Spatial Distribution of Polychlorinated Biphenyls(PCBs)Contaminants in the Tidal-flat Sediments of Yangtze Estuary

PCBs pollutants are measured on tidal-flat sediments of Yangtze estuary by a high resolution capillary column gas chromatography ( HP6890 ) equipped with an 63Ni electron capture detector ( ECD ). The concentration tendency of PCBs is Phragmites zone > Scirpus zone > bare mudflats. There are linear relations between PCBs and TOC and > 63μm grain size percentage ( in volume ). The low chlorinated congeners may be more important than the high chlorinated congeners in this area. PCBs prefer to accumulate in the sediments near sewage outlets and Phragmites zone. The sediments’ PCBs pollution ( 10.7 ~ 28.6 ng/g, dry weight ) in the Yangtze estuary tidal-flat is less serious than that of the most of other areas in the world .But the detected ratio is 100%, even the Jiuduansha shoal has detected PCBs, so much attention should be paid to this area for PCBs.

Biodegradation of Tritium Labeled Polychlorinated Biphenyls (PCBS) by Local Salt Tolerant Mesophylic Bacillus Strains

Salt-resistant Bacillus strains, isolated from agricultural soils in Uzbekistan, were tested for degradation activity towards a mixture of polychlorinated biphenyls (PCBs) under aerobic conditions. The study employed the use of tritium labeled PCB congeners and traced the tritium label in cultures with high salt content. The experiments show that most of the selected strains were able to adsorb a part of the radioactivity, indicating transformation of the added PCBs. Gas chromatography demonstrated transformation of PCBs. The radioactive label was removed from several cultures by up to 91%, indicating also mineralization of PCBs. The study suggests that the isolated strains might be good candidates for the bioremediation of contaminated high-salt soils in Uzbekistan and other Central-Asian countries.

水生环境中OH-PCBs的来源、污染现状及其内分泌干扰机制研究进展

羟基多氯联苯(hydroxylated polychlorinated biphenyls,OH-PCBs)是典型持久性污染物多氯联苯(polychlorinated biphenyls,PCBs)在环境中经多种机制氧化产生的主要产物之一,属于二代环境持久性污染物,在水生环境中被广泛检出(水体<4.12 ng·g^(−1),沉积物<26.0 ng·g^(−1),水生生物<1838.38 ng·g^(−1)).水生环境中OH-PCBs的来源主要包括两方面,一方面,PCBs在生物体内由细胞色素P450(CYP450)单加氧化酶系直接氧化或经氧化芳烃介导而产生OH-PCBs;另一方面,PCBs能够与大气中的羟基自由基发生反应转化为OH-PCBs,最终环境中的OH-PCBs经过雨水冲刷、大气沉降等作用进入水生环境中.水生环境介质中痕量的OH-PCBs经食物链的传递和放大作用,不仅对水生生物的生理活动造成影响,而且能够通过水产品等食物途径进入到人体.由于部分OH-PCBs的结构与天然雌激素、甲状腺激素等内分泌物质类似,在动物体内会导致一系列内分泌干扰效应,但其干扰机制仍未阐明;并且蓄积在生物体内的OH-PCBs能够进一步发生代谢转化,产生的多种代谢产物及其毒理效应有待进一步研究.本文对目前OH-PCBs在水生环境中的污染现状、生物体内的蓄积及“再代谢”特征及其内分泌干扰效应机制研究进展进行综述,进而为OH-PCBs的暴露风险评价、蓄积代谢规律以及毒理学效应研究提供参考.

Distribution characteristics of polychlorinated biphenyls (PCBs) in coastal areas of Okinawa Island,Japan

Surface sediment and seawater samples were collected from coastal areas around Okinawa Island from September 2001 to May 2002. The samples were analyzed for total polychlorinated biphenyl (PCB) levels and homolog composition. The results show that total PCB levels ranged from 0.32 to 128.7 ng/g (dry wt.) in sediment and 1.59 to 2.48 ng/L in seawater. The levels exceed the Environmental Quality Standard (EQS) for water pollution of Japan. The distribution of PCB homolog showed different patterns in the sediments and seawaters. Penta-chlorobiphenyls (CBs) comprised the main congener group in seawater, while hexa-CBs were more abundant homologs in the sediments. The heavily contaminated sites featured higher CBs, including penta-CBs, hexa-CBs, and hepta-CBs, than those in less contaminated sites where tri-CBs dominated. This study provides current distribution and geochemical behavior of PCBs in the coastal areas around Okinawa Island.

