Geometric Weight Research Articles

Modelling catalytic combustion of carbon monoxide and hydrocarbons over catalytically active wire meshes

A new way of preparing catalytically active wire meshes through a thermal-spray technique is described. A metal substrate (e.g. Kanthal AF) was plasma-sprayed with a composite ceramic/polymer-powder. The polymer content of the sprayed layer was burnt off whereupon a well-defined macro-porosity was created. By treating the so obtained material with an alumina-sol the specific surface area could be increased by a factor of 50 or more. The ceramic layer was finally activated with precious metals through an impregnation step. A numerical model was developed to compare the performance of wire-mesh-, monolith- and pellets catalysts. The model describes the resistance to internal and external mass- and heat transfer and the effects of axial dispersion. The wire-mesh model was verified through experiments. Different evaluation parameters were derived to compare the catalyst performance relative to the catalyst volume, the geometric weight, the catalyst weight, the pressure drop and the temperature response. Wire-mesh catalysts offer the following advantages: high mass and heat transfer numbers, moderate pressure drop, insignificant effects of pore diffusion and axial dispersion, thermal and mechanical strength, geometric flexibility, excellent thermal response, simplicity in the catalyst recovery. The cost of a wire-mesh catalyst is expected to be competitive to other alternatives.

Geometrically weighted semiconductor Frisch grid radiation spectrometers

A new detector geometry is described with relatively high gamma ray energy resolution at room temperature. The device uses the geometric weighting effect, the small pixel effect and the Frisch grid effect to produce high gamma ray energy resolution. The design is simple and easy to construct. The device performs as a gamma ray spectrometer without the need for pulse shape rejection or correction, and it requires only one signal output to any commercially available charge sensitive preamplifier. The device operates very well with conventional NIM electronic systems. Presently, room temperature (23°C) energy resolutions of 2.68% FWHM at 662 keV and 2.45% FWHM at 1.332 MeV have been measured with a 1 cm 3 prism shaped CdZnTe device.

Weighted effective-medium approximations for elastic quasisymmetric completely random composites

Abstract The envelopes of the realizable effective-medium hierachical models contain a major central part in the middle between the available bounds on the elastic moduli of isotropic quasisymmetric inhomogeneous materials and hence are expected to cover most (if not all) the property range for the realistic quasisymmetric completely random composites, the constituents of which are combined randomly (i.e. in the utmost uncorrelated manner). A simple effective-medium approximation scheme, based on a weighted sum of the extreme models and containing a few geometric weight parameters, is proposed to describe the effective curves for the mixtures. The geometric parameters can be evaluated from the respective dilute suspension results, or from measurements of the effective properties at some proportions of the components of particular composites.

Objective Analysis by Cumulative Semivariogram Technique and Its Application in Turkey

Abstract A cumulative semivariogram (CSV) method is proposed as an optimum analysis technique for producing gridded fields of meteorological regional variables that are sampled at irregular sites as sparse data. After having discussed the basis of the CSV and its theoretical representations by functional models, the procedure of obtaining weighting functions useful for simple optimum analysis calculations from the CSVs is explained. The experimental CSVs are obtained from monthly rainfall data for northwestern Turkey. Following the interpretation of these experimental CSVs, they are converted into experimental weighting functions necessary for optimum analysis. Comparison of these experimental functions is made on an individual monthly basis with other mathematically simple but geometric weighting functions that are available in the meteorology literature. It is observed that none of the available geometric weighting functions represents completely the regional variation within one month. However, the exp...

Gompertzian growth curves in parathyroid tumours: further evidence for the set‐point hypothesis

