1,247 research outputs found
Dirty Recycling: Auto Salvage and Its Potential Impacts on Marginalized Populations
The salvage yard represents the final waypoint in the cradle-to-grave cycle of the automobile. Residual amounts of petroleum hydrocarbons, heavy metals, and acids used in automobiles can be extremely harmful to human health and the environment if not managed correctly. The purpose of this study was to assess the extent to which minority populations were exposed to the hazards of the auto salvage industry. Census data for population, income, race/ethnicity, sex, and age were organized using ArcGIS software. Population demographics were analyzed in the areas surrounding 98 auto salvage yards found in Philadelphia and Adams Counties, Pennsylvania. In Philadelphia County, the results showed that low-income minorities, females, and 65+ individuals are over represented groups near auto salvage yards. Conversely, Adams County showed few spatial relationships in demographic distribution. Our findings suggest that in urban counties, such as Philadelphia, depressed property values have resulted in a large percentage of below average income minorities inhabiting areas in close proximity to auto salvage yards. On the other hand, auto salvage yards in rural areas, such as Adams County, do not appear to have the same effect because population density and racial diversity are much lower
Student team projects and natural resources education: Are we achieving educational objectives?
As college instructors have recognized the benefits provided by cooperative and active learning, many have shifted from their traditional teaching style, dominated by lectures, to a new style where students work together and learn from each other as well as from the instructor. One strategy commonly used to implement cooperative learning in the classroom is to require students to work in teams to complete a class project. This strategy is particularly attractive to natural resources educators because natural resource issues are generally complex and interdisciplinary providing a natural setting for teaching concepts regarding natural resources ecology and management using student team projects. Further, natural resources agencies are seeking to employ individuals who have the skills to work in interdisciplinary teams to address current problems. Thus, assigning projects to student teams in natural resources classes can serve several important purposes: it can aid student mastery of the subject matter by creating a cooperative learning environment; it can provide a hands-on, problem solving context for student learning; and it can provide students with the necessary skills and experience to work effectively in teams as professionals. Although using student team projects has many potential benefits, the effectiveness of this approach as a teaching tool can vary greatly. We reflect on our experiences with using the team approach in three different courses: Fishery Management, designed for junior and senior level students; Natural Resources Decisions, a capstone course designed for seniors in the School of Forest Resources; and Watershed Management Planning, a graduate level course. As a result of our collective experiences in these three courses, we propose that investing a relatively small amount of class time to introduce students to the concept of a team and how teams work can increase the effectiveness of teaching by using student team projects
Natural Circulation in the ATUCHA-I PHWR Nuclear Power Plant
A systematic study of natural circulation (NC) in a postulated, varying primary mass inventory
scenario at residual power fractions has been performed for a nuclear power plant operating in
Argentina. It is a pressurized heavy water reactor, cooled and moderated by heavy water. The analysis
seems particularly relevant at present, because a second nuclear power plant (NPP), of similar design
and nearly 745 MWe, is now under finalization. NRC-RELAP5/MOD3.3 was the code used to
perform the simulations. Results obtained are presented in the form of natural circulation flow maps.
The trends obtained fit in the expected limits for integral test facilities representative of PWRs. In
addition, the validity of a simplified analysis to scale single and two-phase core flow has been verified.
A set of constants has been obtained, which permits predicting NC core mass flow rate (CMFR) for
this NPP. Results are partially validated, for single-phase NC flow, using a documented plant transient,
showing reasonable agreement. Also, the effect of pressurizer size on the predicted evolution curve in
the NC flow map (NCFM) is discussed
Experimental investigation on a geocontainer Submerged reef
Geotextile sand containers (GSC) have been used as permanent construction elements in coastal works for more than 20 years,becoming more and more popular as an alternative to the most typical coastal structures. Aim of this work is to analyze the hydrodynamic, stability and morphodynamic response of a GSC submerged reef by means of an experimental campaign. The first investigated aspect concerned the hydrodynamics. The reflection and transmission coefficients for regular and random waves were determined: the reflection coefficient decreases with increasing of kh; the transmission coefficient decreases with the increase of the incident wave. As regards the stability of the structure, it was observed that the strongest waves were able to lift the row of GSC more exposed to the wave action. An instability curve for the GSC as a function of the hydrodynamic characteristics was then found. Flow visualization close to the reef was performed by means of ink, showing that the flow becomes asymmetric in the proximity of the structure. Concerning the morphodynamics, long-term tests were performed to calculate the scour. This reached its maximum value at the end of each test and it is present in all three cases. The scour causes serious problems of instability to the structure
Confronto fra valutazioni del run-up fatte con un modello matematico e una formula empirica con misure di campo
La posizione planimetrica della linea di riva, soli
tamente, viene determinata
attraverso l\u2019uso di immagini aeree ed utilizzata pe
r la ricostruzione dell\u2019evoluzione
storica dei litorali. Tuttavia, le informazioni est
ratte da tali immagini, descrivendo il
confine istantaneo acqua-terra, consentono l\u2019indivi
duazione della linea di riva
esclusivamente come limite asciutto-bagnato proprio
nel momento della ripresa. Per
una pi\uf9 corretta localizzazione della linea di riva
, \ue8 quindi necessario quantificare,
oltre agli effetti di marea e di trasporto solido,
gli effetti prodotti dal moto ondoso
su tale posizione e in particolare il cosiddetto ru
n-up.
