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AbstractBackground and aimsCannabis and alcohol are frequently detected in fatal and injury motor vehicle crashes. While epidemiological meta‐analyses of cannabis and alcohol have found associations with an increase in crash risk, convergent evidence from driving performance measures is insufficiently quantitatively characterized. Our objectives were to quantify the magnitude of the effect of cannabis and alcohol—alone and in combination—on driving performance and behaviour.MethodsSystematic review and meta‐analysis. We systematically searched Academic Search Complete, CINAHL, Embase, Scopus, Google Scholar, MEDLINE, PsycINFO, SPORTDiscus and TRID. Of the 616 studies that underwent full‐text review, this meta‐analysis represents 57 studies and 1725 participants. We extracted data for hazard response time, lateral position variability, lane deviations or excursions, time out of lane, driving speed, driving speed variability, speed violations, time speeding, headway, headway variability and crashes from experimental driving studies (i.e. driving simulator, closed‐course, on‐road) involving cannabis and/or alcohol administration. We reported meta‐analyses of effect sizes using Hedges’ g and r.ResultsCannabis alone was associated with impaired lateral control [e.g. g = 0.331, 95% confidence interval (CI) = 0.212–0.451 for lateral position variability; g = 0.198, 95% CI = 0.001–0.395 for lane excursions) and decreased driving speed (g = –0.176, 95% CI = –0.298 to –0.053]. The combination of cannabis and alcohol was associated with greater driving performance decrements than either drug in isolation [e.g. g = 0.480, 95% CI = 0.096–0.865 for lateral position variability (combination versus alcohol); g = 0.525, 95% CI = 0.049–1.002 for time out of lane (versus alcohol); g = 0.336, 95% CI = 0.036–0.636 for lateral position variability (combination versus cannabis; g = 0.475, 95% CI = 0.002–0.949 for time out of lane (combination versus cannabis)]. Subgroup analyses indicated that the effects of cannabis on driving performance measures were similar to low blood alcohol concentrations. A scarcity of data and study heterogeneity limited the interpretation of some measures.ConclusionsThis meta‐analysis indicates that cannabis, like alcohol, impairs driving, and the combination of the two drugs is more detrimental to driving performance than either in isolation.

Abstract The load-frequency control (LFC) problem is investigated on assumptions considered realistic for most power systems. Voltage and frequency dependence of system loads, and load inertia effects, are taken into account. Results include system dynamic response to changes in load, and effects of LFC parameter settings. Using a performance index based on squared tie-line flow error plus squared area frequency error, the effect of load representation on optimum integrator gain is examined.

Forests are expected to expand into alpine areas because of climate warming, causing land-cover change and fragmentation of alpine habitats. However, this expansion will only occur if the present upper treeline is limited by low-growing season temperatures that reduce plant growth. This temperature limitation has not been quantified at a landscape scale. Here, we show that temperature alone cannot realistically explain high-elevation tree cover over a >100-km 2 area in the Canadian Rockies and that geologic/geomorphic processes are fundamental to understanding the heterogeneous landscape distribution of trees. Furthermore, upslope tree advance in a warmer scenario will be severely limited by availability of sites with adequate geomorphic/topographic characteristics. Our results imply that landscape-to-regional scale projections of warming-induced, high-elevation forest advance into alpine areas should not be based solely on temperature-sensitive, site-specific upper-treeline studies but also on geomorphic processes that control tree occurrence at long (centuries/millennia) timescales.

Abstract Oils that are potential candidates for in situ combustion recovery processes are often screened by means of their oxidation characteristics: in particular, the kinetics of the ignition process and the transition from low-temperature to high-temperature oxidation through what is known as the "negative temperature gradient region". These characteristics are readily studied in ramped-temperature oxidation tests, which involve the controlled heating of recombined, oil-saturated cores in a one-dimensional plug flow reactor under a flowing stream of air (or oxygen-containing gas). The purpose of these tests is to study the global oxidation behavior and reaction kinetics under controlled conditions, with the end purpose of providing realistic data for incorporation into a numerical simulator which can he used to predict field performance. A ramped-temperature oxidation apparatus was used to conduct a detailed, two-year parametric study of the oxidation characteristics of Athabasca Oil Sands bitumen. The test matrix involved various levels of pressure gas injection rate, oxygen content of the injected gas and maximum ramp temperature. This paper details the principal findings for the 45-test study: in particular, the need to maintain high reaction temperatures >380 C) in order to mobilize and produce heavy oils under conditions of dry in situ combustion. Design considerations and operational guidelines for successful field projects which can be suggested from the results of this study are also discussed. Introduction In order to successfully exploit the vast potential of processes based on the injection of air or an oxygen-containing gas for the recovery of conventional and heavy oils, it is necessary to understand the nature of the oxidation reactions which are involved. The traditional concept of in situ combustion, which is based on the high-temperature combustion of a coke-like fuel, will not explain the combustion behavior which is observed in many field projects or even in laboratory combustion tube experiments. For this reason, a number of experiments have been developed which concentrate on the global oxidation kinetics. These studies normally involve exposing the crude oil to a programmed rate of heating while in contact with the oxidizing gas. The oxidation kinetics are then observed using effluent gas analysis techniques, and differential thermal techniques such as the differential thermal analysis (DTA) work of Vossoughi et al., the pressurized differential scanning calorimetry (PDSC) studies of Phillips et al., and Belkharchouche and Hughes and the accelerating rate calorimetry (ARC) technique of Yannimaras et al. Previous investigations of the oxidation reactions which occur during in situ combustion processes have shown the existence of at least two temperature ranges over which the oxygen uptake rates are significant. While Kisler and Shallcross have reported that the light (40.2 API) Australian oil which they studied exhibited at least three temperature ranges over which localized maxima in the oxygen uptake rate were observed, the majority of heavy oils for which oxidation data have been reported exhibit only two distinct local maxima in the oxidation rates. For convenience, the two temperature ranges where elevated oxygen uptake or energy generation rates are observed are denoted as the low-temperature oxidation and high-temperature combustion regions. For heavy oils, the range of temperatures associated with the low-temperature oxidation region is roughly from 150 to 300 C, while the high-temperature combustion region generally corresponds to reaction temperatures in the range from 380 to 800 C. The transition temperature range which falls between the temperatures corresponding to the low-temperature oxidation and high-temperature combustion regions is characterized by reduced oxygen uptake and energy generation rates. The lower temperature portion of this transition range in which the oxygen uptake and energy generation rates decrease with increasing temperature is the "negative temperature gradient region". The significance of this region will be more fully explored in the following sections of this paper. Description of Test Procedure Equipment The ramped-temperature oxidation apparatus and test procedures have been described in detail by Moore et al. The apparatus essentially consisted of a plug flow reactor with an inside diameter of 22.1 mm and an inside length of 320.7 mm. The reactor was equipped with five Inconel-sheathed Type K thermocouples which were spaced 50.8 mm apart and inserted radially to the centerline of the core. The reactor was mounted in an aluminum beating block which was equipped with strap heaters. Temperature control and monitoring were achieved using an in-house developed computer-based system. A mass-flow meter controlled the oxidizing gas injection rate and a backpressure control valve maintained the desired operating pressure at the reactor outlet.

