Generation of groups by rank-2 tori

Let k be a field of characteristic different from 2 and 3. In this paper, we study the number of rank-2 k-tori required (in fact exhibit such tori explicitly) for the generation of groups of type A₂, G₂ and F₄ arising from division algebras and subgroups of type D₄ of Aut(A), for A an Albert division algebra, over infinite perfect fields.     

Energy and CO2 emission performance in electricity generation: A non-radial directional distance function approach

This paper presents a non-radial directional distance function approach to modeling energy and CO₂emission performance in electricity generation from the production efficiency point of view. We first define and construct the environmental production technologies for the countries with and without CHP plants, respectively. The non-radial direction distance function approach is then proposed and several indexes are developed to measure energy and CO₂ emission performance of electricity generation. The directional distance functions established can be computed by solving a series of data envelopment analysis models. We then conduct an empirical study using the dataset for over one hundred countries. It is found that OECD countries have better carbon emission performance and integrated energy-carbon performance than non-OECD countries in electricity generation, while the difference in energy performance is not significant.     

F_2+vF_2上的循环码

本文研究了环F_2+vF_2上的循环码.利用标准形生成元集刻画了环F_2+vF_2上的循环码的代数结构,证明了环F_2+vF_2上的每一个非零的循环码均有唯一的标准形生成元集,进而得到了每一个循环码均是由一个多项式生成的.     

A methodology for modelling travel distances by Bias estimation

Round norms τl _p, p ∈ (1,2] and block norms have been utilised for modelling actual distances in transportation networks. A geometric setting will permit the establishment of a relationship between bias of the road network distance and trajectory deviations, which will be used to separate the set of origin-destination pairs into two samples and also to analyse each sample using regression, thus obtaining several types of estimators. What will be demonstrated in this paper is that these functions can be combined through either a weighted sum, or by means of the introduction of the expected distance concept applied to the bias, to obain distance predicting functions for the region considered.     

Supporting hydrogen based transportation: case studies with Global MARKAL Model

Steadily growing prices of oil and emissions coming from conventional vehicles, might force a switch to an alternative and less polluting fuel in the coming future. In this article we analyze the potential influence of selected factors for successful market penetration of hydrogen fuel cell vehicles in hydrogen based private transportation economy. Using a world scale, full energy system, bottom-up, optimization model (Global MARKAL Model—GMM) we address the possibility of supporting the fuel cell vehicle technology to become competitive in the markets. In a series of optimizations we evaluate the potential influence of governmental supports and the internalization of externalities related to CO₂ and local pollution emissions originating from the transportation sector, as well as preferential crediting options and demonstration projects promoting fuel cell vehicles. The results suggest that the crucial element is the price of fuel cells and their further potential to reduce costs. This reduction of costs may be triggered by governmental support such as direct subsidies to fuel cells, preferential crediting options for the buildup of hydrogen infrastructure as well as penalization of emitters of CO₂ and/or local pollutants.     

A computational model of a transcritical R744 ejector based on a homogeneous real fluid approach

A mathematical model of the compressible transonic single- and two-phase flow of a real fluid is discussed in this paper. The model was originally developed to simulate a refrigerant flow through a heat pump ejector. In the proposed approach, a temperature-based energy equation is replaced with an enthalpy-based formulation, in which the specific enthalpy, instead of the temperature, is an independent variable. A thermodynamic and mechanical equilibrium between gaseous and liquid phases is assumed for the two-phase flow. Consequently, real fluid properties, such as the density, the dynamic viscosity and the diffusion coefficient, are defined as functions of the pressure and the specific enthalpy. The energy equation formulation is implemented in commercial CFD software using subroutines that were developed in-house. The formulations was tested extensively for a single-phase flow of the R141b refrigerant, and for a two-phase flow of the R744 fluid (carbon dioxide) that occurred in a 3-D model of the ejector motive nozzle. In the model validation procedure, a satisfactory comparison between the experimental and computational results of the primary and secondary mass flow rates was obtained for both flow regimes. In addition, in the case of the R744 flow, the pressure distribution along the centre line of the ejector was accurately predicted as well. Furthermore, the results also shows that geometry modelling and measurement accuracy play an important in the final numerical results. As a result of the reasonable computational times, this method can be effectively used for the design of ejectors and also in geometric optimisation computations.     

