bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model Simulation for Generation and Migration of Methane Hydrate
Authors: Katoh Arata , Nakayama Kazuo , Baba Kei , Uchida Takashi 
Published: October 2002

A one-dimensional numerical simulation model has been developed to forecast the distribution of methane hydrate in the subsurface. The model includes the generation and migration of methane, and the process of methane-hydrate formation after sedimentation. The following processes are consideredfor each cell within the model; 1) Calculation of methane generated within the sediment 2) Process of migration of dissolved methane with compacting water 3) Process of migration of gaseous methane as a separate phase, by buoyancy 4) Evaluation of sealing capacity from the hydrostatic equilibrium equation 5) Calculation of the amount of methane hydrate formation from in-situ temperature and pressure The model will predict the distribution of methane hydrate after applying the above processes for all the sediments. We use this model to simulate the process of methane hydrate formation at ODP Leg 164 Site 997 at Blake Ridge, offshore Atlantic coast of the USA. At this location, the methane hydrate zone indicated by the bottom simulating reflector (BSR) is about 100 m shallower than the base of gas (methane) hydrate stability zone (BGHS) which is calculated from the model using measured temperatures and pressures. To explain this difference, the following hypotheses are proposed; 1) The BSR is a remnant of the past the BGHS that was created when temperature was higher or sea level was lower. 2) Methane hydrate is being generated between the BSR and the BGHS at present. The model simulation indicates that analysis, based not only on present physical conditions but also on the geohistrical time scale, is necessary to explain the present day distribution of methane hydrate.
Oil Company Profitability: Observations on the Use of Oil Product Price Assessments and Associated Errors
Authors: Jenkins Gilbert 
Published: October 2002

Oil companies often report the exact price obtained for crude oil sales. Furthermore, crude oil prices may be linked to the price of Brent crude oil which is actively and very transparently traded on the International Petroleum Exchange. Brent crude oil prices are reported worldwide electronically and in many newspapers on a daily basis. Gas oil (No2. Fuel oil in the USA) is actively traded on the IPE and on NYMEX and the prices are also reported worldwide almost instantaneously. One grade of unleaded gasoline is traded on NYMEX but all other oil products do not have regulated and transparent markets. The prices of these products are assessed by price reporters following daily discussions with active oil traders. Two prices are assessed and reported, the bid (low) and offer (high) even if no trade has taken place. The oil industry itself and oil products consumers make much use of these assessed prices. The object of this paper is to provide some statistical detail on the differences between various product price assessments made through 2000. From these differences, it is possible to provide an indication of the precision of oil product price assessments. However, it is doubtful if precision data based on a simple determination of the standard deviation of the differences between the assessment made by the various price reporting services would be of practical use.
The Microporosity of Activated Carbon Fibre KF1500 Assessed by Combined CO2 Adsorption and Calorimetry Techniques and by Immersion Calorimetry
Authors: Guillot A. , Stoeckli F. , Bauguil Y. 
Published: October 2002

The microporous structure of the activated carbon fibre KF1500 was investigated by applying a new technique as presented here. This was based on a combination of high-pressure CO2 adsorption measurements between 253 K and 353 K with direct measurement of the differential heats of adsorption at 298 K at low and medium coverages. The validity of this approach was tested by using two activated carbons which has been characterized previously by a variety of techniques, including immersion calorimetry. It appears that a combination of high-pressure adsorption and calorimetry with CO2 alone is a useful tool for the characterization of the whole range of microporosity. This approach confirms earlier observations, according to which the initial stage of adsorption by strongly activated carbons corresponds to adsorption on the walls of large micropores rather than to the primary filling of small micropores.
Oscillatory Adsorption as the Determinant of the Fluctuating Behaviour of Different Heterogeneous Systems
Authors: Patrylak Kazymyr , Patrylak Lyubov , Taranookha Oleg 
Published: October 2002

