RETRIEVAL OF AEROSOL OPTICAL THICKNESS BY MEANS OF THE LEAST-MEDIAN-SQUARES ROBUST ALGORITHM

Atmospheric aerosols play an active role in the atmospheric radiative energy transfer by interacting with the solar energy through light scattering and/or absorption. Such an interaction has the potential to counter balance or enhance the warming caused by the greenhouse gases (e.g. carbon dioxide, water vapor, and methane). The interactions would depend on a variety of factors such as the microphysics and chemistry of aerosol particles, and the environmental conditions. To model the energy transfer processes accurately, several aerosol parameters such as aerosol optical thickness (AOT), single scattering albedo, scattering phase function, refractive index, and chemical composition of aerosols have to be known. In this report, a robust method for aerosol optical thickness is presented. The method is based on the least median squares (LMS) regression technique. The LMS-based technique is fundamentally different from the traditional least-squares (LS) technique commonly used today to retrieve AOT. The LMS technique was found to resist influential outliers and sustain the impacts of outliers much better than the LS in our application. The outlier-resistance property is an important design consideration for an automatic AOT retrieval algorithm. We demonstrated the strength of the new technique by using the shortwave irradiance measurements taken by one of the Multi-filter Rotating Shadow-band Radiometers installed at the Southern Great Plains in Oklahoma, U.S.A., one of the three sites operated by the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program. The data cover a time period from September 1995 to May 1997. The LMS-retrieved mean top-of-atmosphere solar irradiance values (i.e. I₀) were stable based on the one-tailed Student’s t tests. It was also found that the difference between the 75th and 25th percentiles (a non-parametric robust estimate of variation) of I₀ over the 2-year period was 0.2 for the 499-nm channel, and 0.05 for the 860-nm channel. The monthly averaged AOT values over the 2-year period were from 0.05 to 0.30 for the 499-nm channel and from 0.03 to 0.15 for the 860-nm channels. AOT values peaked between May and September and reached minima in between November and January. The synoptic flow from the North might have contributed to the low level of AOT values during the wintertime, while the southerly flow, traversing through more industrial areas before reaching the site, could have contributed to the influx of particles during the summertime.     

THE ON-LINE CHEMICAL ANALYSIS OF SINGLE PARTICLES USING AEROSOL BEAMS AND TIME OF FLIGHT MASS SPECTROMETRY

This paper describes an on-line instrument, capable of measuring the size and chemical composition of single, aerosol particles. Possible applications include monitoring aerosol reactors and studying atmospheric chemistry. The main conclusion is that a working prototype has been built and tested. It uses a three stage vacuum system to generate an aerosol beam with a low divergence angle and a high transmittance. The pressure is reduced sufficiently to allow the application of a time-of-flight mass analyzer. The aerosol beam is probed in the analysis section by the focused beam of a low-power helium-neon laser. Every particle crossing the laser beam scatters light, which is detected by two photomultiplier tubes, mounted at angles of 45 and 90°. The signal is stored when both detectors produce a pulse simultaneously, and this event triggers the chemical analysis cycle. A pulsed Nd: YAG laser vaporizes the particle and generates ions, which are next analyzed by a time-of-flight mass spectrometer. In this way combined information on the size and the composition of the particle is obtained.     

THE EFFECT OF VORTICES INDUCED BY BAFFLES ON CONCENTRATION POLARIZATION

A numerical analysis was performed to investigate the effect of recirculations formed by rectangular or triangular baffles on depolarization of concentration in a flat sheet membrane module. The k- ? turbulent model was used to predict the flow field in the flat channel. Control-volume-based finite difference methods were employed to solve for the two-dimensional fluid velocity and solute concentration distributions. We examined rigorously the effect of various parameters including the velocity, diffusivity, permeate flux, baffle size, baffle shape, and interbaffle spacing in an effort to find optimum operating conditions which may provide enhanced mass transfer. The vortices induced by the baffles on the membrane are found to be extremely effective in depolarizing the retained solutes at the membrane surface. The predictions show that baffle configurations and flow conditions have a great influence on depolarization of concentration. To achieve effective concentration depolarization, the baffle height should be greater than 0·5 (h = half the channel height) and the interbaffle spacing around 2h to 3h for the Reynolds number from 1,250 to 25,000. The simulated results indicate that the optimal Reynolds number is around 5,000 to 8,000 in view of both concentration polarization and energy consumption.     

THE EFFECT OF FREE STREAM CONCENTRATION ON HEAT AND BINARY MASS TRANSFER WITH THERMODYNAMIC COUPLING IN CONVECTION ON A ROTATING DISC†

Simultaneous heat and mass transfer, which arises from injecting a gas (helium or hydrogen) from or through the solid surface into a flowing external stream, has been studied for a rotating disc geometry. The effects of concentration levels of the injected gas in the external stream on the thermodynamic coupling in the presence of centrifugal force have been investigated over a wide range of T_w/T_e.