Dolbeault Cohomology for G2-Manifolds

Cocalibrated G₂-manifolds are seven-dimensional Riemannian manifolds with a distinguished 3-form which is coclosed. For such a manifold M, S. Salamon in Riemannian Geometry and Holonomy Groups (Longman, 1989) defined a differential complex related with the G₂-structure of M.In this paper we study the cohomology of this complex;it is treated as an analogue of a Dolbeault cohomologyof complex manifolds. For compact G₂-manifoldswhose holonomy group is a subgroup of G₂ special propertiesare proved. The cohomology of any cocalibrated G₂-nilmanifold \K is also studied.     

On Relative K 2-Group of Split Radical Ideals

Let I be a split radical ideal of a ring R. In this article, the exact sequence 1 → K ₂(R, I) → U _R (I) → V(R, I) → 1 is given by using the method of extension of groups, where U _R (I) is determined by generators and relations. The results of Maazen and Stienstra on the presentation for relative K ₂ group of split radical pairs are extended and amplified.     

I2-convergence and I2-cauchy double sequences

In this article, we prove a decomposition theorem for I₂-convergent double sequences and introduce the notions of I₂-Cauchy and I^*₂)-Cauchy double sequence, and then study their certain properties. Finally, we introduce the notions of regularly (I₂,I)-convergence and (I₂,I)-Cauchy double sequence.     

Simulation with system dynamics and fuzzy reasoning of a tax policy to reduce CO2 emissions in the residential sector

This methodological paper presents a planning and control methodology illustrated by a simplified case study on the carbon-tax design in the residential sector. The first objective is to show how to simulate with system dynamics the consumers’ behaviour and the continuous tax-control mechanism depending on few important feedbacks, often ignored in static macroeconomic modelling. A second objective is to show how to aggregate external data driving this model and stemming from different sources with various credibility levels. This is realised by means of fuzzy-reasoning techniques incorporated into the system-dynamics model.     

CO2 emissions trading planning in combined heat and power production via multi-period stochastic optimization

The EU emissions trading scheme (ETS) taking effect in 2005 covers CO₂ emissions from specific large-scale industrial activities and combustion installations. A large number of existing and potential future combined heat and power (CHP) installations are subject to ETS and targeted for emissions reduction. CHP production is an important technology for efficient and clean provision of energy because of its superior carbon efficiency. The proper planning of emissions trading can help its potential into full play, making it become a true “winning technology” under ETS. Fuel mix or fuel switch will be the reasonable choices for fossil fuel based CHP producers to achieve their emissions targets at the lowest possible cost. In this paper we formulate CO₂ emissions trading planning of a CHP producer as a multi-period stochastic optimization problem and propose a stochastic simulation and coordination approach for considering the risk attitude of the producer, penalty for excessive emissions, and the confidence interval for emission estimates. In test runs with a realistic CHP production model, the proposed solution approach demonstrates good trading efficiency in terms of profit-to-turnover ratio. Considering the confidence interval for emission estimates can help the producer to reduce the transaction costs in emissions trading. Comparisons between fuel switch and fuel mix strategies show that fuel mix can provide good tradeoff between profit-making and emissions reduction.     

Mathematical modelling of the oxygen uptake kinetics during whole-body endurance exercise and recovery

In this study, we elucidate four different mathematical models of the kinetics of oxygen uptake during whole-body endurance exercise at different intensities and throughout the subsequent recovery periods. We employ the hypothetical inductive–deductive method and forecast four different models for the oxygen kinetic. The VO₂ development using these models compared with experimental results where an elite cross-country skier performed laboratory tests while running with poles on a treadmill, in which the rate of oxygen uptake and blood lactate concentration as a function of time were measured. The most developed model accounted for the delayed superimposed slow component of oxygen uptake and the influence of lactic power production on the oxygen kinetics. The rate of change in oxygen with this model is consistent with the accumulated oxygen deficit model and matched the data well, even for intensities above the lactate threshold and during recovery.     