Heterogeneous, catalytic oscillatory reactions as well as the oscillatory process of complex formation based on solid urea have been analysed in an attempt to ascertain the cause of such oscillatory mechanisms. In this context, oscillatory adsorption/desorption, phase transitions of the supported metal employed as the catalyst in the relevant oscillatory oxidation–reduction reactions as well as the reactions themselves have been considered. Based on an analysis of two oscillatory systems, of which one (i.e. the oscillatory alkylation of isobutane with butenes on a metal-free zeolite catalyst) is not complicated by any phase transitions, whilst the other (i.e. the oscillatory formation of an urea–octane complex via the interaction of urea with a binary vapour mixture of octane and non-complex-forming hydrocarbons) is not complicated by any chemical reactions, it is possible to infer that the source of the oscillatory properties of heterogeneous systems which involve the chemical interaction of their components is oscillatory adsorption which occurs as an uncomplicated self-supporting process which appears to proceed without any increase in the entropy of the system. The occurrence of oscillatory adsorption in a heterogeneous system leads to an oscillatory behaviour in the corresponding process, involving its simultaneous retardation in a similar manner as does the pendulum of a clock with respect to the untwisting of a spring or the oscillatory circuit of an electromagnetic system with respect to the discharge of a dry battery.
Catalytic Conversion of Ethanol over γ-Irradiated CuO/MgO
Authors: El-Shobaky H.G. , El-Boohy H.A. , Doheim M.M. 
Published: October 2002

Copper oxide supported on MgO was prepared by the wet impregnation method using basic magnesium carbonate and copper nitrate. Thus, a known weight of basic magnesium carbonate was treated with a known amount of copper nitrate dissolved in the least amount of distilled water necessary to make a paste. The paste was dried and then precalcined for 5 h at 400°C, 500°C or 600°C, respectively. The solids obtained were exposed to different doses of γ-rays ranging between 0.2 MGy and 1.6 MGy. Catalytic conversion of ethanol was carried out at 250–400°C over various irradiated solids employing a micropulse technique. Other techniques used were nitrogen adsorption measurements at −196°C, IR spectroscopy and XRD measurements. The results obtained revealed that all the catalysts investigated were selective towards dehydration, their activities decreasing slightly on increasing the precalcination temperature over the range 400–600°C. γ-Irradiation brought about a progressive decrease in their catalytic activities with a dose of 0.8 MGy being sufficient to effect a decrease of more than 90% in the initial value. The irradiated catalysts regained virtually all their initial activity upon increasing the γ-ray dose to 1.6 MGy. These results were discussed in terms of the progressive removal of OH groups from the solid surface by exposure to γ-irradiation in the range 0.2–0.8 MGy. The attainment of the initial catalytic activity upon exposure to a dose of 1.6 MGy was attributed to the creation of surface OH groups due to the interaction between the catalyst samples and water liberated during the early stages of the dehydration reaction.
Some Surface and Catalytic Properties of V2O5–Cr2O3/SiO2, MoO3–Cr2O3/SiO2 and NiO–Cr2O3/SiO2 Ternary Solid Catalysts
Authors: Youssef A.M. , Ahmed A.I. , Samra S.E. , El-Assy N.B. , El-Sharkawy E.A. 
Published: October 2002

