Entrance Widths Research Articles

Multi structural parameter analysis based on the labyrinth valve design with high pressure drop and low noise

Labyrinth channel design is a key for achieving high pressure loss for the labyrinth valve in a thermal power plant. However, the labyrinth channel structures are relatively complex, with many influencing parameters. An unreasonable design generates high noise, adversely affecting personnel and equipment. In this paper, pressure drop is used as a typical parameter for evaluating pressure loss performance, while cavitation, flow velocity, and transmission loss are used as characteristic parameters for assessing noise performance. A comprehensive evaluation criteria of noise performance is constructed. The numerical models with various stage numbers, entrance widths, channel depths, transition part parameters, and expansion coefficients are established, the effects of different structural parameters on the labyrinth channel pressure loss and noise performance are systematically studied to achieve a labyrinth valve design with high pressure loss and low noise. The results show that the influence of different structural parameters on the labyrinth channel pressure loss and noise performance is not the same. The parameter selection of multi-stage, small entrance width, medium channel depth, large transition part parameters, and high expansion coefficient is important way for realizing the design of high pressure loss and low noise labyrinth valve.

Examination of Hacking and Blunt Force Skeletal Trauma.

Hacking trauma is prevalent in forensic cases involving genocide and dismemberment, but research into the identification of this type of trauma is lacking. The present study examines characteristics of hacking and blunt force skeletal trauma in order to determine if there is a point at which blunt force trauma becomes distinguishable from hacking trauma. Ten implements with a range of blade angles (i.e., the striking surface of the implement) were used in conjunction with a controlled-force hacking device to impact 100 limb bones of white-tailed deer (Odocoileus virginianus). Observations of the trauma included the occurrence and degree of fragmentation, the entrance widths of the impacts, and composite scores of six hacking characteristics, especially the distinctive V-shaped kerf. ANOVA tests and regression analyses were used to assess the relationships between these characteristics and the blade angles. A significant relationship (p-value = 0.011) was found between the composite hacking scores and the blade angles, indicating that blunt force and hacking trauma can be distinguished. The entrance widths of the impacts exhibited a significant relationship with the blade angles (p-value = 0.037). There was also a significant relationship between the visibility of a V-shaped kerf in the bones (p-value = 0.003), with visibility decreasing around the 60° blade angle. These data should assist in establishing guidelines to differentiate hacking and blunt force skeletal trauma in cases where the implement is on a spectrum between sharp and blunt.

Influence of Evacuation Walkway Design Parameters on Passenger Evacuation Time along Elevated Rail Transit Lines Using a Multi-Agent Simulation

Passenger evacuation on elevated railway lines has always been an important issue for elevated rail transit safety management, because it is challenging to evacuate passengers efficiently in the event of man-made calamities and natural disasters. Therefore, an evacuation walkway has been designed as a primary solution to assist passenger evacuation during an emergency on elevated rail transit lines. However, investigations on how evacuation walkway designs influence passenger evacuation time are still limited. This study established two evacuation scenarios of interval evacuation on elevated rail transit lines and put forward a new evacuation time measurement method, based on the concept of ‘evacuation time for passengers leaving the evacuation walkway risk zone’. Then, the evacuation time for 90 combinations of entrance widths and walkway widths was simulated by a multi-agent evacuation simulator, Pathfinder, considering 1032 passengers being evacuated both unidirectionally and bidirectionally. The results show that the entrance width and walkway width have a combined effect on passenger evacuation time. An increase in the walkway width from 0.7 m to 1.5 m may potentially reduce the evacuation time by 54.5% in unidirectional evacuation, and 35.2% in bidirectional evacuation. An increase in the entrance width results in a noticeable evacuation time fluctuation when the walkway width is 0.7 and 0.8 m for both evacuation scenarios, while in a bidirectional evacuation, a noticeable fluctuation also can be observed when the walkway width is within the range of 1.4–1.5 m. According to the study, a potentially good design parameter combination for a newly built evacuation walkway is 1.3 m and 1.4 m for the walkway width and entrance width, respectively. The findings from this study may provide a useful reference in the optimization of the design of evacuation facilities and improvement of passenger evacuation safety in rail transit systems.

