EFFECT OF DIFFERENT OPERATION METHODS ON METHANE HYDRATE FORMATION

Three experiments of static state storage method, low-temperature and constant-pressure storage method and low-temperature and constant-pressure storage method were carried out to investigate which method was best in gas hydrate. The relationships of hydrate rate, capacity and liquid temperature versus time were derived and three results were contrasted. The experimental results show lowtemperature and constant-pressure method is better than the other two methods because it's operation period is shorter and storage capacity is larger than the other two. Low-temperature and constant-pressure method is the best method. So new method will be new research objective.

FORMATION ENTHALPIES FOR FCC METAL BASED BINARY ALLOYS BY EMBEDDED ATOM METHOD

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A new method of formation evaluation for fractured and caved carbonate reservoirs:A case study from the Lundong area,Tarim Basin,China

The carbonate reservoirs in the Tarim Basin are characterized by low matrix-porosity,heterogeneity and anisotropy,which make it difficult to predict and evaluate these reservoirs.The reservoir formations in Lundong area experienced a series of diagenesis and tectonic evolution stages.And secondary storage spaces such as fractures and dissolution caves were developed while nearly all the primary pores have disappeared.Based on a summary of different types of storage spaces and their responses in conventional logs,FMI and full waveform sonic logs which are sensitive to different reservoirs,the comprehensive probability index （CPI） method is applied to evaluating the reservoirs and a standard of reservoir classification is established.By comparing the evaluation results with actual welllogging results,the method has proven to be practical for formation evaluation of carbonate reservoirs,especially for the fractured carbonate reservoirs.In reservoir fluid identification,the multivariate stepwise discriminant analysis （MSDA） method is introduced.Combining the CPI method and MSDA method,comprehensive formation evaluation has been performed for fractured and caved carbonate reservoirs in the Tarim Basin.Additionally,on the basis of secondary pore inversion results,another new method of formation evaluation is also proposed in the discussion part of this paper.Through detailed application result analysis,the method shows a promising capability for formation evaluation of complex carbonate reservoirs dominated by various secondary pores such as holes,caves,and cracks.

INVESTIGATION OF THE PALEOGEOTHERMAL TECTONIC HISTORY ON DONGPU DEPRESSION AND OIL/GAS FORMATION BY FISSION-TRACK METHOD

Dongpu depression is a fault basin at residual-mobility period of Diwa stage, it developed on the strata of the Mesozoie and Pre-Mesozoie. It is one of the important oil/gas- bearing basin during Cenozoie era along the East China. The strueture in Dongpu geodepression is very complex. There exists a strueture pattern with east- and west-depression belts and one central swell belt, it is divided into the southern- and northern-division by Gaopingji (orMeng Ju ) -Xieheng fault.

Two Species of Zosterophyllum from South China and Dating of the Xujiachong Formation with a Biostratigraphic Method

ZosterophyUum longa sp. nov. is reported from the Lower Devonian Pingyipu Formation, Jiangyou District, northern Sichuan of China. This new plant has vertically elongate sporangia differing from all known species of Zosterophyllum, demonstrating morphological variations in Zosterophyllophytina. New materials of Zosterophyllum yunnanicum from the Lower Devonian Xujiachong Formation, Qujing District, eastern Yunnan of China show that fertile axes of this species are anisotomous or pseudomonopodial or K-shaped in branching. Sometimes fertile lateral axes are very short and bear an axillary axis at the dividing point. Distinct thickening occurs along the whole margin of a sporangium, with sporangial lobes undeveloped. The evolution of ZosterophyUum is tentatively discussed. A biostratigraphic method of Gerrienne and Streel is introduced and applied to dating of the Lower Devonian Xujiachong Formation, which is considered as of the late Pragian-early Emsian.

The Quantum Scattering Study for Ion-pair Formation Reaction Na+I_2→Na^+I_2^- with the LCAC-SW method

The selected-state probabilities of collinear ion-pair formation process Na+I2→Na++I2-on Aten-Laming-Los two-State potential energy surface have been calculated by using LCAC-SW method. The results show that reaction probabilities are oscillatory with collision energy; the threshold energy of this ioniZation reaction is 2.8 ev, which is in modest agreement with experimental result.

