Departure Period Research Articles

Effects of Horseshoe Crab Harvest in Delaware Bay on Red Knots: Are Harvest Restrictions Working?

Each May, red knots (Calidris canutus rufa) congregate in Delaware Bay during their northward migration to feed on horseshoe crab eggs (Limulus polyphemus) and refuel for breeding in the Arctic. During the 1990s, the Delaware Bay harvest of horseshoe crabs for bait increased 10-fold, leading to a more than 90% decline in the availability of their eggs for knots. The proportion of knots achieving weights of more than 180 grams by 26–28 May, their main departure period, dropped from 0.6–0.8 to 0.14–0.4 over 1997–2007. During the same period, the red knot population stopping in Delaware Bay declined by more than 75%, in part because the annual survival rate of adult knots wintering in Tierra del Fuego declined. Despite restrictions, the 2007 horseshoe crab harvest was still greater than the 1990 harvest, and no recovery of knots was detectable. We propose an adaptive management strategy with recovery goals and annual monitoring that, if adopted, will both allow red knot and horseshoe crab populations to reco...

Travel time unreliability on freeways: Why measures based on variance tell only half the story

In recent years, travel time reliability has become one of the key performance indicators of transportation networks and corridors around the globe. Travel time reliability indicators are mostly related to properties of the day-to-day travel time distribution on for example a freeway corridor. On the basis of empirical data a number of key characteristics of this day-to-day distribution can be identified. Most importantly, this distribution is not only very wide but also heavily skewed. The (economic) consequences of this skew are substantial. For example, it is shown that in some peak periods the 5% most “unlucky drivers” incur almost five times as much delay as the 50% most fortunate travelers. We argue this implies first of all that (besides the variance of travel times) skew must be considered an important contributing factor to travel time unreliability. Secondly, it suggests that most of currently used unreliability measures (which are predominantly based on travel time variance), should be used and interpreted with some reservations, since they only account for a part of the costs (that is, delays) of unreliability. This is further substantiated by a comparison on the basis of empirical data from a densely used freeway in the Netherlands between a new travel time reliability measure based on both width and skew, and a number of travel time reliability measures commonly used in practice. The analysis clearly illustrates the inconsistency between all measures, both old and new. In illustration, in cases where the commonly used misery index dubs a particular departure period very unreliable, another common measure (buffer time) considers these periods relatively reliable. Although without objective and quantitative criteria (e.g. economic or societal costs) a choice for any of these measures in road network performance analyses will remain subject to debate, this article provides empirically underpinned arguments to prefer measures incorporating the skew of the travel time distribution.

Postfledging Dependence Period of Migratory Golden Eagles (Aquila Chrysaetos) in Denali National Park and Preserve, Alaska

Abstract The postfledging dependence period is not well documented for many species of raptors, including Golden Eagles (Aquila chrysaetos). From 1997 to 1999, we used satellite telemetry to estimate the length of the postfledging dependence period, and the finite survival rate of fledglings during that period, for migratory Golden Eagles in Denali National Park and Preserve, Alaska. Length of the postfledging dependence period averaged 50.1 days and ranged from 39 to 63 days. The post- fledging dependence period was longer for Golden Eagles that hatched earlier, but hatching date did not influence the date they departed their natal area. Average date of departure from the natal area was 25 September. The departure period spanned a 17-day period from 15 September to 5 October, and coincided with a series of environmental changes including decreases in day length, temperature, and prey diversity. Probability of survival during the postfledging dependence period was 0.98 (95% CI = 0.94 to 1.00). Período de Dependencia Posterior al Emplumamiento de Aquila chrysaetos en el Parque Nacional y Reserva Denali, Alaska

Flight activity of bats at the entrance of a natural cave

Activity patterns of bats were investigated at the entrance of a natural karstic cave (Kateřinská cave, Czech Republic). The activity was recorded automatically with a double infrared light barrier allowing discrimination between those bats leaving and those entering the cave. Five periods were defined on the basis of bat flight activity: A) Hibernation period (November–late March), with very low activity; B1) Departure period 1 (late March–mid April), with intensive departure during the first quarter of the night; B2) Departure period 2 (mid April–beginning of June), with emergence activity in the first quarter, and a small number of bats entering the cave in the fourth part of the night. The peak of activity was in the second part of the night. C) Summer period (mid June–mid July), with low activity. D) Autumn period (late July–late October), with very high activity and increasing number of bats entering the cave. The peak of activity was around midnight. All periods showed a non-random temporal distribution and a concentration of flight activity around specific time. There was a positive correlation between the number of bat passes through the entrance and outside ambient temperature and a negative correlation between the number of passes and barometric pressure. Rain had no significant effect on the level of bat activity.