Extended phenotypes and foraging restrictions: ant nest entrances and resource ingress in leaf‐cutting ants

AbstractSeveral factors may restrict the acquisition of food to below the levels predicted by the optimization theory. However, how the design of structures that animals build for foraging restricts the entry of food is less known. Using scaling relationships, we determined whether the design of the entrances of leaf‐cutting ant nests restricts resource input into the colony. We measured nests and foraging parameters in 25 nests of Atta cephalotes in a tropical rain forest. Ant flux was reduced to up to 60% at nest entrances. The width of all entrances per nest increased at similar rates as nest size, but the width of nest entrances increased with the width of its associated trail at rates below those expected by isometry. The fact that entrance widths grow slower than trail widths suggests that the enlargement of entrance holes does not reach the dimensions needed to avoid delays when foraging rates are high and loads are big. The enlargement of nest entrances appears to be restricted by the digging effort required to enlarge nest tunnels and by increments in the risk of inundation, predator/parasitoid attacks and microclimate imbalances inside the nest. The design of the extended phenotypes can also restrict the ingress of food into the organisms, offering additional evidence to better understand eventual controversies between empirical data and the foraging theory.Abstract in Spanish is available with online material.

The influence of radial entrance width of the circular cavity on incident shock wave focusing

Despite the achievement of shock wave focusing with certain reflectors, the influence of the radial entrance width of a circular cavity on the flow field has yet to be addressed. In this study, we systematically investigated the effects of the shock wave focusing process in a cavity based on the radial entrance widths. An experimental system was installed to research the evolution of the flow field under conditions with different radial entrance widths of 3.0, 11.1, 19.5, and 33.0 mm. A schlieren system was used to photograph the structures of the flow field in the cavity, and a data acquisition system was used to record the dynamic pressure histories of different points. A numerical simulation was carried out to investigate greater details of the shock wave focusing process. A third-order strong stability-preserving Runge-Kutta method, third-order weighed essential non-oscillation scheme, and an adaptive mesh refinement algorithm were adopted to simulate the shock wave reflection, diffraction, and focus process. Good agreement between the experimental and numerical results was observed. By comparing the evolution process of the flow field under the conditions of four different entrance cavity widths, we found that when the entrance width was 19.5 mm, there was the stronger intensity of the shock wave focusing in the focal region, and the larger pressure value at the apex of the cavity than the other three entrance widths, occur. This study improves our understanding of shock wave focusing.

STUDY OF AUXILIARY GAS PRESSURE ON LASER CUTTING TECHNOLOGY

Two types of electrical sheet steel M250-35A and M530-50A were used to cut by melting with a TruLaser 1030 technological system. It was observed that pressure of auxiliary gas had a major effect on kerf width b and cut angle deviation α. Nitrogen as an assisted gas has been taken. The basic parameters as laser power, cutting speed, focus position were constantly supported and the pressure was changed from 4 bar to 20 bar by step 2 bar. As well as the experimental results of gas pressure on entrance and exit kerf widths, have been analyzed and discussed in this study.

Lophozonia tree cavities used for nesting by Slender-billed Parakeets (Enicognathus leptorhynchus) in the central valley of southern Chile: a potentially vanishing keystone resource

