High temperature rate coefficient for the reaction of O(P) with H2 obtained by the resonance absorption of O and H atoms

The reaction of O(³P) with H₂ has been studied behind reflected shock waves in the temperature range of 1713–3532K at total pressures of about 1.4–2.0 bar by Atomic Resonance Absorption Spectroscopy using mixtures of N₂O and H₂ highly diluted in Ar. The O atoms were generated by the fast thermal decomposition of N₂O and the reaction with H₂ was followed by monitoring the time dependent O and H atom concentrations in the postshock reaction zone. For the experimental conditions chosen, the measured O and H atom concentrations were primarily sensitive to the well-known N₂O dissociation and to the studied reaction and hence its rate coefficient could be deduced. The measured rate coefficient data are fitted by the least-squares method to obtain the following three parameter expression: K₄=3.72×10⁶(T/K)^2.17exp(−4080K/T)cm³ mol⁻¹8⁻, which is in excellent agreement with the recent ab initio calculations for the rate coefficient of this reaction in the overlapping temperature range. The present result is also compared to the experimental results reported by earlier investigators.     

Radiation damage studies on the first wall of a HYLIFE-II type fusion breeder

The radiation damage on the first wall [made of (1) a ferritic steel (9Cr–2WVTa), (2) a vanadium alloy (V–4Cr–4Ti) and (3) SiC_f/SiC composite] of an inertial fusion energy (IFE) reactor of HYLIFE-II type is investigated. A protective liquid wall with variable thickness, containing Flibe + heavy metal salt (UF₄ or ThF₄) is used for first wall protection. The content of heavy metal salt is chosen as 4 and 12 mol%. Neutron transport calculations are performed with the aid of the SCALE4.3 System by solving the Boltzmann transport equation with the XSDRNPM code in 238 energy groups and S₈–P₃ approximation.

A flowing wall with a thickness of 60 cm can extend the lifetime of the solid first wall structure to a plant lifetime of 30 years for 9Cr–2WVTa and V–4Cr–4Ti, whereas the SiC_f/SiC composite as first wall needs a flowing wall with a thickness of 85 cm to maintain the radiation damage limit. Substantial extra revenue can be gained through the insertion of a heavy metal salt constituent into Flibe, which allows breeding fissile fuel for external reactors and increasing energy multiplication (²³³U with a value of up to 1,000,000,000 $/year or ²³⁹Pu for few 100,000,000 $/year).     

Numerical study of turbulent flow in two-dimensional channel with surface mounted obstacle

This paper presents the numerical predictions of the fluid and heat transfer characteristics for the turbulent channel flow with one and two obstacles. The turbulent governing equations are solved by a control-volume-based finite-difference method with non-uniform staggered grids and the well-known k-ε model and its associated wall function to describe the turbulence structure. The velocity and pressure terms of momentum equations are solved by the SIMPLE method. The parameters interested include entrance Reynolds number (between 10⁴ and 10⁶), the ratio of channel height to obstacle height (B/H) and the dimensionless distance between two obstacles (PR). Computations are carried out for three working mediums, air, water and Freon R-12. The predicted attachment point located at x/H = 12.24 are compared with the experimental results of x/H = 12.3 for the unheated single obstacle case with B/H = 15. The predicted heat transfer around the attachment point is much better than that in the recirculation region due to the strong impact at the attachment point.     

An explanation for the high stability of polycarboxythiophenes in photovoltaic devices—A solid-state NMR dipolar recoupling study

Continuous operation of a polymer photovoltaic device under accelerated conditions for more than 1 year has been demonstrated (8760 h at 72 °C, 1000 W m⁻², AM1.5, under vacuum). Formation of hydrogen-bonded networks is proposed to be responsible for the long lifetime and high stability observed in photovoltaic devices employing polythiophene substituted with carboxylic-acid moieties under oxygen free conditions. ¹H and ¹³C solid-state NMR, IR, and ESR spectroscopy of unmodified and isotopically labeled polythiophenes were studied. Distances between the isotopically labeled carboxylic acid carbon atoms were measured by ¹³C solid-state magic-angle-spinning (MAS) NMR using symmetry-based double-quantum (2Q) dipolar recoupling. This revealed the presence of ¹³C–¹³C distances of 3.85 Å, which correspond to the C–C distance in hydrogen-bonded carboxylic acid dimers. In spite of the presence of carboxylic groups in the polymer as demonstrated by ¹³C CP/MAS NMR and IR spectroscopy, the absence of carboxylic protons in solid state ¹H NMR spectra indicate that they are mobile. We link the extraordinary stability of this system to the rigid nature, cross-linking through a hydrogen-bonded network and a partially oxidized state.     

