皆伐作业对林地土壤因子的影响

对福建省永安市元沙林业采育场杉阔混交人工林林地皆伐作业前后土壤理化性质变化进行试验研究.结果表明,皆伐作业使林地土壤许多理化性质发生改变.皆伐导致土壤容重增大0.13 g·cm-3,土壤结构体破坏率提高12.50%,最大持水量下降6.65%,总孔隙度减小3.88%; 同时土壤主要化学性质,如有机质、全N、水解性N、全P、速效P、全K、速效K等普遍降低,它们的含量分别下降8.14 g·kg-1、0.18 g·kg-1、7.20 mg·kg-1、0.38 g·kg-1、39.98 mg·kg-1、6.95 g·kg-1和12.31 mg·kg-1; 此外,对皆伐作业造成土壤理化性质变化的原因进行了分析,并从森林生态采运角度出发,提出减少皆伐作业对林地土壤破坏的技术措施.     

扩展卡尔曼滤波算法在矿用救生舱舱内气体浓度测控中的应用

为有效控制矿用移动式救生舱内气体浓度,确保救生舱内环境质量,保障舱内人员生命安全;根据《煤矿井下紧急避险系统建设管理暂行规定》的指标要求,采用扩展卡尔曼滤波方法对救生舱舱内气体参数的变化过程进行辨识,得出舱内气体浓度的状态空间模型,并应用迭代优化控制方法对气体浓度进行控制调节;在矿用救生舱模型和现场样机中分别进行了模拟和现场试验。结果表明,测控系统能有效控制救生舱舱内气体浓度进行,满足各项指标要求,且具有较好的鲁棒性。     

异养硝化-好氧反硝化菌株的分离筛选及复配菌剂对河水的净化效果

从天然河水中富集分离出8株异养硝化-好氧反硝化（HN-AD）菌株.将单菌株根据其自身的种属类别及脱氮性能复配成5种由不同菌株构成的菌剂,优选出脱氮效果最佳的复配菌剂-2,其包括6株菌株,分别为Pseudomonas stutzeri MR1,Pseudomonas sp. MR2,Pseudomonas sp. MR3,Pseudomonas balearica MR4,Klebsiella variicola MR6和Catellibacterium terrae MR8.将复配菌剂-2投加至COD_Cr/TN比分别为20和5的河水中,其对NO₃^--N的去除率分别为87.1%和97.5%,期间无NO₂^--N积累;对NH₄⁺-N去除效果在第1 d分别达到96.6%和57.6%.复配菌剂可以获得对河水较高的反硝化脱氮效率,并可以强化河水中NH₄⁺-N的去除,对实际河水的脱氮净化具有较强的应用潜能.     

城市污水厂混合污泥好氧消化处理研究

以城市污水处理厂的初沉污泥与剩余污泥的混合污泥为对象,研究了影响污泥好氧消化处理的各项因素.通过测定氧摄取速率(OUR)和此污泥好氧速率(SOUR),对实验结果进行了探讨.     

WATER YIELD IMPROVEMENT BY VEGETATION MANAGEMENT1

ABSTRACT: Vegetation management aimed at increasing the amount of usable water yield from precipitation falling on upstream watersheds may be one alternative for supplementing water supplies. Indications are that water yields can be increased within a multiple-use framework, which can benefit or at least be compatible with other natural resource objectives. Through changes in vegetation on a watershed, it is possible to reduce evaporation losses only slightly but significantly increase streamflow runoff. In an assessment of potentials for water yield improvement in Arizona, experimental studies on various vegetation zones are reviewed. Because of either limited acreage or limited rainfall, the alpine, grassland, aspen, and desert shrub vegetation zones are not realistic management areas for Arizona. Furthermore, manipulation of pinyon-juniper woodlands does not appear promising at this time. Conversion of chaparral to grasses and forbs does appear to be a possible treatment for water yield improvement, as well as various silvicultural treatments of mixed conifer and ponderosa pine forests. Streamflow increases are given for experiments in chaparral, mixed conifer, and ponderosa pine vegetation zones. However, complete information on possible constraints for these zones is not currently available. Specific assessment of water yield management options for riparian vegetation is difficult to make, due to incomplete knowledge of water yield changes and other constraints for this vegetation zone. Prior to the final adoption of management practices, results of experimental work must be coupled with economic and social considerations.     

SEDIMENT CHEMISTRY AS INFLUENCED BY VEGETATION AND BEDROCK IN THE SOUTHWESTERN UNITED STATES1

ABSTRACT We hypothesized that sediment from small watersheds with uniform bedrock and a single vegetative community would have uniform chemical characteristics for the sand and fine (silt and clay) size fractions. Channel sediment was collected from three vegetative communities (spruce-fir, mixed conifer, and Ponderosa pine), each on four bedrock types (basalt, limestone, sandstone, and granite), and analyzed for digestable Ca, Mg, Na, K, Cu, Mn, Fe, Zn; total N and P; extractable Ca, Mg, K; cation exchange capacity; and organic matter. With the exception of organic matter content in the sand size fraction, either vegetation, bedrock, or their interaction were significant in explaining the observed variation for all analyses in both size fractions. Replicate studies of sites with similar bedrock and vegetation combinations are needed to determine if each watershed has similar or unique sediment chemistry.     