Determination of 7 Indictor Polychlorinated Biphenyls (PCBs) Residues in Porphyra by Ultrasonic Extraction and Gas Chromatography (GC)

A method was developed for determination of 7 indictors the polychlorinated biphenyls (PCBs) residues in porphyra by gas chromatography (GC) with electron capture detector (ECD). The PCBs were extracted with hexane/methylene chloride (1:1, v/v) by ultrasonic extraction and the samples were cleaned up by concentrated sulfuric acid and Alumina-N solid phase extraction cartridge. The analytes were quantified by an internal standard method. Under optimal experimental conditions, good linearity was observed in the range of 5 - 200 ng/mL and the correlation coefficients were 0.9994 - 0.9998. The limit of quantitation (LOQ) for target analytes ranged from 6.0 to 10.0 μg/kg. At the spiked levels of 10, 50, 100 μg/kg, the average recoveries ranged from 90.9% to 102% with the relative standard deviations 2.12% - 6.32%. The result showed that the proposed method was rapid, and could be used for the determination of the PCBs in porphyra.

Development of Different Strategies for the Clean-Up of Polychlorinated Biphenyls (PCBs) Congeners Using Pressurized Liquid Extraction

The extracted fish samples (w/w) using pressurized liquid extraction (PLE) were cleaned up by applying different adsorbent materials such as: combination of acidic/ basic silica and alumina, florisil, and silica gel either alone or in combination with another sort of sorbent. Different solvents such as hexane (H), dichloromethane (DCM), with different compositions were used to elute the PCBs target compounds from the spiked fish samples. Overall the mean percentage recoveries for all PCBs congeners using PLE were ranging from 78.6% to 98.7%;from 79.4% to 91.8%;from 65.8% to 104.5% and from 82.4% to 100.9% for cases A, B, C, D and E, respectively. However, the overall mean percentage recoveries for the 13C-PCBs surrogate including: 101, 138, 153, 180 and 209 were ranging from 88.2% to 97.6%;from 79.4% to 90.2%, from 88.3% to 96.4%, from 79.8% to 90.4% and from 83.9% to 95.9%, for cases A, B, C, D and E, respectively. The limits of detection of the proposed method were varied from 0.01 to 0.28 ng/g (w/w) for different PCBs congeners. The proposed method has linear dynamic range from 21.5 ng/g to 109 ng/g. This method was applied to fish samples for the determination of the target PCBs components.

Residues of Polychlorinated Biphenyls (PCBs) in Fish, Water and Sediment from Shing Mun River

The level and pattern of contamination by polychlorinated biphenyls (PCBs) were investigated in tilapia, Oreochromis mossambicus (Peters), sediment, and water from the Shing Mun River. The range of total PCBs was 12.9 ng/g to 181.6 ng/g wet weight in tilapia, 12.7 ng/g to 46.0 ng/g freeze-dried weight in sediment, and 3.8 ng/L to 13.6 ng/L in water. The effect of biomagnification was also observed, PCB concentrations increased from water to sediment to tilapia. PCB congeners occurred in such a way that lower chlorinated PCBs comprised a higher fraction of the total PCBs in water, sediment, and tilapia muscle, whereas higher chlorinated PCBs were more commonly found only in tilapia.

Treatment of Materials Contaminated with Polychlorinated Biphenyls(Pcbs):Comparison of Traditional Method and Supercritical Fluid Extraction

The objective of this study was to develop an experimental methodology for the extraction of polychlorinated biphenyls (PCBs) from contaminated soil and wood material using the Soxhlet extraction method and supercritical fluid technology. The sample PCB contents were quantified using Gas Chromatography-Mass Spectrometry (GC/MS). Conventional extractions of PCBs from soil samples showed higher extraction yields for samples with the highest initial PCB levels and longest extraction times. Specific PCBs yielded 74.0% - 78.3% removal using ethanol as the solvent. 91.0% - 94.3% removal of the total PCB content was achieved using hexane as the solvent. Supercritical fluid extraction of soil samples resulted in 50.0% - 70.5% removal for specific PCBs and 57.3% removal of the total PCB content. For wood, the use of Soxhlet extraction resulted in 87.0% - 94.0% removal for specific PCBs and 95.0% - 96.3% removal of the total PCB content. Supercritical fluid extraction of wood samples resulted in 91.1% - 95.0% removal of specific PCBs and 95.1 % of the total PCB content.