Chimney effect in a “T” form cavity with heated isothermal blocks: The blocks height effect

In this paper, a numerical study of natural convection from a two dimensional “T” form cavity with rectangular heated blocks is conducted. The blocks are identical, and the domain presents a symmetry with respect to a vertical axis passing through the middle of the opening. The governing equations are solved using a control volume method, and the SIMPLER algorithm for the velocity–pressure coupling is employed. Special emphasis is given to detail the effect of Rayleigh number and block height on the heat transfer and the flow rate generated by the chimney effect. The results are given for the parameters of control as, 10⁴Ra3×10⁶, Pr=0.71, opening diameter (C=l^′/H^′=0.15), blocks gap (D=d^′/H^′=0.5) and blocks height (1/8B=h^′/H^′1/2). These results show that the heat transfer variation with Ra is in the same manner as those met in the case of the vertical smooth or ribbed channels.     

Weighing the Universe and its smallest constituents

The masses of both the neutrino and the Universe are derived from a mutually consistent set of equations in which the neutrino is coupled to the ground state of the Universe. A mass of m_v<10^-69 kg (energy equivalent ~10^-33 eV) is found for the neutrino. The equations yield a mass M~10⁵⁴ kg (~5×10⁸⁰ proton masses) for the Universe. It is found that the Universe is a black hole. Possible solutions of the missing solar neutrino flux problem are discussed. Interpretations of Planck's constant and the Planck mass are also found. The Planck mass appears to be about the largest single-particle mass which can exhibit quantum mechanical effects. The approach used is the only one that yields both the neutrino mass and the Universe mass, the smallest and largest masses, as a consistent solution of the same set of fundamental equations     

Tracing N, K, Mg and Ca released from decomposing biomass to new tree growth. Part II: A model system simulating root decomposition on clearfell sites

The decomposing roots of harvested trees are a potential source of nutrients for new trees on both conventional and whole-tree harvested clearfell sites. Roots contain significant reservoirs of nutrients, but little is known about the magnitude and rate of their release. The aim of this study was to use stable isotope techniques in a model system to trace nutrients released by decomposing roots. Labelled biomass was obtained by growing Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings with a generous or poor nutrient supply containing elevated ¹⁵N, ⁴¹K, ²⁶Mg and ⁴⁴Ca. Labelled trees were re-potted in sand and in two contrasting soils types to remove them from the enriched isotope supply. After re-potting, the labelled above-ground biomass was harvested, removed and used in a separate study described previously (Part I of II). In the study described here (Part II of II), new Sitka spruce seedlings were planted alongside the labelled root systems. A full destructive harvest was undertaken after one growing season. Enriched ¹⁵N, ⁴¹K, ²⁶Mg, and ⁴⁴Ca were recovered in the new seedlings in both sand and soils. The elevated amounts of ¹⁵N, ⁴¹K, ²⁶Mg and ⁴⁴Ca recovered in new seedlings indicate that nutrients released from decomposing roots can make a direct contribution to the growth of new trees on restock sites. The success of this model system will provide guidance for the application of similar techniques in field experiments.     

Singlet methylene removal by saturated and unsaturated hydrocarbons

The technique of laser flash phyotolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylene, ¹CH₂ (ã¹A₁), with various saturated and unsaturated hydrocarbons. The removal rate constants for CH₄, C₂H₆, C₃H₈, C₂H₄, C₃H₆, C₂H₂, CH₂CCH₂, and C₆H₆ were found to be in excellent agreement with previously reported results. Removal rate constants were also measured for n-C₄H₁₀, i-C₄H₁₀, n-C₅H₁₂, c-C₃H₆, c-C₆H₁₂, 1-C₄H₈, cis-2-C₄H₈, trans-2-C₄H₈, and 1-C₄H₆, and determined to be (3.17 ± 0.15), (2.53 ± 0.11), (3.35 ± 0.24), (1.63 ± 0.08), (3.77 ± 0.21), (3.80 ± 0.20), (3.67 ± 0.16), (3.43 ± 0.16) and (4.05 ± 0.18) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹, respectively. This series of hydrocarbons forms the basis of a larger series of compounds containing a wide variety of organic functional groups. The removal rate constants are reported here, both as a series within its own right, and as a reference point for future work.     

Optimum operating conditions for a laser uranium enrichment plant

Operating conditions of the laser uranium enrichment plant to obtain cheaper enriched uranium are optimised by using the standard optimisation procedure. A simple kinetic model is given to obtain the ion production rate as a function of the laser energy density, ultraviolet light energy density, atomic density and depth and height of the reaction region. The unit cost of enriched uranium is chosen as a value function instead of the unit cost of the separative work. The construction cost is expressed by means of an exponential function to take the scale merit into account.

