Optimal incentive-compatible pricing for M/G/1 queues

This paper extends the applicability of the pricing results of Mendelson and Whang (Oper. Res. 38 (5) (1990) 870) and Balachandran and Radhakrishnan (Management Sci. 40 (10) (1994) 353) for congested service facilities by considering general, class-dependent, service time distributions. Two theorems for nonpreemptive M/G/1 queues and preemptive-resume M/G/1 queues are presented.     

Fused silica capillary column GC/MS for the analysis of priority pollutants

Operational characteristics have been determined for fused silica capillary column (FSCC) GC/MS as applied to “extractable” priority polutants. Chromatographic data show excellent relative retention time (RRT) intralaboratory precision and interlaboratory accuracy when multiple internal standards are empolyed. Potential chromatographic problems, such as column overload and “double peaking”, are addressed. Response factor relative standard deviations (RSD) at 50 ng for most of the extractable priority pollutants over the long term indicated precise determination (i.e. RSD generally ≤ 10%). Linearity was demonstrated over two orders of magnitude for FSCC GC/MS analysis of compounds with relatively low and high RF (response factor) values. Potential quantitative problems, such as saturation, are discussed. For certain aromatic priority pollutants interlaboratory RF agreement was observed. This was noted as perhaps the most important property of FSCC GC/MS analysis when the multiple internal standard approach is utilized. Determinations of extractable priority pollutants are directly compared for paced column GC/MS and FSCC GC/MS analysis of separate and composited extracts. For six extracts analyzed in triplicate, the latter configuration was shown to produce more consistent results. In view of the superior analysis logistics of composite extract FSCC GC/MS analysis, this approach was established as the preferred method for the analysis of priority pollutants classified as extractable.     

渗透汽化膜处理含酚废水

用四种不同结构的聚二甲基硅氧烷及其改性有机硅膜分离舍酚废水.研究了分离温度、酚浓度以及不同种类酚对透过速率及分离系数的影响。结果表明聚合物中有机硅成份的含量对透过速率及分离系数均有较大影响。渗透汽化法分离含酚废水是一个有前途的方法。     

Method development for the analysis of particle phase substituted methoxy phenols and aromatic acids from biomass burning using capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI-MS)

A method is developed for the determination of substituted methoxy phenols and aromatic acids in biomass burning aerosol using capillary electrophoresis (CE) coupled to an electrospray ionization mass spectrometer. Background electrolytes (BGEs) containing ammonium acetate, ammonium hydroxide and 10% (v/v) methanol at pH 9.1 and ammonium hydroxide at pH 11 are investigated for their suitability. A good linearity is found for all analytes in the range of 1-50 microM for the ammonium acetate based BGE and 1-40 microM for the ammonium hydroxide BGE. The detection limit ranged from 0.1 to 1.0 microM for the ammonium acetate based BGE and 0.3 to 0.7 microM for the ammonium hydroxide BGE. The relative standard deviation (R.S.D.) is typically less than 0.5% (ammonium acetate based BGE) and 4.2% (ammonium hydroxide BGE) for the migration time and 3-9% (ammonium acetate based BGE) and 2.5-8% (ammonium hydroxide BGE) for the peak area (n = 5). The analytical time was less than 10 min for both methods. The proposed methods are fast, sensitive and quantitative and can be applied to the analysis of complex biomass burning aerosol samples without complex pre-treatment. The results from the analysis of real biomass burning samples demonstrate the suitability of the proposed methods to the analysis of low concentration water soluble organic carbon (WSOC) in biomass burning samples. The fast analytical time and high sensitivity of the proposed methods enables the analysis of a large number of size segregated impactor samples from biomass burning aerosols.     

