基于反向模拟的毛坯外形设计

毛坯外形设计是工艺设计的重要环节 ,它直接影响工件的成形质量。精确计算毛坯外形极其困难 ,目前尚无通用的方法。反向模拟结合了塑性形变理论和有限元技术 ,直接由工件反算出毛坯。文中着重指出反向模拟与一般增量正向模拟的区别 ,对其应用于毛坯设计的原理作了阐述 ,并通过标准考题验证了方法的有效性 ,最后将其应用于一实际生产零件的毛坯外形设计。     

The fate of the recombinant DNA in corn during composting

In order to make regulations that safeguard food and the environment, an understanding of the fate oftransgenes from genetically modified (GM) plants is of crucial importance. A compost experiment including mature transgenic corn plants and seeds of event Bt 176 (Zea mays L.) was conducted to trace the fate of the transgene cryIA(b) during the period of composting. In bin 1, shredded corn plants including seeds were composted above a layer of cow manure and samples from the corn layer were collected at intervals during a 12-month period. The samples were tested for the transgene persistence and microbial counts and also the compost was monitored for temperature. In bin 2, piles of corn seeds, surrounded by sheep manure and straw, were composted for 12 months. A method combining nested polymerase chain reaction (PCR) and southern hybridization was developed for detection of the transgene in compost. The detection sensitivity was 200 copies of the transgene per gram of dry composted corn material. Composting commenced on day 0, and the transgene was detected in specimens from bin 1 on days 0 and 7 but not on day 14 or thereafter. The transgene in corn seeds was not detectable after 12 months of composting in bin 2. Temperatures in both bins rose to about 50 degrees C within 2 weeks and remained above that temperature for about 3 months, even when the ambient temperature dropped below -20 degrees C. Extracts from compost were inoculated onto culture plates and then were incubated at 23 to 55 degrees C. Within the first 2 weeks of composting in bin 1, the counts of bacteria incubated at 55 degrees C increased from 3.5 to 7.5 log10, whereas those incubated at 23 degrees C remained at about 7.5 log10. The counts of fungi incubated at 45 degrees C increased slightly from 2.5 to 3.1 log10, but those incubated at 23 degrees C decreased from 6.3 to 3.0 log10. The rapid degradation of the transgene during composting of Bt corn plants suggested that the composting process could be used for safe disposal of transgenic plant wastes.     

光合细菌处理维生素B12废水影响因素的试验研究

利用正交试验设计研究pH值、光照时间和温度等生长因子对光合细菌处理维生素B₁₂废水效果的影响，结果表明，当pH为7.0、昼夜自然光照、温度为30℃时，净化效果最佳，并对不同溶解氧条件下的废水处理效果进行了对比试验。     

周期性风温下矿井巷道围岩换热教学实验装置研制*

为开展矿井热害防治的实验教学,设计并搭建周期性风温作用下巷道非均质围岩换热实验装置,能直观展示高温围岩各岩层的温度变化。利用实验数据可计算出巷道壁面热流密度,进而定量估算巷道围岩的散热量。结果表明:周期性风温通过后,模拟巷道围岩体各处温度随时间也呈简谐波变化;对于非均质的围岩体,导热系数越大的岩层,周期性风温的调热能力越强;巷道壁面处的热流密度也呈周期性变化,但围岩体总体表现为散热,且散热量随时间快速减小,并最终稳定在1.3×104 kJ/m2。     

Temporal variations and source apportionment of volatile organic compounds at an urban site in Shijiazhuang, China

