Application of static and dynamic enclosures for determining dimethyl sulfide and carbonyl sulfide exchange in Sphagnum peatlands: Implications for the magnitude and direction of flux

A static enclosure method was applied to determine the exchange of dimethyl sulfide (DMS) and carbonyl sulfide (OCS) between the surface of Sphagnum peatlands and the atmosphere. Measurements were performed concurrently with dynamic (flow through) enclosure measurements with sulfur-free air used as sweep gas. This latter technique has been used to acquire the majority of available data on the exchange of S gases between the atmosphere and the continental surfaces and has been criticized because it is thought to overestimate the true flux of gases by disrupting natural S gas gradients. DMS emission rates determined by both methods were not statistically different between 4 and >400 nmol m−2 h−1, indicating that previous data on emissions of at least DMS are probably valid. However, the increase in DMS in static enclosures was not linear, indicating the potential for a negative feedback of enclosure DMS concentrations on efflux. The dynamic enclosure method measured positive OCS flux rates (emission) at all sites, while data using static enclosures indicated that OCS was consumed from the atmosphere at these same sites at rates of 3.7 to 55 nmol m−2 h−1. Measurements using both enclosure techniques at a site devoid of vegetation showed that peat was a source of both DMS and OCS. However, the rate of OCS efflux from decomposing peat was more than counterbalanced by OCS consumption by vegetation, including Sphagnum mosses, and net OCS uptake occurred at all sites. We propose that all wetlands are net sinks for OCS.

柴达木盆地地震勘探关键技术研究

The rugged surface topography determined the seismic data acquisition construction conditions and the seismic wave explosive and receiver quality in Qaidam Basin. This dissertation systematically researched the seismic acquisition, imaging process and the attribute analysis techniques of complicated oil and gas reservoir. The main research achievements and cognitions are as follows: 1. Through the stimulation effects research and analysis from the aspect of lithologic water-containing differences, it’s specific that stable hydrous sand layer can effectively enhance the stimulation effects combined with the corresponding field tests. The seismic data S/N ratio has been improved due to the combination explosive stimulation. Through the fold number and maximum offset analyses of target horizon, the complicated geometry has been optimized and the S/N ratio of seismic data has been improved, which made an important basis for improvement of 3D seismic data. 2. It has been proved that the first arrival refraction static correction method under the model constraint of fine surface survey is suitable to the Qaidam Basin of western areas by the real seismic data processing. Although the refraction horizon of near surface has some changes in a certain extent, it’s steady basically. The refraction horizon can be continuously traced in sections, so it’s qualified for the refraction static correction method on the whole. 3. The research is based on the curved-ray pre-stack time migration techniques of rough topography, and improved the imaging precision of complex areas. This techniques adopted the constant and variable velocity scanning mode and enhanced the velocity analysis precision. The 3D pre-stack time migration techniques reasonably solved the imaging and velocity multiple solutions problems of steep-dip faults and the intersections of horizontal layers. What’s more, fine velocity analysis and mute are very important to enhance the imaging precision of the seismic data in complicated Wunan areas. 4. The 3D seismic data edge-preserving processing methods have been realized due to the image process techniques. Because this method uses the large range filter, it can attenuate the noise maximally. The faults, break points, lithologic pinchout points and lithologic body of small scale such as river will not be influenced by blur because of the edge-preserving characterization of the method which is really an effective assistant technique of low S/N ratio seismic data attribute analysis. 5. The use of spectral decomposition technique can effectively identify the reservoirs. The special geology body which will not be identified (or without obvious characters) in the seismic profile may be found through the details changes of different frequencies in the amplitude profiles.