Clinical and cell kinetic data in parathyroid tumours show that their rate of growth slows down progressively and that tumour size approaches an asymptotic value. The Gompertz equation has been widely used in oncology to model growth retardation in malignant tumours; we describe its first application to a benign tumour. In 41 patients with radiation associated hyperparathyroidism, individual solutions were derived for the Gompertz equation: Nt = Exp[A/ a(1 - Exp - at)], where A is the rate constant (years-1) for initial exponential growth and a is the rate constant (years-1) for exponential decline in A. Input data comprised three estimates of tumour age at surgery, 100%, 75% and 50% of the time since irradiation, cell number estimated from tumour weight, and current tumour growth rate, representing the difference between current cell birth rate, estimated from the prevalence of mitotic figures, and an assumed mean rate of cell loss of 5%. With 100% tumour age, geometric mean values were 2.76 for A, 0.134 for a, and 0.87 g for the growth asymptote. As assumed tumour age decreased, the rate constants increased and the growth asymptotes declined from 22% to 9% greater than the geometric mean tumour weight. Depending on assumed tumour age, the rate constants were about 15-45 times smaller than in myeloma and in testicular tumours, and the growth asymptotes about 2500 and about 60 times smaller, respectively. A and a were highly correlated (r2 = 0.993), with a slope of 20.9 and no significant intercept. Depending on assumed tumour age, the geometric mean time from the initial mutation to the first cell division ranged from 39 to 92 days, much longer than in malignant tumours. (1) The Gompertz modelling demonstrates that both the nonprogressive clinical course and the slow growth of parathyroid tumours can be accounted for by a single mutation. (2) The extremely low values for A and a, and consequent very long delay before the first cell division, support the notion that the initial mutation does not affect a growth regulatory gene, but increases growth indirectly via an increase in secretory set-point, the clone of mutant cells behaving as if they were in a hypocalcaemic environment until the plasma calcium rises to the new set-point. (3) The clinical characteristics of radiation-induced parathyroid tumours are modelled more closely if there is a substantial delay between time of irradiation and onset of tumour growth. (4) The rate constants A and a are highly correlated because the variability of tumour weight on a logarithmic scale is much lower than the variability of the rate constants.

Gompertzian growth curves in parathyroid tumours: further evidence for the set-point hypothesis

Background: Clinical and cell kinetic data in parathyroid tumours show that their rate of growth slows down progressively and that tumour size approaches an asymptotic value. The Gompertz equation has been widely used in oncology to model growth retardation in malignant tumours; we describe its first aplication to a benign tumour. Methods: In 41 patients with radiation associated hyperparathyroidism, individual solutions were derived for the Gompertz equation: Nt= Exp[A/a(1–Exp–at)], where A is the rate constant (years-1) for initial exponential growth and a is the rate constant (years-1) for exponential decline in A. Input data comprised three estimates of tumour age at surgery, 100%, 75% and 50% of the time since irradiation, cell number estimated from tumour weight, and current tumour growth rate, representing the difference between current cell birth rate, estimated from the prevalence of mitotic figures, and an assumed mean rate of cell loss of 5%. Results: With 100% tumour age, geometric mean values were 2.76 for A, 0.134 for a, and 0.87 g for the growth asymptote. As assumed tumour age decreased, the rate constants increased and the growth asymptotes declined from 22% to 9% greater than the geometric mean tumour weight. Depending on assumed tumour age, the rate constants were about 15–45 times smaller than in myeloma and in testicular tumours, and the growth asymptotes about 2500 and about 60 times smaller, respectively. A and a were highly correlated (r2= 0.993), with a slope of 20.9 and no significant intercept. Depending on assumed tumour age, the geometric mean time from the initial mutation to the first cell division ranged from 39 to 92 days, much longer than in malignant tumours. Conclusions: (1) The Gompertz modelling demonstrates that both the nonprogressive clinical course and the slow growth of parathyroid tumours can be accounted for by a single mutation. (2) The extremely low values for A and a, and consequent very long delay before the first cell division, support the notion that the initial mutation does not affect a growth regulatory gene, but increases growth indirectly via an increase in secretory set-point, the clone of mutant cells behaving as if they were in a hypocalcaemic environment until the plasma calcium rises to the new set-point. (3) The clinical characteristics of radiation-induced parathyroid tumours are modelled more closely if there is a substantial delay between time of irradiation and onset of tumour growth. (4) The rate constants A and a are highly correlated because the variability

Optimization of spheroid production by centrifugal rotary processing

The reproducibility in the preparation of spheroids from powder mixture by centrifugal rotary processing based on a large number of production runs was investigated. Optimization of the process conditions by varying the amount of moistening liquid and spray rate was carried out. The quality of the spheroids produced was evaluated using three criteria, namely the percent yield between 0.85 and 1.18 mm, the geometric weight mean diameter and the geometric standard deviation of the spheroids. From the response surfaces and contour plots, it is apparent that the optimized region of percent yield of spheroids was at an amount of moistening liquid between 38–42% and spray rate between 35–43 ml/min. The release kinetics of the spheroids containing a highly water-soluble drug, chlorpheniramine maleate or a less water-soluble drug, paracetamol, fitted the square-root of time equation, thereby following an inert matrix release mechanism.