Two numerical results are given. In case 1, the laser power and efficiency are subject to the restraints determined by the present technical levels and in case 2, they are free. The unit cost of the enriched uranium is higher than those of the gaseous diffusion and gas centrifuge methods by a factor of 2 11. Results indicate that laser uranium enrichment is probably competitive with the other uranium enrichment methods, provided that the laser efficiency is improved by up to 1% and the laser lifetime is extended several times.     

A correlation for heat transfer by natural convection from horizontal cylinders that accounts for viscous dissipation

Eight previously published correlation equations plus one new correlation for heat transfer by natural convection from horizontal isothermal cylinders are tested against a fairly extensive body of experimental data culled from the literature for 10⁻⁸ < Ra < 10⁸ and 0.7 < Pr < 4 × 10⁴. The new equation, which represents the Nusselt number as a function of the Prandtl and Rayleigh numbers plus an additional dimensionless parameter that accounts for viscous dissipation, is shown to correlate the experimental data more accurately than does any one of the eight previously published equations. It is concluded that viscous dissipation may not be neglected in all cases of natural convection from horizontal cylinders, and further, that the inclusion of a viscous dissipation term in certain related problems, such as natural convection in porous media, may lead to more accurate correlation equations.     

Combined heat and mass transfer by natural convection at horizontal cylinder electrodes

Simultaneous heat and mass transfer in free convection at horizontal cylinder electrodes has been investigated experimentally using the electrochemical limiting diffusion current technique. The convective flow patterns occuring have been observed using Schlieren photography. The results confirmed the use of a combined Grashof number (GR_m) to account for thermal and concentration buoyancy effects. Various combinations of electroactive species concentration, cylinder diameter and cylinder surface temperature have been used. Results have been successfully correlated by the equations , 7×10⁷ < GR_mSc< 4×10⁹ and , 4×10⁹ mSc<10¹¹ The experiments cover the range of mass transfer and heat transfer Grashof numbers 3.64×10⁴ m <3.02×10⁶, 5.67×10⁴ h <6.55×10⁶     

Assessment of oil and natural gas resources in the Gulf Cooperation Council countries

This paper deals with the assessment of oil and natural gas resources in the Gulf Cooperation Council. Currently, the reserves of oil and natural gas are estimated at 461.70 × 10⁹ barrels and 615.58 × 10¹² SCF, respectively. Data are given and analyzed on reserves and production for the period 1978–1989.     

Outward phase change in a cylindrical annulus with axial fins on the inner tube

A theoretical analysis is presented for the phase change process occurring in a cylindrical annulus in which rectangular, uniformly spaced axial fins, spanning the annulus, are attached to the inner isothermal tube, while the outer tube is kept adiabatic. The model assumes conduction to be the only mode of heat transfer. The governing equations are solved by finite-difference methods. The time-wise evolution of the interface profile, phase-change fraction and energy stored/discharged and the effect of all the nine prescribable parameters are presented here. Based on the analysis a working formula VF = 1.1275 (Fo Ste T_f)^0.624 (N)^0.028 (L)^−1.385(W)^−0.049 is suggested for engineering design purposes.     

Biomass system model estimates of short-rotation hardwood production in Hawaii

By coupling a short-rotation, intensive-culture (SRIC) biomass production model with a geographical information system and database, potential biomass supply (dry Mg) and delivered cost ($(dry Mg)⁻¹) of three promising tropical hardwoods, Eucalyptus grandis, E. saligna, and Leucaena leucocephala, were estimated at all locations identified as potentially available for tree plantations on the island of Maui. Analyses were performed at two scales-island-wide (10⁵ ha order of magnitude) for general land-use planning, and specific-site (10² ha order of magnitude) for field-level recommendations. The results are presented as yield and delivered cost maps and biomass supply curves for the entire island, and as management strategies depicted graphically as functions of growing space and rotation age that provide least-cost biomass feedstocks delivered from two specific field sites to a designated bioconversion facility on Maui. The methodology is a cost- and time-efficient means to provide useful information to land owners and other decision makers contemplating SRIC forestry as an alternative land use.     