徐家围子断陷连片叠前时间偏移处理方法研究

In this paper, the detailed analysis of fundamental seismic data and theoretical method are given, and the tests of some new technologies are performed. For seismic data processing assembly, some key technologies are developed and applied, such as global static correction, amplitude consistency processing, wavelet consistency shaping, fine velocity model establishing and prestack time migration. These technologies can efficiently settle the problems during the course of multiple- block– jointed prestack time migration processing, and it is highly significant for holding the oil output of 40,000,000 tons for Daqing oilfield. Through the research of this dissertation, the following important contributions are shown: (1) The combination of near-surface model method and refraction static correction method is developed, and is applied to solve global static correction for the whole merging area. (2) Prestack amplitude normalization processing method based on fold is developed. The method eliminates the effects of fold on amplitude uniformity, and solves the problem of energy uniformity for tie-area prestack migration processing. (3) Wavelet consistency is investigated. For multiple survey blocks existing in the area, the optimum method of wavelet shaping is developed, which removes the waveform variance between two adjacent blocks. (4) Controlled velocity inversion (CVI) technique is used to establish migration velocity field. It can largely shorten the period of velocity modeling, and improve velocity analysis precision. (5) Float datum level technique is employed, and is able to guarantee prestack migration results of subsurface shallow layers. (6) The static partition of seismic data volume relating to migration aperture is firstly developed. And the precious imaging for huge data volume by prestack time migration is realized. (7) The numerical forward simulation and prestack migration processing is primarily combined to discuss the migration technique for a complex geology structure from practical field information. The combination of numerical simulation and prestack migration is a feasible way to solve the fine imaging of complex volcanic structure. And the combination approach can help to select appropriate migration parameters.

KEL-TI介质的地震波场响应与成像方法研究

To deal with the problems in multi-component converted seismic wave exploration in coal fields, the wave propagating features and imaging methods of multi-component converted waves in coal measure strata are researched in this thesis firstly. The relations between viscoelasticity and anisotropy in coal measure strata are analyzed to build KEL-TI model, and which seismic wave propagating and attenuating features are researched. The disadvantages of converted wave imaging methods based on common converted point gather are analyzed and constant velocity no NMO converted wave imaging method based on common scattering point gather is put forward, according to Huygens-Fresnel principle, which applicabilities in the elastic isotropic, elastic TI and KEL-TI situations are discussed. To different model simulation data, the common scattering point gathers’ and stacked profiles’ features are analyzed. The results show that the method can image compressional waves and converted waves with high precision. Secondly, the resolution enhancing theories and methods of converted wave are researched by Rayleigh wave suppressing, converted wave static correction and poststack inverse-Q filtering. 1) The polarization filter is designed by the instantaneous polarization information of seismic waves, and the Rayleigh wave suppressing method is researched. From the spectrum analysis before and after filtering, it can be derived that the amplitudes are kept relatively. 2) To constant velocity no NMO converted wave imaging method, the static correction method based on common equivalent offset point gather is put forward and tested to the actual converted waves. 3) The relation between equivalent quality factor of converted wave, compressional wave quality factor and the ratio of compressional to shear wave velocity is derived. The compressional wave quality inversion method by first arrivals of none-offset VSP is researched, and which is then transformed to the equivalent quality factor to perform inverse-Q filtering of actual converted waves. The result has shown that the method can recover the high frequency energy of converted waves. At last, the theories and methods researched in this thesis are practiced to the 3D3C seismic exploration in Guqiao coal mine in Huainan and achieve good results.

Comparison Of The Quasi-Static Method And The Dynamic Method For Simulating Fracture Processes In Concrete

Concrete is heterogeneous and usually described as a three-phase material, where matrix, aggregate and interface are distinguished. To take this heterogeneity into consideration, the Generalized Beam (GB) lattice model is adopted. The GB lattice model is much more computationally efficient than the beam lattice model. Numerical procedures of both quasi-static method and dynamic method are developed to simulate fracture processes in uniaxial tensile tests conducted on a concrete panel. Cases of different loading rates are compared with the quasi-static case. It is found that the inertia effect due to load increasing becomes less important and can be ignored with the loading rate decreasing, but the inertia effect due to unstable crack propagation remains considerable no matter how low the loading rate is. Therefore, an unrealistic result will be obtained if a fracture process including unstable cracking is simulated by the quasi-static procedure.

Static shape control of repetitive structures integrated with piezoelectric actuators

In this paper, several simplification methods are presented for shape control of repetitive structures such as symmetrical, rotational periodic, linear periodic, chain and axisymmetrical structures. Some special features in the differential equations governing these repetitive structures are examined by considering the whole structures. Based on the special properties of the governing equations, several methods are presented for simplifying their solution process. Finally, the static shape control of a cantilever symmetrical plate with piezoelectric actuator patches is demonstrated using the present simplification method. The result shows that present methods can effectively be used to find the optimal control voltage for shape control.

