2,494 research outputs found

    Investigation of the Dual-Fuel Conversion of a Direct Injection Diesel Engine

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    The transportation sector is the second largest energy-consuming sector in the United States. With heavy-duty vehicles comprising 20% of the sector and petroleum products being used as 93% of the sector\u27s fuel, alternatives fuels continue to be investigated to offset petroleum usage. Natural gas is increasingly being considered as a fuel source due to its abundance in the Marcellus Shale Formation. Compressed natural gas (CNG) is a promising energy source for dual-fuel combustion. It appears to benefit the environment and the economy. With the ability to reduce oxides of nitrogen (NOx) emissions, carbon dioxide (CO2) emissions, and particulate matter (PM) emissions, dual-fuel operation is environmentally viable. CNG costs less than petroleum derived diesel and would enable the United States to reduce its dependence on oil imports. Thus, dual-fuel operation promises to be economically practical.;Dual-fuel operation reduces the amount of diesel fuel used during combustion and replaces it with an energy-equivalent amount of CNG. CNG is injected into the intake air stream during the intake stroke of the dual-fuel converted diesel engine\u27s four-stroke cycle. CNG is utilized as the main energy source while diesel fuel is direct injected to initiate the ignition process due to its compression ignition characteristics. The objective of this work was to investigate dual-fuel combustion characteristics and resultant emissions to determine if the partial replacement of diesel fuel with CNG is an applicable technology in the transportation industry. To fulfill this objective, a dual-fuel capable 2005 Mercedes OM-460LA 12.8 liter engine outfitted with in-cylinder pressure and exhaust emissions measurement capabilities was operated at steady-state conditions. Combustion characteristics and resultant emissions were compared between the dual-fuel and diesel operations. To certify a dual-fuel conversion kit with the Environmental Protection Agency\u27s (EPA\u27s) Clean Alternative Fuel Conversion Program, research and development work was also completed on a 2005 Mack AC-460P 12.0 liter engine. Exhaust emissions were collected over steady-state and transient conditions. In-use operation cost comparisons and fuel efficiencies between dual-fuel operation and diesel-only operation were completed with the certified conversion kit.;The combustion characteristics that most affected emission formations were decreased combustion efficiencies (. 39.9%) and decreased maximum in-cylinder gas temperatures (. 15.2%). With the dual-fuel conversion kit meeting certification requirements, NOx emissions decreased for steady-state (10.1%) and transient (7.29%) operations while PM emissions increased for steady-state (14.2%) operation and decreased for transient (27.4%) operation. CO2 emissions decreased for steady-state (8.87%) and transient (7.81%) operations while carbon monoxide (CO) emissions increased for steady-state (754%) and transient (836%) operations. Non-methane hydrocarbon (NMHC) emissions increased for steady-state (34.4%) and transient (59.3%) operations while methane hydrocarbon (MHC) emissions were prominent due to the combustion of CNG for steady-state (4.05 g/bhp-hr) and transient (7.95 g/bhp-hr) operations. The reduction of CO2 emissions is outweighed by the increase in MHC emissions due to a GWP increase of 35% for the steady-state SET and 85.2% for the transient FTP.;Dual-fuel operation yielded operation cost savings of {dollar}17,932/year based on a 2.27-year return of investment timeframe. Though brake specific fuel consumption (BSFC) increased (. 24.2%) and miles per gallon (MPG) efficiencies decreased (. 18.1%), dual-fuel operation still yielded desirable cost savings due to the low price of CNG. Dual-fuel operation cost savings proved to be most effective when the vehicle was operated on highways and accumulated high yearly mileages. The dual-fuel conversion kit successfully showed compliance with the EPA\u27s emissions standards and marketable cost savings

    The Epitheliome: agent-based modelling of the social behaviour of cells

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    We have developed a new computational modelling paradigm for predicting the emergent behaviour resulting from the interaction of cells in epithelial tissue. As proof-of-concept, an agent-based model, in which there is a one-to-one correspondence between biological cells and software agents, has been coupled to a simple physical model. Behaviour of the computational model is compared with the growth characteristics of epithelial cells in monolayer culture, using growth media with low and physiological calcium concentrations. Results show a qualitative fit between the growth characteristics produced by the simulation and the in vitro cell models

    Quasi-local first law of black-hole dynamics

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    A property well known as the first law of black hole is a relation among infinitesimal variations of parameters of stationary black holes. We consider a dynamical version of the first law, which may be called the first law of black hole dynamics. The first law of black hole dynamics is derived without assuming any symmetry or any asymptotic conditions. In the derivation, a definition of dynamical surface gravity is proposed. In spherical symmetry it reduces to that defined recently by one of the authors (SAH).Comment: Latex, 8 pages; version to appear in Class. Quantum Gra

    The era of the wandering mind? Twenty-first century research on self-generated mental activity

