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目前大学生的英语口语表达能力总体很差,在口语交流上也出现各种障碍,其原因除学生英语学习能力较差以外,态度问题、动机偏差、缺乏自信、不耐挫折、缺乏热情、过于紧张、性格内向等心理因素也起着关键的作用。对于大学生英语口语交流存在的障碍,可以通过激发兴趣、心理暗示、教师鼓励、减少心理压力、结交外国朋友等有效方法,指导学生进行口语训练,提高学生口语水平。 相似文献
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Changwei Hu Yuxiong Ou Dayi Zhang Hui Zhang Cheng Yan Yongjun Zhao Zheng Zheng 《Environmental science and pollution research international》2012,19(9):4168-4175
The Waigang River, a major tributary of the Qinhuai River system, has suffered from long-standing pollution because of lack of management. Restoration was commenced in April 2006 to reduce pollutants and improve water quality. Four ecological areas and ten surface carriers were constructed for the culture of plants (mainly water hyacinth (Eichhornia crassipes) and ryegrass (Lolium perenne L.)) for phytoremediation. Chemical oxygen demand (COD), total suspended solids (TSS), total phosphorus, total nitrogen (TN), ammonia?Cnitrogen (NH3?CN), water transparency, and variations in phytoplankton population were investigated to evaluate the effects of restoration. Over 36?months, TSS, COD, TN, and NH3?CN levels decreased by 91.1, 55.3, 91.5, and 86.5?%, respectively. Transparency increased from 25?cm in 2006 to 165?cm in 2009. Improvements in water quality significantly enhanced the diversity of phytoplankton, which were harmed by pollution stress. Our results show that the water hyacinth and ryegrass cultured in the ecological areas and the surface carriers can be used to restore other heavily polluted rivers with conditions similar to those of the Waigang River, especially in the initial stages of restoration. 相似文献
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Thuan-Quoc Thach Chit-Ming Wong King-Pan Chan Yuen-Kwan Chau G. Neil Thomas Chun-Quan Ou Lin Yang Joseph S.M. Peiris Tai-Hing Lam Anthony J. Hedley 《Atmospheric environment (Oxford, England : 1994)》2010,44(11):1437-1442
We assessed confounding of associations between short-term effects of air pollution and health outcomes by influenza using Hong Kong mortality and hospitalization data for 1996–2002.Three measures of influenza were defined: (i) intensity: weekly proportion of positive influenza viruses, (ii) epidemic: weekly number of positive influenza viruses ≥4% of the annual number for ≥2 consecutive weeks, and (iii) predominance: an epidemic period with co-circulation of respiratory syncytial virus <2% of the annual positive isolates for ≥2 consecutive weeks. We examined effects of influenza on associations between nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matter with aerodynamic diameter ≤10 μm (PM10) and ozone (O3) and health outcomes including all natural causes mortality, cardiorespiratory mortality and hospitalization. Generalized additive Poisson regression model with natural cubic splines was fitted to control for time-varying covariates to estimate air pollution health effects. Confounding with influenza was assessed using an absolute difference of >0.1% between unadjusted and adjusted excess risks (ER%).Without adjustment, pollutants were associated with positive ER% for all health outcomes except asthma and stroke hospitalization with SO2 and stroke hospitalization with O3. Following adjustment, changes in ER% for all pollutants were <0.1% for all natural causes mortality, but >0.1% for mortality from stroke with NO2 and SO2, cardiac or heart disease with NO2, PM10 and O3, lower respiratory infections with NO2 and O3 and mortality from chronic obstructive pulmonary disease with all pollutants. Changes >0.1% were seen for acute respiratory disease hospitalization with NO2, SO2 and O3 and acute lower respiratory infections hospitalization with PM10. Generally, influenza does not confound the observed associations of air pollutants with all natural causes mortality and cardiovascular hospitalization, but for some pollutants and subgroups of cardiorespiratory mortality and respiratory hospitalization there was evidence to suggest confounding by influenza. 相似文献
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Hexabromocyclododecanes in surface sediments and a sediment core from Rivers and Harbor in the northern Chinese city of Tianjin 总被引:1,自引:0,他引:1
In the present study, hexabromocyclododecanes (HBCDs) were investigated in the sediment from Haihe River (HR), Dagu Dainage Canal (DDC) and Tianjin Harbor (TH) at Bohai Bay using a total of 51 samples of surface sediments and a sediment core collected from May to September in 2010, and its diastereomer- and enantiomer-specific profiles were analyzed. The concentration of total HBCDs were generally high, with mean value and ranges of 31.0 and 1.35–634 ng g?1 dw, respectively. The contamination followed the order of TH > DDC > HR. Higher levels (up to 634 ng g?1 dw) occurred in the lower reach of HR and DDC located in an industrial area of Tianjin. This is the first time to report so high concentration of HBCDs in sediment in Southeast Asia. The γ-diastereomer dominated in most samples (44 out of 51), and this is in agreement with the diastereomer distribution pattern in industrial products, while α-HBCD was the dominant diastereomer in the other seven samples. However, only few samples exhibited γ-diastereomer ratio similar to that (75–89%) in technical products, indicating the inter-transformation and variable degradation of the different isomers. The high ratio of γ-diastereomer could be used as an indicator for fresh contamination input. Enantiomeric factors (EFs) of HBCD isomers in most of the samples were statistically different from technical products (p < 0.05), showing a trend of more easily enrichment of the (?)-HBCD-enantiomer compared to the (+)-HBCD-enantiomer. The δ- and ε-diastereomers were frequently detected but at low level. The HBCDs in the sediment core showed several peaks, and the greatest value occurred in 2005, when a plastic manufacture plant using HBCD was set up nearby. 相似文献
16.