Static Study of Cantilever Beam stiction under Electrostatic Force Influence

The model and analysis of the cantilever beam adhesion problem under the action of electrostatic force are given. Owing to the nonlinearity of electrostatic force, the analytical solution for this kind of problem is not available. In this paper, a systematic method of generating polynomials which are the exact beamsolutions of the loads with different distributions is provided. The polynomials are used to approximate the beam displacement due to electrostatic force. The equilibrium equation offers an answer to how the beam deforms but no information about the unstuck length. The derivative of the functional with respect to the unstuck length offers such information. But to compute the functional it is necessary to know the beam deformation. So the problem is iteratively solved until the results are converged. Galerkin and Newton-Raphson methods are used to solve this nonlinear problem. The effects of dielectric layer thickness and electrostatic voltage on the cantilever beamstiction are studied.The method provided in this paper exhibits good convergence. For the adhesion problem of cantilever beam without electrostatic voltage, the analytical solution is available and is also exactly matched by the computational results given by the method presented in this paper.

A time domain computation method for dynamic behavior of mooring system

A quasi-steady time domain method is developed for the prediction of dynamic behavior of a mooring system under the environmental disturbances, such as regular or irregular waves, winds and currents. The mooring forces are obtained in a static sense at each instant. The dynamic feature of the mooring cables can be obtained by incorporating the extended 3-D lumped-mass method with the known ship motion history. Some nonlinear effects, such as the influence of the instantaneous change of the wetted hull surface on the hydrostatic restoring forces and Froude-Krylov forces, are included. The computational results show a satisfactory agreement with the experimental ones.

Molecular/Cluster Statistical Thermodynamics Methods To Simulate Quasi-Static Deformations At Finite Temperature

The rapid evolution of nanotechnology appeals for the understanding of global response of nanoscale systems based on atomic interactions, hence necessitates novel, sophisticated, and physically based approaches to bridge the gaps between various length and time scales. In this paper, we propose a group of statistical thermodynamics methods for the simulations of nanoscale systems under quasi-static loading at finite temperature, that is, molecular statistical thermodynamics (MST) method, cluster statistical thermodynamics (CST) method, and the hybrid molecular/cluster statistical thermodynamics (HMCST) method. These methods, by treating atoms as oscillators and particles simultaneously, as well as clusters, comprise different spatial and temporal scales in a unified framework. One appealing feature of these methods is their "seamlessness" or consistency in the same underlying atomistic model in all regions consisting of atoms and clusters, and hence can avoid the ghost force in the simulation. On the other hand, compared with conventional MD simulations, their high computational efficiency appears very attractive, as manifested by the simulations of uniaxial compression and nanoindenation. (C) 2008 Elsevier Ltd. All rights reserved.

Improvement in growth and toxin production of Alexandrium tamarense by two-step culture method

The growth and toxin content of the dinoflagellate Alexandrium tamarense ATHK was markedly affected by culture methods. In early growth phase at lower cell density static or mild agitation methods were beneficial to growth, but continuous agitation or aeration, to some extent, had an adverse effect on cell growth. Static culture in 2 L Erlenmeyer flasks had the highest growth rate (0.38 d(-1)) but smaller cell size compared with other culture conditions. Cells grown under aerated conditions possessed low nitrogen and phosphorus cell yields, namely high N and P cell-quota. At day 18, cells grown in continuous agitated and 1 h aerated culture entered the late stationary phase and their cellular toxin contents were higher (0.67 and 0.54 pg cell(-1)) compared with cells grown by other culture methods (0.27-0.49 pg cell(-1)). The highest cell density and cellular toxin content were 17190 cells mL(-1) and 1.26 pg cell(-1) respectively in an airlift photobioreactor with two-step culture. The results indicate that A. tamarense could be grown successfully in airlift photobioreactor by a two-step culture method, which involved cultivating the cells statically for 4 days and then aerating the medium. This provides an efficient way to enhance cell and toxin yield of A. tamarense.

