电子印前系统色彩管理实施方法的分析

对电子印前系统中色彩管理实施方法及其研究现状进行了分析,指出当前实施色彩管理方面存在的问题和发展趋势,在此基础上,提出目前的任务和努力的方向。     

Stability and Grid Dispersion of the P-SV 4th-Order Staggered-Grid Finite-Difference Schemes

Stability and grid dispersion in the P-SV 4th-order in space, 2nd-order in time, displacement-stress staggered-grid finite-difference scheme is investigated in the case of a homogeneous unbounded medium. All results, however, also apply to the velocity-stress and displacement- velocity-stress finite-difference schemes. Independent stability conditions for the P and S waves are obtained by exact separation of equations for the two types of waves. Since the S-wave group velocity can differ from the actual velocity as much as 5% for the sampling ratio 1/5, commonly used in numerical modelling, the sampling of the minimum S wavelength by 6 grid spacings (with the velocity difference not larger than 2.5%) is recommended. Grid dispersion is strongest for a wave propagating in a direction of a coordinate axis and weakest for a wave propagating along a plane diagonal. Grid dispersion in the 4 ^th -order scheme for the sampling ratios s = 1/5 and s = 1/6 is smaller than grid dispersion in the 2 ^nd -order scheme for s = 1/10 and s = 1/12, respectively.     

Observations on New Approaches for the Determination of Platinum-Group Elements, Gold and Silver in Different Geochemical Samples from Siberia and the Far East

Some recent experiments on the determination of Au and the platinum-group elements (PGE) in geochemical samples are reviewed. Emphasis is given to the determination of ultra-low levels of PGE concentrations in resistant matrices, including chromites, molybdenites and ultrabasic ores. The problems and features of PGE determination in samples of various chemical composition are considered. For each sample type studied, a series of sample preparation techniques are proposed. These techniques included acid digestion, fusion with sodium peroxide, cold sintering with an oxidizing mixture of Na₂O₂+ Na₂CO₃ and also oxidizing fluorination with bromine trifluoride. A new approach for preparing geochemical material prior to digestion, based on mechano-chemical activation with simultaneous hyperfine grinding, is proposed and studied. The instrumental determination of PGE contents was carried out directly by AAS from extracted organic phases. It was found that a combination of digestion processes was required to achieve geochemical background levels of Au and PGE concentrations with the following detection limits: Pd, Rh - 1 ng g⁻¹, Pt, Ru - 10 ng g⁻¹, Au - 0.2 ng g⁻¹, Ag - 0.1 ng g^−1. The uncertainty in PGE and Au determination in geochemical samples is dependent on metal concentration, and also on their distribution in samples. The total analytical uncertainty of the proposed method is between 15-30%.     

华贵栉孔扇贝(Chlamys nobilis)壳色遗传规律的研究

采用双列杂交方法对华贵栉孔扇贝三种壳色(桔黄色、枣褐色、紫褐色)的遗传规律进行了研究。结果显示,桔黄色♂×枣褐色♀和桔黄色♂×紫褐色♀的子代均全部表现为桔黄色,桔黄色♀×枣褐色♂和桔黄色♀×紫褐色♂的子代壳色比例分别为桔黄色:枣褐色=1:1和桔黄色:紫褐色=3:1,表明桔黄色对枣褐色和紫褐色均为显性,且不存在母性遗传;在桔黄色♂×桔黄色♀的两个家系中,一个家系的子代全部表现为桔黄色,另一个家系的子代中桔黄色:枣褐色约为3:1,表明第1家系有一个亲本为显性纯合,第2家系2个亲本均为杂合;在枣褐色♂×枣褐色♀和紫褐色♂×紫褐色♀两个家系中,其子代分别全部表现为其亲本的颜色,表明枣褐色和紫褐色个体均为隐性纯合体。实验所设各家系子代壳色均表现出了与亲本相同的颜色,表明华贵栉孔扇贝的壳色属质量性状,能够稳定遗传,并非由环境决定,对华贵栉孔扇贝壳色的选育有效。     