Limits and rates of convergence for the distribution of search cost under the move-to-front rule

We derive upper and lower bounds on total variation distance to stationarity for the distribution of search cost under the move-to-front (MTF) rule for self-organizing lists with i.i.d. record requests. These enable us to obtain sharp rates of convergence for several standard examples of weights, including Zipf's law and geometric weights, as the length of the list becomes large. The upper bound also shows that a number of moves of the order of the length of the list is uniformly sufficient for near-stationarity over all choices of weights. Concerning the stationary search cost distribution itself, we use a representation obtained by considering the continuized MTF Markov chain to derive, for each of the standard examples, the asymptotic distribution for long lists.

Proportional Discounting of Future Costs and Benefits

Social benefits in the distant future receive very little importance when a public policy analysis uses a constant-discounting model with its geometric timing weights to compare future benefits with present costs. This paper defines conditions on social preferences that imply a model having arbitrary timing weights. We then introduce a condition on preferences that restricts this general model to one in which the timing weights are linear fractional This model is proposed as an alternative to the constant-discounting model. It accords far more importance to the distant future than does constant discounting, and like constant discounting it depends on the assessment of a single parameter.

A methodology for machine tools error correction using reference parts

Abstract In this paper, a methodology is presented for machine tool error correction which uses reference parts as metiological standards. These reference parts have the same geometric shape and weight as real workpieces. Consequently, the proposed methodology minimizes the uncertainty which arises from geometric interpolation, but still yields satisfactory results for multi-axis machine error characterization. A generalized error model is derived lo describe the relative error motion between the tool and the workpiccc. Iterative search algorithms are presented which increase the effectiveness of the error characterization process. Three case studies arc described which demonstrate the application of the methodology for four sample reference parts on three different machines. The results from these studies show that the error correction method can be used to characterize the positioning errors with estimation accuracy approaching the resolution of the machines.

Quick and exhaustive descrambling methodology for high-density static random access memories using voltage contrast

The external test previous to any failure analysis of a static RAM provides the logical address of each failure. We developed a methodology allowing a fast mapping of SRAMs, passivated or not, by voltage contrast in a scanning electron microscope, with minimum initial information. It uses voltage coding and the phase-selective voltage contrast. The first observations permit to distinguish the row bits from the column bits, and to sort the address bits according to the order of geometrical binary weight. The second part of the mapping consists in determining the symmetries associated with each address bit. Voltage coding observation needs only a few images. The second method requires at least as many images as address bits, but can be efficiently used with buried lines. This methodology was designed to be efficient whatever the matrix map may be. It was applied successfully on 64 kbit to 1 Mbit passivated CMOS SRAMs.

Vibrational nonequilibrium effects on diatomic dissociation rates

The collision-induced dissociation rate of diatomic molecules from a ladder of rotational and anharmonic vibrational states is developed, and the correction for vibrational nonequilibrium is considered. The result is similar to an analytic correction derived by Hammerling et al. (1959) for harmonic oscillators. An empirical correction algorithm suggested by Park (1987, 1990) gives similar results when vibrational temperature is comparable to kinetic temperature but underestimates the dissociation rate when vibrational temperature is small compared with the kinetic temperature. This algorithm uses an effective temperature in the experimentally determined Arrhenius expression for the rate coefficient, which is a weighted average of the vibrational and kinetic temperature, whereas theory indicates that kinetic temperature should appear only in the exponential term of the Arrhenius expression. Nevertheless, an effective temperature can always be found that will numerically duplicate the proper rate coefficient at any given condition, but a constant weighting factor cannot be expected to provide this. However, the algorithm can he adjusted to give reasonable results over a range of conditions if the geometric weighting factor is taken to be a simple linear function of the ratio of vibrational to kinetic temperature in the gas.

