High precision phase measurement using adaptive sampling

The conventional phase measurement techniques introduce error in the phase when the input signals are distorted by harmonics. A novel technique, known as adaptive sampling, for high-precision phase measurement is introduced. A digital signal-processing approach is used in this technique. The maximum sampling rate required for this technique is h+2 samples/cycle of the input signals, i.e. (h+2) f sampless, where h, is the highest harmonic present in the signals and f is the fundamental frequency of the signals. This sampling rate is way below the Nyquist sampling rate (more than 2hf samples/s) when h is a large number. In the adaptive sampling technique the sampling rate is started from three samples/cycle and then is gradually increased until the phase is correctly measured. This phase measurement technique has been verified using synthesized signals     

Source identification and health risk of polycyclic aromatic hydrocarbons associated with electronic dismantling in Guiyu town, South China

In this study the concentrations and distribution of sixteen polycyclic aromatic hydrocarbons (PAHs) were investigated in gas and total suspended particle (TSP) samples collected during daytime and night time. The sampling locations included an electronic waste dismantling workshop (EW), a plastic recycling workshop (PW) and a waste incineration field (WF) in Guiyu, China. A large residential area (RA) in this region was used as a control site. In the daytime, the highest concentration was found at WF (1041 ng m⁻³); while in the night time the highest concentration was found outside of EW (744 ng m⁻³). Comparison between work hours (daytime) and rest hours (night time) displayed that the total PAHs (gas + particulate phase) concentrations and the percentages of PAHs associated with TSP were higher at night than those in the daytime in all sampling workshops except WF. Source diagnostic-ratio analysis revealed that unwanted materials and smoldering honeycomb coals were the main sources of PAHs in EW, WF and PW. Benzo[a]pyrene equivalent [BaPeq] concentrations calculated by using the toxic equivalent factors [TEFs] suggested that the occupational exposure levels were not significantly high when compared with other occupational exposure. Additionally, our study suggested that the smoldering of unwanted materials could produce much more toxic PAHs compounds.     

ESR study of degraded bovine bone

A comparison is made between the electron spin resonance (ESR) spectra obtained from bovine bone samples after (i) mechanical degradation, (ii) -irradiation, and (iii) mechanical degradation followed by -irradiation. Mechanical degradation is achieved by filing in either liquid nitrogen or air at room temperature. -irradiation is performed at 77 K. The stability of the radical species produced at 77 K is studied as a function of temperature. It is concluded that the spectra obtained in all instances arise from radicals formed both in the collagen and mineral phase of the bone, those from the collagen predominating. The relative radical concentrations from the collagen and mineral phase vary with the degradation method employed. It is observed that additional hydrogen atom radicals are produced only in the case of the -irradiated samples.On leave of absence from C.N.R. Centre for Macromolecular Physics, University of Bologna, Italy.     

Radiation dose in the high background radiation area in Kerala, India

A systematic radiological survey has been carried out in the region of high-background radiation area in Kollam district of Kerala to define the natural gamma-radiation levels. One hundred and forty seven soil samples from high-background radiation areas and five samples from normal background region were collected as per standard sampling procedures and were analysed for (238)U, (232)Th and (40)K by gamma-ray spectroscopy. External gamma dose rates at all sampling locations were also measured using a survey meter. The activities of (238)U, (232)Th and (40)K was found to vary from 17 to 3081 Bq kg(-1), 54 to 11976 Bq kg(-1) and BDL (67.4 Bq kg(-1)) to 216 Bq kg(-1), respectively, in the study area. Such heterogeneous distribution of radionuclides in the region may be attributed to the deposition phenomenon of beach sand soil in the region. Radium equivalent activities were found high in several locations. External gamma dose rates estimated from the levels of radionuclides in soil had a range from 49 to 9244 nGy h(-1). The result of gamma dose rate measured at the sampling sites using survey meter showed an excellent correlation with dose rates computed from the natural radionuclides estimated from the soil samples.     