Boundary layer equations for heat and mass transfer were solved numerically. Exact and linearized approximate solutions were obtained. The results have shown that the thermal diffusion effect on mass transfer becomes increasingly important as the free stream concentration increases and as T_w/T_e departs from unity. The diffusion thermo effect on heat transfer was found to be the most important when the free stream concentration is zero and as T_w/T_e approaches unity.     

ON THE ROLE OF CONCENTRATION LEVEL OF NONDIFFUSING SPECIES IN GAS PHASE MASS TRANSFER AT HIGH TRANSFER RATES

Re-evaluation of high mass flux literature data from evaporation and absorption experiments suggest the validity of y_BM as a good correlation variable for predicting gas phase mass transfer at high transfer rates. This was done by testing Greiner and Winter's engineering model where y_BM explicitly emerges after manipulating their model equations. The manipulated model agrees well with the literature data within the range of 0.961 ≥y_BM ≥ a 0.549 and 7.3333 ≥ B ≥ -0.4757 which covers the mostly commonly chemical engineering conditions and geometries. Thus, the y_BM serves not only as a good correlation variable as has been commonly used under low to moderate mass transfer rales, but also applies to the controversial case of high mass transfer rates.     

电渗析浓缩回收硫酸钠溶液的实验研究

本文介绍了采用离子交换膜电渗析法对硫酸钠溶液进行浓缩回收的试验研究,结果表明,采用该法浓缩回收硫酸钠溶液是理想的新型处理方法。     

超滤法浓缩纯化透明质酸钠

本文报道了采用丙烯腈三元共聚物中空纤维超滤膜浓缩纯化透明质酸钠。结果表明，经超滤浓缩纯化制得的透明质酸钠产品外观及理化指标均好，回收率高。丙烯腈三元共聚物中空纤维膜对透明质酸钠溶液有良好的抗污染性能，料液的透明速率稳定在３０Ｌ／ｍ＾２．ｈ左右，采用生理盐水正反冲洗结合方法可以使膜的性能基本恢复。     

INFLUENCE OF SOLUTE TEMPERATURE AND CONCENTRATION ON THE COMBINED OSMOTIC AND AIR DRYING

ABSTRACT

The effect of solute concentration (15–45 % sugars) and temperature (10–40 °C) on the osmotic dehydration of apple was investigated. Cylindrical samples of apple were immersed in glucose or sucrose solutions and the water loss, the volume of solids and the porosity were measured as a function of time. Water loss was proportional to the square root of time, while the volume of solids decreased and the porosity increased with time. Sugar gain and water loss decreased the compression stress of the apple samples. Osmotic pre-treatment reduced the shrinkage and the porosity of apple solids during air-drying, compared to the no-treated samples. The results of this investigation are useful in the design of efficient osmotic dehydration processes, and in the evaluation of texture of dehydration of products.     

加碱曝气-A／O组合工艺处理高浓度医药中间体废水

医药中间体三甲氧基笨甲醛(TMBA)废水色度大,有机物含量高达20 000mg·L-1以上,可生化性差.针对上述特点,采用了加碱曝气法有效地增加了废水的可生化性,BOD/COD由原来的0.24增加到0.35,采用了厌氧-好氧组合工艺处理,最终出水COD小于100mg·L-1,出水基本无色,达到工业水污染排放一级标准.     

QUALITATIVE OBSERVATIONS OF HEAT AND MASS TRANSFER EFFECTS ON THE BEHAVIOUR OF A TRICKLE BED REACTOR

This paper examines the effect of simultaneous heat and mass transfer on the hydrogenation of cyclohexene in a trickle bed reactor with particular attention given to the problem of liquid phase evaporation and transition to the gas-phase regime of operation. The reaction rates are obtained as a function of temperature and hydrogen flow rate; the concentration of the substrate in the feed displays considerable hysteresis due to an abrupt increase of the reaction rate arising from temperature gradients within the bed and in the gas film surrounding the catalyst pellet, during the transition from the liquid to the gas-phase regime. The transition is accompanied by the change of apparent kinetics of the model reaction as well as by a change of regime and operation of the pellet. In the liquid phase a pellet originally showing inter-phase and intra-particle diffusion resistances changes into the gas-phase regime with a large resistance due to inter-phase diffusion.     

INFLUENCE OF SOLUTE TEMPERATURE AND CONCENTRATION ON THE COMBINED OSMOTIC AND AIR DRYING

The effect of solute concentration (15-45 % sugars) and temperature (10-40 °C) on the osmotic dehydration of apple was investigated. Cylindrical samples of apple were immersed in glucose or sucrose solutions and the water loss, the volume of solids and the porosity were measured as a function of time. Water loss was proportional to the square root of time, while the volume of solids decreased and the porosity increased with time. Sugar gain and water loss decreased the compression stress of the apple samples. Osmotic pre-treatment reduced the shrinkage and the porosity of apple solids during air-drying, compared to the no-treated samples. The results of this investigation are useful in the design of efficient osmotic dehydration processes, and in the evaluation of texture of dehydration of products.     

