7,618 research outputs found
Interplanetary Coronal Mass Ejections observed by MESSENGER and Venus Express
Interplanetary coronal mass ejections (ICMEs) observed by the MESSENGER (MES)
and Venus Express (VEX) spacecraft have been catalogued and analysed. The ICMEs
were identified by a relatively smooth rotation of the magnetic field direction
consistent with a flux rope structure, coinciding with a relatively enhanced
magnetic field strength. A total of 35 ICMEs were found in the surveyed MES
data (primarily from March 2007 to April 2012), and 84 ICMEs in the surveyed
VEX data (from May 2006 to December 2013). The ICME flux rope configurations
have been determined. Ropes with northward leading edges were about four times
more common than ropes with southward leading edges, in agreement with a
previously established solar cycle dependence. Ropes with low inclinations to
the solar equatorial plane were about four times more common than ropes with
high inclinations, possibly an observational effect. Left and right-handed
ropes were observed in almost equal numbers. In addition, data from MES, VEX,
STEREO-A, STEREO-B and ACE were examined for multipoint signatures of the
catalogued ICMEs. For spacecraft separations below 15{\deg} in heliocentric
longitude, the second spacecraft observed the ICME flux rope in 82% of cases;
this percentage dropped to 49% for separations between 15 and 30{\deg}, to 18%
for separations between 30 and 45{\deg}, and to 12% for separations between 45
and 60{\deg}. As spacecraft separation increased, it became increasingly likely
that only the sheath and not the flux rope of the ICME was observed, in
agreement with the notion that ICME flux ropes are smaller in longitudinal
extent than the shocks or discontinuities that they often drive. Furthermore,
this study has identified 23 ICMEs observed by pairs of spacecraft close to
radial alignment. A detailed analysis of these events could lead to a better
understanding of how ICMEs evolve during propagation.Comment: 28 pages, 7 figure
A Method for Modeling Low-Probability, High- Consequence Risk Events: Vessel Traffic on the Lower Mississippi River
[Excerpt] A variety of commodities, from chlorine to corn and petroleum to passengers, are transported on the lower Mississippi River regularly. Corn, wheat and coal are the most commonly carried commodities. From a human health and safety perspective, these are relatively benign products in that a vessel accident and spill of these are not directly hazardous to people, whatever other ecological disturbances may ensue. However, over eighty million tons of petroleum products are transported on the river annually. Over a million tons of liquid natural gas traverse the river through the center of New Orleans. Additionally, over 400,000 tons of ammonium nitrate2 pass through the center of Baton Rouge annually. The potential for a technological disaster is certainly present […]
The vast majority of the literature relevant to the question of vessel accident risk concerns the question of on-board causes of vessel accidents. It is assumed that the predictors of which vessel will have an accident are on-board the vessel (i.e., vessel and crew characteristics). The most commonly cited on-board hazards include: the size of the vessel; the age of the vessel; the length of the vessel; whether the vessel is single or double hulled; the maintenance of the vessel; the classification society under which the vessel is registered; the type of ownership; the history of ownership; where the vessel is flagged (i.e., flag of convenience or traditional maritime nation); license qualifications of mates and engineers; the vessel’s casualty history; the vessel’s history of violations; whether the vessel has system (e.g., steering) redundancy; and personnel history (including manning levels and the comparison of the present levels of manning with that of the vessel in the past and with similar type vessels)
Single pilot IFR operating problems determined from accidental data analysis
The accident reports examined were restricted to instrument rated pilots flying in IFR weather. A brief examination was made of accidents which occurred during all phases of flight and which were due to all causes. A detailed examination was made of those accidents which involved a single pilot which occurred during the landing phases of flight, and were due to pilot error. Problem areas found include: (1) landing phase operations especially final approach, (2) pilot weather briefings, (3) night approaches in low IFR weather, (4) below minimum approaches, (5) aircraft icing, (6) imprecise navigation, (7) descending below minimum IFR altitudes, (8) fuel mismanagement, (9) pilot overconfidence, and (10) high pilot workload especially in twins. Some suggested areas of research included: (1) low cost deicing systems, (2) standardized navigation displays, (3) low cost low-altitude warning systems, (4) improved fuel management systems, (5) improved ATC communications, (6) more effective pilot training and experience acquisition methods, and (7) better weather data dissemination techniques
The Library Movement in British Columbia
"In reviewing the earliest library movement in British Columbia one must cast his mind back to the days when the western portion of British North America was little more than a huge fur reserve, and the only contact with civilization was through the fur trading posts scattered at great distances throughout this vast territory. The Hudson's Bay Company had so-called libraries at all their district offices, the size of the library depending largely on the situation of these small communities.