Polychlorinated biphenyl congeners (PCBs) in nursing primiparous and multiparous women

Impact of PCBs was studied as a major source of physiological effects even very low concentration of PCBs transferred to the infants by mother’s milk. Milk samples were collected from primipara and multipara women. A significant variation pattern was observed in the level of PCB congeners, as PCBs are lipophilic in nature, another possibility arises that great deals of residues are passed on to infants through mother’s milk. A technique was developed to find out polychlorinated biphenyls (PCB) in breast milk. PCBs were extracted by Matrix Solid-Phase Dispersion (MSPD) and analyzed by Gas Chromatography with Electron Capture Detector. The precision (RSD < 10%, n = 125), recovery (85% to 110%) and limit of quantification (between 0.50 and 3.00 μg&middotL-1), the chi square analysis at p ≤ 0.05 has shown that the PCB level was higher in multipara as compared to primipara. The analysis of the thirty samples revealed PCB levels above 6.85 μg&middotL-1 in breast milk samples by analyses of a mixture of PCB congeners. All PCB congeners (28, 52, 101, 123 (+149), 118, 114, 153, 105, 138 (+163), 167, 156 (+171), 157, 180, 170, 189) were found at high level in primiparous and multiparous. Thus, a high correlation between the contamination of breast milk and environmental pollution of PCBs was observed.

Modification by Polychlorinated Biphenyls(PCBs)of Cadmium Induced Lesions in the Planarian Model,Dugesia dorotocephala

The appearance of abnormal growths on the planarian, Dugesia dorotocephala, in response to cadmium with and without pre-exposure to L-buthionine-R, S-sulfoximine (BSO) and concurrent exposure to the polychlorinated biphenyls (PCBs) Aroclor 1254, PCB 28, PCB 110 or PCB 126 is described. Pigmented rose thorn (PRT) lesions were non-invasive and appeared in response to PCBs. Post-head (PH) lesions developed in up to 100% of the animals within 6-20 days post-dosing, progressed rather rapidly and were highly invasive. Round tail tip (RTT) lesions appeared in lower frequencies within 10-30 days, but progressed extremely rapidly resulting in tail loss within 48 h. We have referred to these types of lesions as 'tumors', but they are not necessarily characteristic of vertebrate neoplasms.PCBs interacted with cadmium in a complex way, in some cases increasing total lesions and decreasing time-to-lesion and in other cases having the opposite effects. A three-factor (PCB, PCB dose, Cd dose) nested analysis of variance model was used to determine lesion rates in order to compare PCB potencies as potentiators or antagonists. The Aroclor mixture was always the least potent co-toxicant but appeared to be the most potent antagonist; the coplanar PCB 126 was the most potent co-toxicant. The complex response surfaces and the lack of stoichiometry in dose-response relationships indicate that multiple mechanisms are responsible for PH and RTT lesions in planarians. These results emphasize the complexity of PCB toxicities and suggest further studies to validate the planarian model as a screen for combinations or environmental mixtures which may have altered biological potency in other species.

浦东新区环境空气中PCBs和OCPs的污染特征研究

多氯联苯和有机氯农药这2类物质都属于大气中典型的持久性有机污染物,其具有环境持久性和一定的健康影响。该研究建立了基于聚氨酯泡沫(PUF)+玻璃纤维滤膜和索氏提取-气相色谱三重四级杆质谱(GC-MS/MS)分析大气环境中8种多氯联苯(PCBs)和10种有机氯农药(OCPs)化合物的检测方法。以浦东新区监测站和惠南分站作为2个采样站点,分别代表城市中心地区和郊区,进行了2021年冬季、春季和秋季3个不同时间段大气PCBs和OCPs的分析。PCBs和OCPs在浦东新区监测站的平均浓度分别为(21.73±6.93)pg/m^(3)、(205.68±42.74)pg/m^(3)。这2类物质的浓度相较文献报道的国内其他城市的数值低很多,与一些发达国家城市水平相当。

