Hook Method Research Articles

Smooth fitting with a method for determining the regularization parameter under the genetic programming algorithm

Abstract This paper deals with the smooth fitting problem under the genetic programming (GP) algorithm. To reduce the computational cost required for evaluating the fitness value of GP trees, numerical weights of GP trees are estimated by adopting both linear associative memories (LAM) and the Hook and Jeeves (HJ) method. The quality of smooth fitting is critically dependent on the choice of the regularization parameter. So, we present a novel method for choosing the regularization parameter. Two numerical examples are given with the comparison of generalized cross-validation (GCV) B-splines.

Examining the effects of changes in the minimum legal sizes used in the Hauraki Gulf snapper ( Pagrus auratus) fishery in New Zealand

A minimum legal size (MLS) is seen as a fisheries management tool with the ability to protect juvenile fish, maintain spawning stocks, and control the sizes of fish caught. Described here is a simulation study examining the effects of different MLS strategies in the Hauraki Gulf snapper ( Pagrus auratus) fishery. This fishery is currently managed under two separate MLSs, 270 mm for recreational fishers and 250 mm for commercial fishers. Results showed that the current MLSs were larger than those which would assist in short term stock rebuilding, but that they were closer to those that would maximize rebuilding over the longer term. It is shown that increases in the current MLS for longline and recreational fishing methods would reduce population rebuild in the short term due to the impact of the increased fishing effort required to catch the ‘quota’. Within the snapper fishery the different fishing gears were separated into two groups based on their fishing patterns, one for mesh methods and one for hook and line methods. It was found that due to the higher selectivity (of smaller fish) and higher rates of discard mortality for the mesh methods, very low or no MLSs were optimal. Overall, it was found that selectivity, catch allowances, and population size were the important determinants of the optimal MLS. The importance of these indicated that the effects of different MLS strategies may be examined both with a population dynamics model and within a yield-per-recruit framework.

A simple apparatus for determining column density and absolute photoabsorption cross sections

This article presents a simple measuring apparatus that is capable of measuring column density and absolute photoabsorption cross sections. The apparatus includes a simple high-temperature heatpipe furnace, an MKS Instruments Baratron, a hydrogen discharge lamp, and an optical detecting system. The heatpipe furnace provides an absorbing medium with a steady total pressure in a closed system so that the column density can be obtained using the ideal gas relation. The apparatus is designed for a working temperature range below 1000 K and a pressure range up to 10 Torr. Encountered experimental difficulties and their found solutions will be discussed in detail. In this work, the absolute photoabsorption cross section of Mg is measured near the 3s threshold using this apparatus. The absolute photoabsorption cross section result at the 3s threshold, which is 2.1±0.3 Mb, is in good agreement with hook method data (2.36 Mb).

Experimental investigation of deviations from local thermodynamic equilibrium in high-pressure mercury discharges

The determination of the radial profile of the ground state density without assuming local thermodynamic equilibrium (LTE) conditions in around atmospheric pressure (0.01 MPa<p<0.3 MPa) discharges used as light sources is a worthy investigation subject. This work deals with the high-pressure mercury discharge which could be considered as a “test case.” Particularly useful for the diagnostics of these plasmas is the self-reversed resonance mercury line 253.7 nm. In this article, two independent experimental methods were used: emission spectroscopy, called the “ΔλR method,” and interference shift measurements “hook method.” Using the Hg-253.7 nm resonance line, both experimental methods indicate similar deviations from LTE in particular for the lower pressure discharges (p<0.04 MPa). In those cases, the experimental errors for both methods are significantly lower than the detected deviations. Furthermore, the measured deviations are in good agreement with predicted values from a two-temperature, two-dimensional fluid model developed elsewhere.