Do Large Females Lay Small Eggs? Sexual Dimorphism and the Allometry of Egg and Clutch Volume

This paper describes the use of comprehensive models of the relations between egg volume and body weight and clutch volume and body weight to provide insight into hypotheses relating to the evolution and adaptive significance of sexual dimorphism in body size. Mean egg dimensions and adult body weights were obtained for 326 species, mainly of raptors (including owls), shorebirds, frogmouths (including nightjars and allies) and storks (including the New World vultures); groups in which there is a range of dimorphism, in both direction and degree. In addition to female body weight, sexual dimorphism (D) in body size, phylogenetic relationship, and clutch size all added significantly to the overall model of egg volume, which was curvilinear in form and accounted for 98.3% of the variation. Approximately, egg volume was proportional to D026. For clutch volume our model accounted for 90% of the variation. After controlling for body weight, dimorphism accounted for a significant proportion of the residual variation and clutch volume was proportional to D-)22 approximately. Amongst species exhibiting reversed sexual dimorphism (RSD: female the larger sex) in body size, the more dimorphic species had relatively small eggs and a small clutch volume for the weight of the female. Conversely, NRSD (nonreversed dimorphism; male larger) species had relatively large egg and clutch volume. The geometric mean weight of the sexes, rather than female weight or male weight and dimorphism, was the best descriptor of egg volume. We argue that these results are compatible with the hypothesis that patterns of size dimorphism in predatory birds are determined by sexual selection.

High-performance mass spectrometers of third-order focusing

Ion optics of high-performance mass spectrometers of double-focusing type is investigated. The characteristics of mass spectrometers are normally determined by the resolving power and the transmission of the apparatus. In addition to these, its geometrical size, cost and weight are also important factors. In order to estimate these characteristics numerically, a performance factor, PF, and an aberration factor, AF, are introduced and defined. Ion-optical systems with the field arrangement QQQOHQC (quadrupole, quadrupole, quadrupole, octupole, homogeneous magnetic sector, quadrupole, cylindrical electric sector) are investigated with the objective to obtain large PF and AF simultaneously. Almost perfect second- and third-order focusing and high performance are attained.

Practical exponential smoothing credibility

Since some time so-called credibility estimators with geometric weights are of some practical importance. As alternatives one can use so-called exponential smoothing credibility estimators. In the present paper the second ones are prepared for practical application.

A Comparison of the Growth of Vertically-Migrating and Nonmigrating Kokanee (Oncorhynchus nerka) Fry

A comparison of the growth of vertically-migrating kokanee (Oncorhynchus nerka) fry and nonmigrating fry confined to the epilimnion in thermally-stratified Kootenay Lake, British Columbia rejected the bioenergetic efficiency hypothesis for the adaptive significance of vertical migration. Growth rates were higher for nonmigrating fry than for vertically-migrating fry. Geometric mean wet weights in early October were 2.88 g for non-migrating fry and 1.40 g for vertically-migrating fry of the same stock. The geometric mean weight of fry of a second stock rearing in the isothermal West Arm, in which behavioural thermoregulation by vertical migration was not possible, was 8.54 g in early October.

Bonus hunger and credibility estimators with geometric weights

In the present paper we study the bonus hunger effect in experience rating schemes based on credibility estimators with geometric weights under different assumptions about the strategy of the policyholder and the experience rating scheme. Some numerical examples are given.

The Model Compounds and Conformational Analysis of Poly(thiotrimethylene) Using Molecular Mechanics Method

Abstract Several model compounds of poly(thiotrimethylene), including one to four thiotrimethylene units, were studied by means of a molecular mechanics method. The geometric and statistical weight parameters were directly derived from the results of molecular mechanics calculations concerning several conformers of these model compounds. Although the first-order interactions of poly(thiotrimethylene) were significantly larger than those of poly(oxyalkylenes), the second-order interactions of this polymer were much smaller. The “gauche effect” by sulfur atoms seemed to be mainly caused by small second-order interactions. By means of the model, compounds including more than three repeating units, the calculated configuration-dependent properties were in better agreement with the experimental ones than that calculated earlier. The better agreement was obtained by varying some of the geometric parameters. Compounds including more than three repeating units of the polymer were available as model compounds. Since this was also true in poly(oxyalkylenes), it was found that a combination of the methods of molecular and statistical mechanics was sufficiently effective to investigate the configurational properties of poly(thiotrimethylene).

