975 resultados para Period wave characteristics


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National Highway Traffic Safety Administration, Office of Driver and Pedestrian Programs, Washington, D.C.

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Prototype scale tests of the mooring load and wave transmission characteristics of a floating tire breakwater were conducted in the large wave tank at the Coastal Engineering Research Center. Standard Goodyear Tire and Rubber Co. 18-tire modules connected to form breakwaters, 4 and 6 modules (8.5 and 12.8 meters, 28 and 42 feet) wide in the direction of wave advance, were tested in water depths of 2 and 4 meters (6.56 and 13.12 feet). Monochromatic waves with a 2.64- to 8.25-second period range and heights up to 1.4 meters (4.6 feet) were used in the tests. Test results indicate that wave transmission is mainly a function of the breakwater width to incident wavelength ratio with a slight dependence on the incident wave height. However, the mooring forces are mainly a function of the incident wave height with only a slight dependence on the incident wavelength and breakwater width. Recommended design curves for the wave transmission coefficient versus breakwater width to wavelength ratio and mooring load as a function of incident wave height are presented. (Author).

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For the most part a reissue with new title pages, of "Kirby's wonderful and scientific museum," later "Kirby's wonderful and eccentric museum." which was published at London from 1803 to 1820. cf. Brit. mus. Catalogue.

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"Interim report for period January 1976-February 1976."

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Freshwater Bay (FWB), Washington did not undergo significant erosion of its shoreline after the construction of the Elwha and Glines Canyon Dams, unlike the shoreline east of Angeles Point (the Elwha River’s lobate delta). In this paper I compare the wave energy density in the western and eastern ends of the Strait of Juan de Fuca with the wave energy density at the Elwha River delta. This indicates seasonal high- and low-energy regimes in the energy density data. I group multi-year surveys of four cross-shore transects in FWB along this seasonal divide and search for seasonal trends in profile on the foreshore. After documenting changes in elevation at specific datums on the foreshore, I compare digital images of one datum to determine the particle sizes that are transported during deposition and scour events on this section of the FWB foreshore. Repeat surveys of four cross-shore transects over a five-year period indicate a highly mobile slope break between the upper foreshore and the low-tide delta. Post-2011, profiles in eastern FWB record deposition in the landward portion of the low-tide terrace and also in the upper intertidal. Western FWB experiences transient deposition on the low-tide terrace and high intra-annual variability in beach profile. Profile elevation at the slope break in western FWB can vary 0.5 m in the course of weeks. Changes in surface sediment that range from sand to cobble are co-incident with these changes in elevation. High sediment mobility and profile variation are inconsistent with shoreline stability and decreased sediment from the presumed source on the Elwha River delta.

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The water characteristics in cooked pressure-heat treated (45 degreesC for 45 min prior to pressurisation at 150 MPa for 30 min) and non-pressurised, cooked (control) samples of beef Longissimus aged for 1, 3, 8 or 16 days were studied by nuclear magnetic resonance microscopy. A multi-echo sequence was used to obtain T2 images, and independent of ageing period, the T2 values were found to be lower in pressure-heat treated meat revealing alterations in water characteristics of pressure-treated, cooked meat compared with cooked meat. With increasing ageing duration, the T2 values in both pressure-treated, cooked and cooked meat decreased indicating that the water became more tightly trapped in the protein network. In addition, independent of length of ageing period the relationship between cooking loss in the cooked meat and transverse relaxation differed between non-pressurised and pressure-treated meat. which reveals that the mechanisms changing the water properties in beef during ageing are different from those occuring during pressure-heat treatment of meat. (C) 2003 Elsevier Ltd. All rights reserved.

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Germ cells in the mouse embryo remain undifferentiated until about 13.5 days post-coitum (dpc), when male germ cells enter mitotic arrest and female germ cells enter meiosis. The molecular signals and transcriptional control mechanisms governing the differential fate of germ cells in males and females remain largely unknown. In order to gain insights into the behavior of germ cells around this period and into likely mechanisms controlling entry into meiosis, we have studied by wholemount in situ hybridization the expression pattern of two germ cell-specific markers, Oct4 and Sycp3, during mouse fetal gonad development. We observed a dynamic wave of expression of both genes in developing ovaries, with Oct4 expression being extinguished in a rostro-caudal wave and Sycp3 being upregulated in a corresponding wave, during the period 13.5-15.5 dpc. These results indicate that entry into meiosis proceeds in a rostro-caudal progression, in turn suggesting that somatically derived signals may contribute to the control of germ cell entry into meiosis in developing ovaries. (C) 2004 Wiley-Liss, Inc.

