Does time of day matter at highway work zone crashes?

Introduction: It is widely agreed that highway work zones pose significant threats to road users because driving conditions in work zones are quite different from the normal ones, particularly when traffic volumes approach a highway capacity. Therefore, work zone safety is a critical aspect for state agencies and traffic engineers. Method: In the current study, a total of 10,218 crashes that occurred in highway work zones in the state of Washington for the period between 2007 and 2013 were used. Time of day is disaggregated into four subgroups: (1) Morning from 6:00 to 11:00 a.m. (2) Midday from 12:00 to 5:00 p.m. (3) Night from 6:00 to 11:00 p.m., and (4) Late night from 12:00 to 5:00 a.m. Then, four mixed logit models were estimated to account and correct for heterogeneity in the crash data by considering three injury severity levels: severe injury, minor injury, and no injury. Results: The estimation results reveal that most contributing factors are uniquely significant in a specific time of day period, whereas three factors affect injury severity regardless of time of day such as the indicators of not deployed airbag, one passenger vehicle involved in the crash, and rear-end collision. Further, some factors were found to affect injury severity into two or three time periods, such as female drivers that found to decrease the probability of no injury in morning and night time periods, while increasing severe injury outcome in midday time. Conclusions: The effect of time of day on injury severity of work-zone related crashes should be modeled separately rather than using a holistic model. Practical applications: As a starting point, findings of the current study can be used by transportation officials to reduce fatalities and injuries of work zone crashes by identifying factors that uniquely contribute to each time of day period.     

Phyt'Eaux Cités: application and validation of a programme to reduce surface water contamination with urban pesticides

This paper presents first results of Phyt’Eaux Cités, a program put in place by the local water supply agency, the SEDIF (Syndicat des Eaux d’Ile-de-France), in collaboration with 73 local authorities, private societies and institutional offices (365 km²). The challenges included: measurement of the previous surface water contamination, control of urban pesticide applications, prevention of pesticide hazard on users and finally a overall reduction of surface water contamination. An inquiry on urban total pesticide amount was coupled with a surface water bi-weekly monitoring to establish the impact of more than 200 molecules upon the Orge River. For 2007, at least 4400 kg and 92 type of pesticides (essentially herbicides) were quantified for all urban users in the Phyt’Eaux Cités perimeter. At the outlet of the Orge River (bi-weekly sampling in 2007), 11 molecules were always detected above 0.1 μg L⁻¹. They displayed the mainly urban origin of pesticide surface water contamination. Amitrole, AMPA (Aminomethyl Phosphonic Acid), demethyldiuron, diuron, glyphosate and atrazine were quantified with a 100% of frequency in 2007 and 2008 at the Orge River outlet. During the year, peaks of contamination were also registered for MCCP, 2,4 MCPA, 2,4 D, triclopyr, dichlorprop, diflufènican, active substances used in large amount in the urban area. However, some other urban molecules, such as isoxaben or flazasulfuron, were detected with low frequency. During late spring and summer, contamination patterns and load were dominated by glyphosate, amitrole and diuron, essentially applied by cities and urban users. Both isoproturon and chlortoluron were quantified during autumn and winter months according to upstream agricultural practices. In conclusion, 3 years after the beginning of this programme, the cities reduced the use of 68% of the total pesticide amount. An improvement on surface water quality was found from 2008 and during 2009 for all pesticides. In particular, glyphosate showed a decrease of the load above 60% in 2008, partly related to the Phyt’Eaux Cités action.     

Analysis of mixed halogenated dibenzo-p-dioxins and dibenzofurans (PXDD/PXDFs) in soil by gas chromatography tandem mass spectrometry (GC-MS/MS)

Mixed halogenated dibenzo-p-dioxins and dibenzofurans (PXDD/PXDFs, X = Br, Cl) are formed through combustion processes, and may be more toxic than their corresponding chlorinated and brominated analogues. With 4600 potential congeners, limited analytical standards, and complex environmental matrices, PXDD/PXDFs present a significant analytical challenge. Gas chromatography tandem mass spectrometry (GC-MS/MS) offers both selectivity and sensitivity through multiple reaction monitoring of unique transitions in a novel approach to PXDD/PXDF congener identification. Method validation was performed through analysis of soil samples obtained from a recycling plant fire. Of the PXDD/PXDFs examined, monobromo-dichlorodibenzofuran was the most prevalent, ranging in concentration from 8.6 ng g⁻¹ to 180 ng g⁻¹. Dibromo-dichlorodibenzo-p-dioxin, a compound of toxicological concern, ranged from 0.41 ng g⁻¹ to 10 ng g⁻¹. Concentrations of PXDD/PXDFs were between 6% and 10% that of the corresponding polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDFs), with the exception of dibromo-dichlorodibenzo-p-dioxin concentrations, which were 36% that of tetrachlorodibenzo-p-dioxins. Higher levels of polybrominated PXDD/PXDFs may indicate a significant bromine source was present during combustion.     

Developing and Implementing Multiple-Use Forest Management Planning in Turkey

This paper explains briefly the conceptual framework of an ecosystem-based multiple-use forest management planning focusing on biodiversity conservation and participation. Some results from a case study were documented to realize the implementation of the concept. A strong liaison between the related institutions and major stakeholders and the effective use of Geographic Information System (GIS) and Remote Sensing (RS) are necessary. Effective participation is evident only with the involvement of enthusiastic and skillful stakeholders. A case study of ??neada, Turkey, supported the idea that participation as communication has better possibilities to promote multiple-use forest management than participation as information gathering. Primary challenges relate to the effectiveness of conservation program, availability of coherent biodiversity data, capacity building; awareness, training, and common understanding of biodiversity and protected area concept; coordination among the related institutions and stakeholders; and willingness and enthusiasm of authorities to accept and implement the concept.     

