典型温冰川区湖泊的稳定同位素空间分布特征

2014年8月对拉市海表层及不同深度湖水进行采样,分析拉市海湖水的氢氧稳定同位素的空间变化及其影响因素,探讨典型温冰川区域湖泊的水文补给特征.结果表明,拉市海表层湖水的δ~(18)O、δD值分别在-12.98‰~8.16‰和-99.42‰~-73.78‰之间波动,平均值分别为-9.75‰和-82.23‰;表层湖水的δ~(18)O及过量氘表现出相反的空间变化特征,有河水注入的区域δ~(18)O值较低而过量氘值较高;垂直方向上过量氘随深度变化较小,表明湖水在垂直方向上混合较充分,不同深度层上过量氘表现出自东向西先增大后减小的变化趋势,这可能与入湖河流的分布、湖泊所处的地理位置及自然条件等密切相关;同位素对比研究发现,拉市海的主要补给源为大气降水及河水,冰雪融水可能间接补给拉市海;对拉市海与青藏高原地区典型湖泊和非冰川区湖泊的氧同位素组成对比发现,冰川区湖泊中稳定同位素表现出明显的高程效应(拉市海除外),δ~(18)O随海拔升高而降低.非冰川区湖泊蒸发效应较为明显,同位素值明显偏正.     

Perils of using speed zone data to assess real-world compliance to speed limits

Objective: Real-world driving studies, including those involving speeding alert devices and autonomous vehicles, can gauge an individual vehicle's speeding behavior by comparing measured speed with mapped speed zone data. However, there are complexities with developing and maintaining a database of mapped speed zones over a large geographic area that may lead to inaccuracies within the data set. When this approach is applied to large-scale real-world driving data or speeding alert device data to determine speeding behavior, these inaccuracies may result in invalid identification of speeding. We investigated speeding events based on service provider speed zone data.

Methods: We compared service provider speed zone data (Speed Alert by Smart Car Technologies Pty Ltd., Ultimo, NSW, Australia) against a second set of speed zone data (Google Maps Application Programming Interface [API] mapped speed zones).

Results: We found a systematic error in the zones where speed limits of 50–60 km/h, typical of local roads, were allocated to high-speed motorways, which produced false speed limits in the speed zone database. The result was detection of false-positive high-range speeding. Through comparison of the service provider speed zone data against a second set of speed zone data, we were able to identify and eliminate data most affected by this systematic error, thereby establishing a data set of speeding events with a high level of sensitivity (a true positive rate of 92% or 6,412/6,960).

Conclusions: Mapped speed zones can be a source of error in real-world driving when examining vehicle speed. We explored the types of inaccuracies found within speed zone data and recommend that a second set of speed zone data be utilized when investigating speeding behavior or developing mapped speed zone data to minimize inaccuracy in estimates of speeding.     

The sources of the Kuznets relationship between the road deaths to road injuries ratio and economic growth

Introduction: Past empirical studies indicated that there is a Kuznets or reverse U-shaped relationship between road deaths and per capita income, such that the number of road death increases at a low level of per capita reverse U-shaped relationship was observed between road injuries and per capita income. While these studies explored the impact of per capita income on road deaths and road injuries, no studies have examined the relationship between per capita income and road death to road injury ratio (DPI). Method: Using a fixed effects panel regression analysis from 67 countries spanning over a period of five decades (1960–2013), the present study sought to explore the impact of per capita gross domestic product (per capita GDP) on the DPI ratio and the underlying factors responsible for the relationship. Results: Our result suggests that per capita GDP followed a reverse U-shaped relationship with DPI. Moreover, the relative improvements in higher mobility roads as compared to improvements in higher accessibility roads, motorcycle ownership to passenger car ownership ratio, percentage of population living in an urban area, infant mortality rate, and the percentage of population below 15 years of age and above 64 years of age contributed to this relationship. Practical Applications: This implies that, at lower level of economic growth where road deaths exceed road injuries, countries should implement low-cost measures to combat road deaths cases. Such measures include mandating wearing of quality helmets and daytime running headlights for motorcycles. On the other hand, at higher level of economic growth where road injuries surpass road deaths, countries are encouraged to devote more resources to improving medical technology and services to treat road injury victims, mandating seatbelt use, as well as enhancing and promoting public transportation service.     