A comprehensive analysis of low-back disorder risk and spinal loading during the transferring and repositioning of patients using different techniques

Although patient handlers suffer from low-back injuries at an alarming rate worldwide, there has been limited research quantifying the risk for the specific tasks performed by the patient handlers. The current study used both a comprehensive evaluation system (low-back disorder risk model) and theoretical model (biomechanical spinal loading model) to evaluate risk of LBD of 17 participants (12 experienced and five inexperienced) performing several patient handling tasks. Eight of the participants were female and nine were male. Several patient transfers were evaluated as well as repositioning of the patient in bed; these were performed with one and two people. The patient transfers were between bed and wheelchair (fixed and removable arms) and between commode chair and hospital chair. A ‘standard’ patient (a 50 kg co-operative female; nonweight bearing but had use of upper body) was used in all patient handling tasks. Overall, patient handling was found to be an extremely hazardous job that had substantial risk of causing a low-back injury whether with one or two patient handlers. The greatest risk was associated with the one-person transferring techniques with the actual task being performed having a limited effect. The repositioning techniques were found to have significant risk of LBD associated with them with the single hook method having the highest LBD risk and spinal loads that exceeded the tolerance limits (worst patient handling job). The twoperson draw sheet repositioning technique had the lowest LBD risk and spinal loads but still had relatively high spinal loads and LBD risk. Thus, even the safest of tasks (of the tasks evaluated in this study) had significant risk. Additionally, the current study represented a ‘best’ case scenario since the patient was relatively light and co-operative. Thus, patient handling in real situations such as in a nursing home, would be expected to be worse. Therefore, to have an impact on LBD, it is necessary to provide mechanical lift assist devices.

Application of the hook method and emission spectroscopy for the determination of radial density and temperature profiles in high-pressure mercury discharges

The radial distributions of the temperature and particle density are of decisive importance for the understanding of high-pressure gas discharges. The present paper deals with the measurement of radial density profiles of the excited Hg states 6, 6 and 6 and the determination of the temperature profiles in conventional 250 W high-pressure Hg and discharge lamps. The population densities are determined using the interferometric hook method and the arc temperature by emission spectroscopy. From the density distribution the radial temperature profiles are deduced. They agree well with those determined by emission spectroscopy. It is demonstrated that the hook method is also applicable to such discharges sustained in cylindrical discharge tubes which are usually not very suitable for interferometric measurements.

Afterglow ground-state copper density behavior in kinetically enhanced copper vapor lasers

The interferometric Hook method has been used to measure the copper ground-state density during the interpulse period for a 38 mm bore diameter copper vapor laser (CVL) operated in kinetically enhanced (KE) mode (Ne-HCl-H/sub 2/ gas mixture) and in conventional mode (pure neon and Ne-H/sub 2/ gas mixtures). It was found that the rate of regrowth of the axial copper density during the afterglow of the KE-CVL is 3-4 times faster, and the axial prepulse ground-state copper density is 2-3 times higher, than that observed for pure Ne or Ne-HI buffer gases. We conclude that the primary action of the HCl+H/sub 2/ additives is to increase the interpulse plasma relaxation rate and to increase the threshold copper density beyond which thermal runaway occurs. These effects are primarily responsible for the elevated pulse rates and increased pulse energies giving improved power scaling characteristics of KE-CVLs.

Hook method: recovery of density information from interferograms distorted by large spatial gradients

The hook method is a well-established technique for measuring the spatial distribution of species' densities in the gas phase, particularly in optically thick plasmas. However, in the presence of large density gradients (such as those occurring in a metal vapor laser plasma), the hook interferogram suffers severe distortion and the standard hook equation is invalid. By the use of a computer simulation of fringe formation, it is shown that this effect arises as a result of the strong wavelength-dependent lensing of probe rays in the test medium. On the basis of this lensing mechanism, a criterion has been derived for the maximum permissible density gradient, above which the standard hook analysis cannot be accurately applied. Finally, a new technique is presented that permits density data to be recovered from interferograms that are too distorted to analyze by the use of standard techniques. This technique is based on extracting density gradient values from distortion-free features of the fringe pattern. The new technique also permits density data to be obtained with an increased spatial resolution over that of the standard hook analysis.