Concentration and congener patterns of polychlorinated biphenyls in industrial and municipal waste incinerator flue gas, Korea

In the present study, individual PCB congeners were determined in the flue gases of 10 industrial and 5 municipal solid waste incinerators using HRGC/HRMS. The total PCBs concentration of all congeners (168 tetra to deca-chlorinated congeners) ranged from 26 to 343 ng/Nm(3), and from 36 to 1095 ng/Nm(3) in industrial waste incinerators (IWI) and municipal solid waste incinerators (MSWI), respectively. The total TEQ concentrations of PCBs, calculated using WHO-TEF values, varied from 0.001 to 0.55 ng-TEQ/Nm(3) and from 0.001 to 8.29 ng-TEQ/Nm(3) in the industrial waste incinerators and municipal solid waste incinerators, respectively. In all samples, the contribution of PCB 126 to total TEQ of PCBs was higher than 87%. The homologue pattern of PCBs in the incinerator flue gas samples was generally dominated by tetra- and penta-CBs. The distribution of other homologues was less than 15% in most of the incinerators. The fraction of co-PCBs against to total PCBs ranged from 1% to 19% and from 2% to 31% in IWI and MSWI flue gas samples. Results of the present study reveal that the presence of non-ortho PCB congeners in the flue gas originated form the combustion process.     

非抑制型离子色谱法测定印制电路板表面阳离子污染物

本文提出了一种利用非抑制型离子色谱法测定印制电路板表面五种无机阳离子污染物的方法。样品用异丙醇水溶液提取后,用Sep-PakC18小柱净化试样,用离子色谱分离,电导检测器检测。五种阴离子的检测限介于0.01~0.02μg/ml之间,回收率为98~103%。方法准确、可靠,可用于印制电路板洁净度的评价分析。     

Distribution of organochlorine pesticides in surface water and sediments from Qiantang River, East China

The levels of 13 organochlorine pesticides (OCPs) in surface water and sediments from Qiantang River in East China were investigated to evaluate their potential pollution and risks. A total of 180 surface water samples at 45 sampling sites and 48 sediment samples at 19 sampling stations were collected along the river in four seasons of 2005. Soil samples and wet deposition samples were also collected to provide evidence on the source of OCPs pollution. The total OCPs concentrations in surface water and sediments were 7.68-269.4 ng/L and 23.11-316.5 ng/g-dry weight (dw), respectively. The concentrations of OCPs in sediments were in the range of 8.22-152.1 ng/g-dw for HCHs (alpha-, beta-, gamma-, delta-HCH), 1.14-100.2 ng/g-dw for DDTs (p,p'-DDD, p,p'-DDE, p,p'-DDT o,p'-DDD), 9.41-69.66 ng/g-dw for other OCPs (aldrin, diedrin, endrin, heptachlor, heptachlor epoxide). The total OCPs concentrations in soils and wet deposition were 5.04-214.9 ng/g-dw and 16.18-242.4 ng/L, respectively. Among the OCPs, HCHs, DDTs and heptachlor were the most dominant compounds in the sediments. The dominant OCPs in water were gamma-HCH among HCHs, heptachlor among other OCPs and p,p'-DDE among DDTs. Also, different contamination patterns among sampling seasons were found. The concentrations of OCPs in sediment collected in spring were higher than those in summer and autumn. In contrast, the concentrations of OCPs in surface water in summer and autumn were higher among four sampling seasons. Distribution of HCHs, DDTs and other OCPs were different indicating their different contamination sources. The notable contamination was found in Fuchun reservoir. Composition analyses in sediments indicated a recent usage or discharge of lindane into the river.     