Local air pollutant emission reduction and ancillary carbon benefits of SO2 control policies: Application of AIM/CGE model to China

While a great deal of literature has been published in recent years on the ancillary benefits of greenhouse gas mitigation (e.g., reductions in local air pollution), less attention has been focused on the climate benefits of local air pollution strategies themselves. Local air pollution is, however, a more immediate issue now faced by developing countries. This study assesses the impacts on local air pollutant emission reduction and ancillary CO₂ emission reduction of SO₂ control policies in China, such as a sulphur tax, SO₂ total emissions control (TEC), and improvement of energy efficiency, based on the Asia-Pacific Integrated Model (AIM)/Computable General Equilibrium (CGE) country model. The simulation period is from 1997 to 2020. Major conclusions include the following: an SO₂ emission cap will help to control SO₂ emissions, but will result in a large GDP loss; the role of a SO₂ emission tax at the present level is very limited; and an ancillary carbon reduction benefit can be achieved through the introduction of SO₂ control policies in China.     

Phase transition in layered perovskite-like manganate Ca3Mn2O7 under high pressure

In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca₃Mn₂O₇ powder under pressures were performed by using the diamond anvil cell with synchrotron radiation. The results show that the structure of layered perovskite-like manganate Ca₃Mn₂O₇ is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca₃Mn₂O₇ underwent two phase transitions under pressures in the range of 0–35 GPa. One was at about 1.3 GPa with the crystal structure changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic back to another tetragonal.     

On GC2 modules and their endomorphism rings

Let R be a ring. A module M_R is said to be GC₂ if for any N≤ M with N? M, N is a direct summand of M. In this article, we give some characterizations and properties of GC₂ modules and their endomorphism rings, and many results on C ₂ modules and GC₂ rings are generalized to GC₂ modules.     

Δ 2 0 -copies of linear orderings

It is proved that, for any n ∈ ω, there exist countable linear orderings L_n whose Δ ₂ ⁰ -spectrum consists of exactly all non n-low Δ ₂ ⁰ -degrees. Properties of such orderings are examined, for n = 1 and n = 2. Supported by RFBR grant No. 02-01-00169 and by RF Ministry of Education grant No. E02-1.0-177. __________ Translated from Algebra i Logika, Vol. 45, No. 3, pp. 354–370, May–June, 2006.     

ON K 2 OF DIVISION ALGEBRAS

ABSTRACT

In this paper, it is proved that if F is a global field, then for any integer n > 3, there is an extension field E over F of degree n such that K ₂ E is not generated by the Steinberg symbols {a, b} with a ∈ F*, b, ∈ E*. If however, F is a number field and D is a finite-dimensional central division F-algebra with square free index, then K ₂ D is always generated by the Steinberg symbols {a, b} with a ∈ F*, b ∈ D*. Finally, the tame kernels of central division algebras over F are expressed explicitly.     

Phonon spectroscopy and transport properties of Y1-x Nd x Sr2Cu2.7Mo0.3O7-δ

The Raman and infrared spectra, resistivity as well as thermoelectric power of Y_1-xNd_xSr₂Cu_2.7Mo_0.3 O₇ δ(.x =0, 0.1. 0.2. 0.5, 0.8 and 1.0) are studied carefully. It was found that the structure characteristics of RSr₂Cu_2.7Mo_0.3O₇ δ cuprates are different from those of RBa₂Cu₃0₇ δ. The variations of the microstructure in Y_1-x Nd_xSr₂Cu_2.7Mo_0.3O₇ δ with Nd-doping affect the carrier distribution. so as a result the superconductivity changes. Furthermore, it is pointed out that the microstructure variations with the large rare earth ionic substitution cause the widely existing rare earth ionic size effect in HTSC. Project supported by the National Natural Science Foundation of China and the National Center for R & D Superconductivity.     

Fibrous Filler-Matrix Interaction in Oxide Composites

The interaction between a fibrous alumina filler and a hydrated zirconia matrix during the fabrication of ceramic composites is studied. The influence of the crystal structure and porosity of the filler on the properties of the ZrO₂-Al₂O₃ composite material is investigated. It is found that, as a result of addition of alumina fibers of cubic and monoclinic structures (- and -phases), the ZrO₂ hydrogel interacts with fibers and solid ZrO₂ solutions of tetragonal structure are formed. These solutions exist over the range of 600 to 1200°C and, at annealing above 1200°C, due to crystallographic transitions the of - and -phases, they break down, namely Al₂O₃ transforms into -corundum and ZrO₂ into a monoclinic modification. However, the material does not fail and a stable porous ceramic composite is formed. To manufacture a composite with improved mechanical characteristics, fibrous alumina fillers with the structure of -corundum must be used.