The large-scale vug is a kind of important oil and gas reservoir space in the Tahe oilfield, of relatively simple reservoir types and with abundant energy supply. In this paper, experimental simulations are carried out for the large-scale cave elastic reservoir. Physical models of two different energy supply forms are established, that is, the filled cave model and the matrix supply and flowing model. Experiments for different degrees of cave filling, different matrix permeability and different oil production rates are carried out. The results show that for the filled cavity model, the oil production rate mainly affects the pressure difference between the bottom of filling and the inside of caves. The permeability of filling mainly affects the speed of energy supplies. For the cavity model with substrate supply, the pressure assumes a linear variation in a single logarithmic coordinate in the early period, and then decreases with different rates in the later period, and the permeability of the substrate directly affects its liquid flow channeling ability. The relation curves of the cumulative production and the cumulative pressure drop are linear in the early period, and then assume an obvious upturned segment in the later period, which apparently shows that the substrate channeling supply section exists.

In order to meet the requirements of minimizing the maximum distance between the response function and the sample values in practical engineering problems, a new method of fitting the response surface function is proposed in this paper. The problem of fitting the response surface function with sample points is transformed into one of solving a linear programming problem in this method. A mathematical model about sample points is established. Linear and quadratic response surface function expressions are fitted by numerical methods. Comparing the fitted results of minimizing the maximum difference by the Kreisselmerier-Steinhauser (K-S) function method and those by the least squares method, the method used in this paper give results better agreed with those of the K-S function method, with the maximum differences smaller than that of the least squares method. Four numerical examples show that this method is reasonable and effective. In addition, this method provides a new constructing method for the response surface function.

The main purpose of this paper is to investigate the complex dynamics that the time delay induces in a kind of single degree-of-freedom self exciting vibration systems with linear delayed position feedbacks. The mathematical model under consideration is a delayed Duffing system, which is obtained by applying linear time delayed position feedbacks to a van der Pol-Duffing oscillator. The Hopf bifurcation of the delayed system derived by time delay is studied qualitatively. And it is found quantitatively that the time delay can make the multiple quasi-periodic and chaotic motions coexisting in the controlled system. Then the quasi-periodic attractors and chaotic attractors and their basins of attraction under different values of time delay in the delayed system are also classified by the 4th Runge-Kutta approach and Monte Carlo method. It is shown that each boundary of the basin of attraction in the delayed system is smooth and not fractal even if the attractor is chaotic. This paper shows some potential applications for the further study of the mechanism of chaotic motions.

Quasi-pentadiagonal linear equations are important in computational mathematics and scientific/engineering computing, which would arise during the solution of boundary value problems for elliptical or parabolic partial differential equation(s) with periodical boundary conditions, and the quintic interpolating splines with periodical boundary conditions. Based on the ideas of the forward elimination and backward substitution algorithm for pentadiagonal linear equations and the matrix decomposition, a four parameter algorithm for quasi-pentadiagonal linear equations is proposed in this paper. It involves four steps. In the first step, the first two unknowns x1, x2 and the last two unknowns xn-1, xn are taken as the four parameters, which are responsible for the non-zero elements at corners of the quasi-pentadiagonal matrix. In the second step, other unknowns of the equations are expressed explicitly by the four parameters. Then the standard pentadiagonal linear equations can be formed with the help of special matrix decomposition and solved conveniently with the help of the forward elimination and backward substitution algorithm. In the third step, the four parameters are solved with the help of the first two equations and the last two equations with decomposed matrixes. At last, all unknowns are solved efficiently when the four parameters are substituted into the equations with the decomposed matrix. With this algorithm, two methods of solving the four parameters are presented in this paper. One is that all other unknowns are expressed explicitly by the four parameters. Then the four parameters are solved with the help of the first two equations and the last two equations. The other is that the four parameters are regarded as known quantities and are substituted into the 3~n-2 equations, which are to be solved. Then the four parameters can be solved when x3, x4, xn-3, xn-2 are substituted into the first two equations and the last two equations. The computation cost of the two methods is almost the same for large scale pentadiagonal equations. The stability analysis shows that the four parameter algorithm is stable if the coefficient matrix is a strictly diagonally dominant matrix. The numerical example indicates that the computational time of the two algorithms is consistent with the theoretical result.