Ternary vanadia–chromia/silica, molybdena–chromia/silica and nickel oxide–chromia/silica solid catalysts were prepared by the impregnation method. Their structural characteristics were examined using differential thermal analysis (DTA) and X-ray diffraction techniques. The catalytic activities of the prepared samples towards the conversion of isopropanol and cyclohexanol and the kinetics of these catalytic conversions were studied with the aid of a microcatalytic pulse technique. In addition, the surface acidities of selected samples were measured from the percentage of propene produced by the poisoned catalysts. X-Ray diffraction and differential thermal analysis revealed that the only detectable phase was α-Cr2O3 with the presence of all other phases or spinel not being confirmed. The order of the surface acidities was found to lie in the sample sequence: 3 wt% V2O5–20 wt% Cr2O3/SiO2 > 3 wt% MoO3–20 wt% Cr2O3/SiO2 > 20 wt% Cr2O3/SiO2 > 3 wt% NiO-20 wt% Cr2O3/SiO2, all samples having been precalcined at 500°C. Catalytic conversion of isopropanol gave propene and acetone, whereas cyclohexene, cyclohexanone and methylcyclopentene (as an isomerization product) were produced from the catalytic conversion of cyclohexanol. The catalytic activity was found to be influenced considerably by the type of impregnating ion employed and by the precalcination temperature, and hence by the surface acidity of the examined catalysts. On the other hand, the Bassett–Habgood and Kiperman equations could be applied in a satisfactory manner to the generation of the various reaction products. The calculated activation energies for the catalytic conversion of isopropanol and cyclohexanol were compared.
Adsorption of Textile Dyes on to Activated Carbons Synthesized from Solid Waste: Decolourizing Power in Relation to Surface Properties
Authors: El-Sharkawy E.A. 
Published: October 2002

Powdered wood of Eucalyptus rostrata (Myrtaceae family) obtained as a solid waste was carbonized at 873 K in a nitrogen flow. The resulting products were activated with steam (CS), zinc chloride (CZ) and phosphoric acid (CA) to obtain three series of activated carbon. The textural properties, including surface area, mean pore radius and total pore volume, were examined from the low-temperature adsorption of nitrogen at 77 K. FT-IR spectroscopy and the base neutralization capacity were used for the detection of surface groups. The adsorption power of the prepared samples for the decolourization of Remazol Brilliant Blue (RBB) and New Coccine (NC) dyes, present as carcinogenic materials in wastewater, was studied at 296 K and 318 K, respectively. FT-IR spectroscopy and the base neutralization capacities indicated the presence of carboxylic and phenolic groups on the carbon surfaces. The type and amount of activator employed had a considerable influence on the textural characteristics of the samples investigated. An increase in the activator/carbon ratio was also associated with the development of porosity and hence with an increase in the specific surface area. The Dubinin–Radushkevich (DR), Langmuir, Freundlich and Weber–Morris equations were all applied satisfactorily for the calculation of various adsorption parameters, e.g. Ym, a, KF and Eads. In addition, the enthalpy of adsorption was also calculated over the temperature interval 296–318 K. It was found that the structures of the two dyes studied and the types and amounts of activators employed had a considerable influence on the adsorption parameters estimated.
Sound Transmission Loss of Thick Perforated Panels
Authors: Chen K. T. , Jan S. H. 
Published: October 2002

A study is reported of the sound transmission loss of perforated panels. The study includes a theoretical analysis and measurement by means of sound intensity. The predicted transmission loss is similar to that measured above 630 Hz. The maximum discrepancy is less than 2 dB. The perforation in a thick panel is found to reduce the coincidence effect at the critical frequency.
Inter-Laboratory Test of Sound Insulation Measurements on Heavy Walls: Part II — Results of Main Test
Authors: Meier A. , Schmitz A. , Raabe G. 
Published: October 2002

This second part, of a two part paper, presents and analyses the results of an Inter-Laboratory Test (ILT) for a heavy single leaf wall. Significant differences were found in the measured sound reduction index (SRI) for the participating laboratories. These differences were not caused by the measurement technique. During the ILT the damping of the test wall in terms of the total loss factor in each laboratory was measured in addition to other measurements. The damping of the test element was controlled by the design of the transmission suite supporting walls. It is shown that the results of the damping measurements can be used to reduce the variations of SRI. Other influences of the transmission suite such as flanking transmission are also discussed. It is found that the principle reason for the differences in the sound reduction index is the type of construction of the transmission suite. From this study suggestions for the improvement in the reliability of sound insulation measurements are given, which could provide improvements in standardisation.
An Investigation into the Reproducibility Values of the European Inter-Laboratory Test for Lightweight Walls
Authors: Smith R.S. , Pompoli R. , Fausti P. 
Published: October 2002