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    The first decade of the twenty-first century was characterized by renewed scientific interest in self-generated mental activity (activity largely generated by the individual, rather than in direct response to experimenters’ instructions or specific external sensory inputs). To understand this renewal of interest, we interrogated the peer-reviewed literature from 2003 to 2012 (i) to explore recent changes in use of terms for self-generated mental activity; (ii) to investigate changes in the topics on which mind wandering research, specifically, focuses; and (iii) to visualize co-citation communities amongst researchers working on self-generated mental activity. Our analyses demonstrated that there has been a dramatic increase in the term “mind wandering” from 2006, and a significant crossing-over of psychological investigations of mind wandering into cognitive neuroscience (particularly in relation to research on the default mode and default mode network). If our article concludes that this might, indeed, be the “era of the wandering mind,” it also calls for more explicit reflection to be given by researchers in this field to the terms they use, the topics and brain regions they focus on, and the research literatures that they implicitly foreground or ignore

    An evaluation of the spatial resolution of soil moisture information

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    Rainfall-amount patterns in the central regions of the U.S. were assessed. The spatial scales of surface features and their corresponding microwave responses in the mid western U.S. were investigated. The usefulness for U.S. government agencies of soil moisture information at scales of 10 km and 1 km. was ascertained. From an investigation of 494 storms, it was found that the rainfall resulting from the passage of most types of storms produces patterns which can be resolved on a 10 km scale. The land features causing the greatest problem in the sensing of soil moisture over large agricultural areas with a radiometer are bodies of water. Over the mid-western portions of the U.S., water occupies less than 2% of the total area, the consequently, the water bodies will not have a significant impact on the mapping of soil moisture. Over most of the areas, measurements at a 10-km resolution would adequately define the distribution of soil moisture. Crop yield models and hydrological models would give improved results if soil moisture information at scales of 10 km was available

    Individual Difference Correlates of Being Sexually Unrestricted Yet Declining an HIV Test

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    Which individual differences accurately predict one’s decision to get tested for human immunodeficiency virus (HIV), and do individuals who have regular short-term sex get tested at higher rates? Two studies—one lab study (total valid N = 69, with n = 20 who were tested) and one involving a student health center (valid N = 250, n = 4 who were tested)—involved participants (total valid N = 319, with n = 24 who got tested) taking a number of personality and individual difference measures, including the dark triad (Machiavellianism, narcissism, and psychopathy). Then, in both studies, participants had the opportunity to actually get tested for HIV. After analyzing data from Study 1, for Study 2 we preregistered the prediction that narcissistic participants would tend to (a) show disinclination to get tested for HIV, and (b) show proclivity for unrestricted short-term sexual behavior, manifesting in (c) a significant difference between these two correlations. As predicted, such a difference in correlations was evident for narcissism as well as psychopathy (the latter, however, was not predicted), suggesting that such individuals are not likely to seek HIV diagnostic information, but are taking more sexual risks. A research synthesis was consistent with these ideas (although controlling for demographic factors diminished the effects). Narcissistic and psychopathic individuals may be undetected hubs in the network of sexually active individuals with HIV. These results are silent on whether the typical HIV patient is narcissistic or psychopathic; the results merely implicate narcissistic and psychopathic traits in the spread of the virus

    Spatial distribution of shore-based fishers in the greater Perth Metropolitan area over summer 2010/2011

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    Aerial surveys are a useful technique for estimating numbers of recreational fishers. Following the success of a pilot study to examine the spatial patterns of recreational shore-based fishing activity in the Perth Metropolitan area from April – June 2010, another survey was conducted from December 2010 – February 2011 between Lancelin – Bunbury. More than 7,000 shorebased fishers were counted during 36 aerial flights, with significantly more recorded on morning and afternoon flights, when compared to those conducted at midday. Flights on weekends/public holidays also recorded more fishers than weekdays. The spatial distribution of fishers was variable along the coast, with sandy beaches at the northern and southern sections of the study area having high counts of fishers, along with groynes in the central section. Comparisons with the previous (autumn) study revealed that the northern beaches generally had higher numbers of shore-based fishers in summer, while those in the south had more during autumn. Data from this study assists with understanding the patterns of shore-based recreational fishing occurring along the greater Perth Metropolitan coast. Such information can be used to assist in the design of future on-ground surveys, compliance and education activities

    Dissociation of Subjectively Reported and Behaviorally Indexed Mind Wandering by EEG Rhythmic Activity

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    Inattention to current activity is ubiquitous in everyday situations. Mind wandering is an example of such a state, and its related brain areas have been examined in the literature. However, there is no clear evidence regarding neural rhythmic activities linked to mind wandering. Using a vigilance task with thought sampling and electroencephalography recording, the current study simultaneously examined neural oscillatory activities related to subjectively reported and behaviorally indexed mind wandering. By implementing time-frequency analysis, we found that subjectively reported mind wandering, relative to behaviorally indexed, showed increased gamma band activity at bilateral frontal-central areas. By means of beamformer source imaging, we found subjectively reported mind wandering within the gamma band to be characterized by increased activation in bilateral frontal cortices, supplemental motor area, paracentral cortex and right inferior temporal cortex in comparison to behaviorally indexed mind wandering. These findings dissociate subjectively reported and behaviorally indexed mind wandering and suggest that a higher degree of executive control processes are engaged in subjectively reported mind wandering
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