Determination of the Minimum Testing Time for Wireline Formation Testing with the Finite Element Method

The wireline formation tester （WFT） is an important tool for formation evaluation, such as calculating the formation pressure and permeability, identifying the fluid type, and determining the interface between oil and water. However, in a low porosity and low permeability formation, the supercharge pressure effect exists, since the mudcake has a poor sealing ability. The mudcake cannot isolate the hydrostatic pressure of the formation around the borehole and the mud seeps into the formations, leading to inaccurate formation pressure measurement. At the same time, the tool can be easily stuck in the low porosity/low permeability formation due to the long waiting and testing time. We present a method for determining the minimum testing time for the wireline formation tester. The pressure distribution of the mudcake and the formation were respectively calculated with the finite element method （FEM）. The radius of the influence of mud pressure was also computed, and the minimum testing time in low porosity/low permeability formations was determined within a range of values for different formation permeabilities. The determination of the minimum testing time ensures an accurate formation pressure measurement and minimizes possible accidents due to long waiting and testing time.

COMPARISON OF TWO METHODS IN SATELLITE FORMATION FLYING

Recently, the research of dynamics and control of the satellite formation flying has been attracting a great deal of attentions of the researchers. The theory of the research was mainly based on Clohessy-Wiltshire' s (C-W's) equations, which describe the relative motion between two satellites. But according to some special examples and qualitative analysis , neither the initial parameters nor the period of the solution of C-W' s equations accord with the actual situation, and the conservation of energy is no longer held. A new method developed from orbital element description of single satellite , named relative orbital element method ( ROEM) , was introduced. This new method, with clear physics conception and wide application range, overcomes the limitation of C-W s equation , and the periodic solution is a natural conclusion. The simplified equation of the relative motion is obtained when the eccentricity of the main satellite is small. Finally, the results of the two methods (C-W' s equation and ROEM) are compared and the limitations of C-W s equations are pointed out and explained.

Initial estimation of hydrate formation temperature of sweet natural gases based on new empirical correlation

Production,processing and transportation of natural gases can be significantly affected by clathrate hydrates.Knowing the gas analysis is crucial to predict the right conditions for hydrate formation.Nevertheless,Katz gas gravity method can be used for initial estimation of hydrate formation temperature （HFT） under the circumstances of indeterminate gas composition.So far several correlations have been proposed for gas gravity method,in which the most accurate and reliable one has belonged to Bahadori and Vuthaluru.The main objective of this study is to present a simple and yet accurate correlation for fast prediction of sweet natural gases HFT based on the fit to Katz gravity chart.By reviewing the error analysis results,one can discover that the new proposed correlation has the best estimation capability among the widely accepted existing correlations within the investigated range.

PREPARATION OF CAULIFLOWER-LIKE PMMA PARTICLES AND THEIR FORMATION MECHANISM

A simple technique for preparing cauliflower-like PMMA particles by a self-formation method is proposed. PMMA particles can be obtained with tunable surface morphology by varying the polymerization time. Experimental results show that the formation of these cauliflower-like particles can be attributed to the special particle growth mechanism in the self-formation method.

Hydrodynamic Performance of a Newly-Designed Pelagic and Demersal Trawls Using Physical Modeling and Analytical Methods for Cameroonian Industrial Fisheries

This study proposed the newly-designed Pelagic and demersal trawls for the fishing vessels operating in Cameroonian waters in pelagic and demersal fishing grounds. The engineering performances of both trawls were investigated using physical modelling method and analytical method based on the predicted equations. In a flume tank, a series of physical model tests based on Tauti’s law were performed to investigate the hydrodynamic and geometrical performances of both trawls and to assess the applicability of the analytical methods based on predicted equations. The results showed that in model scale, the working towing speed and door spread for the pelagic trawl were 3.5 knots and 1.85 m, respectively, and for the bottom trawl net they were 4.0 knots and 1.8 m. At that speed and door spread, the drag force, net opening height, and wing-end spread of the pelagic model trawl were 36.73 N, 0.89 m, and 0.86 m, respectively, and the swept area was 0.76 m2. Bottom trawl speed and door spread were 30.43 N, 0.38 m, and 0.45 m, respectively, and the swept area was 0.25 m2. The maximum difference between the experimental and analytical results of hydrodynamic performances was less than 56.22% and 41.45%, respectively, for pelagic and bottom trawls, the results of the geometrical performances obtained using predicted equations were close to the experimental results in the flume tank with a maximum relative error less than 12.85%. The newly developed pelagic and bottom trawls had advanced engineering performance for high catch efficiency and selectivity and could be used in commercial fishing operations in Cameroonian waters.