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Objective: This study examined the pattern of criminal convictions in persons with schizophrenia over a 25-year period marked by both radical deinstitutionalization and increasing rates of substance abuse problems among persons with schizophrenia in the community. Method: The criminal records of 2,861 patients (1,689 of whom were male) who had a first admission for schizophrenia in the Australian state of Victoria in 1975, 1980, 1985, 1990, and 1995 were compared for the period from 1975 to 2000 with those of an equal number of community comparison subjects matched for age, gender, and neighborhood of residence. Results: Relative to the comparison subjects, the patients with schizophrenia accumulated a greater total number of criminal convictions (8,791 versus 1,119) and were significantly more likely to have been convicted of a criminal offense (21.6% versus 7.8%) and of an offense involving violence (8.2% versus 1.8%). The proportion of patients who had a conviction increased from 14.8% of the 1975 cohort to 25.0% of the 1995 cohort, but a proportionately similar increase from 5.1% to 9.6% occurred among the comparison subjects. Rates of known substance abuse problems among the schizophrenia patients increased from 8.3% in 1975 to 26.1% in 1995. Significantly higher rates of criminal conviction were found for patients with substances abuse problems than for those without substance abuse problems (68.1% versus 11.7%). Conclusions: A significant association was demonstrated between having schizophrenia and a higher rate of criminal convictions, particularly for violent offenses. However, the rate of increase in the frequency of convictions over the 25-year study period was similar among schizophrenia patients and comparison subjects, despite a change from predominantly institutional to community care and a dramatic escalation in the frequency of substance abuse problems among persons with schizophrenia. The results do not support theories that attempt to explain the mediation of offending behaviors in schizophrenia by single factors, such as substance abuse, active symptoms, or characteristics of systems of care, but suggest that offending reflects a range of factors that are operative before, during, and after periods of active illness.

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In the granitic Seychelles, many shores and beaches are fringed by coral reef flats which provide protection to shores from erosion by waves. The surfaces of these reef flats support a complex ecology. About 10 years ago their seaward zones were extensively covered by a rich coral growth, which reached approximately to mean low water level, but in 1998 this was largely killed by seawater warming. The resulting large expanses of dead coral skeletons in these locations are now disintegrating, and much of the subsequent modest recovery by new coral recruitment was set back by further mortalities. A mathematical model of wave energy reaching shorelines protected by coral reef flats has been applied to 14 Seychelles reefs. It is derived from equations which predict: (1) the raised water level, or wave set-up, on reef flats resulting from wave breaking, which depends upon offshore wave height and period, depth of still water over the reef flat and the reef crest profile, and (2) the decay of energy from reef edge to shoreline that is affected by width of reef flat, surface roughness, sea level rise and 'pseudo-sea level rise' created by increased depth resulting from disintegration of coral colonies. The model treats each reef as one entity, but because biota and zonation on reef flats are not homogenous, all reefs are divided into four zones. In each, cover by both living and dead biota was estimated for calculation of parameters, and then averaged to obtain input data for the model. All possible biological factors were taken into account, such as the ability of seagrass beds to grow upwards to match expected sea level rise, reduction in height of the reef flat in relation to sea level as zones of dead corals decay, and the observed 'rounding' of reef crests as erosion removes corals from those areas. Estimates were also made of all these factors for a time approximately a decade ago, representing a time before the mass coral mortality, and for approximately a decade in the future when the observed rapid state of dead coral colony disintegration is assumed to have reached an end point. Results of increased energy over the past decade explain observations of erosion in some sites in the Seychelles. Most importantly, it is estimated that the rise in energy reaching shores protected by fringing reefs will now accelerate more rapidly, such that the increase expected over the next decade will be approximately double than that seen over the past decade. (c) 2005 Elsevier Ltd. All rights reserved.

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Studies have shown that increased arterial stiffening can be an indication of cardiovascular diseases like hypertension. In clinical practice, this can be detected by measuring the blood pressure (BP) using a sphygmomanometer but it cannot be used for prolonged monitoring. It has been established that pulse wave velocity (PWV) is a direct measure of arterial stiffening but its usefulness is hampered by the absence of non-invasive techniques to estimate it. Pulse transit time (PTT) is a simple and non-invasive method derived from PWV. However, limited knowledge of PTT in children is found in the present literature. The aims of this study are to identify independent variables that confound PTT measure and describe PTT regression equations for healthy children. Therefore, PTT reference values are formulated for future pathological studies. Fifty-five Caucasian children (39 male) aged 8.4 +/- 2.3 yr (range 5-12 yr) were recruited. Predictive equations for PTT were obtained by multiple regressions with age, vascular path length, BP indexes and heart rate. These derived equations were compared in their PWV equivalent against two previously reported equations and significant agreement was obtained (p < 0.05). Findings herein also suggested that PTT can be useful as a continuous surrogate BP monitor in children.