BIOLOGICAL INDICATORS AND BIOLOGICAL EFFECTS OF ESTUARINE/COASTAL POLLUTION1

ABSTRACT: Sustained interest in and concern about the health status of the aquatic environment has resulted in extensive research focused on (1) effects of pollution on survival, growth, and reproduction of resource species at all life stages; (2) diseases of fish and shellfish, as they may be related to pollution and as they may serve as indicators of environmental stress; and (3) contaminant body burdens in fish and shellfish - their effects on the aquatic animals and their potential effects on humans. Effects, lethal and sublethal, of pollutants on life history stages of fish and shellfish have been documented, as have impacts on local stocks in badly degraded habitats, but as yet there has been no adequate quantitative demonstration of effects on entire aquatic species - probably because of the difficulty in sorting out relative effects of the many environmental factors that influence abundance. Sublethal effects, especially those that result in disease, have been examined intensively, and some diseases and disease syndromes have been associated statistically with pollution. Other pollution indicators (biochemical, physiological, genetic, behavioral, and ecological) have also received some attention, as have body burdens of contaminants in aquatic species. Research, especially that conducted during the past decade, has done much to clarify the many pathways and toxic effects of contaminants on aquatic animals, and has also helped to identify mechanisms for survival of fish and shellfish in the presence of environmental changes caused by human activities.     

基于FLACS CFD的不同气油比油气混输管道泄漏火灾后果对比

不同气油比的油气混输管道泄漏后果危害形式和风险差异的准确判断对于管道泄漏应急处置至关重要。以中国西部某油田集输管道为研究对象,针对不同气油比管道泄漏的火灾危害进行了对比分析,构建了FLACS CFD模型,并研究了油气混输管道原油泄漏形成池火的火灾特征和影响范围,以及天然气泄漏形成喷射火的高温分布和影响规律。研究结果表明:应急处置应考虑不同气油比下池火与喷射火危害的差异。在油气混输管线泄漏10 min形成稳定火焰的场景中,气油比低于100 m3/t时,原油池火为火灾危险的主要影响因素;气油比高于200 m3/t时,天然气喷射火为主要影响因素;气油比超过250 m3/t,高温覆盖距离不再明显增加;40 m为此场景下混输油气泄漏喷射火致死距离上限,120 m为温度影响上限。     

Driver injury severity related to inclement weather at highway–rail grade crossings in the United States

Objective: Previous studies on crash modeling at highway–rail grade crossings were aimed at exploring the factors that are likely to increase the crash frequencies at highway–rail grade crossings. In recent years, modeling driver's injury severity at highway–rail grade crossings has received interest. Because there were substantial differences among different weather conditions for driver's injury severity, this study attempts to explore the impact of weather influence on driver injury at highway–rail grade crossing.

Method: Utilizing the most recent 10 years (2002–2011) of highway–rail grade crossing accident data, this study applied a mixed logit model to explore the determinants of driver injury severity under different weather conditions at highway–rail grade crossing.

Results: Analysis results indicate that drivers' injury severity at highway–rail grade crossings is strongly different for different weather conditions. It was found that the factors significantly impacting driver injury severity at highway–rail grade crossings include motor vehicle speed, train speed, driver's age, gender, area type, lighting condition, highway pavement, traffic volume, and time of day.

Conclusions: The findings of this study indicate that crashes are more prevalent if vehicle drivers are driving at high speed or the oncoming trains are high speed. Hence, a reduction in speed limit during inclement weather conditions could be particularly effective in moderating injury severity, allowing more reaction time for last-minute maneuvering and braking in moments before impacts. In addition, inclement weather-related crashes were more likely to occur in open areas and highway–rail grade crossings without pavement and lighting. Paved highway–rail grade crossings with installation of lights could be particularly effective in moderating injury severity.     

Prediction of dissolved gases content in power transformer oil using BASA-based mixed kernel RVR model

In this paper, beetle antennae search algorithm-based mixed kernel relevance vector regression (BASA-MkRVR) model is presented and applied to predict the dissolved gases content in power transformer, and beetle antennae search algorithm (BASA) is used to select the appropriate kernel parameters and controlled parameter. The RVR model with RBF kernel (RBFRVR) and the RVR model with Sigmoid kernel (SigmoidRVR) are, respectively, used to compare with the proposed BASA-MkRVR model in order to testify the superiority of BASA-MkRVR compared with RBFRVR and SigmoidRVR. The experimental results indicate that BASA-MkRVR has more excellent prediction ability for the dissolved gases content in power transformer oil than RBFRVR and SigmoidRVR.