For any positive integern, the Smarandache power function SP(n) is defined as the smallest positive integermsuch that mm is divisible by n. The main purpose of this paper is to study the solvability of equations SP(n)=?准(n), k=1, 2, 3 (for the Euler function) and all the positive integer solutions and other related issues, based on the nature of the series{SP(n)}, 1st mean, asymptotic formula, the convergence of infinite series SP(n) and its related identity. The analytic methods are used to get the distribution properties of the k-th Powers of SP(n). For any real number x≥3, given the real numbers k, l (k>0, l≥0), and all the prime numbers p, any positive number ε and the Riemann Zeta-function, we give and prove the corresponding asymptotic formula. For any real number x≥3 and a given real number k′>0, we also give and prove the corresponding asymptotic formula. For any given real numbers x≥3 and real numbers l≥0, the corresponding asymptotic formula is also given and proven together. Thus, the asymptotic formula of ■nl(SP(n))k and ■■(k>0, l≥0) is given, when l=0, k=1/k′, k=1,2,3 and ζ(2)=π2/6, ζ(4)=π4/90, and it could be found that the theorem is a further extension of the related results.

The preparation of CoFe2O4 ferrofluids by Massart's method is discussed in this paper. The structure and the shape of CoFe2O4 nanoparticles are characterized by X-ray diffraction and transmission electron microscopy, respectively, and the results show that the particles' size follows a logarithmic normal distribution, with the average diameter of 12.76nm and the crystal particle's average diameter is 11.15nm. The magnetization curve of CoFe2O4 particles is determined at room temperature by VSM, with the saturation magnetization of CoFe2O4 particles of 217.50kA/m. The magnetization curves of ferrofluids with volume fractions of 1%, 1.2% and 1.5% are determined at room temperature by VSM. It is found that the saturation magnetization of ferrofluids is significantly less than particle's saturation magnetization fVMps, because of bulk aggregations, chain-like aggregations and ring-like aggregations in ferrofluids at the same time. The bulk aggregations and the ring-like aggregations reduce the saturation magnetization of ferrorluids. The saturation magnetization of ferrofluids after frozen is greater than that before frozen, as the ring-like aggregations are broken by H2O molecule's interaction during the frozen process, which increases the parameter γ and the saturation magnetization of ferrofluids after frozen.

Prediction of the coalmine gas concentration is an important part and the fundamental task of gas accident prevention in coalmine. In order to predict the coalmine gas concentration, the grey self-memorization model is established by combining the grey system theory with the self-memorization theory. Substituting the differential equation deduced from the grey system theory into the discrete self-memorization equation, the memorization coefficient of the grey self-memorization model for the coalmine gas concentration is calculated by the least-squares method. The model is applied to predict the gas concentration at the 304 comprehensive mining coal face in Liyazhuang coal mine and the result is compared with that of the grey G(1, 1) model. The optimal awkward moment of the grey self-memorization model is determined to be seven through trial methods. The research results show that the grey self-memorization model can combine the merits of the self-memorization theory and the grey system theory, to predict the overall trend and the fluctuation of coalmine gas concentration. The proposed method enjoys a good accuracy in forecasting various engineering events, especially, as a new approach to predict the coalmine gas concentration.

Jack-up rigs are widely used in offshore oil and marginal oil field development. According to statistics, punch-through accidents account for more than 50% of jack-up rigs' accidents, leading often to serious damages of the jack-up rigs and casualties. Taking the Arab drill 19 jack-up and a Chinese jack-up as examples, the causes of the accidents and the seriousness of consequences are analyzed. The projected area method is used to study the possibility of punch-through for a domestic jack-up at a well site in Bohai Bay. It is found that the punch-through risk at the well site is high. The calculated penetration depth does not agree very well with the actual operational record, with a great error, which is analyzed in this paper based on new research results of punch-through. It is shown that during punch-through in a jack-up rig, a sand plug will be formed under the spudcan of the jack-up rig, which increases the ultimate bearing capacity of soil, and reduces the actual depth.

The heterogeneity of Chang 8 Member in Heshui Area in Ordos Basin is studied from the aspects of interlayer heterogeneity, intralayer heterogeneity and plane heterogeneity. The distribution of sandbodies is similar in both Chang 81 and Chang 82. The heterogeneity of interlayer permeability is weak. The thickness of barrier beds between Chang 81 and Chang 82 is quite changeable. The interlayer heterogeneity is weak as a whole. The barrier beds in Chang 81 and Chang 82 are well developed, with several highly-permeable beds. The variation coefficient, the rush coefficient and the differentials of intralayer permeability are large, and the intralayer heterogeneity is strong. The distribution of flow units in Chang 81 and Chang 82 in the studied area is mainly controlled by microfacies. There are more bad and intermediate flow units and less good ones. The good ones are mostly located in submarine distributary channel microfacies and mouth bar microfacies. The intermediate and bad ones are mostly located in distal bar and distributary interchannel microfacies. The heterogeneity of reservoirs is one of the most important factors to control the distribution of oil and water in the studied area. The heterogeneity of reservoirs has a pivotal effect on the distribution of remaining oil, and has a crucial effect on the oilfield development. Developing plans should be made and adjusted based on the reservoir heterogeneity.