High extraction efficiency for POPs in real contaminated soil samples using accelerated solvent extraction

Systematic investigations were performed to study the dependence of the extraction efficiency of persistent organic pollutants (POPs), including chlorobenzenes, HCH isomers, DDX, PCB congeners, and PAHs, on the accelerated solvent extraction (ASE) operating variables solvent and temperature. Mixed soil samples from two locations with considerable differences in soil properties and contamination in the Leipzig-Halle region (Germany) were used. The objective was to optimize ASE for the extraction of POPs from real soil samples and to improve on the results achieved with Soxhlet extraction (SOX). Solvents with differing polarities were tested. Quadruple and triple determinations were performed on the two soils, respectively, between 20 and 180 degrees C in 20 degrees C steps. All the results were compared with those obtained by SOX, as well as, in some cases during preliminary studies, by ultrasonic extraction (USE). In ASE, the optimum conditions proved to be two extraction steps at 80 and 140 degrees C (average RSD 10.7%) with three static cycles (extraction time 35 min) using toluene as solvent and at a pressure of 15 MPa. Owing to the superior analyte/matrix separation by ASE, in many cases for real soil samples analytical values better by up to 1 order of magnitude or even more were obtained compared to SOX results.     

Solid-phase microextraction and headspace solid-phase microextraction for the determination of polychlorinated biphenyls in water samples

A solid-phase microextraction (SPME) method has been developed for the quantification of polychlorinated biphenyls (PCBs) in water samples. Parameters such as sampling time, volume of water, volume of headspace, temperature, addition of salts, and agitation of the sample were studied. Because the time for reaching equilibrium between phases takes several hours or days, depending on the experimental conditions, it was necessary to work in nonequilibrium conditions to keep the sample analysis to a reasonable time. The possibility of sampling the headspace over the water sample (HSSPME), instead of immersing the fiber into the water (SPME), was also investigated, and despite the low partition of PCB into the headspace, HSSPME offered higher sensitivity than SPME at 100 °C. The adsorption kinetics for SPME at room temperature, SPME at 100 °C, and HSSPME at 100 °C were investigated and compared. The proposed HSSPME method exhibits excellent linearity and sensitivity. The detection limit was in the sub-ng/L level. This method has been applied to a real industrial harbor water and compared with liquid-liquid extraction. Both techniques offered similar results, but HSSPME was much more sensitive and considerably faster, by eliminating all the manual process intensive sample workup, and reduces solvent consumption entirely. The only drawback was that matrix effects were observed, but with the addition of deuterated surrogates to the sample or the use of a standard addition calibration, accurate quantification can be achieved.     

On stability sampling strategy at the slope scale

Snow slope stability evaluation is often based on a single test location within a slope. However, we know that snow cover properties and stability may vary at the slope scale. Reliably estimating the slope-scale variability requires many samples, ideally more than 100. As this is unpractical, it has been proposed to perform at least two tests — about 10 m apart — on a given slope. In addition, if small column stability tests are used (such as the compression test), it seems reasonable to perform two tests at each of the two locations. Differences between the two tests at one location allow one to assess the small (or pit-) scale variability (and/or the test uncertainty), whereas differences between the pairs at different locations may hint at the slope-scale variability. We analyzed 22 small slopes each with four pairs of stability tests. In 61-75% of the cases the two stability tests at a specific location provided consistent results, depending whether we focused on the CT score or the fracture character (which was less variable). Comparing the different sampling locations on a given slope (∼ 10-15 m apart) showed that at the slope-scale the differences between sampling locations (59-75%) were similar to the differences found at the pit-scale. Rather stable slopes tended to have more pit-scale variation than rather unstable slopes. Based on our analysis, we suggest an interpretation scheme and an adjusted sampling procedure. In particular, a second pit on a slope seems only necessary if the first pit does not indicate instability. In all other cases, a second pit can reduce the number of false-stable predictions.     

