanoparticles and could help facilitate the evaluation of their environment risks.     

紫外波长与粒径对纳米TiO_2光催化效果的影响

以甲基橙为光催化降解对象,研究了不同波长紫外灯与不同粒径TiO2组合(365 nm紫外灯+10 nm TiO2,365 nm紫外灯+50 nm TiO2,254 nm紫外灯+10 nm TiO2,254 nm紫外灯+50 nm TiO2)光催化降解甲基橙的效果。结果表明,不同波长紫外灯与不同粒径TiO2组合影响光催化降解甲基橙的效果。其中,254 nm紫外灯+10 nm TiO2组合降解效果最好,其次为254 nm紫外灯+50 nm TiO2组合,再其次为365 nm紫外灯+10 nm TiO2组合,降解效果最差的为365 nm紫外灯+50 nm TiO2组合。由此可见,254 nm紫外灯+10 nm TiO2组合的光催化降解甲基橙的效果最好。     

Two-phase flow insights into open-channel flows with suspended particles of different densities

The effect of particle density on the turbulent open-channel flow carrying dilute particle suspensions is investigated using two specific gravities and three concentrations of solid particles. The particles, identical in size and similar in shape, were natural sand and a neutrally buoyant plastic. The particles were fully suspended, and formed no particle streaks on the channel’s bed. Accordingly, the changes in the flow are attributed to the interactions between suspended particles and flow turbulence structures. Measurements were obtained by means of image velocimetry enabling simultaneous, but distinct, measurement of liquid and particle velocities. The experimental results show that, irrespective of particle specific gravity, particle suspension influences bulk velocity of flow and the Kármán coefficient, while friction velocity essentially remains constant. The results also show that particles in suspension modify local water turbulence over the flow depth, but in ways not accurately predicted using the customary parameters for characterizing turbulence modification.     

Seasonal and particle size-dependent variations in gas/particle partitioning of PCDD/Fs

This study monitored particle size-dependent variations in atmospheric polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Two gas/particle partitioning models, the subcooled liquid vapor pressure (P(L)(0)) and the octanol-air partition coefficient (K(OA)) model, were applied to each particle sizes. The regression coefficients of each fraction against the gas/particle partition coefficient (K(P)) were similar for separated particles within the same sample set but differed for particles collected during different periods. Gas/particle partitioning calculated from the integral of fractions was similar to that of size-segregated particles and previously measured bulk values. Despite the different behaviors and production mechanisms of atmospheric particles of different sizes, PCDD/F partitioning of each size range was controlled by meteorological conditions such as atmospheric temperature, O(3) and UV, which reflects no source related with certain particle size ranges but mixed urban sources within this city. Our observations emphasize that when assessing environmental and health effects, the movement of PCDD/Fs in air should be considered in conjunction with particle size in addition to the bulk aerosol.     

颗粒污泥粒径的工程测定方法

厌氧反应器污泥粒径分布的测试方法目前主要有激光粒度分析、照相、沉降法和筛分法.快速方便的实用方法是筛分法,但筛分时需用缓冲剂,考察了分别用缓冲液和自来水作为冲洗介质的筛分结果.结果表明,作为现场应用自来水替代缓冲液是可行的,能够准确反映出污泥颗粒粒径变化的趋势,同时给出了试验测定方法和原则,确定了最佳污泥取样量为20 mL.     

上流式多级处理厌氧反应器（UMAR）处理棉浆黑液

棉浆黑液是高浓度有机废水,有较好的厌氧可生化性。利用上流式多级处理厌氧反应器处理棉浆黑液,容积负荷在14．4—24kg／（m^3·d）之间,平均COD去除率可达到80％,同时可产生沼气,具有很好的应用前景。     

苏南典型河段磷的分布及释放特性研究

通过测定常州典型河段河水和底泥中的磷含量,同时分析了磷在不同底泥颗粒中含量分布的变化,阐述了河流中磷的分布和转移趋势。结果表明:河水中的磷含量通常低于底泥间隙水中的磷含量,但当河流发生富营养化后,底泥中的磷大量向上层水体释放,使得河水中的磷含量不断增加。底泥有效磷与总磷含量之间没有明显相关性,而与底泥间隙水的磷含量之间存在着交换平衡。底泥颗粒以2μm~50μm的粒级为主,即以细砂和粉砂质有机-无机聚合体矿物颗粒为主。磷在底泥颗粒中的含量随着底泥粒径的增大而减少,且粒径越大的颗粒对磷的吸附能力越弱,其中的磷向外释放的可能性越大。     

Characterization of submicron aerosol particles in winter at Albany, New York

A thorough understanding of chemical composition, particle pH, and pollutant emissions is essential to address the climate and human health effects of atmospheric particles. In this study, we used a High-Resolution Time-of-Flight Aerosol Mass Spectrometer(HR-ToF-AMS)and Scanning Mobility Particle Sizer(SMPS) to characterize the composition of submicron particles. Moreover, we applied the ISORROPIA-II model to analyze the particle acidity effect on the compositional characterization of submicron ...