基于融合MBAM与YOLOv5的PCB缺陷检测方法

随着电子信息产业迅速发展,PCB行业作为电子信息产业的基础,其产品质量对后续生产的电子产品有着决定性影响。针对PCB缺陷目标较小,缺陷类型多,特征不明显,在实际生产过程中易产生误检、漏检等问题,提出了一种多分支注意力MBAM模块方法,在3个不同维度对特征图进行关注,以增强特征提取的能力,对缺陷区域给予更多的注意力表示。通过改进YOLOv5结构,将MBAM与YOLOv5网络结合,有效的提升了对PCB中小目标的检测性能。最后通过在网络不同位置添加MBAM模块进行对比实验,选取了最佳的添加位置。通过在PCB缺陷数据集上的实验结果表明,改进后的PCB缺陷检测算法具有良好的检测性能,优于其他对比算法,最终的AP达到了96.7%,对比标准YOLOv5的94.7%提高了2个百分点,其他项指标均有涨点,在保持检测速度基本不变的情况下,精准地识别PCB缺陷类型。

三相CLLC谐振变换器磁集成平面变压器设计与优化

三相CLLC谐振变换器凭借其高效率、大容量、低器件应力等优势而受到广泛关注。然而,多相结构的磁性元件数量多、体积大,是制约功率变换器尺寸的主要因素。随着宽禁带(WBG)半导体器件的出现,功率变换器的开关频率显著提高,这也为印制电路板(PCB)绕组的使用提供了有利条件。与传统绕线式绕组相比,PCB绕组的扁平特性更适用于平面磁性元件。此外,由于高频带来的低电感需求也使得基于PCB绕组的平面磁性元件更有利于实现集成。该文提出一种新型的基于PCB绕组的电感和变压器的集成结构,详细分析磁心结构的磁路模型,并给出集成磁件的优化设计方法,最后通过搭建一台基于SiC器件的800 V/10 kW的实验样机进行验证。实验结果表明,该集成方案可有效减小变换器的体积和损耗,具有高功率密度和高效率。

一种基于模式布线的柔性电路板布线规划算法

为解决柔性电路板整板自动化布线算法布线效率低、布线效果较差的问题,提出基于模式布线的柔性电路板布线规划算法,采用模式布线近似拟合详细布线,缩小详细布线和布线规划之间的精度误差。同时,根据人工经验设计4种布线模式和若干扇出模式,模拟扇出区内部资源分配和扇出区间排列组合可能出现的情况。针对层分配问题,设计了根据当前布线结果以及未来对其他线网的影响综合评价的层分配算法,针对通道区不允许打孔的约束,根据通道连接扇出区的位置顺序求得通道内布线线网拓扑不交叉序列,并作为分割线上过点位置排列顺序约束。最后,综合比较每个模式下的结果,选择代价最小的结果作为最终布线规划的结果。使用多个工业用例进行测试,实验结果表明,与已有柔性电路板布线规划算法相比,本文布线规划算法可以提升详细布线效率和布线结果。

搅拌子吸附-热脱附-气相色谱-质谱法分析北京大气中33种多氯联苯

用包覆聚二甲基硅氧烷(PDMS)吸附层的搅拌子作被动大气采样器,建立了搅拌子吸附-热脱附-气相色谱-质谱法(SBSE-TD-GC-MS)分析大气中多氯联苯(PCBs)的方法。优化后的热脱附温度为280℃,热脱附时间为6 min,聚焦冷阱的温度为-40℃,33种PCB单体的热脱附残留比例低于7%。验证了方法的线性、精密度和重复性。标准曲线5个点线性关系良好,33种PCB单体的相关系数r>0.998。方法精密度验证的相对标准偏差(RSD)为0.79%~20.2%(n=8),日内重复性实验的RSD为0.43%~29.8%(n=10),日间重复性实验的RSD为3.20%~29.6%(n=20),方法检出限(LOD)为0.01~2.51 pg,回收率为98%±18%。将建立的方法用于北京大气中PCBs的分析。检出8种PCB单体,质量为2.94~129 pg。在32 d的采样周期内PCB-52、PCB-123、PCB-155一直处于线性吸附阶段,而PCB-1和PCB-3经过了线性吸附阶段、曲线吸附阶段和平衡阶段。研究结果表明,SBSE-TD-GC-MS可以用于大气中PCBs的样品采集和快速分析。