Visualization of Bubble Dynamics for Pool Boiling of Binary Refrigerant Mixture R11-R113

A digital photographic study of pool boiling with binary mixture R11(CCl 3)-R113(CCl 3CF 3) was performed on a horizontal transparent heater at pressure of 0.1MPa. A high speed digital camera was applied to record the bubble behaviors in boiling process. Strong effects of composition on bubble departure diameter, departure time, nucleation density were observed, which was attributed to the nature of the activation of the boiling surface and mass diffusion effects. The bubble departure diameter, departure period and nucleation density as functions of composition for binary mixtures R11-R113 were presented respectively. From the video images, it can be concluded that evaporation of microlayer is very important to the growth of bubble. It is also observed that there is not any liquid recruited into the microlayer below the bubble.

POSTFLEDGING DEPENDENCE PERIOD OF MIGRATORY GOLDEN EAGLES (AQUILA CHRYSAETOS) IN DENALI NATIONAL PARK AND PRESERVE, ALASKA

The postfledging dependence period is not well documented for many species of raptors, including Golden Eagles (Aquila chrysaetos). From 1997 to 1999, we used satellite telemetry to estimate the length of the postfledging dependence period, and the finite survival rate of fledglings during that period, for migratory Golden Eagles in Denali National Park and Preserve, Alaska. Length of the postfledging dependence period averaged 50.1 days and ranged from 39 to 63 days. The post- fledging dependence period was longer for Golden Eagles that hatched earlier, but hatching date did not influence the date they departed their natal area. Average date of departure from the natal area was 25 September. The departure period spanned a 17-day period from 15 September to 5 October, and coincided with a series of environmental changes including decreases in day length, temperature, and prey diversity. Probability of survival during the postfledging dependence period was 0.98 (95% CI = 0.94 to 1.00). Período de Dependencia Posterior al Emplumamiento de Aquila chrysaetos en el Parque Nacional y Reserva Denali, Alaska

Subcooled boiling heat transfer and dryout on a constant temperature microheater

An experimental study of single-bubble subcooled boiling heat transfer (Δ T sub=31.5 K) on a small heater with constant wall temperature has been performed to better understand the boiling heat transfer associated with this unique configuration. The heater of 0.27 mm × 0.27 mm is set at different superheats to generate vapor bubbles on the microheater surface. For each superheat, the heater temperature is maintained constant by an electronic feedback control circuit while its power dissipation is measured at a frequency of 4.5 kHz. The single-bubble boiling is characterized by a transient bubble nucleation–departure period and a slow growth period. For the superheat range of 34–114 K in this study, at wall superheats below 84 K, the heater remains partially wetted following bubble departure and subsequent nucleation, and this period is characterized by a heat flux spike. At wall superheats above 90 K, the heater is blanketed with vapor following bubble departure and the heat flux experiences a dip during this period. At all superheats, the slow growth period is characterized by an almost uniform heat flux, and it has been observed that the heater surface is mostly covered by vapor. The unique heat transfer processes associated with boiling on this microheater are considerably different than those typically observed during boiling on a large heater.

Stomach Contents of Breeding Common Murres Caught in Gillnets off Newfoundland

Abstract We examined the stomach contents of 64 male and 43 female Common Murres (Uria aalge) caught in gillnets during late chick rearing/early chick departure period in August 2002 near breeding colonies in Witless Bay, Newfoundland, Canada. Twenty-six percent of stomachs contained no food. All others contained exclusively fish, and Capelin (Mallotus villosus) was the only fish positively identified. Gravid female Capelin were found in 82% of murre stomachs with contents. The number of fish ingested by murres differed between the sexes, with a mean of 2.7 fish in male stomachs and 1.6 fish in female stomachs. Mean mass of stomach contents did not differ between the sexes (males: 27.0 g; females: 22.6 g). Overall, results were similar to Common Murre diets recorded in the 1980s, despite changes in Capelin distribution and biology. The sample of Common Murres collected as gillnet bycatch was male-biased (59%). Males may have been more vulnerable to being caught in gillnets, perhaps because they were engag...

Enhancement of Bubble Departure and Critical Heat Flux in Saturated Pool Boiling under Microgravity Conditions.

All the correlations and analytical models of critical heat flux in saturated pool boiling predict that the critical heat flux under microgravity conditions becomes much smaller than the terrestrial value. In the present paper, aiming at the enhancement of the critical heat flux under microgravity conditions, a novel technique to shorten the bubble departure period τd in saturated pool boiling under microgravity conditions was proposed. The technique proposed is based on the self round-off motion of bubbles induced by surface tension. Such self round-off motion is expected to occur by setting ribs of an asdequate height on the boiling surface. In the present experiment, to realize and simulate such a boiling system, saturated boiling experiments were conducted using a ribbon heater sandwiched by two glass plates. In the experiments, the glass plate height H was changed from 0.5mm to 20mm. Experimental data under microgravity conditions indicate the following results. In the cases of H=0.5-4.5mm, the bubble departure period of ethanol under microgravity conditions is as short as the terrestrial value and then the critical heat flux is as high as the terrestrial value. The critical heat flux is caused when the value of τdq reaches a maximum. The equivalent liquid-film thickness calculated from the experimental data of τdq is much smaller than the macrolayer thickness calculated from the model proposed by Haramura and Katto.