The variation of the oil well production against time is controlled by several factors, in an extremely complicated nonlinear manner. The conventional petroleum reservoir engineering method suffers often from uncertainty of the correlation parameters and a large prediction error. Our analysis shows that the oil well production data have some features of time series. Therefore, the technique of the phase space reconstruction and the G-P method can used to obtain the optimal embed dimension and then to identify the time series of the well oil production. On this basis, by using the support vector machine method, the chaos-SVM model with time varying character is built,. with a very high precision for short-term well productions. In a real application, we can supplement the new historical data in real time to make the rolling prediction. The example W8-5 well application indicates that the relative error of the forecast results is only 7%, which shows that the coupling model has a good forecast ability and is of practical value.

The purpose of the research is to select and cultivate plants with strong adaptability to environment, high coverage, well-developed root system, low nitrogen content during the initial construction days of the constructed wetland, and these wetland plants will be used for treatment of landfill leachate after the wetland is constructed. The main characteristics of soil before treatment are analyzed, and the parameters obtained will provide some reference for the design of sewage treatment. The plants selected are Phragmites communis, Glycine soja, Oryza sativa, Rumex acetosa and Artemisia argyi, and the soil is on a constructed wetland in Wafangdian Municipal Landfill. The cover degree, biomass, nitrogen content of those plants, particle size composition of the soil, nitrogen and carbon contents of the soil in different size and different plant areas were analyzed. The results show that: (1) The cover degree, stem-leaf and root biomass of Rumex acetosa, Phragmites communis and Artemisia argyi are significantly higher than those of others (P<0.05). (2) The weight percentage contents of the soil with the diameter of 0~0.2, 0.2~0.9 and 0.9~4.0mm were about 4.59%, 19.00% and 36.18%. (3) The nitrogen and carbon contents of the soil where Phragmites communis grows are significantly higher than those of others (P<0.05). (4) The nitrogen and carbon contents of the soil with the diameter of 0.9~4.0mm are significantly lower than those of others (P<0.05). It is concluded that Rumex acetosa, Phragmites communis and Artemisia argyi should be further cultivated, and used for sewage treatment as the main wetland plants; the soil with the diameter of 0.9~4.0mm will become the main part of the matrix for the sewage treatment; Phragmites communis does not require very high contents of nitrogen and carbon, so it should be mixed with the related plant species in order to achieve a better treatment results.

Chrysanthemum (Chrysanthemum morifolium Ramat.) plants were treated with a solution containing different concentrations of CaCl2 and 150mmol/L of NaCl by watering. After 30 days, the period of bloom of chrysanthemum, the content of malondialdehyde (MDA), the activity of peroxidase (POD) and superoxide dismutase (SOD), and the chlorophyll(a+b) in the leaves were determined. Results show that with the treatment of chrysanthemum plants by both chemicals NaCl and CaCl2, as compared with the treatment by NaCl only, the flowering period is increased by 2 days, the fresh weight/dry weight ratio is increased by 7.2%~33.3%, the content of POD is increased by 17.4%~67.8%, and the activity SOD is enhanced by 1.4%~2.7%, the chlorophyll(a+b) content is increased by 10.7%~70.0%, but the content of MDA is decreased by 6.6%~26.0% in leaves. It is concluded that: (1) The application of 0~2mmol/L of exogenous calcium under salt stress would enhance the activity of SOD and POD remarkably. Decrepitude degrees of the cell membrane could also be alleviated distinctly. 2mmol/L of exogenous calcium is the best concentration to prolong the floral organ's life span. (2) The application of exogenous calcium under salt stress would prolong the profuse flowering period of chrysanthemum for about 2 days at the concentration of 1mmol/L of CaCl2. (3) In the mean time, under salt stress, the application of exogenous calcium could increase chlorophyll contents in the new leaves of chrysanthemum. In a word, this experiment shows that exogenous calcium could enhance salt tolerance of chrysanthemum plants, and 1mmol/L of CaCl2 produces the best effect.

