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261.
大学生受电脑电磁辐射的研究 总被引:1,自引:0,他引:1
为了研究大学生受电脑电磁辐射的实际状况,采用EMR300电磁辐射分析仪,对电脑电磁辐射在100kHz~3GHz的电场强度值(V/m),进行了实验室研究性监测和宿舍、机房内的现场监测.监测的结果表明:宿舍中心处电磁辐射环境强度(100kHz~3GHz频率范围内的综合电场强度)低于0.5V/m;距离显示器屏幕前方0.4m以上操作电脑,则眼睛处辐射强度在安全值内.而目前,机房内台式电脑按行紧密摆放,前排电脑操作者后脑正对后一排电脑显示器突出的后部处,在后脑处辐射强度可超过10V/m;此外,学生宿舍空间拥挤,鼠标、键盘通常与显示器近距离摆放在一起,造成显示器辐射与键盘、鼠标自身辐射叠加,导致在键盘和鼠标处手掌受到的辐射强度大,不容忽视. 相似文献
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264.
Influence of Polyol Plasticizers on the Properties of Polyvinyl Alcohol Films Fabricated by Melt Processing 总被引:1,自引:0,他引:1
In this work, high-alcoholysis polyvinyl alcohol (PVA) films were fabricated by melt processing and the plasticizing effect
of compound polyol plasticizers on PVA were investigated with X-ray diffraction (XRD), differential scanning calorimetry (DSC),
rheological measurements, mechanical tests etc. Hydrogen bonding interactions occurred between PVA and plasticizer. With the
increase of plasticizer, the flowability of PVA was improved and reached the maximum value at the plasticizer of 20%. Glass
transition temperature (T
g) and melting point (T
m) decreased with the increase of plasticizer content. For the heterogeneous nucleation effect of plasticizer, new polymorph
of PVA formed. The viscosity was sensitive to the shear rates. The incorporation of plasticizers into PVA resulted in the
increase of elongation at break and impact strength, as well as the decrease of tensile strength. 相似文献
265.
北京市西三环地区大气颗粒物中多环芳烃的分布特性 总被引:2,自引:1,他引:1
于2012年3—12月在北京市西三环地区按粒径分6级采集大气颗粒物样品,采用气相色谱-质谱(GC-MS)对颗粒物样品中16种优控PAHs(多环芳烃)进行分析. 结果表明:颗粒物中ρ(∑16PAHs)(PAHs的总质量浓度)季节变化显著,表现为冬季>春季>秋季>夏季,并且与ρ(PM)(PM为颗粒物)呈良好线性相关;不同粒径颗粒物中ρ(PAHs)呈向小粒子富集的趋势,PM2.1中ρ(PAHs)约占ρsum(∑16PAHs)〔6级颗粒物中ρ(∑16PAHs)总和〕的64%~87%;除夏季3环PAHs占优势外,其他季节均以4~ 5环PAHs占优势;同时,随着粒径的减小,PAHs有向高环数富集的趋势. 运用主成分分析和多元线性回归法进行源解析发现,机动车尾气排放和燃煤是本地区大气颗粒物中PAHs的主要来源;不同粒径颗粒物中的PAHs来源有差异,2.1~10.2μm粒径段颗粒物中PAHs主要来源于机动车尾气排放,贡献率为63.0%;而1.3~2.1μm和<1.3μm的颗粒物中PAHs均主要来源于燃煤,贡献率分别为56.8%和58.7%. 相似文献
266.
PRB(可渗透反应墙)是地下水治理中新型的原位修复技术,具有成本低、处理效果好、对环境干扰小等优点,已逐渐应用到实际. 原位修复技术中PRB根据结构的不同可分为单处理系统PRB和多单元处理系统PRB,单处理系统PRB适用于单一污染物、污染浓度较低、污染羽规模较小的场地,多单元系统用于污染场地较复杂、污染种类较多的场地. 零价铁PRB去除地下水中无机污染物及有机组分的反应机理主要是氧化还原反应和还原性脱卤反应. 实际场地PRB的运行中存在的主要问题是零价铁钝化及PRB堵塞,现阶段的解决方法主要包括超声、电化学等,但为了提高PRB技术的实用性,铁材料的解钝化技术、实际场地PRB的设计与安装、PRB体系的长期运行及服务期满后的处置均需进一步的研究探索. 相似文献
267.