Yanwei Zhang Hongwen Sun Fang Liu Yuanyuan Dai Xuebo Qin Yuefei Ruan Lijie Zhao Zhiwei Gan 《Chemosphere》2013
To interpret the distribution of hexabromocyclododecanes (HBCDs) in various organisms, we measured the concentrations and diastereomer and enantiomer profiles of HBCDs in 21 different species of limnic and marine cohorts from Tianjin, China. The concentration ranges of HBCDs in limnic and marine organisms were 64.3–1111 ng g−1 lw and 85.5–989 ng g−1 lw, respectively. Living habitat and feeding habits had important impacts on HBCD diastereomer distribution. Most of the species appeared to preferentially select (+)-α-, (−)-β- and (−)-γ-HBCD. There is a tendency that the total and α-HBCDs were magnified as trophic level increased with trophic magnification factors (TMFs) around 2. The concentrations of HBCDs in the limnic and marine fishes were highest in the liver, followed by the gill, skin, and muscle. In terrestrial plants, the highest concentrations of HBCDs were observed in the leaf, followed by the root and the rhizosphere soil. Plants showed enantioselectivity for HBCD enantiomers, which varied with plant species and organs (leaf vs. root) of the same plant. Higher estimated daily intakes (EDIs) of HBCDs were observed from fish than from wheat. 相似文献
17.
三维电极法深度处理维生素生产废水 总被引:1,自引:0,他引:1
采用三维电极法对维生素废水进行深度处理,分别以钛涂钌铱板、铁板和不锈钢板作为电极阳极,石墨板作为电极阴极,柱状活性炭作为粒子电极,结果表明,当以钛涂钌铱板作为阳极,以粒径为1 mm的柱状活性炭作为粒子电极时电解效果最好,COD和色度去除率最高。实验选择电解电压、电极板间距、电解时间和初始pH值作为主要影响因素进行正交实验,实验研究证明,各因素的影响大小为电解电压>电极板间距>电解时间>初始pH值,得到的最佳参数组合分别为:电解电压为10 V,电极板间距为8 cm,电解时间为20 min,初始pH值为4,得到COD和色度最大去除率分别为59.5%和93.57%。 相似文献
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自20世纪40年代以来,无数臣轮在日本以南空旷清冷的海面上神秘失踪,它们中的大多数在失踪前都没能发出求救讯号,也没有任何线索可以解答它们失踪后的相关命运。如在地图上标出这片海域的范围,它恰恰是一个与百慕大极为相似的三角区域,这就是令人恐惧的日本龙三角. 相似文献
20.
In this study, co-composting of food waste and green waste at low initial carbon to nitrogen (C/N) ratios was investigated using an in-vessel lab-scale composting reactor. The central composite design (CCD) and response surface method (RSM) were applied to obtain the optimal operating conditions over a range of preselected moisture contents (45–75%) and C/N ratios (13.9–19.6). The results indicate that the optimal moisture content for co-composting of food waste and green waste is 60%, and the substrate at a C/N ratio of 19.6 can be decomposed effectively to reduce 33% of total volatile solids (TVS) in 12 days. The TVS reduction can be modeled by using a second-order equation with a good fit. In addition, the compost passes the standard germination index of white radish seed indicating that it can be used as soil amendment. 相似文献