Based on the mechanism of heat and moisture transfer through porous media, the dynamic mathematical equations for the coupled heat and moisture transfer in building components are derived, in which the humidity gradient is considered as the heat source or heat sink ,and the temperature gradient is considered as the moisture source or moisture sink. Meanwhile, an analytical method by using the transfer function is proposed to study the processes of coupled heat and moisture transfer in building elements. In this paper, the analytical calculations are carried out for the coupled heat and moisture transfer in bamboo plywood of a bamboo composite wall, to obtain the transient distributions of temperature and moisture content by using the above method. The results agree with the measured data, which shows that the mathematical equations and the solving method presented are reliable, and can be used to study bamboo composite walls, as well as for the development of bamboo as a new building material.

The energy-saving effect of a new residential building is controlled by various factors. How to evaluate the energy-saving effect objectively is an important research issue. Based on the extension theory, an extension method which combines qualitative and quantitative evaluations of the energy-saving effect for residential buildings is proposed. Taking a real project as an example, various factors are comprehensively considered, and the evaluation indicators and standards of the energy-saving effect for residential buildings are established. The weight of a factor is determined by a simple correlation function, to avoid subjective speculations in practices. On this basis, the extension theory is adopted. The matter element model for the evaluation of the energy-saving effect for residential buildings is constructed. The correlation and the grade are accurately calculated, to objectively and comprehensively evaluate the residential building's energy-saving effect. Results show that the proposed approach is effective and efficient and the extension method can be used to estimate the energy-saving effect of new residential buildings.

The global atmospheric electrical circuit is closely related to the human activities, and the electrical conductivity is an essential parameter of the atmosphere electrodynamics. In 1905, the cylinder capacitive conductivity instruments were developed by the Gerdien, and the atmospheric electrical conductivity could be measured in-situ on balloon ascents. From then on, the atmospheric electrical conductivity measurement technology has been developing continually and found wide applications, especially with the development of the microelectronics technology and the atmospheric electricity. Now, the Gerdien conductivity meter has developed into an efficient tool for the atmospheric detection, for atmospheric electric conductivity, concentrations of positive and negative ions, air aerosol, and for the investigation of large-scale distributions of radioactive mineral areas. This paper reviews the atmospheric conductivity measurement, including its applications, concepts and roles, and the international measurement progress of atmospheric conductivity. The measurement principle, improvement, application of the Gerdien condenser is mainly discussed. In China, only a few studies have been carried out in the atmosphere conductivity detection area and much more studies are necessary in the basic electrical parameter detection.

Because of Organic Light-Emitting Diodes (OLEDs) have excellent properties of high light-emitting efficiency, high brightness, low driving voltage, fast response, potential for fabrication of large-area full-color flat panel display and so on, the OLEDs have been extensively studied due to their possible applications for flat panel color displays and illumination source. The choice of organic electroluminescent materials, which include polymer and molecular material, is a key issue for the preparation and optimization of the OLEDs. The organic small molecular electroluminescent materials have the properties of definite molecular mass, high chemical modification, wide select range, easy purification, high fluorescence quantum yield and variety of color such as red, green, and blue and so on. Hence, the research and development of light-emitting layer of OLEDs materials have been caused extensive attention all over the world. In this work, the recent progress of organic electroluminescent materials at home and abroad was introduced and various kinds of organic small molecular materials used for organic electroluminescence at present were mainly described. Extensive application prospect and developing tendency of OLEDs were briefly described as well.

Energy is an important factor in the economic and social progress of human society. Facing social and environmental problems induced by increasing energy consumption, the energy conservation and emission reduction becomes a consensus. As an important component of energy technology, the low-grade waste heat recovery technique has a great potential. However, the current techniques suffer from a number of difficulties, such as the poor performance of materials, the low level of encapsulation techniques, and the limitation of heat exchangers, which hampers its progress to some extent. This paper reviews the domestic and international researches on the utilization of low-grade waste heat, especially, the key links between heat transfer and utilization. Based on the assessment of the current techniques, the application of room temperature liquid metals is proposed, for their excellent heat transfer performance and low power driving property, to partly replace water, as is usually adopted in the conventional waste heat recovery process. In this way, a new generation device with high efficiency in recovery of waste heat and power generation can be developed. The concept of water free heat exchanger is discussed, together with the key scientific and technological issues. With the development of the liquid metal heat exchanger technology, it is expected that a new field of utilizing industrial waste heat would emerge, which would bring about deep impact in many respects such as energy and water conservation, energy consumption reduction and environmental protection.

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Science & Technology Review. 2010, 28 (17): 118-118. ; doi:
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