基于深度学习的PCB缺陷检测技术

印刷电路板(printed circuit board,PCB)是电子产品的关键部件。在实际生产过程中,PCB难免会产生多种缺陷,对缺陷进行及时、精准检测具有一定的研究意义与应用价值。传统的检测方法存在速度慢、成本高、精度低的问题。针对PCB缺陷检测问题,开展基于YOLO系列算法研究,在相同的实验环境下,以平均精度、精确率、召回率、每秒传输帧数作为评价性能指标。实验研究发现,YOLOv7在精度方面比YOLOv5有一定的提升,而YOLOv5在训练和推理的速度上比YOLOv7更快。提出融合CBAM(convolutional block attention module)注意力机制模块的YOLOv5改进算法用于PCB缺陷检测。经实验验证,改进算法在PCB缺陷检测的精确性和速度性能上均得到提升,其中,平均精度、精确度和召回率分别提升了7.40%,3.57%和5.63%。

基于SMT-YOLOv8的PCB缺陷检测研究

针对PCB缺陷检测中目标尺寸小、权重文件庞大难以部署的问题,提出一种改进的YOLOv8小目标缺陷检测方法。该方法将SE注意力机制融入C2f中,使网络能够根据通道域的信息给图像不同位置赋予不同的权重,获取更重要的特征信息;在SPPF中引入Basic RFB以增强网络感受野,提升网络的特征提取能力;新增小目标检测尺度,提升模型对微小缺陷的检测能力;舍弃大目标检测尺度,降低计算负荷并缩小权重文件。实验结果表明,在公开的PCB缺陷数据集,改进后的YOLOv8较原算法平均精度提升了2.6%、权重文件缩小了27.3%、FPS达到34.4 ms/帧。

立创EDA在高校电子信息类课程实践教学中的应用

电子线路CAD是电子信息类专业中一门实践性要求很高的专业课程,在培养学生的工程实践与创新能力方面发挥了关键作用。基于以成果为导向的OBE教学理念,引入我国自主知识产权、简单易用的立创EDA软件,为课程的实践教学环节提供有力支持。通过这一软件,学生得以完成从电路仿真到元件选型,再到原理图和PCB绘制,以及最终PCB打样的完整流程。立创EDA软件还在学科竞赛、课程设计以及毕业设计等环节获得了较好的应用,帮助学生更深层次理解电子产品的设计和制造流程,为学生将来的职业发展奠定了坚实的基础。

PCB可靠性测试评估方法简述

印制电路板(PCB)技术向高密度、高集成化等方向发展,导致PCB可靠性问题日益凸显。针对PCB失效机理,并结合现有PCB标准及实践应用情况,详细介绍了3种PCB可靠性测试评估的方法——失效率预计法、加速试验预计法和试验鉴定法,以期为从业者开展PCB可靠性测试评估提供一定的帮助。

基于自谐振线圈参数优化的多中继无线供电系统效率提升研究

印刷电路板(printed circuitboard,PCB)自谐振线圈可以避免绕线引起的偏差,且不受分立补偿电容的影响,应用在多中继无线供电系统中极具前景。针对PCB自谐振线圈结构参数优化不完全所导致的多中继无线供电系统传输效率低下的问题,该文给出了一种用以提升系统传输效率的PCB自谐振线圈结构参数优化设计方法。首先,建立了多中继无线供电系统的传输效率模型,并分析了线圈的电参数对传输效率的影响机理;其次,详细推导了线圈电参数与线圈的匝数、介质厚度、线宽、铜箔厚度、介质损耗角正切值以及介电常数之间的关系;然后,基于上述关系,以传输效率最高为目标,优化了线圈参数;最后,利用优化后的PCB自谐振线圈搭建了一套五线圈无线供电系统实验样机。实验结果表明,采用优化后的PCB自谐振线圈传输效率最高可达76.5%,相比优化前33.1%的传输效率,提高了43.4%。