Formation of Uniform Oil-Soluble Fe_3O_4 Nanoparticles via Oil-Water Interface System

Nowadays,the novel oil water interface method has attracted a considerable attention owing to the advantages of mild reaction conditions,simple operation,low cost,and high efficiency.In this paper,uniform oil-soluble Fe_3O_4 nanoparticles(NPs) were synthesized by oil-water interface method from mixing iron tristearate of 0.067mol/L in cyclohexane with ferrous sulfate in water.The as-prepared products were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),vibrating sample magnetometer(VSM),Fourier transform infrared spectroscopy(FT-IR) and thermogravimetric analyzer(TGA).TEM images and XRD profiles showed that the size of the oil-soluble products ranged in 1.7-6.9 nm.VSM indicated that the Fe_3O_4 NPs were superparamagetic.FT-IR and TGA proved that oleic acid was combined to the surface of Fe_3O_4 NPs closely.TEM images and XRD profiles revealed that the most suitable reaction concentration of NH_3·H_2O,oleic acid/water in volume,reaction temperature and reaction time were 4.5 mol/L,50:1 000,80℃ and 6 h,respectively.The formation mechanism of the nearly monodispersed Fe_3O_4 NPs was that the preformed Fe_3O_4 nuclei were capped by oleic acid as early as the nucleation occurred in oil-water interface and subsequently entered into oil phase to stop growing.

Evaluation of Cavity Formation and the Use of Cut-off Wall to Reduce the Risk of Washing Subsurface Fine Material

This study shows the results of mapping numerous cavities and distress which appeared and detected in Qassim area, Saudi Arabia. This phenomenon was observed near a school building and residential area and became a serious risk to occupants and residents. The survey was carried out applying geotechnical techniques which included advancing rotary boreholes to depths of 23 m to 30 m with sampling and testing. The evaluation process also included resistivity imaging profiles using 2D electrical resistivity measurements. Results obtained from this research showed a thick top layer of silty clayey sand soil rich of gypsum and carbonate presenting a hazardous and high-risk soil type. The percentage of fines that are likely to be washed out as a result of chemical disintegration and exposure to significant hydraulic gradient was of great concern. Assessment was made using combined geotechnical and geophysical approach in addition to chemical tests. Based on the data collected and analysis of test results a practical solution was suggested to solve this problem. The use of “cut-off wall” in order to reduce the level of subsurface scour and cajuvity formation were found appropriate. The depth of the cut off wall was determined based on the subsurface geological profile. Advantages of this approach and concerns need to be considered in adopting typical solutions that are presented.

Adding Sub-chain Method for Structural Synthesis of Planar Closed Kinematic Chains

For at least the past five decades,structural synthesis has been used as a main means of finding better mechanisms with some predefined function.In structural synthesis,isomorphism identification is still a problem unsolved well,and to solve this problem is very significant to the design of new mechanisms.According to the given degree of freedom（DOF） and link connection property of planar closed chain mechanisms,vertex assortment is obtained.For solving the isomorphism problem,a method of the adding sub-chains is proposed with the detailed steps and algorithms in the synthesizing process.Employing this method,the identification code and formation code of every topological structure are achieved,therefore many isomorphic structures could be eliminated in time during structural synthesis by comparing those codes among different topological graphs,resulting in the improvement of synthesizing efficiency and accuracy,and the approach for eliminating rigid sub-chains in and after the synthesizing process is also presented.Some examples are given,including how to add sub-chains,how to detect simple rigid sub-chains and how to obtain identification codes and formulation codes et al.Using the adding sub-chain method,the relative information of some common topological graphs is given in the form of table.The comparison result is coincident with many literatures,so the correctness of the adding sub-chain method is convinced.This method will greatly improve the synthesizing efficiency and accuracy,and has a good potential for application.

Gas compression and likely triggered star formation in the infrared bubble N107

The expansion of HII regions can regulate the evolution of their natal clouds and the star for-mation therein. Infrared dust bubbles, which are frequently associated with HII regions, are ideal labora-tories to test whether impulse（s） driven by the expanding bubbles enhances or suppresses star-formation. In this work, we present a comprehensive study of a 20-pc scale infrared bubble N107 to reveal the com- pression of the neutral gas and associated star-forming activities. We obtain column density （NH2） and dust temperature （Tdust） maps via fitting modified blackbodies to multi-band far-infrared Herschel data. The shell structure can be recognized on the column density map. The molecular gas along the rim of N107 fragments into 94 dense clumps at an angular resolution of 18＂. Besides, based on the GLIMPSE point source catalog, we have identified 228 young stellar objects （YSOs） which are categorized into 55 Class I objects, 127 Class II objects and 46 transition disks （TDs）. The 94 clumps and 55 Class I type YSOs are mainly distributed along the shell, which may suggest triggered star formation exists in N107. In addition, analysis of NH2 probability density functions （PDFs） helps us reveal the condition of natal clouds. The two lognormal profiles of PDFs suggest that the surrounding molecular gas has been compressed due to expansion of the bubble. This compression may trigger the star formation process. Moreover, we find the shape of the PDFs changed after removing the background. Taken together, this big bubble seems to compress the surrounding gas and strongly regulate star formation therein.