焦炉烟气中有机污染物的GC-MS测定

以玻璃纤维滤膜采集焦炉烟气样品,比较了索氏提取和超声波提取两种前处理方法效果,用ＧＣ－ＭＳ法进行分析研究,检出苯并「ａ」芘等多种多环芳烃类有机污染物,并对部分化合物进行了定量分析。     

Investigation of the Montmorillonite clay-catalyzed [1,3] shift reaction of 3-methyl-2-butenyl phenyl ether

The [1,3] shift reaction of 3-methyl-2-butenyl phenyl ether was catalyzed more effectively by Montmorillonite K10 clay than Montmorillonite KSF clay, and proceeded with greatest ortho-selectivity in carbon tetrachloride at room temperature.     

对室内空气污染的探讨

空气污染问题越来越受到整个社会的关注,本文旨在阐述由室内建材造成的空气污染现状、主要化学污染物及常用防治方法。     

Determination of brominated phenols in water samples by on-line coupled isotachophoresis with capillary zone electrophoresis

A method for determination of nine brominated phenols as environmental risk compounds was developed by on-line coupled capillary isotachophoresis and capillary zone electrophoresis (ITP–CZE). For ITP step, 1 × 10⁻² mol L⁻¹ hydrochloric acid with 3 × 10⁻² mol L⁻¹ ammediol pH 9.1 was used as the leading electrolyte, and 3 × 10⁻² mol L⁻¹ β-alanine with 2 × 10⁻² mol L⁻¹ sodium hydroxide pH 10.05 was used as the terminating electrolyte. As the background electrolyte for CZE separation, 2.5 × 10⁻² mol L⁻¹ β-alanine with 2.5 × 10⁻² mol L⁻¹ lysine pH 9.6 was used. All electrolytes contained 0.05% or 0.1% (m/v) hydroxyethylcellulose to suppress the electroosmotic flow. UV detection at wavelength 220 nm was used. Detection limits in order of tens of nmol L⁻¹ were achieved. Good repeatability of migration times (less than 0.33% RSD) and good repeatability of peak areas (less than 7.19% RSD) at concentration level 5 × 10⁻⁸ mol L⁻¹ were observed. Developed ITP–CZE method was applied to determination of brominated phenols in spiked tap and river water samples.     

Optimisation of a simple and reliable method based on headspace solid-phase microextraction for the determination of volatile phenols in beer

A simple, accurate and sensitive method based on headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography–tandem mass spectrometry (GC–MS/MS) was developed for the analysis of 4-ethylguaiacol, 4-ethylphenol, 4-vinylguaiacol and 4-vinylphenol in beer. The effect of the presence of CO₂ in the sample on the extraction of analytes was examined. The influence on extraction efficiency of different fibre coatings, of salt addition and stirring was also evaluated. Divinylbenzene/carboxen/polydimethylsiloxane was selected as extraction fibre and was used to evaluate the influence of exposure time, extraction temperature and sample volume/total volume ratio (V_s/V_t) by means of a central composite design (CCD). The optimal conditions identified were 80 °C for extraction temperature, 55 min for extraction time and 6 mL of beer (V_s/V_t 0.30). Under optimal conditions, the proposed method showed satisfactory linearity (correlation coefficients between 0.993 and 0.999), precision (between 6.3% and 9.7%) and detection limits (lower than those previously reported for volatile phenols in beers). The method was applied successfully to the analysis of beer samples. To our knowledge, this is the first time that a HS-SPME based method has been developed to determine simultaneously these four volatile phenols in beers.     

Acetyl chloride-3,5-di(tert-butyl)-4-hydroxy-N,N-dimethylbenzylamme salt in the benzylation of organic and inorganic sulfur-containing compounds

The reactions of the quaternary acylammonium salt formed on treatment of3,5-di-tertbutyl-4-hydroxy N,N-dimethylbenzylamine with acetyl chloride, with various organic and inorganic sulfur-containing compounds were studied. The possibility of using this salt for the introduction of a sterically hindered phenol moiety in various sulfur-containing compounds was shown.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 98–102, January, 1994.