Number concentration and size distributions of submicron particles in Jinan urban area:Characteristics in summer and winter

The aerosol number concentration and size distribution were measured with the newly developed Wide-range Particle Spectrometer in summer and winter of 2006 at the urban site of Jinan City. Here reported the characteristics of fine particles of the different observation seasons. Relative high number concentrations for the particles in the diameter range of 10-500 nm were observed in both seasons. It was found that the dominant number distributed in particle diameter smaller than 100 nm and the percentage over the number concentration of all air particles is much higher than what has been measured in other urban sites over the world. The number mean diameter in summer was much smaller than in winter, strongly suggesting the different origin of ultrafine particles in different seasons. That is, particles in ultrafine mode mainly came from nucleation and new particle formation in summer while from traffic emission in winter. The diurnal variation also supported this point. Number concentration in the diameter range of 10-200 um got their peak values at noontime, well correlated with the mixing ratio of SO2 and the intensity of solar radiation in summer. While in winter, those in the same diameter range showed the main peaks during the traffic hours happened in the morning and evening.

Seasonal Variations of Number Size Distributions and Mass Concentrations of Atmospheric Particles in Beijing

Particle number and mass concentrations were measured in Beijing during the winter and summer periods in 2003, together with some other parameters including black carbon (BC) and meteorological conditions. Particle mass concentrations exhibited low seasonality, and the ratio of PM2.5/PM10 in winter was higher than that in summer. Particle number size distribution (PSD) was characterized by four modes and exhibited low seasonality. BC was well correlated with the number and mass concentrations of accumulation and coarse particles, indicating these size particles are related to anthropogenic activities. Particle mass and number concentrations (except ultra-fine and nucleation particles) followed well the trends of BC concentration for the majority of the day, indicating that most particles were associated with primary emissions. The diurnal number distributions of accumulation and coarse mode particles were characterized by two peaks.

Evaluation of the WDM6 scheme in the simulation of number concentrations and drop size distributions of warm-rain hydrometeors: comparisons with the observations and other schemes

The number concentrations and drop size distributions(DSDs)of warm-rain hydrometeors play an important role in the simulation of microphysical processes.To evaluate the performance of the WDM6 scheme,which predicts the cloud number concentration(Nc)explicitly in aspects of warm-rain hydrometeors number concentrations and DSDs,the simulation of the WDM6 scheme is compared with airborne observations of a flight trial,as well as with the simulations of the Thompson scheme and Morrison scheme.Results show that the WDM6 scheme produces smaller(larger)cloud(rain)number concentrations and wider cloud DSDs compared to the observations,with the largest biases at upper levels of stratiform cloud(SC).The Thompson scheme and the Morrison scheme,both of which set the Nc as a constant,compare better to the observations than the WDM6 scheme in aspects of Nc and DSD.Sensitivity tests of the initial cloud condensation nuclei(CCN)number concentration(CCN0)of the WDM6 scheme show that a better choice of the initial CCN0 may improve the simulation of convective cloud but helps little in terms of SC.The simulation of rain number concentration and DSD is not sensitive to the CCN0 in the WDM6 scheme.

MEASUREMENTS OF PARTICLE NUMBER SIZE DISTRIBUTIONS AND NEW PARTICLE FORMATION EVENTS DURING WINTER IN THE PEARL RIVER DELTA REGION,CHINA

Particle number size distribution(PNSD) between 10 nm and 20 μm were measured in the Pearl River Delta(PRD) region in winter 2011.The average particle number concentration of the nucleation mode(10-20 nm),Aitken mode(20-100 nm),accumulation mode(100 nm-1μm) and coarse mode(1-20 μm) particles were 1 552,7 470,4 012,and 19 cm-3,respectively.The volume concentration of accumulation mode particles with peak at 300 nm accounted for over 70% of the total volume concentration.Diurnal variations and dependencies on meteorological parameters of PNSD were investigated.The diurnal variation of nucleation mode particles was mainly influenced by new particle formation events,while the diurnal variation of Aitken mode particles correlated to the traffic emission and the growth process of nucleation mode particles.When the PRD region was controlled by a cold high pressure,conditions of low relative humidity,high wind speed and strong radiation are favorable for the occurrence of new particle formation(NPF) events.The frequency of occurrence of NPF events was 21.3% during the whole measurement period.Parameters describing NPF events,including growth rate(GR) and source rate of condensable vapor(Q),were slightly larger than those in previous literature.This suggests that intense photochemical and biological activities may be the source of condensable vapor for particle growth,even during winter in the PRD.