Geotomography with local earthquake data

The inversion of local earthquake data (LED) for three‐dimensional velocity structure requires the simultaneous solution of the coupled hypocenter‐model problem. The Aki‐Christoffersson‐Husebye method (ACH) involves the inversion of large matrices, a task that is often performed by approximative solutions when the matrices become too big, as is the case for most LED, considering the coupled inverse problem. Such an approximate method (herein referred to as approximate geotomographic method) is used to perform tests with LED to obtain the best suited inversion parameters, such as velocity damping and number of iteration steps. The ACH method has been proposed for use of teleseismic data. Several adjustments to the original ACH method, which are necessary for use of LED, have been developed and are discussed. Such adjustments are the separation of the unknown hypocentral from the velocity model parameters for the inversion, the use of geometric weighting and step length weighting, the calculation of a minimum one‐dimensional (1D) model as the starting three‐dimensional (3D) model for the model inversion, and the display of an approximate resolution matrix (ray density tensors) before the inversion is performed. The ray density tensors allow the block cutting, e.g., the definition of the 3D velocity grid, to better correspond with the resolution capability of the specific data set. The adjustments to the method are tested by inversion of realistic LED of known variance. Synthetic LED are also used to demonstrate the effects of systematic errors, such as mislocations of seismic stations, on the resulting velocity field. Using the data sets from Long Valley, California, Yellowstone National Park, Wyoming, and Borah Peak, Idaho, the effects of improvements to the ACH method and of the data filtering process are shown. The use of the minimum 1D models for routine earthquake location improves this location procedure, as shown with the relocation of shots for the Long Valley and Yellowstone areas. The three‐dimensional velocity fields obtained by the ACH method for the Long Valley and Yellowstone areas show local anomalies in the p velocity that can be correlated with tectonic and volcanic features. A pronounced anomaly of low p velocity below the Yellowstone caldera can be interpreted as a large magma chamber. However, the bulk of the paper addresses problems of the inversion method. The LED from the areas mentioned above are used to numerically and theoretically tune the inversion method for the defects that all real data contain. It is shown that one of the most important steps for any inversion of LED is the selection of the data for quality and for geometrical distribution.

Uterine Decidual ization in Hypophysectom ized-Ovariectom ized Rats: Effects of Pituitary Hormones1

Decidualization of the endometrial stroma occurs in rats in response to implanting blastocysts or after the application of an appropriately timed artificial stimulus. It is well established that decidualization is regulated by estrogens and progesterone (P). The present study investigated the role of pituitary hormones in this response. Decidualization produced by the bilateral intrauterine injection of 100 microliter sesame oil was compared in ovariectomized (OVX) and hypophysectomized (HYPOX)-OVX rats. All animals were treated with a sequence of 17 beta-estradiol (E2) and P that in OVX rats supported decidualization. As assessed by uterine weights 5 days after uterine stimulation, decidualization was much greater in OVX than in HYPOX-OVX rats (geometric mean uterine weights of 1539 and 376 mg, respectively). To determine the ability of pituitary hormones to restore decidualization in HYPOX-OVX rats, animals were treated with ovine prolactin (oPRL, 2 x 100 micrograms daily), bovine growth hormone (bGH, 2 x 125 micrograms daily), and thyroxine (1 microgram/day, replacement for thyrotropin) in addition to E2 and P. Combined treatment with bGH + thyroxine resulted in decidualization which was not significantly different from that obtained in OVX rats; the effects of bGH and thyroxine were additive. oPRL had no significant effect. Administration of bGH + thyroxine during the prestimulation period resulted in decidualization which did not differ significantly from that obtained when the hormones were administered both pre- and poststimulation; administration during the poststimulation period only, when growth and differentiation of decidual cells occurs, resulted in much less decidualization. Because an increase in endometrial vascular permeability is a prerequiste for decidualization, [125I]-labeled bovine serum albumin was used to assess permeability 8 h after uterine stimulation. Uterine concentrations of radioactivity indicated that endometrial vascular permeability was increased to the same extent in bGH + thyroxine-treated HYPOX-OVX rats as in OVX animals; this increase was significantly reduced in vehicle-treated HYPOX-OVX rats. Because prostaglandins (PGs) are involved in decidualization, the possibility that the reduced responses in vehicle-treated HYPOX-OVX rats were a consequence of a decreased capacity of the uterus to produce PGs in response to the deciduogenic stimulus was investigated. As indicated by uterine PGE and PGF concentrations 15 min after uterine stimulation, uterine PGE and PGF production was increased by the stimulus in both vehicle-treated and bGH + thyroxine-treated HYPOX-OVX rats.(ABSTRACT TRUNCATED AT 400 WORDS)