Tracing N, K, Mg and Ca released from decomposing biomass to new tree growth. Part I: A model system simulating harvest residue decomposition on conventionally harvested clearfell sites

It is necessary to assess the effects of removing nutrient-rich harvest residues (brash) from clearfell sites because there is a growing market for this brash as bioenergy. The aim of this study was to use stable isotope techniques in a model system to trace nutrients released by decomposing brash. Labelled biomass was obtained by growing Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings with a generous or poor nutrient supply containing elevated ¹⁵N, ⁴¹K, ²⁶Mg, and ⁴⁴Ca. This biomass was used in two subsequent studies. In this study (Part I of II), the above-ground biomass was harvested and placed on soil in a pot containing a newly planted seedling. Soils from two forests, Ae and Teindland, of contrasting nutritional status were used. A full destructive harvest was undertaken after one growing season. Enriched ¹⁵N, ⁴¹K, ²⁶Mg, and ⁴⁴Ca were recovered in the new seedlings. The percentage contribution from labelled biomass to new tree growth was small, but discernible. The N contribution from labelled biomass to new trees was greater in Ae soil, but the base cation contribution was greater in Teindland soil. Results are discussed with reference to the initial nutrient concentrations of each soil. The elevated ¹⁵N, ⁴¹K, ²⁶Mg and ⁴⁴Ca in new seedlings indicate that nutrients in brash can make a direct contribution to new tree growth. The success of this model system will provide guidance for the application of similar techniques in field experiments.     

基于三角模糊数的湖北省灰水足迹评价

为解决传统灰水足迹模型污染物容许限值不确定性的问题,基于三角模糊数理论,建立了改进的灰水足迹模型和污染风险评估模型,并将其应用于湖北省的灰水足迹评估中.结果 表明,2017年,湖北省COD、总氮、氨氮、总磷的灰水足迹依次为三角模糊数(129.8×108,259.7×108,346.2×108)、(360×108,720...     

Entropy generation due to conjugate natural convection in enclosures bounded by vertical solid walls with different thicknesses

Entropy generation due to conjugate natural convection heat transfer and fluid flow has been studied inside an enclosure with bounded by two solid massive walls from vertical sides at different thicknesses. Enclosure is differentially heated from vertical walls and horizontal walls are adiabatic. Governing equations which are written in streamfunction-vorticity form solved by finite difference technique for the governing parameters as Rayleigh number, 10³ ≤ Ra ≤ 10⁶, length ratio of solid walls as ₁ (for left vertical wall) and ₂ (for right vertical wall) and thermal conductivity ratio of solid to fluid (k), 1 ≤ k ≤ 10. Entropy generation contours due to fluid friction and heat transfer irreversibility, isotherms, streamlines, Nusselt numbers and velocity profiles were obtained. It is found that entropy generation increases with increasing of thermal conductivity ratio and thicknesses of the walls. Entropy generation due to heat transfer is more significant than that of fluid flow irreversibility for all values of thickness of the solid vertical walls.     

Optimum design of multi-stage isotope separation process by exergy analysis

A separation process of carbon isotopes, ¹²C (98.9%), ¹³C (1.1%) and ¹⁴C (trace), by the chemical exchange reactions between CO₂ and amine carbamate was designed by the exergy analysis technique and the applicability of the exergy analysis to the design of isotope-separation process is discussed. The exergy loss (EXL) for the single-column process was increased exponentially toward the product end, because of the mixing of isotopes between gas and liquid flows. By the application of ideal cascade without the mixing of ¹⁴C and ¹²C, the EXL value was reduced to 10% of that for the single-column process. The ideal cascade gives the minimum volume of separation column reasonably, however, is impracticable as an industrial process, because of the complexity of process configuration and operation. From the viewpoint of practical use, a squared-off cascade with three columns, whose diameters were reduced toward the product end, was designed under the condition that the difference of EXL between the squared-off cascade and the ideal one was minimized. The EXL value of this process was evaluated as about 12% of that of single-column process and the separation performance was similar to that for the ideal cascade. These results suggest that the process design method based on exergy analysis is very useful as a tool to design an optimum squared-off cascade.     

Energy overview for the sultanate of oman

Since 1967, exporting crude oil has been the leading hard-currency earner for Oman: 9×10⁵ barrels of crude oil per day being extracted in 1997. The total remaining oil reserves, which can be harnessed economically now, amount to approximately 5.2×10⁹ barrels, but this commercially-available resource is expected to be depleted completely by the year 2015. The second most important source of energy in the country is natural gas: present economically-harnessable reserves are approximately 724×10⁹ Nm³. In 1994, the amount extracted was merely 2.4×10⁹ Nm³. This resource is expected to be exhausted by the year 2064. From 1990 to 1995, the Government-run electricity-generation power-capability rose from 1277 to 1642 MW: the peak demand has grown simultaneously by 59%. The total-power generation in 1995 was 6500 GWh, while the annual consumption was 6173 GWh; the domestic sector accounting for approximately 60% of the total consumption. The rate of energy consumption pattern is seasonal in nature, with the mid-summer electric demand being nearly triple that of mid-winter. Private cars accounted for 54% of the total number of vehicles in Oman in 1994, and this number is rising rapidly. The associated freedom of choice to use the private car in order to satisfy the desires for increased mobility and privacy will not be sustainable in the long term.