Drift Characteristics Research Articles

Computer Simulation of Positron Annihilation and Diffusion Characteristics in Kr and Xe

Analysis of spectra, annihilation rates, and drift and diffusion characteristics of slow positrons is carried out in the heavy gases Kr and Xe. These properties are quite sensitive to the external electric and magnetic fields. Comparison with experiment is made where measurements are available.

Suppression of crosstalk drift in Ti:LiNbO/sub 3/ waveguide switches

The authors report on DC drift characteristics with short relaxation times (typically 20-30 s) of LiNbO/sub 3/-based electrooptic switches for use at the wavelength of 1.3 mu m. They evaluated the switch elements without oxide buffer layers to focus on the substrate. Sputter-etching of more than 20 nm of the substrate surface after waveguide fabrication results in a remarkable suppression of the drift: drift-induced crosstalk of below -25 dB has been achieved. The sputtering process also reduces the range of scatter of voltage drift among four switches fabricated on a single substrate. With data on the capacitance and resistance between a pair of electrodes, the above effects are attributed to the removal of the surface layer by sputtering.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effect of reflections on the drift characteristics of a fiber-optic passive ring-resonator gyro

We show the effect of reflections at the fiber ends on the drift characteristics of a fiber-optic passive ring-resonator gyro. A rotation-detection sensitivity as low as 3 x 10(-5) rad/sec (tau = 30 sec) was obtained by reducing the effect of reflected lights with an optical phase modulator.

Analysis and interpretation of spaced receiver scintillation data recorded at an equatorial station

Ultrahigh frequency satellite signals from the Pacific FleetSat (53° elevation angle) and L band signals from the Pacific Marisat (50° elevation angle) were recorded in Guam, an equatorial station, from April 1982 through May 1, 1983. Three receivers aligned in the magnetic east‐west direction were used, with the most widely separated receivers (457.2 m separation) recording the UHF signal amplitudes and the middle receiver recording the L Band signal amplitudes. These data are analyzed for the drift characteristics of ionospheric irregularities. The digitized spaced receiver data are processed to yield the scintillation index, the cross‐correlation function and the self‐power spectrum. By assuming a locally frozen flow, several methods have been devised to compute the drift velocity, V0, and the characteristic random velocity, VC. These methods seem to show internal agreement. They also show that the velocity fluctuations decrease markedly during the first few hours after local sunset. The spectral index of the self‐power spectrum roll‐off was also determined during times of both weak and strong scintillation. For the weak scintillation cases, the slopes were observed to gradually steepen as the night progressed into the postmidnight period. This steepening suggests the decaying of smaller‐sized irregularities. There were a few exceptions to this observed decay. For the strong scintillation cases, the shape and slope of the self‐power spectrum were observed to be influenced by the drift velocity and scattering strength of the irregularities.

Characteristics of a mini Drift chamber

The characteristics of a drift chamber with 3 mm drift gap were investigated at a particle beam momentum of 10 GeV/ c. The chamber has good linearity of the drift characteristics. It was tested and could reliably work in a particle flux of ∼ 3 × 10 5 s −1 cm −2. A spatial resolution of ∼ 45 μm in the centre of the drift gap has been achieved.

An Assessment of the Long-Term Performance of Gas Continuous Emission Monitoring Systems

A field test program was conducted to evaluate the long-term performance of several gas continuous emission monitoring systems (CEMS).* This paper presents the results gathered on the long-term accuracy and calibration drift characteristics of ten CEMS installed at scrubber-controlled, coal-fired power plants. The program involved periodic accuracy audits and a review of available calibration drift data for selected CEMS. Accuracy audit results show that both SO2 and NOx CEMS are capable of providing accurate data on a long-term basis. However, frequent audits are necessary in order to verify the performance of an individual CEMS. The results of the calibration drift data evaluation show that despite infrequent occurrences of excessive drift, CEMS operated with a significant bias for extended time periods simply because corrective action was not taken in a timely manner.

Drift Characteristic of Capacitive Transducer Using Glued Electrodes

The drift characteristics in glued electrodes of a capacitive transducer for small displacements were measured for two kinds of adhesives. The factors determining drift in the nanometer range are discussed.

Convection electric fields and electrostatic potential over 61° &lt; Λ &lt; 72° invariant latitude observed with the European Incoherent Scatter Facility: 1. Initial results

Convection electric fields are observed with the European Incoherent Scatter Common Program CP‐3 which probes the F2 region of the auroral ionosphere between 61° and 72° invariant latitude for 24‐hour runs. Several examples of convection fields are discussed, corresponding to various levels of magnetospheric activity. The principal characteristics of the convection drifts are discussed in the light of indices of magnetospheric activity level. It is shown that depending on the level of magnetospheric activity as revealed by the Kp index, the two‐cell convection pattern is more or less present in the field of view of the radar and that the convection velocities around dawn and dusk increase with increasing activity. A method is described which assumes that the 24‐hour convection pattern is due to a steady state potential viewed by the radar rotating with the earth under its ionospheric induced structures; as this assumption can be wrong, in some extreme circumstances of very high and unsteady magnetospheric activity, a test is proposed to ascertain the validity of the method. Inferred potential distributions are then discussed; it is shown in particular that the potential drop from dawn to dusk increases with the magnetospheric activity index Kp. A preliminary analysis of the shapes and positions of the two convection cells is then presented.