矿井火区可燃性混合气体爆炸三角形判断法及其爆炸危险性分析

矿井火区可燃性混合气体爆炸危险性的判断 ,目前常用单纯的瓦斯爆炸三角形判别法。此法对实际的判断往往未综合考虑火区温度的影响。为此 ,笔者论述了矿井火区多种可燃性气体同时存在时 ,其混合气体爆炸三角形各参数的工程计算方法 :爆炸界限可用 Le Chatelier法 ,但需根据火区实测温度进行修正 ;爆炸时的临界氧浓度 ,则需用另一种三角形图示法予以确定。由此画出的混合气体爆炸三角形分析图 ,可用于矿井火区 ,尤其是矿井大面积火区的密闭和启封过程中 ,作为可燃性混合气体爆炸危险性的综合判断及其防爆措施的制定 ,都具有实用价值和指导意义     

紫色土小流域不同土地利用类型的土壤氮素时空分异特征

以紫色土区12.10 km²的万安小流域为研究区域,于2011年4月(旱季)和8月(雨季)小麦和玉米收获期共采集552个表层土壤(0~15 cm)样品,利用传统统计学和地统计学相结合的方法对流域土壤全氮和硝态氮的时空变异特征进行研究.结果表明,不同土地利用类型土壤全氮含量差异显著,并呈以下顺序:水旱轮作田>林地>旱地;同一土地利用类型旱季、雨季土壤全氮含量不存在显著差异.其中,4月和8月林地、旱地、水旱轮作田土壤全氮含量分别为1.16、0.90、1.21 g·kg^-1和1.13、0.94、1.29 g·kg^-1.但旱季和雨季土壤硝态氮含量差异显著,其中,4月和8月林地、旱地、水旱轮作田硝态氮含量分别为12.08、24.22、31.22 mg·kg^-1和3.98、11.18、2.27 mg·kg^-1,表现出土壤硝态氮旱季累积、雨季流失的特点;受到内部因素和外部因素共同作用,旱地、水旱轮作田土壤全氮空间分布具有中等空间相关性,而林地土壤全氮的强烈空间相关性主要受到内部因素的影响.本研究分析了紫色土区不同土地利用类型条件下的流域土壤氮素的时空变异特征,将会为流域土地资源管理和环境修复提供较好的科学依据.     

乳化油在汽车发动机上的应用及探讨

本文对乳化油的乳化性能和在汽车发动机上的发展现状进行了探讨,分析对比了混合燃料的优缺点。研究表明：汽车发动机燃用乳化油可提高热效率,有效降低NOx及碳烟排放,但动力性略差,CO排放有所增加。最后阐述了我国乳化油未来发展优势。     

Aeration optimization through operation at low dissolved oxygen concentrations: Evaluation of oxygen mass transfer dynamics in different activated sludge systems

In wastewater treatment plants(WWTPs)using the activated sludge process,two methods are widely used to improve aeration efficiency — use of high-efficiency aeration devices and optimizing the aeration control strategy. Aeration efficiency is closely linked to sludge characteristics(such as concentrations of mixed liquor suspended solids(MLSS)and microbial communities)and operating conditions(such as air flow rate and operational dissolved oxygen(DO)concentrations). Moreover,operational DO is closely linked to effluent quality. This study,which is in reference to WWTP discharge class A Chinese standard effluent criteria,determined the growth kinetics parameters of nitrifiers at different DO levels in small-scale tests. Results showed that the activated sludge system could meet effluent criteria when DO was as low as 0.3 mg/L,and that nitrifier communities cultivated under low DO conditions had higher oxygen affinity than those cultivated under high DO conditions,as indicated by the oxygen half-saturation constant and nitrification ability. Based on nitrifier growth kinetics and on the oxygen mass transfer dynamic model(determined using different air flow rate(Q′_(air))and mixed liquor volatile suspended solids(MLVSS)values),theoretical analysis indicated limited potential for energy saving by improving aeration diffuser performance when the activated sludge system had low oxygen consumption; however,operating at low DO and low MLVSS could significantly reduce energy consumption. Finally,a control strategy coupling sludge retention time and MLVSS to minimize the DO level was discussed,which is critical to appropriate setting of the oxygen point and to the operation of low DO treatment technology.     

Skew and attribute non-attendance within the Bayesian mixed logit model

We investigate non-attendance to choice set attributes and the accommodation of preference heterogeneity within the mixed logit model. We propose a generalisation of the mixed logit enabling the degree of skew of marginal utility distributions to be estimated. The implementation is Bayesian with the marginal likelihood used as an arbiter of model performance. We find strong evidence of skew in the distributions of marginal utilities for most attributes. Models incorporating skew are preferred in all cases. The irrelevance of an attribute to significant numbers of respondents is a possible cause of such skew. We test alternative empirical accommodations of self-reported attribute non-attendance (ANA) and continue to find strong evidence of skew in the distributions of marginal utilities even having accounted for ANA. We find that, contrary to some recent findings, respondents who report having ignored an attribute typically do indeed have a zero marginal utility for that attribute.