Methodological refinements in the determination of 146 polychlorinated biphenyls,including non-ortho- and mono-ortho-substituted PCBs,and 26 organochlorine pesticides as demonstrated in heron eggs

A method for the determination of 146 polychlorinated biphenyls (PCBs), including four non-ortho- and eight mono-ortho-substituted congeners, and 26 chlorinated pesticides is described. The method consists of ultrasonic extraction, Florisil cleanup, HPLC fractionation over porous graphitic carbon (PGC), and final determination with GC/ECD, GC/MS, or both. Two PCB congeners (PCB 30 and PCB 161) and two polybromobiphenyls (2,4',5-tribromobiphenyl and 3,3',4,4'-tetrabromobiphenyl) were used as surrogate standards to evaluate the analytical efficiency. Four PCB congeners, PCB 14 and PCB 159 for the first fraction, PCB 61 for the second fraction, and PCB 204 for the third fraction, were used as internal standards to monitor the GC performance. The retention behavior of PCBs and pesticides on the PGC column are discussed. The method was found to be reproducible, effective, and reliable under the operational conditions proposed and was applied successfully to the analysis of individual PCBs and chlorinated pesticides in black-crowned night heron (Nycticorax nycticorax) egg samples.     

非抑制型离子色谱法测定负印制电路板表面阴离子污染物

本文提出了一种利用非抑制型离子色谱法测定印制电路板表面六种无机阴离子污染物的方法。样品用异丙醇水溶液提取后,用Sep—Pak C_(18)小柱净化试样,用离子色谱分离,电导检测器检测。六种阴离子的检测限介于0.01～0.2μg/ml之间,回收率为98～104％。方法准确,可靠,可用于印制电路板洁净度的评价分析。     

Monitoring of the pesticide levels in some water supplies and agricultural land, in El-Haram, Giza (A.R.E.)

Monitoring of pesticide residues were conducted at different locations in the El-Haram region Giza, Egypt. The water samples were collected from El-Haram Giza, canal water supplies (El-Zomor, Abd-el-aal land and seaside and El-Mansorya), in addition to El-Moheet drainage water. The soil samples were collected from the arable land that surrounds water canals. Water samples were obtained by solid phase extraction (SPE) and soil samples by gel permeation chromatography (GPC). The combination of gas chromatography and mass spectroscopy with different ionization techniques was used for determination and identification of the pesticides, which were quantitatively determined as 1 microgram 1(-1) levels in environmental samples. The residues of pesticides were varied between different locations. Also, organochlorine pesticide residues in El-Moheet drainage water were relatively higher than in the canal water. The concentrations of organophosphorous compounds (chlorpyrifos, dimethoate and parathion) seem to be low in water as compared to soil samples. Most findings were less than 1 microgram g(-1), which is considered a low-level finding. Sixteen organochlorine pesticides were detected in most of the water samples and the percent of positive samples followed the order drins > total BHC > total DDT > endosulfan > heptachlor epoxid > heptachlor. Pentachlorophenol (PCP) was detected only in El-Zomor and Abd-el-aal canal water. Results obtained confirm the presence of different pesticide residues representing different chemical classes in the canal waters. This means that the discharging of wastes in to the water supplies must be controlled. Drainage water was highly polluted and contains much more pesticide residues than different canal waters.     

Analysis of corticosteroids in biofluids by capillary electrochromatography with gradient elution

Capillary electrochromatography (CEC) with gradient elution was used to separate mixtures of corticosteroids (adrenosterone, hydrocortisone, dexamethasone, fluocortolone) in extracts of equine urine and plasma. Urine samples were first purified using solid phase extraction. Two purification steps were necessary to prevent contamination of the CEC column. Plasma was purified using automated dialysis. A laboratory-built CEC interface, connected to a gradient HPLC system, delivered samples and mobile phase to the CEC column. CEC was performed in fused-silica capillaries of 50 μm i.d., 24 cm total length, and 16 cm effective length packed with Apex ODS, 3 μm particle size. The mobile phase was ammonium acetate (5 mM) in water/acetonitrile. Acetonitrile in the mobile phase was varied from 9 to 80% (v/v) using the gradient HPLC system. Detection was by UV absorbance at 240 nm. Samples, 10-250 μL, were injected into the mobile phase stream and loaded onto the CEC column under an applied field of 1.04 kV cm(-1) and a CEC column head pressure of 12 bar. Mobile phase flow rate through the sampling interface was 100 μL min(-1). The system was reproducible and could be left in unattended operation for long periods. After injection of 200 urine extracts, a broadening of peaks was observed but the CEC column was still serviceable.     