BackgroundThe Slender-billed Parakeet (Enicognathus leptorhynchus) is a psittacine endemic to southern Chile and an obligate secondary cavity-nester. In the central valley of southern Chile, most (94%) of the known Slender-billed Parakeet nests have occurred in large, mature southern beech (Lophozonia obliqua) trees (locally known as “pellines”). As relicts of the original old-growth forests of southern Chile, most pellines have been lost due to extensive land-clearing throughout the region, potentially threatening long-term persistence of the Slender-billed Parakeet.MethodsWe conducted our study in the central valley of southern Chile, near the city of Osorno during three consecutive nesting seasons (November–January, 2008–2011). Nest trees used by Slender-billed Parakeets were located by direct observation of parakeet activities and through interviews with local residents, some of whom were former parrot nest poachers. Nest cavities were accessed, inspected and measured using single-rope climbing techniques. We report means, standard errors, 95% confidence intervals and ranges for 11 cavity-related variables. We also report clutch sizes encountered in active nests, and age estimates of nest trees based on known growth rates of Lophozonia trees in southern Chile. Linear regressions were used to evaluate potential relationships between cavity-related variables and clutch size.ResultsWe located and measured 38 Lophozonia tree cavities used for nesting by Slender-billed Parakeets. Compared to those used by other psittacines, nest trees were relatively large, averaging 30.4 ± 1.1 m in height with a mean diameter at breast height of 134.5 ± 4.7 cm. Based on estimated annual diameter increment, ages of nest trees ranged from approximately 209–485 years. Nest cavities entrances averaged 12.5 ± 0.9 m in height above ground level. Cavity entrance widths averaged 51.0 ± 13.3 cm (vertical) by 11.5 ± 0.7 cm (horizontal). Cavity entrance orientations were apparently random, with no directional preferences detected. Nest cavities were also relatively large, with a mean internal diameter of 39.6 ± 2.4 cm and mean depth of 90.3 ± 24.2 cm. Clutch sizes (2–9) were unusually large for psittacines of this size (ca. 280–300 g) and broods of up to seven well-developed nestlings were observed.ConclusionsWe found that the deep and spacious cavities provided by pellines facilitate successful rearing of large broods, thereby maximizing productivity and fitness. The existence of pellines has apparently allowed Slender-billed Parakeets to adapt successfully to a wholesale loss of ancestral habitat to anthropogenic modifications. Immediate and strategic conservation measures, such as protection of existing pellines and the regeneration and recruitment of additional ones, are recommended for ensuring the survival of Slender-billed Parakeet populations throughout the central valley of southern Chile.

Experimental and numerical analysis of a parabolic reflector with a radiant heat source

Parabolic heaters, each consisting of a radiant heat source with a parabolic reflector, are used in engineering fields. Although a parabolic heater theoretically heats a target area at the same temperature, temperature distribution is made on the target area in engineered conditions. However, experimental and numerical analyses of parabolic heaters have not been properly conducted. In this work, three types of parabolic heaters with different entrance widths were made and used in the heating experiment. The results of the experiment shows that the temperature distribution is affected by the entrance width of the parabolic reflector. In order to simulate the performance of the parabolic heaters, a numerical model for the simulation of the parabolic reflectors was proposed. The results of finite element simulation using the proposed model were compared with the experimental results. The comparison has validated the usefulness of the numerical model.

Promoting siltation effects and impacts of Hengsha East Shoal on the Yangtze River Estuary

For the Hengsha East Shoal Promoting Siltation Project in the Yangtze River Estuary, this work developed a formula for calculating sediment carrying capacity based on variable coefficients and a mathematical model for suspended sedimentation using variable saturation recovery coefficients. Not only does the model yield good verification, preferably give the hydrodynamics and the sediment concentration, but also reach a good agreement between the simulation results and the measured topographical changes in the promoting siltation zone of the Hengsha East Shoal. Moreover, this article proposes a method for examing the net sediment transportation flux by tide for studying the effects of the project of promoting siltation and comparatively analyzes the current siltation of the Hengsha East Shoal and siltation mouth layouts, entrance widths, entrance bottom elevations, and the impact of the South Main Dike on promoting siltation through calculating the net sediment transportation flux by tide over the fixed bed and the direct movable bed numerical simulations. The results are in good agreement with each other, indicating that the method for calculating the net sediment transportation flux by the tide is also useful for assessing the project in promoting siltation. Finally, we use the modeling results to analyze the water and sediment diversion ratios and the changes in silting and scouring in riverbeds and draw the conclusion that the completion of the Hengsha East Shoal Promoting Siltation Project would not adversely affect the Yangtze River Estuary Deepwater Channel Project.