Influence of air masses on particle number concentration and size distribution at Mt. Waliguan, Qinghai Province, China

Particle size distribution of 12-500 nm was measured at Mt. Waliguan, China Global Atmosphere Watch Baseline Observatory, from Aug. in 2005 to May in 2007.72-hr back-trajectories at 100-m arrival height above ground level for the same period were calculated at 6：00, 12：00, and 21：00 （Beijing Time） for each day using the Hybrid Single-Particle Lagrangian Integrated Trajectory （HYSPLIT-4） model developed by NOAA/ARL. It was found that air mass sources significantly impact particle number concentration and size distribution at Mt. Waliguan. Cluster analysis of back-trajectories show that higher Aitken mode particle number concentration was observed when air masses came from or passed by the northeastern section of Mt. Waliguan, with short trajectory length. High number concentration of nucleation mode was associated with air masses from clean regions, with long trajectory length.

Understanding the Variability of Z-R Relationships Caused by Natural Variations in Raindrop Size Distributions(DSD):Implication of Drop Size and Number

In the issue of rainfall estimation by radar through the necessary relationship between radar reflectivity Z and rain rate R (Z-R), the main limitation is attributed to the variability of this relationship. Indeed, several pre-vious studies have shown the great variability of this relationship in space and time, from a rainfall event to another and even within a single rainfall event. Recent studies have shown that the variability of raindrop size distributions and thereby Z-R relationships is therefore, more the result of complex dynamic, thermody-namic and microphysical processes within rainfall systems than a convective/stratiform classification of the ground rainfall signature. The raindrop number and size at ground being the resultant of various processes mentioned above, a suitable approach would be to analyze their variability in relation to that of Z-R relation-ship. In this study, we investigated the total raindrop concentration number NT and the median volume di-ameter D0 used in numerous studies, and have shown that the combination of these two ‘observed’ parame-ters appears to be an interesting approach to better understand the variability of the Z-R relationships in the rainfall events, without assuming a certain analytical raindrop size distribution model (exponential, gamma, or log-normal). The present study is based on the analysis of disdrometer data collected at different seasons and places in Africa, and aims to show the degree of the raindrop size and number implication in regard to the Z-R relationships variability.

Preliminary Research on the Size Distribution of Aerosols in Beijing

Number concentration and size distribution of atmospheric aerosols were measured in Beijing by an optical particle counter. The relationship between aerosol size distribution and relative humidity is discussed. The results show that the size distribution, diurnal variation, daily variation of atmospheric aerosols have a good relation to relative humidity and Richardson number. Key words Atmospheric aerosol - Number concentration - Size distribution - Relative humidity - Richardson number This work is financially supported by NKBRSF Project (G1999043400), Knowledge Creative Project (8-2101 and 82303) founded by TAP, CAS.The authors would like to express their thanks to Prof. Zhang Wen for his work in this observation.

Genome size evolution of the extant lycophytes and ferns

Ferns and lycophytes have remarkably large genomes.However,little is known about how their genome size evolved in fern lineages.To explore the origins and evolution of chromosome numbers and genome size in ferns,we used flow cytometry to measure the genomes of 240 species(255 samples)of extant ferns and lycophytes comprising 27 families and 72 genera,of which 228 species(242 samples)represent new reports.We analyzed correlations among genome size,spore size,chromosomal features,phylogeny,and habitat type preference within a phylogenetic framework.We also applied ANOVA and multinomial logistic regression analysis to preference of habitat type and genome size.Using the phylogeny,we conducted ancestral character reconstruction for habitat types and tested whether genome size changes simultaneously with shifts in habitat preference.We found that 2 C values had weak phylogenetic signal,whereas the base number of chromosomes(x)had a strong phylogenetic signal.Furthermore,our analyses revealed a positive correlation between genome size and chromosome traits,indicating that the base number of chromosomes(x),chromosome size,and polyploidization may be primary contributors to genome expansion in ferns and lycophytes.Genome sizes in different habitat types varied significantly and were significantly correlated with habitat types;specifically,multinomial logistic regression indicated that species with larger 2 C values were more likely to be epiphytes.Terrestrial habitat is inferred to be ancestral for both extant ferns and lycophytes,whereas transitions to other habitat types occurred as the major clades emerged.Shifts in habitat types appear be followed by periods of genomic stability.Based on these results,we inferred that habitat type changes and multiple whole-genome duplications have contributed to the formation of large genomes of ferns and their allies during their evolutionary history.