Evaluation of performance characteristics of multistep analytical methods from collaborative study of linked samples

Following unexpectedly variable results from an international comparison study of the determination of selected polychlorinated biphenyl (PCB) congeners in shellfish tissue, a group of national metrology institutes collaboratively explored the analytical characteristics of their measurement systems using a designed study with four sample materials. This "Uncertainty Suite" consisted of a 10-congener mixture of PCBs in relatively nonvolatile isooctane, a 5-congener mixture in relatively volatile methylene chloride, a methylene chloride extract of freeze-dried mussel (Mytilus edulis) tissue, and the (homogenized) mussel tissue itself. These related-but-different samples presented the participants' measurement processes with a linked series of analytical challenges. Data evaluation tools were developed to combine and visualize measurement results for the different congeners of interest for each material and, exploiting the linkages among the samples, to help identify causes for observed changes in performance. In addition to characterizing individual measurement processes, (1) the limiting sources of measurement uncertainty were found to be chromatographic separation and signal quantification in a natural matrix, (2) the achievable among-participant total measurement uncertainty for PCB calibration solutions is approximately 1.9% over the mass fraction range from 40 to 500 ng/g, and (3) the achievable among-participant measurement precision for the determination of PCB congeners in mussel tissue at levels above 0.5 ng/g mass fraction is approximately 5.4%.     

Novel hydrophobicity ruler approach for determining the octanol/water partition coefficients of very hydrophobic compounds via their polymer/solvent solution distribution coefficients

A novel hydrophobicity ruler approach for determining the octanol/water partition coefficients of very hydrophobic compounds is proposed, which is an indirect method that measures the polymer/solvent solution distribution coefficients (log Kp/s) of reference and unknown compounds. The log Kp/s values of the unknown compounds can be calibrated to their log Ko/w values via the correlation of the log Kp/s values of the reference compounds with their log Ko/w values. An organic solvent was used to increase the solubility of the very hydrophobic compounds in the aqueous solution, so that their concentrations and absorption amounts were high enough to be measured precisely. The solvent also reduced the hydrophobicity scale of the very hydrophobic compounds and controlled the amounts absorbed into the polymer phase, so that compounds spanning a very wide range of log Ko/w values could be measured in a single measurement and the coexisting compounds would not interfere each other. Poly(dimethylsiloxane) (PDMS), aqueous methanol solutions, and a series of 21 PCB (polychlorinated biphenyl) compounds were used to demonstrate the principle of the hydrophobicity ruler approach. The PCB compounds with known experimental log Ko/w values served as reference compounds, whereas the PCB compounds without known log Ko/w values were determined. The log Ko/w values determined for PCB126, PCB187, PCB197, PCB180, PCB170, and PCB195 were 6.94, 7.84, 8.33, 8.17, 7.92, and 8.49, respectively. The correlation of the log Kp/s values of the reference PCB compounds with their log Ko/w values was linear (log Ko/w=2.56 log Kp/s+1.08, R2=0.95). The hydrophobicity ruler approach is also a valuable tool for validating the experimental and theoretical log Ko/w values and identifying outliers in log Ko/w databases.     