Hollow selection by vertebrate fauna in forests of southeastern Australia and implications for forest management

We examined the types of hollows, and types of hollow-bearing trees, occupied by vertebrate fauna in temperate eucalypt forests in southeastern Australia. Hollow-bearing trees are selected for retention in wood production forests to mitigate the effects of logging on hole-nesting fauna. A total of 471 hollows was examined in 228 trees felled as part of routine logging operations. Fauna had occupied 43% of all hollows (⩾2cm minimum entrance width; ⩾5cm depth). Hollows with small (2–5cm), medium (6–10cm) and large (>10cm) minimum entrance widths had occupancy rates of 29, 44 and 62%, respectively. The internal dimensions of hollows, especially hollow depth, were the best predictors of hollow occupancy, even when variables measured at the tree and site levels were considered. Fauna occupied 57% of all hollow-bearing trees. In a Poisson regression model, the number of hollows in trees that contained evidence of occupancy was positively associated with: (1) the total number of hollows visible in the tree; (2) the proportion of the tree's crown that contained dead branches; and (3) tree diameter. The number of different vertebrate species that occupied trees was positively associated with the same explanatory variables except tree diameter. Thus, our results suggest that trees with multiple hollows and dead branches in the crown should be preferentially selected for occupancy by hollow-using fauna. Our results suggest that trees with the largest diameter are not the most suitable for retention. Possibly because they contain proportionally fewer hollows with small entrances, which are favoured by some vertebrate species.

Nest-Site Characteristics, Reproductive Success and Cavity Availability for Tree Swallows Breeding in Natural Cavities

We examined 10 characteristics of natural cavities and their influence on reproductive success of Tree Swallows (Tachycineta bicolor) nesting in dead trees in beaver ponds. Large ranges were found for entrance height and area, cavity volume, and nearness to shore of nest sites. Other characteristics were less variable: 46% of cavities were less than 2 m above the pond surface, and 48% had entrance widths of 4-5 cm. Tree Swallow nest sites were uniformly dispersed in the ponds. Two cavity characteristics, cavity height and floor area, influenced reproductive success. Lower nest sites were more frequently preyed on and females laid larger clutches in cavities with a large floor area. Five species larger than Tree Swallows used cavities during the study. Girth of the snag at the base and at the cavity, entrance width, and cavity volume were significantly greater at sites used by these species than those used by Tree Swallows. Nest sites suitable for breeding did not appear to be limiting to Tree Swallows, because characteristics of unused cavities did not differ from those used by Tree Swallows and other species. Intraspecific territoriality was likely responsible for the large number of unused cavities in our populations. Other factors influencing cavity availability in our sites include interspecific competition, predation, snag fall, and continuing woodpecker excavation.

The Evolution of Nest-Site Selection among Hole-Nesting Birds: The Importance of Nest Predation and Competition

Minimum nest entrance widths were correlated with the size of the species. Depths of nesting holes were generally similar for different species, but the Blue Tit occupied shallower holes than did the Great Tit. The Starling Sturnus vulgaris, the Nuthatch Sitta europaea, and the Blue Tit occupied holes higher up in the trees than did the Great Tit and the Pied Flycatcher, in accordance with results of other studies. Contrary to what has been found in these, Marsh Tits nested very low. Total rates of nestfailure and predation were greater in low nests than in higher ones for the Starling, the Blue Tit, and the Marsh Tit. Differences between species in nest predation rates in natural holes could be explained by the vulnerability of the nest sites to predators. For the Starling, the Nuthatch and the Blue Tit average nest heights were negatively correlated with their respective population densities. For the Marsh Tit there was no such correlation, but its nest heights correlated negatively with the density of superior nest competitors. Independent nest preference and utilization data suggest that all four species that vary their nest heights in relation to density prefer to nest high. This indicates that there is competition for safe nest sites. The preference for nest sites higher up in the trees is adaptive and I suggest that predation is the factor that has selected for this preference. The Starling reduced the breeding success of the Nuthatch by taking over holes occupied by the latter. The proportion of Nuthatch nesting attempts that failed because of such interference was higher in high nests and when the population density of the Nuthatch was high.