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Characteristics obtained from peripheral pulses can be used to assess the status of cardiovascular system of subjects. However, nonintrusive techniques are preferred when prolonged monitoring is required for their comfort. Pulse transit time ( PTT) measurement has showed its potentials to monitor timing changes in peripheral pulse in cardiovascular and respiratory studies. In children, the common peripheries used for these studies are fingers or toes. Presently, there is no known study conducted on children to investigate the possible physiologic parameters that can confound PTT measure at these sites. In this study, PTT values from both peripheral sites were recorded from 55 healthy Caucasian children ( 39 male) with mean age of 8.4 +/- 2.3 years ( range 5 - 12 years). Peripheries' path length, heart rate, systolic blood pressure, diastolic blood pressure ( DBP) and mean arterial pressure ( MAP) were measured to investigate their contributions to PTT measurement. The results reveal that PTT is significantly related to all parameters ( P< 0.05), except for DBP and MAP. Age is observed to be the dominant factor that affects PTT at both peripheries in a child. Regression equations for PTT were derived for measuring from a finger and toe, ( 6.09 age + 189.2) ms and ( 6.70 age + 243.0) ms, respectively.

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Waves breaking on the seaward rim of a coral reef generate a flow of water from the exposed side of the reef to the sheltered side and/or to either channels through the reef-rim or lower sections of the latter. This wave-generated flow is driven by the water surface gradient resulting from the wave set-up created by the breaking waves. This paper reviews previous approaches to modelling wave-generated flows across coral reefs and discusses the influence of reef morphology and roughness upon these flows. Laboratory measurements upon a two-dimensional horizontal reef platform with a steep reef face provide the basis for extending a previous theoretical analysis for wave set-up on a reef in the absence of a flow [Gourlay, M.R., 1996b. Wave set-up on coral reefs. 2. Set-up on reefs with various profiles. Coastal Engineering 28, 1755] to include the interaction between a unidirectional flow and the wave set-up. The laboratory model results are then used to demonstrate that there are two basic reef-top flow regimes-reef-top control and reef-rim control. Using open channel flow theory, analytical relationships are derived for the reef-top current velocity in terms of the offreef wave conditions, the reef-top water depth and the physical characteristics of the reef-top topography. The wave set-up and wave-generated flow relationships are found to predict experimental values with reasonable accuracy in most cases. The analytical relationships are used to investigate wave-generated flows into a boat harbour channel on Heron Reef in the southern Great Barrier Reef. (c) 2005 Elsevier B.V. All rights reserved.

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Lift, pitching moment, and thrust/drag on a supersonic combustion ramjet were measured in the T4 free-piston shock tunnel using a three-component stress-wave force balance. The scramjet model was 0.567 m long and weighed approximately 6 kg. Combustion occurred at a nozzle-supply enthalpy of 3.3 MJ/kg and nozzle-supply pressure of 32 MPa at Mach 6.6 for equivalence ratios up to 1.4. The force coefficients varied approximately linearly with equivalence ratio. The location of the center of pressure changed by 10% of the chord of the model over the range of equivalence ratios tested. Lift and pitching-moment coefficients remained constant when the nozzle-supply enthalpy was increased to 4.9 MJ/kg at an equivalence ratio of 0.8, but the thrust coefficient decreased rapidly. When the nozzle-supply pressure was reduced at a nozzle-supply enthalpy of 3.3 MJ/kg and an equivalence ratio of 0.8, the combustion-generated increment of lift and thrust was maintained at 26 MPa, but disappeared at 16 MPa. Measured lift and thrust forces agreed well with calculations made using a simplified force prediction model, but the measured pitching moment substantially exceeded predictions. Choking occurred at nozzle-supply enthalpies of less than 3.0 MJ/kg with an equivalence ratio of 0.8. The tests failed to yield a positive thrust because of the skin-friction drag that accounted for up to 50% of the fuel-off drag.

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Mast cell tumours (MCTs) are relatively common tumours of cats, and are the second most common cutaneous tumours in cats in the USA. While the primary splenic form of the disease is far less common, it is usually associated with more severe clinical signs. Signalment, clinical and survival characteristics of mast cell neoplasia were characterised in 41 cats. The most common tumour location was cutaneous/ subcutaneous head and trunk. Stage la was the most common tumour stage at first diagnosis (n = 20), followed by stage 4 (both stage 4a and stage 4b; n = 10). Of 22 cats that underwent excisional biopsy, mast cell neoplasia recurred in four cats during the study period. Three of the 41 cats presented with simultaneous cutaneous and either splenic or lymph node tumours. A comparison between cats with only cutaneous tumours (n = 30) and those with tumours involving the spleen or lymph nodes (n = 11) showed longer survival times for the cutaneous-only group (P = 0.031). Twelve of the 41 cats died of mast cell neoplasia during the study period. When a subgroup of cats with only cutaneous tumours (no lymph node or visceral involvement) were divided according to whether there were multiple (five or more) tumours (n = 6) or a single tumour (n = 19), cats with single tumours survived longer than those with multiple tumours (P = 0.001). Solitary cutaneous feline MCTs without spread to the lymph nodes usually manifest as benign disease with a relatively protracted course. However, multiple cutaneous tumours, recurrent tumours and primary splenic disease should receive a guarded prognosis due to the relatively short median survival times associated with these forms of the disease. (C) 2006 ESFM and AAFR Published by Elsevier Ltd. All rights reserved.