2,531 research outputs found

    Response of the Western Spruce Budworm (Lepidoptera: Tortricidae) to Temperature: The Stochastic Nature of Developmental Rates and Diapause Termination

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    The variability in the developmental rates for the embryos, larvae, and pupae of the western spruce bud worm, Choristoneura occidentalis, was skewed and was well described by a gamma probability density function. At extreme temperatures, the shapes of the frequency distributions for the embryos and pupae were not unimodal, suggesting the presence of thermal biotypes. Variability increased markedly towards the temperature extremes (15 and 31°C) and was greater for female than for male larvae. The shapes of the frequency distributions for larvae terminating diapause ranged from a skewed curve for second-instar larvae held in diapause at O\u27C to a negative exponential curve for larvae held at 5°C. A Monte Carlo simulation model showed that the probability of synchronous emergence of male and female moths was relatively constant (ca. 66%) over a range of average minimum/maximum temperatures. During the larval developmental period, average minimum/ maximum ranged from 2.3/18.1 to 6.0/21.O\u27C. For the pupae developmental period, average minimum/maximum temperatures ranged from 6.0/21.0 to 1l.4/27.1°C. Above these temperatures, the probability of synchronous emergence decreased

    Response of the Western Spruce Budworm (Lepidoptera: Tortricidae) to Temperature and Humidity: Developmental Rates and Survivorship

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    Developmental rates of embryos, larvae, and pupae of the western spruce bud worm, Choristoneura occidentalis, were determined over temperatures ranging from 10 to 31\u27C and RHs ranging from 10 to 100%. Humidity had a trivial influence on developmental rates of all these life stages, whereas temperature had major effects. Several nonlinear developmental rate models and a cubic polynomial model were fit to the data, all of which adequately described the data for each life stage. Development was minimal below IO\u27C for all stages, and maximum rates occurred from 26 to 29\u27C, depending upon sex and life stage. At temperatures above 29\u27C, the rates decreased sharply. Low temperatures induced melanin production in over 30% of the larvae and pupae. Survival of embryos and pupae was determined over temperatures and humidities as noted above. Embryonic survivorship decreased at the temperature extremes and as the humidity decreased. Survival was highest near 220C and 100% RH. Pupal survivorship decreased at both temperature and humidity extremes. Rates were highest near 23\u27C and 75% RH. Survivorship of diapausing larvae decreased at the humidity extremes (10 and 100% RH) and decreased with the length of time in diapause (7 versus 9 months)

    A Study of the Free Oscillations of the Earth

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    Published observations on the toroidal oscillations of the earth are critically reviewed. A supplementary analysis of the record obtained by the Lamont strain seismometer is presented. Eleven toroidal modes are identified, and it is concluded that the periods are known to within 1 per cent. A perturbation scheme involving the ratio of the angular velocity of the earth to the resonant frequency is used in calculating the effects due to the rotation of the earth on the resonant frequency. The free oscillations are viewed as a superposition of traveling waves. In a nonrotating system two traveling waves combine to produce a stationary standing wave. In a rotating system, the rotation distinguishes between waves that travel in the direction of rotation and those that travel in the opposite direction. Rotation removes a degeneracy and results in a splitting of a spectral peak of order l into 2 times l plus 1 peaks. The fractional displacement in frequency for the lowest-order toroidal oscillations is 1/206 and of the same order as the Q of the peak, so that splitting will probably not be observed in the toroidal oscillations. Viewed locally, rotation causes a particle to precess about a direction parallel to the axis of rotation. This precession will cause a variation of amplitude with time if the motion is recorded by an instrument with an anisotropic response function. Care is therefore needed in studying the time decay of a given spectral peak. Rotation also couples the normal coordinates so that a motion that is initially purely horizontal will develop a vertical component. It is expected that vertical seismometers should record particle motion with the toroidal frequencies. The perturbations of the toroidal oscillations due to core-mantle interaction are treated in detail. An exact expression is obtained for the rate of energy dissipated by a finitely conducting plate oscillating across a magnetic field. The energy dissipated at the core-mantle boundary due to viscous and hydromagnetic coupling is shown to be insignificant as compared with the energy dissipated within the mantle. The toroidal magnetic field leaking into the lower mantle combines with the dipole field, resulting in a stress on the mantle, tending to stiffen the lower boundary. The stress is of sufficient magnitude to produce a displacement toward higher frequency in the lower-order toroidal oscillations. Observations on the (sub 0) T (sub 2) oscillations lead to an estimate of the toroidal magnetic field in the lower mantle. A calculation of elastic energy in the low-order oscillations suggests a value of 10 (sup 18) ergs per cycles per hour for the energy density at low frequencies in the Chilean earthquake. Each mode of oscillation has a characteristic radial distribution of elastic energy associated with it. This distribution determines which parts of the earth contribute most heavily in determining a particular resonant frequency. The distribution of energy for the lower 17 modes for a homogeneous and a Gutenberg model earth is calculated. The resonant frequencies for models of the earth based on the Gutenberg and Lehmann distribution of elastic properties are presented. It is shown that the Gutenberg model earth fits the observations more closely than the Lehmann model and that a slight alteration of the Gutenberg model gives a significantly better fit to the observations. The alteration involves a lower shear-wave velocity in the lower mantle while the Gutenberg velocity distribution is maintained in the upper mantle. Various studies of the earth's oscillations coupled with surface-wave investigations substantiate Gutenberg's hypothesis of a layer of low velocity in the upper mantle. The physical conditions required for the formation of a region of low velocity are examined in detail. The results confirm Birch's earlier statement that a temperature gradient in excess of 6 degrees to 7 degrees per kilometer is needed to produce a decrease in velocity. The low-velocity layer does not require that the temperature approach or exceed the melting temperature. If tile upper mantle is homogeneous, the region of lower velocity should commence at the base of the crust and extend to 150 kilometers under the oceans and about 100 kilometers under continental regions. The distribution of thermal conductivity and radioactivity consistent with the low-velocity layer is also considered

