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991.
992.
江静 《防灾科技学院学报》2005,7(2):107-110
本文采用次态卡诺图法对时序逻辑电路的功能进行分析,力图改进传统异步时序电路的分析方法,在保证分析结果正确无误的前提下,简化了常规分析方法中繁琐的步骤,更具有实用性。以一个8421BCD码表示的十进制异步减法计数器为例,给出各触发器状态方程的表达式,并用状态表、状态图分析其逻辑功能。 相似文献
993.
994.
Zhichen Duan Jian Liu Juan Shi Zhen Zhao Yuechang Wei Xiao Zhang Guiyuan Jiang Aijun Duan 《环境科学学报(英文版)》2018,30(3):1-7
A Ce_(0.3)TiO_xoxide carrier was synthesized via a sol–gel process,and Ce_(0.3)TiO_xsupported metal(M=Cd,Mn,Fe,W,Mo)oxide catalysts were prepared by the method of incipient-wetness impregnation.The catalysts were characterized by means of X-ray diffraction(XRD),Brunauer–Emmett–Teller(BET)analysis,scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared(FT–IR)spectroscopy,UV–Visdiffusereflectancespectroscopy(UV–VisDRS),and Temperature-programmed reduction with H_2(H_2-TPR).The catalytic activities for de-NO_(x )were evaluated by the NH_3-SCR reaction.Among all the catalysts tested,the 2 wt.%Cd/Ce_(0.3)TiO_xcatalyst exhibited the best NH_3-SCR performance,with a wide temperature window of 250–450°C for NO conversion above 90%.Moreover,the catalyst showed N_2 selectivity greater than 99%from 200 to 450°C. 相似文献
995.
HPLC法测定废水中苯胺类化合物 总被引:3,自引:0,他引:3
用乙醚为提取有机相,提取前先经碱化,提取后加酸使苯胺成盐,吹去乙醚,用HPLC法测定苯胺类化合物。方法适用于测定废水中苯胺类化合物。检出限:苯胺3.0ng,邻硝基苯胺0.5ng,对硝基苯胺1.0ng。线性范围:苯胺0.817-13.072μg/ml,邻硝基苯胺0.1464-2.3424μg/ml,对硝基苯胺0.253-4.048μg/ml。精密度(CV):苯胺2.38%,邻硝基苯胺1.09%,对硝 相似文献
996.
997.
Nitrogen is essential for forest growth and forest stand development. It is commonly a limited factor for forest productivity. We examined delta (15)N values in soils and plants by studying the sources of N used by vegetation and cycles of N in a 43-year-old plantation of the TieShanPing forest ecosystem in southwestern China, dominated by massone pine (Pinus massoniana). The N concentration of plant materials ranges from 1.1% to 2.2%. The nitrogen concentration of P. massoniana was 1.3% while soils showed the concentration of 0.04-0.15%. Regarding natural abundance of (15)N, large significant variation (-6.0 per thousand to -3.8 per thousand) in delta (15)N values was observed among shrub and tree leaves. delta (15)N values were also significantly varied from -4.7 per thousand to -3.8 per thousand among the pioneer species in the plantation. Soil delta (15)N values (3.1-6.3 per thousand) were significantly enriched compared to those values in plant samples. Despite the negative delta (15)N values of the vegetation cover, the high delta (15)N values in the topsoil indicate that return of N to soils by litter-fall is minimal on TieShanPing and the present forests do not change very much the soil (15)N signals at the surface layer. The positive delta (15)N values may also indicate large N losses from the soil system vial leaching, volatilization and plant uptake. 相似文献
998.
Metal contamination in sediments of the western Bohai Bay and adjacent estuaries, China 总被引:5,自引:0,他引:5
Feng H Jiang H Gao W Weinstein MP Zhang Q Zhang W Yu L Yuan D Tao J 《Journal of environmental management》2011,92(4):1185-1197
Twelve sediment cores were collected in July 2007 in open waters of western Bohai Bay, the Port of Tianjin, and the adjacent estuaries of the Haihe and Yongding Rivers. While overall concentrations of trace metals at incremental depths in these cores met the Marine Sediment Quality (GB18668-2002) criteria of China, the magnitude of both metal enrichment factors (EF) and geoaccumulation indices (I(geo)) suggested that pollution with Ag, Cd, Cr, Cu and Zn was occurring in the estuaries and Port. Risk analysis also suggested that Ag and Ni concentrations were sufficiently elevated as to cause adverse biological effects in the study area. Although metal concentrations in western Bohai Bay were of less concern, a positive relationship between EF values and excess (210)Pb activity for several metals suggested that their concentrations were increasing over time. 相似文献
999.
Shengliu Yuan Xiaoman Jiang Xinghui Xia Haixia Zhang Shaokui Zheng 《Chemosphere》2013,90(10):2520-2525
The liquid chromatography–electrospray ionization-tandem mass spectrometer (LC–MS/MS) method coupled with an automated solid-phase extraction procedure has been developed to identify 22 psychiatric pharmaceuticals, including seven anxiolytic-sedative-hypnotics, six antidepressants, and nine anti-schizophrenia drugs, in wastewater samples from two psychiatric hospital wastewater treatment plants (P-WWTPs) and three municipal wastewater treatment plants (M-WWTPs) in Beijing, China. Analyte recoveries from spiking experiments in the WWTP influent and effluent at three concentrations ranged from 70% to 110%, excluding sulpiride, ziprasidone, and olanzapine. Method detection limits for five, eight, and nine analytes in the WWTP influent and effluent were 20–80, 1–16, and <1 ng L?1, respectively. High psychiatric pharmaceutical concentrations (e.g., ~942 ng L?1oxazepam, 5552–12,782 ng L?1 clozapine, 2762–9832 ng L?1sulpiride, and 2030–4967 ng L?1quetiapine) were frequently observed in P-WWTP influent compared to M-WWTPs. Although P-WWTPs typically had higher removal rates, significantly higher concentrations of the target compounds were observed in the P-WWTP secondary effluent than in the M-WWTP influent (e.g., ~752 ng L?1oxazepam, ~8183 ng L?1 clozapine, ~10,833 ng L?1sulpiride, and ~1168 ng L?1quetiapine). Thus, the discharge control of psychiatric pharmaceuticals from psychiatric hospitals requires improvement. 相似文献
1000.
化工制药工艺残渣燃烧过程固氯研究 总被引:1,自引:0,他引:1
采用管式固定床反应器对化工制药工艺残渣的燃烧分解进行了实验研究,进一步通过加入氧化钙/碳酸钙来防止燃烧过程残渣中氯的释放.实验结果表明,残渣在燃烧时氯主要以氯化氢形式排出,加入固氯剂后能有效地抑制氯化氢的生成,且固氯效果随着钙化物投加量的增加而明显提高.当氧化钙/残渣比(质量比)达到0.8时,固氯率可达97%以上;当碳酸钙/残渣比(质量比)提高到2.0时,固氯率为76%.与此对应的Ca/Cl摩尔比分别为30和40.继续增加钙投加量,固氯效果基本不变.同时发现添加一定量的木屑在助燃的同时有助于提高固氯效果. 相似文献