Size Distribution of Particles Emitted from Liquefied Natural Gas Fueled Engine

The results of measurements conducted to determine the number and mass concentration of particles emitted from the liquefied natural gas （LNG） fueled spark ignition engines are presented. Particle size distributions were measured at different speeds, different loads and ESC cycles. The nanoparticles with diameter smaller than 39 nm, measured by the electrical low-pressure impactor （ELPI）, are dominant in number con- centration that is nearly 92.7 % of the total number of the emitted particles at the peak point. As for the mass of emission particle, it is shown that the mass of the particles greater than 1.2μm is more than 65 % that of the emitted particles.

The influence of Laval nozzle throat size on supersonic molecular beam injection

In this study, finite element analysis （FEA） has been used to investigate the effects of different Laval nozzle throat sizes on supersonic molecular beam. The simulations indicate the Mach numbers of the molecular stream peak at different positions along the center axis of the beam, which correspond to local minimums of the molecular densities. With the increase of the throat diameter, the first peak of the Mach number increases first and then decreases, while that of the molecular number density increases gradually. Moreover, both first peaks shift progressively away from the throat. At the last part, we discuss the possible applications of our FEA approach to solve some crucial problems met in modern transportations.

Research on the fully fuzzy time-cost trade-off based on genetic algorithms

It is very difficult to estimate exact values of time and cost of an activity in project scheduling process because many uncertain factors, such as weather, productivity level, human factors etc. , dynamically affect them during project implementation process. A GAs-based fully fuzzy optimal time-cost trade-off model is presented based on fuzzy sets and genetic algorithms (GAs). In tihs model all parameters and variables are characteristics by fuzzy numbers. And then GAs is adopted to search for the optimal solution to this model. The method solves the time-cost trade-off problems under an uncertain environment and is proved practicable through a giving example in ship building scheduling.

Variation in egg and clutch size of the Black Redstart(Phoenicurus ochruros) at the northeastern edge of the Qinghai-Tibetan Plateau

Background: In birds, the trade-off between the quality and number of nestlings is one of the most important theories of the evolution of life history of birds, which is closely related with climate. We investigated variation in egg and clutch size of the Black Redstart(Phoenicurus ochruros) on the northeastern edge of the Qinghai-Tibetan Plateau in order to explore and test the relation between egg size and clutch size and the rules governing the variation in these two components with climate change.Methods: We monitored each located nest daily to determine the exact laying order of the eggs and measured their sizes. The variations in egg volume and clutch size between 2008 and 2009 were studied by independent sample t tests. The difference in egg volume in the sequence of the laying order was tested by Kendall's W test and we employed Pearson correlations to investigate the relation between egg size and laying order. All statistical analyses were performed with IBM SPSS Statistics, version 19.0Results: In 2008, the mean egg volume of the Black Redstart was 2.40 and clutch size wer± 0.20 cm^3(n e 2.26 = 50), and the mean clutch size 4.90 ± 0.57(n = 11). In 2009, the mean egg volumeation between eg± 0.18 cm^3(n g size and layin= 74) and 5.20 g order(r ± 0.26(n = 15) respectively. We found a significantly positive correl, while egg size was strongly and negatively correlated with clutch size(r = 0.397, p = 0.030) smaller eggs but a larger clutch in a brood in a resource-rich year, w= h-0.274, p ereas large= 0.002). Black Redstarts tend to layr eggs but smaller clutches are produced in a harsh year.Conclusions: The Black Redstart adopted a "brood survival strategy" to ensure that more offspring could survive. The Black Redstart' trade-off in egg volume and clutch size would guarantee that it will gain maximum benefit in any case.