The Application Characteristics of Electrostatic Spraying with Electrodyn (III) Deposit and Drift Characteristics of Charged Droplets

The Application Characteristics of Electrostatic Spraying with Electrodyn (III) Deposit and Drift Characteristics of Charged Droplets

固体製剤の流動性および浮遊性におよぼすコロイダルシリカの添加率の影響

Colloidal silica is usually added to carriers wetted in advance with a small amount of liquid-state agricultural chemicals to improve the flowability in preparing for a solid formation.Since the relationships between the additive amount of colloidal silica and the flowability and drift characteristics of the formed solid have not yet been studied quantitatively, both relationships are examined in this paper, and the following conclusions are derived:1. The additive ratio of colloidal silica (called “white carbon, W. C.”) to SiC giving good flowability, increases with the increasing additive ratio of linseed oil to SiC. SiC and linseed oil were used in place of a carrier and liquid-state agricultural chemicals respectively in this study.2. The bulk density of SiC coated with both linseed oil and W. C. and exhibiting good flowability, decreases with the increase in the additive ratio of W. C. This phenomenon is analyzed by assuming that the thickness of W. C. layers adhering to the surface of SiC with linseed oil increases.3. It seems that there are two cohesive states of W. C. depending upon the additive ratio. It is difficult to exfoliate the W. C., which adheres strongly to the surface of SiC with the enough linseed oil, from the surface of SiC by an external force. Thus, there is hardly any drift of W. C. into the air. On the other hand, the W. C. attached weakly to SiC is easily exfoliated even by the same external force and drifts into the air. The exfoliation ratio reaches approximately 20% by weight of the total additive amount of W. C. at the minimum additive ratio of W. C. to SiC at which SiC with both linseed oil and W. C. shows good flowability.

Profitable stream positions for salmonids: relating specific growth rate to net energy gain

A model is developed to predict potential net energy gain for salmonids in streams from characteristics of water velocity and invertebrate drift. Potential net energy gain, or potential profit, is calculated for individuals of three species of juvenile salmonids in a laboratory stream aquarium, based on the energy available from drift minus the cost of swimming to maintain position. The Michaelis–Menten or Monod model is used to describe the relationship between potential profit and specific growth rate. Potential profit was a better predictor of specific growth rate for coho salmon (Oncorhynchus kisutch) than for brook trout (Salvelinus fontinalis) or brown trout (Salmo trutta). Coho salmon always achieved higher specific growth rates than either brook trout or brown trout in concurrent experiments, and maintained growth to lower resource thresholds. In each experiment, fish established intraspecific hierarchies and dominant fish held positions affording maximum potential profit. The use of potential profit as an optimal foraging model was tested by predicting the potential for net energy gain at coho salmon positions from the overall pattern of flow and invertebrate drift in the stream aquarium, and ranking these positions from highest to lowest potential profit. This predicted ranking was nearly identical to the rank observed in the linear dominance hierarchy. The results of experiments confirm ideas of other investigators about mechanisms of microhabitat selection by stream salmonids.

On the Attitude Estimation of Earth Observation Satellites

A combined attitude estimation algorithm has been proposed, in which two variants of system model are used simultaneously. These models are put together to form two parts of the algorithm with the aim, that the first model provides the estimates of some observable quantities by using the linear kalman filter, while the second model is used to update the estimation of yaw attitude as well as the estimation of all variables in the system, including unknown disturbances, gyro drift characteristics, etc.

Static response of a simple piezoelectric load cell

The design of a simple load cell is presented. The cell is based on piezoelectric methods employing charge amplification, and such a system inevitably results in d.c. drift. The optimization of the drift characteristics to yield quasistatic operation is discussed.

Phenomenological theory of drift characteristics and high-frequency mobility of superlattices

Phenomenological theory of drift characteristics and high-frequency mobility of superlattices

Gases for possible use in diffuse-discharge switches

Desirable electron attachment and electron drift characteristics of gases for possible use in diffuse-discharge switches are indicated. Gas mixtures for possible use in externally sustained (e- beam) diffuse-discharge switches are suggested on the basis of electron attachment rate constants and electron drift velocities measured as a function of the density-normalized electric field E/N. Of particular promise are mixtures of Ar and C3F8.