In an inter-laboratory test programme (ILT) for the measurement of airborne sound insulation of lightweight walls, reproducibility values of up to 12dB were obtained from the sound reduction index measured in 21 participating laboratories. These high reproducibility values were for a test structure composed of lightweight plasterboard panels, forming a double wall, mounted on separate metal ‘C’ channels. This paper presents possible reasons for the large reproducibility values for the double wall using experimental investigations and theoretical models using Statistical Energy Analysis (SEA). Whilst the sound reduction index(SRI) does take into account the different test wall areas and reverberation times of the respective laboratories involved, some factors which may influence the measured SRI values are not. It is suggested that the principle factor which may have effected the SRI values of this test programme for the double wall was the lining material of the test aperture in the various laboratories which can provide a flanking transmission path between both sides of the double wall. Other factors are discussed which may also play a contributory role in causing differences in the measured SRI values such as sill/reveal size, aspect ratio, panel-channel connections and workmanship.
Parametric Study of Tendon Profiles in Prestressed Steel Plate Girder
Authors: Ronghe G. N. , Gupta L. M. 
Published: October 2002

The concept of prestressing steel structures has only recently been widely considered, despite a long and successful history of prestressing concrete members. Several analytical studies of prestressed steel plate girder were reported in the literature, but much of that work was not studied with reference to different parameters like tendon profile, eccentricity, partial span to full span ratio, prestressing force, load carrying capacity etc. associated with prestressing. This paper examines analytically a comparative study of various tendon configurations and prestressing parameters on over all analysis and design of prestressed steel plate girder. The output from the computer Program for analysis and design of steel plate girder prestressed with different tendon configurations are compared among each other. As a Case-study, a prototype model of Prestressed Steel Testing Frame with straight tendon has been designed, constructed and tested in the laboratory for its safe load carrying capacity and maximum deflection.
Random polynomials having few or no real zeros
Authors: Dembo Amir , Poonen Bjorn , Shao Qi-Man , Zeitouni Ofer 
Published: October 2002

Consider a polynomial of large degreennwhose coefficients are independent, identically distributed, nondegenerate random variables having zero mean and finite moments of all orders. We show that such a polynomial has exactlykkreal zeros with probabilityn−b+o(1)n^{-b+o(1)}asn→∞n \rightarrow \inftythrough integers of the same parity as the fixed integerk≥0k \ge 0. In particular, the probability that a random polynomial of large even degreennhas no real zeros isn−b+o(1)n^{-b+o(1)}. The finite, positive constantbbis characterized via the centered, stationary Gaussian process of correlation functionsech(t/2){\mathrm {sech}} (t/2). The value ofbbdepends neither onkknor upon the specific law of the coefficients. Under an extra smoothness assumption about the law of the coefficients, with probabilityn−b+o(1)n^{-b+o(1)}one may specify also the approximate locations of thekkzeros on the real line. The constantbbis replaced byb/2b/2in case the i.i.d. coefficients have a nonzero mean.
Soil resources and their assessment
Authors: Webster R. 
Published: October 2002

The assessment of the soil resource of any region has two parts, namely, an inventory of the kinds of soil and their distribution, and knowledge of the way each kind can be used and its performance under a range of circumstances. Soil varies substantially and intricately over short distances in most parts of the world. Inventory by field survey and air–photo interpretation must be done at a local scale. Inventories may be combined so that an individual nation state or region of similar size can know what kinds of soil it has, how much and where they are, how much each can produce, how to manage each in perpetuity, and the risks of degradation in use. Local classifications, with classes defined simply and identifiably on aerial photographs, will serve for mapping, and in combination with classical statistics can provide sound estimates from stratified sampling and agronomic experimentation.
Sound assessment should also be at this local scale initially. This should combine fundamental understanding of the soil's behaviour, strategic agronomic research on regional stations, and on–farm trials. The last are crucial for estimating productivity of the soil in practice.
Data from all sources can be stored, sorted and displayed by geographic information systems that now have abundant capacity. They should be indexed by soil class and other attributes, with clear distinction being made between assessments of productive potential and basic data. They should be publicly accessible, to ensure that data are readily available and never lost.
Estimates of the soil resource and its productivity for large regions, nation states, and the world can be compiled from local surveys by sampling through a ‘bottom–up’ procedure.
Managing soils for long-term productivity
Authors: Syers J. K. 
Published: October 2002