人工湿地与土壤净化槽处理农村生活污水的对比 总被引:1,自引:0,他引:1
针对我国生活污水处理现状及要求,对比研究了普遍推广的人工湿地技术与新兴的土壤净化槽技术,发现在进水水质、环境条件均相同的情况下,上行流人工湿地处理效果优于下行流人工湿地;基质按照不同需氧层铺设不同粒径填料的土壤净化槽处理效果优于基质直接分层铺设填料的土壤净化槽;土壤净化槽和人工湿地出水水质都很好,出水CODCr、TN、TP、氨氮分别达到了二级、一级A、一级B、一级A标准;土壤净化槽装置占地面积小,为人工湿地的2/3.土壤净化槽技术是适合我国国情的有发展前景的生活污水处理技术. 相似文献
268.
Lei Yuan Xiang Zheng Kaijiao Duan Hao Hu Jinggang Wang Seong Ihl Woo Zhiming Liu 《Frontiers of Environmental Science & Engineering》2013,7(3):457-463
Selective catalytic reduction of NO x by H2 in the presence of oxygen has been investigated over Pt/ Al2O3 catalysts pre-treated under different conditions. Catalyst preparation conditions exert significant influence on the catalytic performance, and the catalyst pre-treated by H2 or H2 then followed by O2 is much more active than that pre-treated by air. The higher surface area and the presence of metallic Pt over Pt/Al2O3 pre-treated by H2 or pretreated by H2 then followed by O2 can contribute to the formation of NO2, which then promotes the reaction to proceed at low temperatures. 相似文献
269.
Songhui Wang Bingren Xiang Yilong Su Qianqian Tang 《Environmental Chemistry Letters》2012,10(4):383-387
This report describes a rapid, onsite method to analyze the dichlorvos pesticide in water. Dichlorvos is a broad-spectrum pesticide that has been used worldwide. As an organophosphorus pesticide, dichlorvos disrupts the nervous system by inhibiting the activity of acetyl cholinesterase. Traditional analysis of dichlorvos by chromatography is time-consuming and environmentally unfriendly. Therefore, rapid, on-site methods to analyze dichlorvos are needed. Here, we used for the first time Fourier transform near infrared spectroscopy combined with partial least square-discriminant analysis to determine the dichlorvos directly in water samples. Results were compared with traditional high-performance liquid chromatography data as reference. We found that over 9,000–8,333?cm?1, the new method had a good performance with a classification accuracy of 100?% and a correlation coefficient of 0.92 between measured and reference data. The new method can also be used as a “concentration sieve” by setting up different levels of boundary, a parameter of partial least square-discriminant analysis, thus allowing rapid on-site screening. 相似文献
270.
Xiaofeng Xiang Li Guo Xing Wu Xiaoxun Ma Yashen Xia 《Environmental Chemistry Letters》2012,10(3):295-300
Urea synthesis, currently the largest use of carbon dioxide in organic synthesis, is conventionally operated at high pressure and high temperature. Here, we report for the first time that urea forms at atmosphere and ambient temperatures by negative corona discharge in gas phase. The conversion of CO2 and yields of a solid mixture of urea and ammonium carbamate, which was identified by the 13C NMR spectrum, rise with reducing temperatures and increasing molar ratios of NH3/CO2 and discharge frequencies. The conversion of carbon dioxide was found to be 82.16?% at 20?°C and 1?atm with a molar flow ratio of n(NH3)/n(CO2) of 2.5. High pressure and high temperature as energy inputs are not necessary. 相似文献