Changes in driving performance after first and second eye cataract surgery: A driving simulator study

Introduction: This study investigated the separate impact of first eye and second eye cataract surgery on driving performance, as measured on a driving simulator. Method: Forty-four older drivers with bilateral cataract aged 55+ years, awaiting first eye cataract surgery participated in a prospective cohort study. They completed a questionnaire, visual tests and a driving simulator assessment at three time points: before first eye, after first eye, and after second eye cataract surgery. Generalized Estimating Equation Poisson or linear regression models were undertaken to examine the change in four driving outcomes of interest after adjusting for cataract surgery and other potential confounders. Results: The rate of crashes/near crashes decreased significantly by 36% (incidence rate ratio (IRR) 0.64, 95% CI 0.47–0.88, p = 0.01) after first eye surgery and 47% (IRR 0.53, 95% CI 0.35–0.78, p < 0.001) after second eye surgery, compared to before first eye cataract surgery, after accounting for confounders. The rate of crashes/near crashes also decreased with better contrast sensitivity (IRR 0.69, 95% CI 0.48–0.90, p = 0.041). A separate model found that time spent speeding 10 kilometers per hour or more over the limit after second eye surgery was significantly less (0.14 min, p = 0.002), compared to before first eye surgery, after accounting for confounders. As contrast sensitivity improved, the duration of speeding also decreased significantly by 0.46 min (p = 0.038). There were no statistically significant changes in lane excursions or speed variation. Practical applications: The findings highlight the importance of timely first and second eye cataract surgery to ensure driver safety, especially as older drivers wait for second eye cataract surgery. It also provides further evidence that contrast sensitivity is probably a better predictor of driving ability in older drivers with cataract than visual acuity, the measure on which driver licensing requirements are currently based, and should also be used when assessing fitness to drive.     

Identifying management practices that drive production-line workers’ engagement through qualitative analysis

Introduction: Engagement research - most often defined by a worker’s psychological state of vigor, dedication, and absorption - pays little attention to production-line workers. This study therefore explores factors that drive workers’ engagement with health and safety (H&S) in a production-line context as well as their perception of managerial influence Furthermore, the study adds to the body of research by exploring H&S engagement concepts through the use of qualitative research methods. Method: 38 semi-structured interviews were conducted and analyzed through template analysis to identify themes that promote and hinder engagement. Results: The main engagement drivers were found to be: (a) the displayed safety focus of the company in organizational and social aspects; (b) the quality of the communication approach with respect to quality, consistency and direction; and (c) the environment encompassing the relationship between workers and supervisors and peers as well as the psychological environment. Notably, a trusting relationship between supervisors and workers appeared to be the most influential driver in determining engaged H&S behavior. Discussion and impact in industry: The study highlights factors that could be adapted to improve engagement and consequently enhance H&S approaches. Originality: The study reported in this paper offers a unique insight into individual production workers’ perceived drivers of H&S engagement using Qualitative Analysis. Practical applications: The study identified the important role that supervisors play in workers’ H&S engagement levels and what skills they need to employ to enhance workers’ engagement in general and in the context of H&S behavior and performance. Furthermore, the importance of psychological and sociological factors in safety approaches are highlighted and were found to be key for creating safer workplaces.     

Dual poroelastic response of a coal seam to CO2 injection

Although the influence of gas sorption-induced coal deformation on porosity and permeability has been widely recognized, prior studies are all under conditions of no change in overburden stress and effective stress-absent where effective stresses scale inversely with applied pore pressures. Here we extend formalism to couple the transport and sorption of a compressible fluid within a dual-porosity medium where the effects of deformation are rigorously accommodated. This relaxes the prior assumption that total stresses remain constant and allows exploration of the full range of mechanical boundary conditions from invariant stress to restrained displacement. Evolution laws for permeability and related porosity are defined at the micro-scale and applied to both matrix and an assumed orthogonal, regular and continuous fracture system. Permeability and porosity respond to changes in effective stress where sorption-induced strains may build total stresses and elevate effective stresses. Gas accumulation occurs in both free- and adsorbed-phases and due to effective grain and skeletal compressibilities. A finite element model is applied to quantify the net change in permeability, the gas flow, and the resultant deformation in a prototypical coal seam under in situ stresses. Results illustrate how the CO₂ injectivity is controlled both by the competition between the effective stress and the gas transport induced volume change within the matrix system and by the dynamic interaction between the matrix system and the fracture system. For typical parameters, initial injection-related increases in permeability due to reduced effective stresses may endure for days to years but are ultimately countered by long-term reductions in permeability which may decline by an order of magnitude. Models suggest the crucial role of stresses and the dynamic interaction between matrix and fractures in correctly conditioning the observed response.     

The case for international emission trade in the absence of cooperative climate policy

We evaluate the efficacy of international trade in carbon emission permits when countries are guided strictly by their national self-interest. To do so, we construct a calibrated general equilibrium model that jointly describes the world economy and the strategic incentives that guide the design of national abatement policies. Countries’ decisions about their participation in a trading system and about their initial permit endowment are made non-cooperatively; so a priori it is not clear that permit trade will induce participation in international abatement agreements or that participation will result in significant environmental gains. Despite this, we find that emission trade agreements can be effective; that smaller groupings pairing developing and developed-world partners often perform better than agreements with larger rosters; and that general equilibrium responses play an important role in shaping these outcomes.