Modelling of the kinetics and parametric behaviour of a copper vapour laser: Output power limitation issues

A self-consistent computer model was used to simulate the plasma kinetics (radially resolved) and parametric behaviour of an 18 mm bore (6 W) copper vapour laser for a wide range of optimum and non-optimum operating conditions. Good quantitative agreement was obtained between modelled results and experimental data including the temporal evolution of the 4p2P3/2, 4s2 D5/22 and 4s2D3/22 Cu laser level populations derived from hook method measurements. The modelled results show that the two most important parameters that affect laser behaviour are the ground state copper density and the peak electron temperature Te. For a given pulse repetition frequency (prf), maximum laser power is achieved by matching the copper atom density to the input pulse energy thereby maintaining the peak Te at around 3 eV. However, there is a threshold wall temperature (and copper density) above which the plasma tube becomes thermally unstable. At low prf (<8 kHz), this thermal instability limits the attainable copper density (and consequently the laser output power) to values below the optimum for matching to the input pulse energy. For higher prf values (>8 kHz), the copper density can be matched to the input pulse energy to give maximum laser power because the corresponding wall temperature then falls below the threshold temperature for thermal instability. For prf >14 kHz, the laser output becomes highly annular across the tube diameter due to a severe depletion of the copper atom density on axis caused by radial ion pumping.

Experimental study of transitionprobabilities of neutral and singlyionized lanthanide atoms

Abstract A method of extended crossed atomic and electron beams is proposed for determination of the branching ratios for excited states. We measured the branching ratios for Gd I, Er I, Dy I, II and Sm I levels for which the lifetimes had previously been measured by different authors using various methods. Using known lifetimes of the excited levels, we found the absolute transition probabilities for 90 spectral lines of Gd I, 41 lines Er I, 35 lines Dy I, 28 lines Dy II and 156 lines Sm I in the 260-800 urn spectral range. The values of the transition probabilities determined in this paper are in good accordance with the results obtained by the hook method. The error of the reported transition probabilities is estimated not to exceed 25.

The crochet hook method of stab avulsion phlebectomy for varicose veins

Excision of varicose veins through ministab incisions is currently the choice for the removal of varicose vein clusters. The crochet hook technique of stab avulsion phlebectomy is described in this paper. This surgical method for the treatment of varicose veins has been widely utilized in a residency training environment during the last twelve years and has been used by the senior author for more than 20 years. The technique is easily mastered, cost effective, and has excellent therapeutic and cosmetic results.

The use of Fourier transform techniques for the analysis of hook interferograms

Hook interferometry is widely used for the measurement of atomic oscillator strengths and atomic energy level populations. The application of Fourier transform techniques to the analysis of hook interferograms is shown to produce greater precision in the determination of hook separation by either the hook or vernier methods. Result obtained for copper density in a magnetron sputtering discharge are presented.

Investigation of the active media in pulsed gas discharge lasers by the Rozhdestvenskii hook method

In this review we generalize the results of our experimental investigations in which the Rozhdestvenskii hook method was first used to look for an inverted population in new spectral transitions. An inverted population in new 3p–3s transitions of the neon atom with λ=588.1, 594.4, 650.6, and 653.2 nm was discovered in the active medium of a Penning plasma laser emitting the λ=585.3 nm neon line in Ne-H2 and Ne-H2-Ar mixtures. Results of investigations of a number of active media are given. An analysis is made of the spatial and temporal distributions of copper atoms in the ground state and of their influence on the lasing efficiency of a copper-vapor laser. Using the rhenium atom as an example, it was shown to be possible to obtain a sufficiently high concentration of refractory metal atoms (>1014 cm−3) in an active medium to form active media of lasers utilizing self-terminating transitions and also plasma lasers.

Absolute copper atom density determination in laser-ablated copper plasmas using hook spectroscopy

Hook spectroscopy has been implemented to measure the absolute density of atomic species in a laser-ablated plasma plume. We use the hook method to determine the density of copper atoms produced by ablation of a copper target in 25 Torr of helium at power densities of ∼1 GW/cm2. The measured copper densities when ablating into 25 Torr of helium backing gas range from 1.5×1015 cm−3 at a delay of 200 μs to 4.4×1013 cm−3 at 5 ms delay. This dramatic decrease in density is due to condensation of the metal vapor to form fine particulate.