Nel presente lavoro si studia il run-up in una spia
ggia naturale a debole pendenza
ricadente nella Sicilia occidentale. Lo studio geom
orfologico del sito precede lo
studio idraulico, che partendo dalle misure di onde
al largo, attraverso la loro
trasposizione e la propagazione simulata con un mod
ello matematico, porta alla
stima delle onde sotto costa. Queste ultime sono ut
ilizzate per valutare il run-up sia
mediante una nota formula empirica sia utilizzando
un modello numerico alla
Boussinesq con una nuova condizione al contorno per
la linea di riva. Il confronto
dei risultati con le misure di campo mostra che i r
isultati migliori si ottengono con
la formula empirica, nella quale \ue8 tuttavia necessa
rio calibrare i coefficienti con
misure in situ
Random Wave Run-up with a Physically-based Lagrangian Shoreline Model
AbstractIn the present paper the run-up of random waves was calculated by means of a numerical method. In situ measurements based on a video imaging technique have been used for the validation of the present numerical model. The on-site run-up measurements have been carried out at Lido Signorino beach, near Marsala, Italy,along a transect, normal to the shore. A video camera and a linear array of rods have been used to obtain field data. Numerical simulations with a 1DH Boussinesq-type of model for breaking waves which takes into account the wave run-up by means of a Lagrangian shoreline model have been carried out. In such simulations random waves of given spectrum have been propagated in a numerical flume having the same beach slope of the measured transect. The comparison between registered and estimated run-up underlined an acceptable agreement. Indeed, the numerical model tends to underestimate the actual R2%, with the maximum underestimate being less than 24%, which is a reasonable error in many cases of engineering interest
Particle tracking in a gap of aquatic vegetation meadow
Aquatic vegetation considerably affects the flow field in water bodies, with influence increasing as the depth decreases. As a consequence, vegetation also affects suspended particle transport. In inshore sandy beds less than 40 m deep of the Mediterranean Sea, meadows of Posidonia oceanica are widespread. This plant is constituted by a tuft of very thin and flexible ribbon-like leaves about 1 cm wide and up to 1.5 m long; the meadow areal density can reach 1000-1200 plant/m2. Frequently, such meadows are not continuous but vegetated areas alternate with sand strips (“gaps”). The presence of such discontinuities noticeably affects the flow field and gaps can actually act as particle traps. Some laboratory experiments were performed aiming at studying the flow field in a gap of artificial Posidonia oceanica canopy. In this paper, the measured flow field is used to track single particles within the gap. A simple particle tracking model which assumes no-slip condition and random velocity fluctuations is adopted. A large number of single-particle tracking were performed considering several release elevations of particles as well as several falling velocities of the latters. The examination of the whole tracks allows one to recognize the particle fate as the simulation parameters vary. In spite of the model assumptions, the study gives useful indications on the behavior of a gap towards the suspended particle transport
Spatial entanglement and state engineering via four-photon Hong-Ou-Mandel interference
The phenomenon of entanglement is the basis of quantum information and
quantum communication processes. Entangled systems with a large number of
photons are of great interest at present because they provide a platform for
streaming technologies based on photonics. In this paper we present a device
which operates with four-photons and based on the Hong-Ou-Mandel (HOM)
interference. The presented device allows to maximize the degree of spatial
entanglement and generate the highly entangled four-dimensional Bell states.
Furthermore, the use of the interferometer in different regimes leads to fast
interference fringes in the coincidence probability with period of oscillations
twice smaller than the pump wavelength. We have a good agreement between
theoretical simulations and experimental results.Comment: 20 pages, 7 figur
Aerobic Training Affects Fatty Acid Composition of Erythrocyte Membranes
The effect of exercise training on the fatty acid composition of erythrocyte membranes was evaluated in an experimental animal model where rats were subjected to a ten-wk aerobic training. Five groups of rats were compared: sedentary rats at 19 or 23 wks of age, rats trained at moderate or high intensity sacrificed at 19 wks of age, and rats trained at high intensity, and sacrificed following 4 weeks of sedentary life. We had already demonstrated that cardioprotection correlates with training intensity and partially persists in detrained rats. Main findings are that rats trained at higher intensity display consistent signs of lipid peroxidation but a lower ω6/ω3 ratio and a lower content of trans fatty acids when compared to rats trained at lower intensity and to older sedentary rats. Trans fatty acids negatively affect cell membrane fluidity and permeability. Detrained rats showed intermediate values. Gene expression evaluation of selected enzymes involved in lipid biosynthesis revealed some of the adaptive mechanisms leading to the maintenance of membrane fatty acid homeostasis following exercise. The decrease in the amount of trans fatty and in the inflammatory pathways (i.e. ω6/ω3 ratio) in high-intensity trained rats underscores the protective effect of high intensity aerobic training
- …