Molecular Weight Distribution of Dissolved Organic Matter in Lake Hongfeng Determined by High Performance Size Exclusion Chromatography (HPSEC) With On-Line UV-Vis Absorbance and Fluorescence Detection

The molecular weight distribution (MWD) of dissolved organic matter (DOM) in lake waters from Lake Hongfeng was examined using high performance size exclusion chromatography (HPSEC) with UV-vis absorbance and fluorescence detection. The elution curves obtained by absorbance and fluorescence techniques expressed similar patterns, with the exception of diminishing of large fraction and the peaks behind several seconds in fluorescence chromatograms. According to its molecular weight (MW), DOM in water samples is divided into several fractions: large ({>3.5} kDa); medium-large ({3.5}-{2.0} kDa); medium ({2.0}-{1.0} kDa) and small ({<1.0} kDa). The average molecular weight was calculated using the elution curve detected by UV-vis absorbance and fluorescence detection techniques. The results showed that the weight-average molecular weight (Mw) and number-average molecular weight (Mn) calculated by UV-vis absorbance techniques range from 1750 to 2050 Dalton and from 1450 to 1850 Dalton, respectively. And the Mw and Mn obtained by fluorescence detection are lower by 50 to 400 Dalton. As a reference, the molecular weight of Fluka humic acid (FHA) is larger than that of water samples by about 200 Dalton. The average molecular weight of DOM for water samples collected in March and July was compared. The results revealed that the molecular weight is lower for water samples obtained in July than that obtained in March, indicating the ambient environment has an influence on the molecular weight, including photo-degradation and biological activity.

Size distribution of inclusions in 12%Cr stainless steel with a wide range of solidification cooling rates

The effect of solidification cooling rate on the size and distribution of inclusions in 12%Cr stainless steel was investigated. A wide range of solidification cooling rates（from 0.05 to 106 K·s^-1） was achieved using various solidification processes, including conventional casting, laser remelting, and melt spinning. The size and distribution of inclusions in the steel were observed and statistically collected. For comparison, mathematical models were used to calculate the sizes of inclusions at different solidification cooling rates. Both the statistical size determined from observations and that predicted from calculations tended to decrease with increasing cooling rate; however, the experimental and calculated results did not agree well with each other at excessively high or low cooling rate. The reasons for this discrepancy were theoretically analyzed. For the size distribution of inclusions, the effect of cooling rate on the number densities of large-sized（〉 2 μm） inclusions and small-sized（≤ 2 μm） inclusions were distinct. The number density of inclusions larger than 1 μm was not affected when the cooing rate was less than or equal to 6 K·s^-1 because inclusion precipitation was suppressed by the increased cooling rate.

泥沙性质对高速水流消失空化数的影响

消失空化数是表征高速水流空化状态的重要判别数,水流含泥沙后对消失空化数的影响引起了研究者的关注。利用自主研发的小型循环式水洞试验装置,对不同含泥沙条件下与清水介质下的水洞喉部(即空化区)消失空化数进行了试验研究。通过配制不同泥沙质量浓度、泥沙粒径、泥沙颗粒级配和泥沙矿物成分等挟沙水流,调节分流阀门降低水流流速,由动态压力数据采集系统(YE6263)实时测量空化区压强,直到压强由负压变为正压的临界压强(相应的消失空化数压强)。研究结果表明:在不同泥沙质量浓度的条件下,循环式水洞喉部的消失空化数随泥沙质量浓度的增加先增大后减小,与清水对比,表现出先促进后抑制空化的发生;在不同泥沙粒径的条件下,喉部消失空化数随粒径的增大而增大,说明泥沙粒径的增大促进了空化的提前发生;在不同泥沙级配的条件下,喉部消失空化数随小于某一粒径泥沙质量分数的增大而增大,表现出随着小于某一粒径泥沙质量分数的增大越容易发生空化;在不同泥沙矿物成分条件下,喉部消失空化数随矿物成分摩氏(Mohs)硬度的增大而增大,说明矿物成分硬度越大越促进空化的发生。

石墨烯在压阻传感器中的应用研究综述

石墨烯藉由其优异的电学特性能够在各种电子器件中得到良好的应用,压阻传感器就是其中之一,石墨烯在其中作为主要的导电材料,发挥着至关重要的作用。本综述旨在从含量、层数、片径、片层形貌以及排列方式这几方面探讨石墨烯对压阻传感器传感性能的影响,为寻求制造更优性能的压阻传感器提供参考。