Modified Lobster Traps for Catching Crabs and Keeping Lobsters Out

Before redesigning lobster traps for capturing crabs and excluding lobsters, laboratory tests were done to determine the ability of both crabs Cancer irroratus and lobsters Homarus americanus to pass through simulated trap entrances and escape holes of various sizes and shapes. A long rectangular opening 44.5 mm (1.75 inches) wide allowed most crabs to enter, yet prevented passage of most legal-size lobsters. For use as escape holes in traps, round openings were found to be more effective than square ones to allow escape of lobsters while retaining commercial-size crabs.Lobster traps were then modified by closing the fishing heads and providing a long rectangular entrance at the top of the trap. Trap entrance widths of 44.5 and 51 mm (1.75 and 2.0 inches) fished crabs equally well; traps with a 38-mm (1.5-inch) entrance, and unmodified lobster traps caught fewer crabs. No lobsters were caught in the modified traps with entrance at the top.

Variation of Erythema With Monochromator Bandwidth

<h3>To the Editor.—</h3> It is well known that the skin response to ultraviolet radiation in the sunburn range (280 to 320 nm) is dependent on the bandwidth of the incident radiation.¹The results presented here show the calculated variation of erythemal effectiveness with monochromator bandwidth for radiation beams of equal fluence, ie, the incident radiation energy per square centimeter (usually expressed as<i>mJ</i>· cm^-2) is constant. In the determination of action spectra, a monochromator with equal entrance and exit slit widths is usually used. In a perfect monochromator, this arrangement gives a triangular distribution of intensity at the exit slit, with a maximum intensity at a central wavelength<i>w</i>₀. The wavelengths present in the beam extend from<i>w</i>₀—<i>B</i>to<i>w</i>₀+<i>B</i>, where<i>B</i>is termed the bandwidth and is equal to the width of the distribution at half the maximum intensity.²

Asymptotic Solutions of Resonances in Harbors with Connected Basins

Asymptotic formulas for the resonant wave numbers are obtained for harbors with connected basins. The number of basins is taken to be two in this paper. However, generalization of the formulas for harbors with more than two basins can easily be obtained. The harbor and the ocean are assumed to have a constant depth. The coast is assumed to be straight but the boundaries of the basins can assume arbitrary shapes. In deriving the asymptotic formulas, the widths of the entrances to each basin are assumed to be small compared with the incident wave length and also with the dimensions of the basins. Comparisons with existing numerical results, however, indicate that these formulas are good even when the entrance widths are comparable to the incident wave lengths and to the dimensions of the basins. The formulas depend only on the eigenvalues of the closed basins and the corresponding normal mode solutions as at entrances. Furthermore, each resonant wave number depends only on the normal modes with wave numbers close to it.

Particle coupling to the octupole state in 89Sr from 88Sr(p, p') 88Sr analog resonances and 88Sr(d, p) 89Sr

A study has been made of the six most pronounced isobaric analog resonances in the 88Sr(p, p') 88Sr (3 −) excitation function at E p = 7.65, 7.80, 7.92, 8.78, 9.75, and 9.90 MeV. They are believed to have a simple structure in the parent nucleus 89Sr consisting of the lowlying positive-parity, single-neutron spectrum of 89Sr weakly coupled to the collective 3 − state in 88Sr. A high-resolution 88Sr(d, p) 89Sr experiment was performed to locate small 2f and 3p admixed fragments in 89Sr which would allow these analog resonances their entrance widths. In addition, on-resonance 88Sr(p, p') 88Sr (3 −) angular distributions were measured in order to determine the partial waves involved in the exit channel. Results are compared to a particlephonon coupling model, and overall selectivity, strengths, and angular distributions of the (p, p') analog resonances are consistent with the above interpretation.

Measurements and second-order calculations of the Eindhoven beam transport system

The horizontal and vertical emittances of the extracted beam from the Eindhoven A.V.F. cyclotron have been measured for different particle energies and yields <25 mm mrad. These areas have been used for linear calculations of beam properties through the beam transport system is doubly achromatic and dispersive modes of operation. The results are compared with measurements. For the 45° bending magnets non-linear effects have been extracted from orbit integrations and comparison is made with the theoretical estimations of the second-order coefficients. These increase the ΔE/ E value calculated by the linear approximation by 0.02%. This implies that with entrance and exit slit widths of 0.5% mm an analysed beam of 2 μA out of 100 μA with an energy spread of 0.05% fwhm is obtainable.