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871.
提出了刊徽设计的原则和要求。所设计的《地震学刊》的刊徽是个由经纬网格所构成的公转着的地球。经纬网格由SJ两个字母和两条细线所组成。SJ为《地震学刊》英文名和江苏的汉语拼音名的缩写。S表示大地震所激发的地球自由振动的一阶振型;两条细线既表示经线,又表示地球自由振动的基振型。 相似文献
872.
873.
Summary This paper examines some problems concerning the present global environmental status, and looks at the principal concepts, aims and objectives of nature conservation. Reference is made to the State of Alagoas in Brazil in relation to its leading environmental problems and the government's efforts to address the situation. The main stumbling-blocks to conservation achievements in Alagoas are also explored. 相似文献
874.
Annelies Lust Luc De Catte Liesbeth Lewi Jan Deprest Philippe Loquet Roland Devlieger 《黑龙江环境通报》2008,28(4):275-279
The aim of this study was to evaluate the effect of selective feticide (SF) compared to expectant management (EM) on perinatal outcome in dichorionic and monochorionic twins discordant for anencephaly. For this purpose, we conducted a systematic review of literature and added ten unpublished cases. As a result, we found that in dichorionic twins, mean gestational age (GA) at birth in the SF group was 38.0 weeks versus 34.9 weeks (P = 0.0002). Mean birth weight was 2922 g in the SF group versus 2474 g (P = 0.03). In monochorionic twins, mean GA at birth was 35.2 weeks versus 32.7 weeks (P = 0.1). Mean birth weight was 2711 g versus 1667 g (P = 0.0001). We conclude that while SF does not reduce perinatal mortality, it does result in significantly longer gestations and higher birth weight, and appears to be the management of choice in dichorionic twins discordant for anencephaly. In monochorionic twins, SF also increases birth weight, but in view of the complexity of this group, no clear recommendations can be made. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
875.
Yan You Can Niu Jian Zhou Yating Liu Zhipeng Bai Jiefeng Zhang Fei He Nan Zhang 《环境科学学报(英文版)》2012,24(4):657-664
A new air exchange rate (AER) monitoring method using continuous CO2 sensors was developed and validated through both laboratory experiments and field studies. Controlled laboratory simulation tests were conducted in a 1-m3 environmental chamber at different AERs (0.1-10.0 hr-1). AERs were determined using the decay method based on box model assumptions. Field tests were conducted in classrooms, dormitories, meeting rooms and apartments during 2-5 weekdays using CO2 sensors coupled with data loggers. Indoor temperature, relative humidity (RH), and CO2 concentrations were continuously monitored while outdoor parameters combined with on-site climate conditions were recorded. Statistical results indicated that good laboratory performance was achieved: duplicate precision was within 10%, and the measured AERs were 90%-120% of the real AERs. Average AERs were 1.22, 1.37, 1.10, 1.91 and 0.73 hr-1 in dormitories, air-conditioned classrooms, classrooms with an air circulation cooling system, reading rooms, and meeting rooms, respectively. In an elderly particulate matter exposure study, all the homes had AER values ranging from 0.29 to 3.46 hr??1 in fall, and 0.12 to 1.39 hr-1 in winter with a median AER of 1.15. 相似文献
876.
为了研究废砂浆中碳化硅粉和硅粉的分离情况,选用混合模型对柱型水力旋流器多相流流场进行数值模拟。模拟结果表明:柱型水力旋流器的分离效率与入口速度、进口浓度等因素有关,并分析出一定条件下当主、次相的入口速度均为1.1m/s时颗粒分离效果较好,分离效率较高,实验检测分离性能较好,为进一步实验研究提供一定的指导。 相似文献
877.
Nitrobenzene is an important raw material and product,which presents a heavy threat to the ecosystem.The potential impacts of nitrobenzene on sediment oxygen demand (SOD) were studied in lake sediment ... 相似文献
878.
Seasonal trend of ambient PCDD/Fs in Tianjin City, northern China using active sampling strategy 总被引:2,自引:0,他引:2
Lei Ding Yingming Li Pu Wang Xiaomin Li Zongshan Zhao Qinghua Zhang Ting Tuan Guibin Jiang 《环境科学学报(英文版)》2012,24(11):1966-1971
The spatial concentrations, seasonal trends, profiles and congener pairs of ambient polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were investigated within a seasonally active sampling scheme during Jun 2008 and Jan 2009 in Tianjin City, northern China. The PCDD/F concentrations ranged 14.2-172 fg I-TEQ/m3 (average 69.3 fg I-TEQ/m3) in summer and (89.8-1.01) × 103 fg I-TEQ/m3 (average 509 fg I-TEQ/m3) in winter, respectively, except for the E-waste dismantling site where much higher values were observed (1.04 × 103 fg I-TEQ/m3 in summer and 7.123 × 103 fg I-TEQ/m3 in winter). The results indicated a significantly seasonal trend with higher TEQ values in winter as compared with summer, which could be related to increased emission sources and seasonal variations of the atmospheric boundary layer height. 2,3,4,7,8-PeCDF was the dominant contributor to the total PCDD/F toxic equivalents, and 2,3,7,8-TCDD was detected at almost all the sampling sites in winter. Most of the similarly substituted PCDD/F congener pairs exhibited high correlations, suggesting that they might have similar environmental fate or sources. But different seasonal and spatial distributions of PCDD/F concentrations indicated that the emission sources might be intermittent. 相似文献
879.
Xiaoping Zhou Xiaoke Wang Lei Tong Hongxing Zhang Fei Lu Feixiang Zheng Peiqiang Hou Wenzhi Song Zhiyun Ouyang 《环境科学学报(英文版)》2012,24(12):2104-2112
The significant warming in urban environment caused by the combined effects of global warming and heat island has stimulated widely development of urban vegetations. However, it is less known of the climate feedback of urban lawn in warmed environment. Soil warming effect on net ecosystem exchange (NEE) of carbon dioxide during the transition period from winter to spring was investigated in a temperate urban lawn in Beijing, China. The NEE (negative for uptake) under soil warming treatment (temperature was about 5℃ higher than the ambient treatment as a control) was -0.71 μmol/(m2.sec), the ecosytem was a CO2 sink under soil warming treatment, the lawn ecosystem under the control was a CO2 source (0.13 μmol/(m2.sec)), indicating that the lawn ecosystem would provide a negative feedback to global warming. There was no significant effect of soil warming on nocturnal NEE (i.e., ecosystem respiration), although the soil temperature sensitivity (Q10) of ecosystem respiration under soil warming treatment was 3.86, much lower than that in the control (7.03). The CO2 uptake was significantly increased by soil warming treatment that was attributed to about 100% increase of α (apparent quantum yield) and Amax (maximum rate of photosynthesis). Our results indicated that the response of photosynthesis in urban lawn is much more sensitive to global warming than respiration in the transition period. 相似文献
880.