Determination of the Relation between Total Absorption of Second Resonance Doublets and Number Density of Alkali Metals by the Hook Method.

Determination of the Relation between Total Absorption of Second Resonance Doublets and Number Density of Alkali Metals by the Hook Method.

Reduced Absorption Coefficients of the 4p-4s Line of K and the 6p-6s Line of Cs under the Conditions of Closed-Cycle MHD Working Gases.

For the measurements of the fraction of seed metal (potassium or cesium) in a closed-cycle MHD (CCMHD) power generation system, the reduced absorption coefficients of the 4p-4s line of potassium (766.5 nm) and the 6p-6s line of cesium (852.1 nm) have been determined experimentally for K-Ar, K-He, Cs-Ar and Cs-He mixtures under the condition of the CCMHD working gas. The column density of the alkali metal was measured using the modified hook method which is not affected by the profile and width of the absorption coefficient. The emissivity of the blue wing of the line was obtained by the emission spectrum. From the reduced absorption coefficient, the number density of the seed metal can be measured by monitoring the change of absorption at a fixed wavelength in the wing of the line.

Atomic f-value measurements of high Rydberg members by pulsed laser-based magneto-optical spectroscopy

The authors describe a novel experimental technique, based on synchronizing pulsed Bitter coils with pulsed tunable laser sources in the ultraviolet, which allows a Faraday rotation method, originally developed for accurate f-value measurements of high Rydberg members with synchrotron radiation to be extended, both in available magnetic field strength and in spectral resolution. By applying their technique, they have extended accurate measurements of f-values for the principal series of Ba I from around n=15, where earlier measurements by the hook method become inaccurate, to n=42, well beyond the present capabilities of alternative experimental methods. Similarly, they have extended earlier magneto-optical measurements for Sr I from n=25 to n=43. Advantages of the new experimental approach are discussed.

Reduced absorption coefficient of the first resonance line of Cs in high-temperature helium

For application to seed-fraction measurements in a closed cycle MHD power- generation system, the relation between the number density of cesium snd the profile of the first resonance line of cesium (7 2 P 3 2 -6 2 S 1 2 , 852.1 nm) has been investigated experimentally in high-temperature helium heated in a shock tube. The column density of cesium was measured by using a modified hook method. The emissivity of the blue wing of the Cs 852.1 nm line was obtained from the emission spectrum. Combining these results, the reduced absorption coefficient of the line was determined for the conditions of closed-cycle MHD working gases. Using this reduced absorption coefficient, the number density of Cs can be measured by monitoring the change of absorption at a fixed wavelength in the wing of the line.

Relation between number densities and total absorption of second-resonance doublets of potassium in potassium-argon mixtures

For application to seed-fraction measurements in a closed cycle MHD power generation system, the relation between the total absorption of second-resonance doublets of potassium (5 2P 3 2 -4 2S 1 2 : 404.4 nm, 5 2P 1 2 -4 2S 1 2 : 404.7 nm) and the potassium number density in a potassium-argon mixture was determined experimentally and compared with previous experimental results based on line broadening measurements. The total absorption could be calculated from line-broadening data assuming an impact approximation in the range from 4.9 x 10 11 to 2.2 x 10 12 sec -1. The column density of potassium which is defined by an integration of the potassium number density along an optical axis, was determined by using a modified hook method and a multichannel spectrometer; a phase change of interference fringes near the absorption spectra of the potassium first resonance lines was measured and fitted numerically to a simple analytic expression for the determination of the column density.

Improved phase method for determination of relative oscillator strengths: application to Cr II

Among spectro-interferometric methods the hook method has been widely used because of the simple data reduction procedure employed. This paper demonstrates how the spectro-interferograms can be analyzed to obtain f-values of significantly higher accuracy by using Fourier analysis rather than applying the classical hook method or phase methods based only on fringe peak detection techniques.