CALCULATION OF DIELECTRIC-CONSTANTS FOR SEMICONDUCTORS - AN APPLICATION OF ABINITIO PSEUDOPOTENTIAL METHOD

We have used ab initio pseudopotential method to generate basis wavefunctions and eigen energies to carry out first principle calculations of the static macroscopic dielectric constant for GaAs and GaP. The resulted converged random phase approximation (RPA) value is 12.55 and 10.71, in excellent agreement to the experimental value of 12.4 and 10.86, respectively. The inclusion of the exchange correlation contribution makes the calculated result slightly worsen. A convergence test with respect to the number of k points in Brillouin zone (BZ) integration was carried out. Sixty irreducible BZ k points were used to achieve the converged results. Integration with only 10 special k points increased the RPA value by 15%.

Integrated electroabsorption-modulated DFB laser by using an improved butt-joint method

An improved butt coupling method is used to fabricate an electroabsorption modulator (EAM) monolithically integrated with a distributed feedback (DFB) laser. The obtained electroabsorption-modulated laser (EML) chip with the traditional shallow ridge exhibits very low threshold current of 12 mA, output power of more than 8 mW, and static extinction ratio of -7 dB at the applied bias voltage from 0.5 to -2.0 V.

Solvent size effect on the static and dynamic properties of polymer chains in athermal solvents

The static and dynamic properties of polymer chains in athermal solvents with different sizes are studied by molecular dynamics method. With increasing solvent size, the radius of gyration and the diffusion coefficient of the polymer decay fast until a critical solvent size is reached. For the polymer diffusion coefficients, this decay only depends on the solvent size; while for the radius of gyration of polymers, this decay depends on both solvent size and the length of the polymers. The increase of solvent size also makes the polymer tend to be thicker ellipsoid until a critical solvent size is reached. The static scaling exponent of the polymer also shows the solvent size dependence. Moreover, four regions are identified where the polymers show different dynamic behaviors according to the dynamic structure factors of the polymer.

Determination of molecular weight and molecular sizes of polymers by high temperature gel permeation chromatography with a static and dynamic laser light scattering detector

Flow-mode static and dynamic laser light scattering (SLS/DLS) studies of polymers, including polystyrene, polyethylene, polypropylene and poly(dimethylsiloxane) (PDMS), in 1,2,4-trichlorobenzene (TCB) at 150 degreesC were performed on a high temperature gel permeation chromatography (GPC) coupled with a SLS/DLS detector. Both absolute molecular weight (M) and molecular sizes (radius of gyration, R-g and hydrodynamic radius, R-h) of polymers eluting from the GPC columns were obtained simultaneously. The conformation of different polymers in TCB at 150 degreesC were discussed according to the scaling relationships between R-g, R-h and M and the rho-ratio (p = R-g/R-h). Flow-mode DLS results of PDMS were verified by batch-mode DLS study of the same sample. The presented technique was proved to be a convenient and quick method to study the shape and conformation of polymers in solution at high temperature. However, the flow-mode DLS was only applicable for high molecular weight polymers with a higher refractive index increment such as PDMS.

A novel method of studying polymer biodegradation

A novel combination of laser light scattering (LLS) and the micronization of a water-insoluble polymer into narrowly distributed nanoparticles stable in water has provided not only an accurate, reliable and microscopic method to study polymer biodegradation, but also a novel and fast way to evaluate the biodegradability of a given polymer. Using poly(epsilon-caprolactone) (PCL) as a typical example, we have shown that its biodegradation time can be shortened by a factor of more than 10(3) times in comparison with the time required to biodegrade a thin film (10 x 10 x 0.1 mm(3)). Moreover, the biodegradation kinetics can be in-situ monitored in terms of the decrease of the time-average scattering intensity and the particle number. A comparison of static and dynamic LLS results revealed that the enzyme, Lipase Pseudomonas, ''eats'' the PCL nanoparticles in an one-by-one manner and the enzymatic biodegradation of PCL follows a zero-order kinetics. (C) 1998 Elsevier Science Ltd. All rights reserved.