电动公交车队规模与充电桩配置协同优化

为了保障电动公交系统的车辆能源供给和线路顺畅运营,本文在多线路与多充电站场景下考虑线路行程时间的随机性,建立面向线路层面的电动公交系统车辆与充电桩配置双层优化模型。模型以车辆和充电桩投资成本与乘客候车成本之和的最小化为目标,对各线路车队规模、各充电站充电桩数量及线路与充电站间的充电匹配关系进行优化决策。在下层模型中,为反映随机行程时间下车辆充电过程对线路运营的影响,引入顾客源有限下的多服务台排队模型来刻画固定线路与充电站匹配下的排队充电过程;在上层模型中,考虑充电站与场站容量约束,对电动公交系统的线路与充电站匹配关系进行优化。在求解方面,首先基于排队模型设计算法求解特定线路与充电站匹配下的车队规模及充电桩数量,进而利用CPLEX求解器对线路与充电站匹配关系进行优化。在实验环节,设计不同规模的算例验证本文所提双层模型与算法框架的有效性,计算结果表明,本文所提的双层模型和算法框架可在满足充电站和场站容量限制的前提下尽可能缩减车队成本、充电桩成本与乘客候车成本;相比较两种人工经验方法,本文算法可将总成本分别降低5.65%和4.54%。

在线激光打孔参数对中支卷烟理化指标的影响

[目的]明确在线激光打孔参数对中支卷烟理化指标的影响,为中支卷烟激光打孔参数的设置提供借鉴。[方法]以物理指标、常规烟气成分释放量和感官质量为衡量指标,分析不同在线激光打孔参数对中支卷烟质量的影响。[结果]激光打孔数量与中支卷烟吸阻呈现负相关关系(P<0.01),与滤嘴通风率、总通风率呈现正相关关系(P<0.01),与TPM、水分、焦油释放量均呈现二次回归关系。激光脉冲时间与中支卷烟吸阻、滤嘴通风率、总通风率均呈现二次回归关系,但其对常规烟气成分释放量无显著影响。激光打孔数量对中支卷烟理化指标的影响程度大于激光脉冲时间,在线激光打孔参数主要影响中支卷烟的香气量、刺激性和协调性。[结论]得到一套在线激光打孔参数和中支卷烟理化指标关系的数学模型,可应用于中支卷烟开发和产品维护中激光打孔参数的设置。

新型三嗪基Gemini表面活性剂的合成与表面活性研究

本文以三聚氯氰、十二胺、乙二胺、1,4-丁二胺、1,6-己二胺、N,N-二甲基-1,3-丙二胺、溴乙烷为原料,合成了3种不同连接基长度的三嗪基Gemini表面活性剂C_(12)-m-C_(12)(m=2,4,6)。通过FT-IR、1H NMR、ESI-MS对其结构进行了表征。利用表面张力法、稳态荧光法、动态光散射法测定了所合成的三嗪基Gemini表面活性剂的表面活性。表面张力测试结果表明,随着连接基亚甲基数从2增加到6,C_(12)-m-C_(12)的临界胶束浓度(CMC)从0.013 mmol/L增加到0.050 mmol/L;动态光散射法测试结果表明,C_(12)-m-C_(12)的粒径随着连接基长度的增加而增加;稳态荧光法研究结果表明,随着连接基长度的增加,表面活性剂越容易形成较大的胶束,C_(12)-2-C_(12),C_(12)-4-C_(12),C_(12)-6-C_(12)在水溶液中的临界胶束聚集数分别为105,76和68。

叶片结构参数对涡流分级机分级性能的影响

为了探究叶片安装角度与叶片数量对涡流分级机分级性能的影响,对6种不同叶片结构的分级轮进行了数值模拟研究。制备了4种不同叶片结构的分级轮分别加工金属硅、碳酸钙和碳素,并得出各个物料的分割粒径、分级精度作为评价涡流分级机性能的指标。结果表明:可通过增加叶片数量与偏移叶片安装角度,达到对环形分级区内外流场的优化效果以保证物料分级的顺利进行。叶片安装角度由15°提升至60°、叶片数量由72片降至48片后,金属硅、碳酸钙和碳素切割尺寸分别由2.45 m、1.679 m和2.822 m降低至2.147 m、1.427 m和1.816 m;金属硅、碳酸钙和碳素的分级精度分别由37.44%、40.48%和40.94%变化至38.58%、40.38%和45.00%。叶片安装角度变化对分级性能影响更为显著。