Relation of modifiable neighborhood attributes to walking
Abstract Background There is a paucity of research examining associations between walking and environmental attributes that are more modifiable in the short term, such as car parking availability, access to transit, neighborhood traffic, walkways and trails, and sidewalks. Methods Adults were recruited between April 2004 and September 2006 in the Minneapolis-St Paul metropolitan area and in Montgomery County, Maryland using similar research designs in the two locations. Self-reported and objective environmental measures were calculated for participants\u27 neighborhoods. Self-reported physical activity was collected through the long form of the International Physical Activity Questionnaire (IPAQ-LF). Generalized estimating equations were used to examine adjusted associations between environmental measures and transport and overall walking. Results Participants (n = 887) averaged 47 years of age (SD = 13.65) and reported 67 min/week (SD = 121.21) of transport walking and 159 min/week (SD = 187.85) of non-occupational walking. Perceived car parking difficulty was positively related to higher levels of transport walking (OR 1.41, 95%CI: 1.18, 1.69) and overall walking (OR 1.18, 95%CI: 1.02, 1.37). Self-reported ease of walking to a transit stop was negatively associated with transport walking (OR 0.86, 95%CI: 0.76, 0.97), but this relationship was moderated by perceived access to destinations. Walking to transit also was related to non-occupational walking (OR 0.85, 95%CI: 0.73, 0.99). Conclusions Parking difficulty and perceived ease of access to transit are modifiable neighborhood characteristics associated with self-reported walking
Reliability Testing of the PABS (Pedestrian and Bicycling Survey) Method
The Pedestrian and Bicycling Survey (PABS) is a questionnaire designed to be economical and straightforward to administer so that it can be used by local governments interested in measuring the amount and purposes of walking and cycling in their communities. In addition, it captures key sociodemographic characteristics of those participating in these activities. Methods: In 2009 and 2010 results from the 4-page mail-out/mail-back PABS were tested for reliability across 2 administrations (test-retest reliability). Two versions--early and refined--were tested separately with 2 independent groups of university students from 4 universities (N = 100 in group 1; N = 87 in group 2). Administrations were 7 to 9 days apart. Results: Almost all survey questions achieved adequate to excellent reliability. Conclusions: Transportation surveys have not typically been tested for reliability making the PABS questionnaire an important new option for improving information collection about travel behavior, particularly walking and cycling
The Sociologist As Mitigation Expert In First Degree Murder Cases
This paper describes the experiences of a sociologist as a mitigation expert during the typical first degree murder case, from indictment through the penalty phase of the trial. The author, who has worked in death penalty cases (capital murder) since 1988, has served as a mitigation expert in over 40 such cases. Topics covered include: working with a death penalty mitigation team and what to expect; interviewing the client, family members and others significant to the defense; making a genogram; making a time line of the client\u27s life; preparing for trial; and the style and content of your testimony and getting qualified
A Penalty Method for the Numerical Solution of Hamilton-Jacobi-Bellman (HJB) Equations in Finance
We present a simple and easy to implement method for the numerical solution
of a rather general class of Hamilton-Jacobi-Bellman (HJB) equations. In many
cases, the considered problems have only a viscosity solution, to which,
fortunately, many intuitive (e.g. finite difference based) discretisations can
be shown to converge. However, especially when using fully implicit time
stepping schemes with their desirable stability properties, one is still faced
with the considerable task of solving the resulting nonlinear discrete system.
In this paper, we introduce a penalty method which approximates the nonlinear
discrete system to first order in the penalty parameter, and we show that an
iterative scheme can be used to solve the penalised discrete problem in
finitely many steps. We include a number of examples from mathematical finance
for which the described approach yields a rigorous numerical scheme and present
numerical results.Comment: 18 Pages, 4 Figures. This updated version has a slightly more
detailed introduction. In the current form, the paper will appear in SIAM
Journal on Numerical Analysi
Genetic algorithms: a pragmatic, non-parametric approach to exploratory analysis of questionnaires in educational research
Data from a survey to determine student attitudes to their courses are used as an example to show how genetic algorithms can be used in the analysis of questionnaire data. Genetic algorithms provide a means of generating logical rules which predict one variable in a data set by relating it to others. This paper explains the principle underlying genetic algorithms and gives a non-mathematical description of the means by which rules are generated. A commercially available computer program is used to apply genetic algorithms to the survey data. The results are discussed
The Game of Wardens and Poachers
This paper is a descriptive analysis of the main aspect of the job of game wardens, the apprehension of poachers. Based on data from interviews with 62 game wardens the author describes the actions of game wardens in attempting to enforce wildlife conservation laws. Extensive quotations from interviews with game wardens are presented. The analysis is focused around their responses to guiding questions regarding the probability of apprehension of poachers. These include: (1) poaching alone, (2) very experienced at poaching, (3) nevertalks about their poaching activities, (4) the use of informants, (5) remaining mobile, (6) being familiar with the geographic area in which one poaches, and (7) poaching in a large area (not relegated to hunting in a small specific area). The concept folk crime is discussed
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