    Coriolis meter density errors induced by ambient air and fluid temperature differentials

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    Coriolis metering technology is widely applied throughout industry. In addition to the mass flow rate, a Coriolis meter can measure fluid density based on the resonant frequency of the flow tube vibration. There is currently increasing interest in utilising this density measurement capability as the primary process value in applications such as precision control for fluid property conditioning, and fluid contamination monitoring. However, within these applications, ambient temperature variation can be significant. This paper details research data obtained using NEL's &lsquo;Very Low Flow&rsquo; single-phase facility. The rig was modified to include a programmable temperature enclosure in which a Coriolis meter was installed. Two commercial meter models from the same manufacturer were tested. Both meters showed fluid density errors when subjected to fluctuations in the surrounding ambient air temperature. The fluid properties of the test medium were confirmed to be stable using NEL's UKAS standard reference instrumentation. Previous temperature effects research for Coriolis meters have focussed on the process fluid temperature and there is little published data on the effects of ambient temperature.</p

    Average Marginal Income Tax Rates in New Zealand, 1907-2009

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    Estimates of marginal tax rates (MTRs) faced by individual economic agents, and for various aggregates of taxpayers, are important for economists testing behavioural responses to changes in those tax rates. This paper reports estimates of a number of personal marginal income tax rate measures for New Zealand since 1907, focusing mainly on the aggregate income-weighted average MTRs proposed by Barro and Sahasakul (1983, 1986) and Barro and Redlick (2011). The paper describes the methodology used to derive the various MTRs from original data on incomes and taxes from Statistics New Zealand Official Yearbooks (NZOYB), and discusses the resulting estimates

    Machining-based coverage path planning for automated structural inspection

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    The automation of robotically delivered nondestructive evaluation inspection shares many aims with traditional manufacture machining. This paper presents a new hardware and software system for automated thickness mapping of large-scale areas, with multiple obstacles, by employing computer-aided drawing (CAD)/computer-aided manufacturing (CAM)-inspired path planning to implement control of a novel mobile robotic thickness mapping inspection vehicle. A custom postprocessor provides the necessary translation from CAM numeric code through robotic kinematic control to combine and automate the overall process. The generalized steps to implement this approach for any mobile robotic platform are presented herein and applied, in this instance, to a novel thickness mapping crawler. The inspection capabilities of the system were evaluated on an indoor mock-inspection scenario, within a motion tracking cell, to provide quantitative performance figures for positional accuracy. Multiple thickness defects simulating corrosion features on a steel sample plate were combined with obstacles to be avoided during the inspection. A minimum thickness mapping error of 0.21 mm and a mean path error of 4.41 mm were observed for a 2 m² carbon steel sample of 10-mm nominal thickness. The potential of this automated approach has benefits in terms of repeatability of area coverage, obstacle avoidance, and reduced path overlap, all of which directly lead to increased task efficiency and reduced inspection time of large structural assets
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