Aerial spraying of fenitrothion in forest programs: some problems and some solutions.

Annually, large tracts of forest in eastern Canada are sprayed aerially with insecticides (fenitrothion, aminocarb) in attempts to control an epidemic infestation by an indigenous forest pest, the spruce budworm (Choristoneura fumiferana, Clemens). The massive size of the spraying programs, the anecdotal reports of human exposure, and the potential for hazard to human health have led one province. New Brunswick, to initiate and fund specific environmental and laboratory studies which will provide adequate data upon which the government can base realistic legislation to protect both the forests and the population. These studies have included some unique field analyses of aerial spray drift conducted by a research group from the National Research Council; comparative subchronic studies in rats of fenitrothion and a new formulation; a nose-only inhalation study of this formulation in rats; field testing of the formulation for drift characteristics. Ongoing research involves the subchronic testing of the emulsifying agents being used routinely in the new formulation and studies of a low-drift additive which will stabilize the particle size of the spray. On the basis of the results to date, the government has been able to modify spraying techniques and to establish realistic buffer zones around human habitation.

Gas scintillation nuclear particle detectors

Gaseous scintillators based on the luminescence of low-pressure (⩽ 1 bar) Ar, Xe and ArN 2 gases can be applied advantageously to the detection of heavy charged particles. At particle energies above 100 MeV, the scintillators provide an energy resolution comparable with ionization gas counters but an improved time resolution of ⩽ 300 ps. The admixture of N 2 to Ar and Xe reduces the light yield but has the advantage to fasten scintillation decay and to avoid the necessity of applying wavelength shifters. These mixtures have also reasonable electron drift and diffusion characteristics allowing the development of combined light- and charge-sensing detectors. At high ionization densities, gas scintillators show no pulse-height defect but conversely an excess in light yield due to the luminiscence accompanying column recombinations. The magnitude of this effect can be controlled by applying an electric field in the interaction volume. For an admixture of 10–15% N 2 to Ar, column recombinations can be avoided by electric fields E/ p of ≲1 V·cm −1·Torr −1, yielding a linear response for particles in the total range of mass (α particles to U ions). First test experiments with solid Xe as scintillation medium have yielded an energy resolution of a few percent both for α particles and heavy ions. Contrary to Xe gas, the solid shows a pulse-height defect with increasing ionization density.

An experiment to measure the one-way velocity of propagation of electromagnetic radiation

In this paper we describe a propagation experiment to measure the one-way velocity of electromagnetic radiation. The experiment utilizes the rotation of the earth to interchange the positions of two rubidium vapor frequency standards over12 h, thereby canceling initial clock phase differences. It is demonstrated that although the drift characteristics of modern rubidium atomic clocks may be large for long-term absolute timing requirements, the short-term random fluctuations are small. It is found that over a24-h period, the long-term drift can be accurately parameterized in retrospect and removed, thereby permitting the detection of temporal variations less than1 nsec in magnitude. With coherent summing techniques this value may be significantly reduced, and it becomes realistic to consider an experiment where the clocks are separated by distances of the order of several hundreds of meters in order to detect velocities of the order of that of the solar system with respect to the center of the galaxy(≈105 m sec−1), thus ensuring that the rotational motion of the earth has a negligible effect in altering the relative inertial characteristics of the reference frames of each clock. It is demonstrated that under such conditions the measurement of the one-way speed of propagation of electromagnetic radiation is not only meaningful, but can be simply implemented with commercially available instrumentation.

Characteristics of thermal drift of the emission frequency of a stripe-geometry semiconductor laser

An investigation was made of tuning of the emission frequency of a stripe-geometry semiconductor laser as a result of heating of the active region during a pump pulse or when the pump current was varied. It was found that the rate of thermal drift of the emission frequency of a stripe-geometry laser changes abruptly on transition from lasing in one transverse mode to lasing in another. It is shown that as the pump current increases, the frequency can either increase or decrease and, for a certain current, the rate of frequency tuning may fall to zero. These characteristics are due to the waveguide confinement of the field in the active region of a semiconductor laser.

A simple jitter-free picosecond streak camera

Using a DC-biased room-temperature photoconductive switching element, a picosecond resolution optical streak camera is operated at sweep rates up to 7 ps/mm. Single-shot jitter is 2 ps with complete absence of short and long-term drift characteristic of all other sweep drivers. This high accuracy allows the streak camera to be used in a single-shot averaging mode which leads to a sub-picosecond absolute timing accuracy. When operated in this manner, the streak camera becomes a highly reliable and accurate device for measuring transient events on a time scale of single picoseconds. The simplicity of this method makes it highly attractive for many applications in laser fusion and picosecond chemistry and photophysics studies where reliable no-drift operation is highly desirable.