Shijiazhuang, the city with the worst air quality in China, is suffering from severe ozone pollution in summer. As the key precursors of ozone generation, it is necessary to control the Volatile Organic Compounds (VOCs) pollution. To have a better understanding of the pollution status and source contribution, the concentrations of 117 ambient VOCs were analyzed from April to August 2018 in an urban site in Shijiazhuang. Results showed that the monthly average concentration of total VOCs was 66.27 ppbv, in which, the oxygenated VOCs (37.89%), alkanes (33.89%), and halogenated hydrocarbons (13.31%) were the main composite on. Eight major sources were identified using Positive Matrix Factorization modeling with an accurate VOCs emission inventory as inter-complementary methods revealed that the petrochemical industry (26.24%), other industrial sources (15.19%), and traffic source (12.24%) were the major sources for ambient VOCs in Shijiazhuang. The spatial distributions of major industrial activities emissions were identified by using geographic information statistics system, which illustrated the VOCs was mainly from the north and southeast of Shijiazhuang. The inverse trajectory analysis using Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) and Potential Source Contribution Function (PSCF) clearly demonstrated the features of pollutant transport to Shijiazhuang. These findings can provide references for local governments regarding control strategies to reduce VOCs emissions.     

平板陶瓷膜深度处理石化废水试验研究

采用平板陶瓷膜中试装置处理石化废水,分析了处理效果与膜污染情况,获得了平板陶瓷膜稳定运行条件下的工艺参数。结果表明:在COD为50~100 mg/L、浊度为2~11 NTU的进水条件下,平板陶瓷膜出水COD与浊度分别为20~42 mg/L和0.05~0.2 NTU,与双层过滤器+中空纤维超滤工艺出水水质较为接近;在运行通量40 L/(m 2·h)、反洗周期45 min、反洗时间60 s的条件下,采用浓度为100~150 mg/L的次氯酸钠每7小时进行1次化学清洗,平板陶瓷膜系统运行较为稳定。     

大庆石油管理局测井公司放射源库及周围环境的放射性水平调查

对大庆测井公司放射源库及周围环境的放射性水平进行了调查,调查内容分为环境空气气溶胶辐射水平、水环境辐射水平、环境地表γ辐射空气吸收剂量率及土壤环境辐射水平四个方面.监测调查结果表明:源库内和源库外总α、总β监测值与对照点比较,均没有显著性差异,说明空气中的环境是安全的;放射源库周围水环境总α、总β监测值符合相应标准规定,说明水环境未受到放射性污染;γ辐射空气吸收剂量率监测值范围均在黑龙江省室外天然本底值21.6×10-9～196.9×10-9 Cy/h范围内,说明放射源库室外地区未受到放射性污染;土壤监测值与黑龙江省土壤放射性水平进行了对比,也未发现放射源库周围土壤环境受到放射性污染.总之,大庆石油管理局测井公司放射源库未形成对周围环境及人群健康的不良影响.     

西藏甲马铜多金属矿床的岩浆热液交代成因:地质与地球化学证据

西藏甲马铜多金属矿床的成因前人已提出了很多种观点。根据野外地质特征的观察 ,并结合矿区和区域岩矿石的微量元素、常量元素和稀土元素的分析与对比 ,作者认为该矿床的成因属于岩浆热液交代矽卡岩型矿床 ,推测其成矿时代为喜山早期。     

厌氧酸化—好氧法处理高浓度洗毛废水尾浆试验研究

采用厌氧酸化－好氧工艺对高浓度洗毛废水尾浆进行处理。试验结果表明，对于ＣＯＤ为２５０００ｍｇ／Ｌ的原废水，经１ｄ的厌氧酸化和１ｄ的二段串联的间歇活性污泥法好氧曝气处理，ＣＯＤ和ＢＯＤ５的总去除率分别达到９２％和９９％以上，生化处理出水ＣＯＤ为１５００～２０００ｍｇ／Ｌ，ＢＯＤ５＜６０ｍｇ／Ｌ。     

有效田间灌水质量指标体系初探

本文根据传统田间灌水质量指标体系存在的不足首次提出了有效田间灌水质量指标体系的概念。作者认为,传统的田间灌水质量指标体系只从灌水结束后通过土壤表面的累计入渗水深来描述灌水质量,缺乏合理的理论根据,不利于直接反映灌水质量与作物生长之间的关系。建议从作物根系吸水机理上研究灌溉入渗水分及其分布状况的有效性,建立有效的田间灌水质量指标体系。文中对有效田间灌水质量指标体系的概念进行了较系统的阐述,最后还初步探讨了田间灌水质量指标体系中的随机性和时空性问题。