基于AOI的印刷电路图像对准算法研究

基于AOI的PCB检测系统中,样本PCB图像与待测PCB图像之间存在错位偏差,需要对准后才能进行下一步的检测工作。首先,依据PCB线路特征,定义了样本图像边缘点的概念,制订了边缘点抽样规则。针对待测PCB图像,提出了基于样本边缘点对准强度评价函数,建立了对准评价模型及对准快速算法。最后,通过PCB对准实验以及大量的实际测试应用,证明对准强度评价模型能准确地描述待测PCB图像与样本图像间的对准程度,对准模型为后期的缺陷搜索提供了可靠的偏移参数。     

Development of group setup strategies for makespan minimisation in PCB assembly

Balancing setup effort and actual production time is an important issue in medium-variety, medium-volume printed circuit board (PCB) assembly. By grouping batches of similar PCB types to be processed with a common machine setup, the total time required for setting up the component feeders in the magazine of the placement machine can be reduced. On the other hand, the assembly times per PCB increase, since it is no longer possible to optimise the feeder locations in the magazine for each PCB type individually. In order to balance the savings in setup time and the increase in assembly time and to minimise the global makespan, we propose efficient grouping procedures which include machine-specific algorithms for fine-tuning the machine operations for a group of PCBs. Hence, the actual placement times are reflected much more accurately, compared with conventional grouping procedures which merely analyse the component similarity between pairs of PCBs. Two different agglomerative clustering techniques are proposed. One is based on average linkage clustering, the other on a novel hierarchical clustering approach using an inclusion tree representation of the PCB types. Both take the limited capacity of the component magazine into account. We demonstrate the effectiveness of our approach in an extensive numerical investigation of a single-gantry collect-and-place machine equipped with a rotary placement head and an interchangeable feeder trolley. Compared to conventional methodologies, the proposed group setup strategies reduce the global makespan for a given number of batches significantly.     

Vertical distribution of polychlorinated biphenyl congeners in sediment core from Thane Creek area of Mumbai, India

In recent years there has been a growing concern all over the globe about the marine pollution due to persistent organic pollutants. Sediments, which is an important component of marine environment can serve as sorbent or concentrator for various persistent organic pollutants including Polychlorinated Biphenyls (PCBs). Transport and fate of PCB congeners in sediment depends on their physicochemical characteristics. In this study, the depth profile of accumulated PCBs in Thane Creek sediments of Mumbai, India, was studied. The sediment core samples were collected using a gravity corer, processed and analysed for different PCB congeners. Analysis of PCBs in the sediment samples were carried out using gas chromatography system equipped with electron capture detector. The study on vertical distribution of PCBs in sediment could reflect the geochemical history including changes due to anthropogenic releases into the system. The surface segment shows the downward trend for these compounds, indicating slow phase out of PCBs after ban. The concentration and composition of different homologues varies at different depth. An attempt has also been made to find out the various sources of PCBs which could have contributed to these compounds by performing factor analysis over the observed concentrations of the PCB compounds in the core sediment.     

High-G drop impact response and failure analysis of a chip packaged printed circuit board

This paper is concerned with constructing a high-G drop impact test condition for investigating the impact-induced failure phenomenon of the solder ball array located in the chip packaged printed circuit board. An impact environment satisfying the JEDEC B service conditions, requiring a 0.5 ms half-sine impact pulse duration with a peak acceleration at 1500 G, were constructed using an instrumented drop tower tester. Fifteen wafer-level CSP chips were installed on a standard printed circuit board (PCB) with a dimension of 132×77×1 mm³. A number of these chip packaged PCB bonded with four different compositions of solder joints with or without lead using the surface-mounted technology (SMT) were studied. During the drop impact tests, the chip packaged PCB circuit was monitored using the multi-event detector system (ETAC) to examine whether circuit fails or not. In addition, the drop impact dynamic response of the PCB and the acceleration at the prescribed location of the drop table were recorded and analyzed. Transient stress responses in the solder joints were provided using the LS-DYNA explicit code. Numerically predicted failure locations of the solder joints are close to those observed from actual drop impact experiments.