Synthesis,Structure,Photoluminescence and Thermal Expansion of a Rare Earth Formate Oxalate Framework

A new lanthanide formate oxalate framework [Eu（C2O4）（HCOO）]n （1） has been synthesized via hydrothermal method and characterized by single-crystal X-ray diffraction （SC-XRD）. The framework crystallizes in the orthorhombic Pnma space group, with a = 7.0984（4）, b = 6.6442（3）, c = 10.6793（6） ？, V = 503.68（4） ？3, Z = 3, C3HO6Eu, Mr = 285.00 g/mol, Dc = 3.7581 g/cm3, F（000） = 520.3796, μ = 12.413 mm-1, the final R = 0.0264 and wR = 0.0628 for 797 observed reflections with I 〉 2σ（I）. The photoluminescence （PL） measurements reveal the significant red emission of the framework is dominated by the （5D0 → 7F2） electronic transition at 614 nm. Further variable-temperature powder X-ray diffraction （VT-PXRD） indicates that framework 1 shows slight negative thermal expansion （NTE） along the a-axis, and positive thermal expansion （PTE） along the b and c axes.

基于图和流体扰动算法的多无人车编队及避障研究

为解决多无人车编队在存在运动目标、移动威胁与突发威胁等多种情况的复杂环境中的避障问题,设计了一种基于刚性图论和流体扰动算法的多无人车编队避障控制算法。首先,针对编队控制问题,采用图论方法描述多无人车之间的协同关系,利用无人车之间的距离约束,基于反步控制理论设计领航-跟随编队控制器。李雅普诺夫分析表明,期望的编队形状是渐近稳定的。其次,针对复杂动态障碍物环境下的编队避障问题,设计了基于流体扰动算法的避障路径规划方法,由领航无人车规划出编队的行驶路径,实现编队的整体避障。最后,基于MATLAB的仿真结果验证了所提算法的有效性。

A statistical method for assessment of the existing correlations of hydrate forming conditions

Hydrate formation in the oil and gas industries has been a serious problem for a long time. It may cause many difficulties for instance in gas pipelines blockages. In order to determine the hydrate forming condition, gas gravity method has been used. Several correlations have been proposed based on gas gravity method. Checking the accuracy of the applied correlations is important. In this paper, the leverage approach is used for this purpose. Leverage approach is a statistical method for detection outliers which identifies the applicability domain （AD） of hydrate data predicting correlations and the quality of the existing data. Moreover, the Williams plot is sketched, which is a graphical depiction for determination of the doubtful points. The obtained results showed the existing correlations are all statistically correct and valid to predict hydrate formation temperature, just one data point is out of the applicability domains, and none of the experimental data can be chosen as outliers.

2-D Seismic Reflection Method Using Iso Velocity Method of Mianwali Area

A seismic reflection of Line 12-B belonging to Mianwali Re-entrant was acquired and processed for 2-D interpretation. The line orients itself NNE-SSW direction. The sections have the shot points from VP-199 to VP-1044. Eleven Reflectors R1, R2, R3, Base Miocene, Pinchout P1, P2, P3, P4, P5P6 (Pinchout) are marked and a basement has been marked and interpreted. All the reflectors above the basement show a downward bending at the center. The depth of each reflector was calculated by iso velocity contour map method. The depth section obtained by this method shows stratigraphic features like Pinchouts. The reflectors are then correlated with the subsurface structures and stratigraphy of the area.

Hydrothermally Synthesizing Nanospheres of Pd Loaded TiO_2 for Photocatalytically Reducing CO_2 in Isopropanol to Isopropyl Formate

Photocatalytic reduction of CO2 was carried out on villiform spherical catalysts of Pd-TiO2 in isopropanol solution.The catalysts were synthesized by hydrothermal method,their structures,morphologies and optical absorption properties were characterized by X-ray diffraction（XRD）,energy dispersive X-ray spectroscopy（EDS）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,highresolution transmission electron microscopy（HRTEM）and UV-vis absorption spectroscopy（UV-vis）.The photocatalytic activities with different loading amounts and morphologies were evaluated for determining the dominant effect and optimizing the catalyst preparation.Based on a villiform spherical TiO2 with the largest specific surface area in our experiments,we prepared a set of catalysts with various loading amounts of palladium and tested them by bubbling CO2 through the slurry of catalyst and isopropanol.The highest formation rate of isopropyl formate was 276.6μmol/g？cat/h.Eventually we proposed the reaction mechanism.