Meeting the goal of long–term agricultural productivity requires that soil degradation be halted and reversed. Soil fertility decline is a key factor in soil degradation and is probably the major cause of declining crop yields. There is evidence that the contribution of declining soil fertility to soil degradation has been underestimated.Sensitivity to soil degradation is implicit in the assessment of the sustainability of land management practices, with wide recognition of the fact that soils vary in their ability to resist change and recover subsequent to stress. The concept of resilience in relation to sustainability requires further elaboration and evaluation.In the context of soil degradation, a decline in soil fertility is primarily interpreted as the depletion of organic matter and plant nutrients. Despite a higher turnover rate of organic matter in the tropics there is no intrinsic difference between the organic matter content of soils from tropical and temperate regions. The level of organic matter in a soil is closely related to the above and below ground inputs. In the absence of adequate organic material inputs and where cultivation is continuous, soil organic matter declines progressively. Maintaining the quantity and quality of soil organic matter should be a guiding principle in developing management practicesSoil microbial biomass serves as an important reservoir of nitrogen (N), phosphorus (P) and sulphur (S), and regulates the cycling of organic matter and nutrients. Because of its high turnover rate, microbial biomass reacts quickly to changes in management and is a sensitive indicator for monitoring and predicting changes in soil organic matter. Modelling techniques have been reasonably successful in predicting changes in soil organic matter with different organic material inputs, but there is little information from the tropics.Nutrient depletion through harvested crop components and residue removal, and by leaching and soil erosion accentuates the often very low inherent fertility of many soils in the tropics. An integrated approach involving inorganic and organic inputs is required where animal and plant residues are returned, as far as practicable. Chemical fertilizers alone cannot achieve long–term productivity on many soils and organic material inputs are required to maintain soil organic matter levels and crop productivity. A major research effort is required to develop improved strategies for halting and reversing soil degradation if long–term productivity is to be secured.
Structure and function of the Nautilus statocyst
Authors: Neumeister H. , Budelmann B. U. 
Published: October 2002

The two equilibrium receptor organs (statocysts) ofNautilusare ovoid sacks, half-filled with numerous small, free-moving statoconia and half with endolymph. The inner surface of each statocyst is lined with 130 000 to 150 000 primary sensory hair cells. The hair cells are of two morphological types. Type A hair cells carry 10 to 15 kinocilia arranged in a single ciliary row; they are present in the ventral half of the statocyst. TypeBhair cells carry 8 to 10 irregularly arranged kinocilia; they are present in the dorsal half of the statocyst. Both type of hair cells are morphologically polarized. To test whether these features allow theNautilusstatocyst to sense angular accelerations, behavioural experiments were performed to measure statocyst-dependent funnel movements during sinusoidal oscillations of restrainedNautilusaround a vertical body axis. Such dynamic rotatory stimulation caused horizontal phase-locked movements of the funnel. The funnel movements were either in the same direction (compensatory funnel response), or in the opposite direction (funnel follow response) to that of the applied rotation. Compensatory funnel movements were also seen during optokinetic stimulation (with a black and white stripe pattern) and during stimulations in which optokinetic and statocyst stimulations were combined.These morphological and behavioural findings show that the statocysts ofNautilus, in addition to their function as gravity receptor organs, are able to detect rotatory movements (angular accelerations) without the specialized receptor systems (crista/cupula systems) that are found in the statocysts of coleoid cephalopods. The findings further indicate that both statocyst and visual inputs control compensatory funnel movements.