AbstractIn this paper, a new model of transverse mixing in a rotating drum is derived from dynamic data collected from an experimental rig. Since the active layer has often been declared as the zone that is responsible for the mixing of solids in a rolling bed, the active layer was characterized so that its properties could be predicted for a wide range of experimental conditions. The mixing model consisted of two correlations, one to predict the mixing rate in the drum and the other to predict the final contact between the two materials. These correlations were linked back to the operational variables of the drum, such as the drumfs loading, size and rotational velocity. By combining these two correlations the time required to fully mix the material in the drum could be predicted. The mixing model was tested against independent data and good agreement was observed between the experimentally derived results and those predicted by the mixing model. Furthermore, this mixing model was designed such that it would be easily applicable to different sized drums. The extrapolation ability was tested on different smaller‐sized drums and found to agree considerably with experimental results.

Sketch-based interface and modelling is an approach to reservoir modelling that allows rapid and intuitive creation of 3D reservoir models to test and evaluate geological concepts and hypotheses and thus explore the impact of geological uncertainty on reservoir behaviour. A key advantage of such modelling is the quick creation and quantitative evaluation of reservoir model prototypes. Flow diagnostics capture key aspects of reservoir flow behaviour under simplified physical conditions that enable the rapid solution of the governing equations, and are essential for such quantitative evaluation. In this paper, we demonstrate a novel and highly efficient implementation of a flow diagnostics framework, illustrated with applications to geological storage of CO2. Our implementation permits ‘on-the-fly’ estimation of the key reservoir properties that control CO2 migration and storage during the active injection period when viscous forces dominate. The results substantially improve the efficiency of traditional reservoir modelling and simulation workflows by highlighting key reservoir uncertainties that need to be evaluated in subsequent full-physics reservoir simulations that account for the complex interplay of viscous, gravity, and capillary forces. The methods are implemented in the open-source Rapid Reservoir Modelling software, which includes a simple to use graphical user interface with no steep learning curve. We present proof-of-concept studies of the new flow diagnostics implementation to investigate the CO2 storage potential of sketched 3D models of shallow marine sandstone tongues and deep water slope channels.

A highly unconsolidated undersaturated reservoir producing heavy oil with an API of 12.1° is located in Lindbergh Field of Elk Point area, Alberta, Canada. A specific well in this reservoir was initially designed to produce oil via a cold heavy oil production with sand (CHOPS) mechanism. However, a large amount of the sand production on a daily basis plugged the progressive cavity pump installed in the well. The cost of well services to unplug the pump on a monthly basis exceeded the revenue from produced oil, and thus, the well was considered uneconomic. Various techniques have been sought to control the sand production and to increase the cumulative oil production and the pump efficiency. Installing screens and meshes in the production interval of the wellbore was analyzed as a solution to the sand production. Installing screens increased the skin factor and resulted in a very low production rate of 0.15 m3/day. The cost of purchasing and installing screens was estimated to be approximately $87,650 with five shut-in days. In addition, the screens also needed further sand clean up, which is an expensive process. Hence, the screens were not recommended for this candidate well. A Back-pressure regulator (BPR) is currently installed on the casing of the well. The initial purpose of installing BPR on the casing was to control the wellbore pressure. The BPR restricts the flow of gas vented through the casing-tubing annulus. This study analyzes the effects of restricting flow of the vented gas such as solution gas reduction, which causes (i) higher settling velocity for the sand grain, (ii) lower Basic sediment and water (BS&W), and (iii) lower in situ oil density. The production data of candidate well obtained from AccuMap (v.18.12) shows that the production hours increased significantly after installing BPR. This is because the number of well services reduced by 90 %. This results in an approximately $34,000 per month increase in profit (assuming $30.00/barrel of oil) for each well. This shows one million dollars savings on a monthly basis when the application of the BPR installation is implemented on 30 similar wells. The cost of the BPR installed on well is $328.00, and there is no operating cost involved since the cost of additional, necessary maintenance and operation is nearly negligible. Moreover, this study provides the field examples of improper BPR operation, which resulted in economic loss. Possible solutions to fix the improper installation of BPR are proposed as well.