表流-潜流人工湿地处理北方城市景观水体研究

根据北方地区城市景观水体的特点以西安某景观湖为例,进行了表流-潜流组合的人工湿地水处理试验。结果表明,表流区对COD、藻类和SS有很好的去除效果,减少了潜流区基质堵塞的几率,再经过潜流区COD、藻类、SS去除率分别达到80%以上;TN、TP、NH3-N主要在潜流区去除,平均去除率分别为63.7%、65.8%、79.7%。表流-潜流组合的人工湿地适合于北方地区城市景观水体的处理,为该地区构建人工湿地提供了理论依据和设计参照。     

煤系高岭土吸附城市生活污水中磷的影响

为了拓宽煤系高岭土的应用前景,利用正交实验考察了反应条件对煤系高岭土吸附城市生活污水中磷的影响,确定了各因素对煤系高岭土吸附城市生活污水中磷的影响顺序依次为:煤系高岭土的用量、搅拌速度、反应时间、反应温度、pH值和生活污水的相对浓度,得到了最佳的反应条件为煤系高岭土的用量为6 g,搅拌速度为45 r/min,反应时间120 min,反应温度35℃,生活污水pH为4,生活污水相对浓度为0.50.在此条件下煤系高岭土吸附城市生活污水中的磷含量达96.80%.     

折点氯化处理低浓度氨氮废水

稀土冶炼废水是一种较难处理的工业废水,有机物含量少,盐度高,难从采用生化处理,使得低浓度NH4 -N无法得到有效去除.为了使该类废水能实现达标排放,对折点氯化去除NH4 -N进行了试验研究.试验表明,pH为7,C1/NH4 为7∶1时,反应10～15min,废水中NH4 -N去除率达98%,并对中和后的草酸沉淀母液进行了试验,发现C1/NH4 为8∶1时NH4-N去除效果最好,余氯经Na2SO3还原后可被完全去除.通过经济分析,NH4 浓度在100mg·L-1左右的废水采用折点氯化处理是经济可行的.     

厌氧水解-分点进水倒置A2/O处理低含量印染废水研究

针对A2/O工艺在脱氮除磷方面存在的矛盾,以及生物难降解印染废水中碳源不足的问题,提出厌氧水解-分点进水倒置A2/O处理印染废水的新工艺。试验结果表明:新工艺仅利用2段生化处理过程,出水COD、BOD5、氨氮、TN、TP、色度分别可达77.12%、70.93%、96.59%4、5.52%、63.33%8、3.11%的平均去除率,分别比常规A2/O工艺提高16.01、27.85、3.92、8.851、9.89、0.65个百分点,显示厌氧水解-分点进水倒置A2/O工艺具有较好的污染物去除效果。     

塑料加工应用情报检索体系的建立与应用

介绍了塑料加工应用情报检索体系的组成与功能.该体系拥有PE、PP、PS等5个专题文献数据库;开通了3个国际联机情报检索系统和4个国内联机情报检索系统.累计已检索课题310个,打印输出信息12000条.产生了较好的经济效益和社会效益.     

固定化高效PVA降解菌处理PVA废水的研究

将一株高效PVA降解菌P-3和PVA培养物固定在填料上,并对系统的启动情况、运行稳定性、抗冲击能力以及活性的调控方法进行探讨。结果表明,固定化高效菌系统与活性污泥相比,启动时间少2d,PVA去除率高35%左右,脱氢酶活性高90μgTF.g-1.h-1左右;系统更稳定,连续运行6个月,PVA去除率维持在80%左右,脱氢酶活性维持在180μgTF.g-1.h-1;耐冲击能力强,最高耐受负荷为2 000 mg.L-1左右,比活性污泥高1 100 mg.L-1左右。当PVA负荷超过2 000 mg.L-1时,PVA负荷每增加10%,分别加入P-3菌悬液5 mL和1 g酵母汁可使系统PVA去除率保持在70%以上。     

铸膜液中水含量对聚砜超滤膜结构和性能的影响

试验在环境温度20℃、相对湿度50%、凝胶浴温度20℃的条件下制膜,在聚砜(PS)铸膜液中添加水为非溶剂添加剂,研究水添加量对铸膜液粘度、膜性能和结构的影响.结果表明,水的添加对铸膜液起到了增粘的作用;30℃ PS的质量分数为14%铸膜液所成膜的纯水通量随铸膜液中水的添加量的增加大体上呈增加的趋势,从59.1增大到126.4 L·m~(-2)·h~(-1);截留率则略有下降;相应的膜表面的孔径增大、孔增多;相同水添加量(质量分数0.05%)PS的质量分数为14%的铸膜液粘度随温度的升高而减小;铸膜液温度的升高,相应的膜的纯水通量随之增加,截留率则略有下降.