Development of Methods To Estimate Unobserved Link Flows and Their Application to the Amsterdam Orbital Motorway

To monitor highway network performance, environmental impacts, and congestion levels, highway authorities maintain statistics on traffic volumes. A typical aggregation level of such statistics is 1 h, and a distinction is made between month and type of day. Traffic volumes usually are observed directly for only part of the network. For the remaining part of the network, these time-dependent traffic volumes need to be estimated using time-dependent traffic data and additional static information, such as trip tables. Six estimation methods are discussed. These methods are characterized by the selection of data used, the assumptions on interdependencies between origin-destination (O-D) demands they represent, and their estimation mechanisms. A methodological novelty is in the modeling of the correlation between errors contained in the O-D cells of the prior matrix in case of common departure period, origin, or destination. All methods were verified and analyzed using synthetic data. Experiments with empirical data from the Amsterdam Orbital Motorway show that, for all methods, bias is the main source of error. This problem can be remedied by collecting and using appropriately aggregated data. Experiments also show improved estimation results for methods that take into account a correlated error structure for the prior O-D matrix.

The timing and departure rate of larvae of the warble fly Hypoderma (= Oedemagena) tarandi (L.) and the nose bot fly Cephenemyia trompe (Modeer) (Diptera: Oestridae) from reindeer

The emergence of larvae of the reindeer warble fly Hypoderma (= Oedemagena) tarandi (L.) (n = 2205) from 4, 9, 3, 6 and 5 Norwegian semi-domestic reindeer yearlings (Rangifer tarandus tarandus (L.)) was registered in 1988, 1989, 1990, 1991 and 1992, respectively. Larvae of the reindeer nose bot fly Cephenemyia trompe (Moder) (n = 261) were recorded during the years 1990, 1991 and 1992 from the same reindeer. A collection cape technique (only H. tarandi) and a grating technique (both species) were used. In both species, dropping started around 20 Apr and ended 20 June. Peak emergence occurred from 10 May - 10 June, and was usually bimodal. The temperature during the larvae departure period had a slight effect (significant only in 1991) on the dropping rate of H. tarandi larvae, and temperature during infection in the preceding summer is therefore supposed to explain the uneven dropping rate. This appeared to be due to the occurrence of successive periods of infection caused by separate periods of weather that were favourable for mass attacks by the flies. As a result, the temporal pattern of maturation of larvae was divided into distinct pulses. Departure time of the larvae in relation to spring migration of the reindeer influences infection levels. Applied possibilities for biological control by separating the reindeer from the dropping sites are discussed.

Growth and dissipation of a traffic jam

IN THIS paper a mathematical method for analysing a highway traffic jam is formulated. While the problem of describing a traffic jam is related to several aspects of the theory of traffic flow (intersections, car-following and hydrodynamical theories in particular) it does not seem to have been considered explicitly in the literature to date, and this paper is an attempt to fill the gap. The method is also interesting in its own right as a generalization of the M/G/l queueing situation, the main extension being that the vehicles are assumed to have finite, variable lengths, so that the traffic jam queue changes in both position and length with the passage of time. We also assume that the vehicle causing the jam has a “departure period” which has a different distribution to that of the succeeding vehicles. Having formulated the situation mathematically, we study various random variables which are of interest. Whereas writers in queueing theory have studied the distribution of individual customer waiting times, a quantity of greater importance in traffic theory is the total delay to all vehicles, since this is directly related to the financial cost of the traffic jam. This variable may be expressed as the integral of a stochastic process, and by imbedding a Markov chain in this process the expected total wait is obtained. Other variables of interest include the jam duration, the number of vehicles delayed and the spatial displacement, and distributions of these quantities are found. Some of the methods of queueing theory carry over with slight generalizations, while in some cases a new type of analysis is required. Some of the results were obtained under less general conditions by Jewel1 (1964).

Observation of roosting flight numbers of the House Swallow from post-breeding to departure period

Number of House Swallows Hirundo rustica (gutturalis) was counted on their rout of roosting flight through a same window-mesh during post-breeding and departure period in three seasons, 1959, 1960 and 1961, in Saga, Kiushiu.The roosting flight was direct and low and began from 90 minutes (with the peak 30-15 min.) before sunset and with seasonal peak in September towards the end of which month they departed. The numbers were greater on fine calm days and markedly dropped when disturbed by typhoons.This roosting flight seems to have been established after the use of insecticides on the plain, since the swallows now mostly move to the hill-side for the day feeding to return to the roost of low land in the evening.