Lebedev scheme for the numerical simulation of wave propagation in 3D anisotropic elasticity‡

This paper presents a Lebedev finite difference scheme on staggered grids for the numerical simulation of wave propagation in an arbitrary 3D anisotropic elastic media. The main concept of the scheme is the definition of all the components of each tensor (vector) appearing in the elastic wave equation at the corresponding grid points, i.e., all of the stresses are stored in one set of nodes while all of the velocity components are stored in another. Meanwhile, the derivatives with respect to the spatial directions are approximated to the second order on two‐point stencils. The second‐order scheme is presented for the sake of simplicity and it is easy to expand to a higher order. Another approach, widely‐known as the rotated staggered grid scheme, is based on the same concept; therefore, this paper contains a detailed comparative analysis of the two schemes. It is shown that the dispersion condition of the Lebedev scheme is less restrictive than that of the rotated staggered grid scheme, while the stability criteria lead to approximately equal time stepping for the two approaches. The main advantage of the proposed scheme is its reduced computational memory requirements. Due to a less restrictive dispersion condition and the way the media parameters are stored, the Lebedev scheme requires only one‐third to two‐thirds of the computer memory required by the rotated staggered grid scheme. At the same time, the number of floating point operations performed by the Lebedev scheme is higher than that for the rotated staggered grid scheme.     

Comment on “An improved gray Lattice Boltzmann model for simulating fluid flow in multi-scale porous media”: Intrinsic links between LBE Brinkman schemes

In this Comment on the recent work (Zhu and Ma, 2013) [11] by Zhu and Ma (ZM) we first show that all three local gray Lattice Boltzmann (GLB) schemes in the form (Zhu and Ma, 2013) [11]: GS (Chen and Zhu, 2008; Gao and Sharma, 1994) [1,4], WBS (Walsh et al., 2009) [12] and ZM, fail to get constant Darcy’s velocity in series of porous blocks. This inconsistency is because of their incorrect definition of the macroscopic velocity in the presence of the heterogeneous momentum exchange, while the original WBS model (Walsh et al., 2009) [12] does this properly. We improve the GS and ZM schemes for this and other related deficiencies. Second, we show that the “discontinuous velocity” they recover on the stratified interfaces with their WBS scheme is inherent, in different degrees, to all LBE Brinkman schemes, including ZM scheme. None of them guarantees the stress and the velocity continuity by their implicit interface conditions, even in the frame of the two-relaxation-times (TRT) collision operator where these two properties are assured in stratified Stokes flow, Ginzburg (2007) [5]. Third, the GLB schemes are presented in work (Zhu and Ma, 2013) [11] as the alternative ones to direct, Brinkman-force based (BF) schemes (Freed, 1998; Nie and Martys, 2007) [3,8]. Yet, we show that the BF-TRT scheme (Ginzburg, 2008) [6] gets the solutions of any of the improved GLB schemes for specific, viscosity-dependent choice of its one or two local relaxation rates. This provides the principal difference between the GLB and BF: while the BF may respect the linearity of the Stokes–Brinkman equation rigorously, the GLB-TRT cannot, unless it reduces to the BF via the inverse transform of the relaxation rates. Furthermore, we show that, in limited parameter space, “gray” schemes may run one another. From the practical point of view, permeability values obtained with the GLB are viscosity-dependent, unlike with the BF. Finally, the GLB shares with the BF a so-called anisotropy (Ginzburg, 2008; Nie and Martys, 2007) [6,8], that is, flow-direction-dependency in their effective viscosity corrections, related to the discretized spatial variation of the resistance forcing.     

绥化市红兴水库渗漏分析及渗控方案模拟预测

为解决水库建成后渗漏较为严重的问题,依据黑龙江省绥化市红兴水库初期蓄水失败后补充的地质勘探资料,分析水库渗漏的主要原因是库区内的粘土层分布不连续。采用三维数值模拟计算,建立红兴水库区地下水流概念模型及其数学模型,运用FEFLOW 软件的剖分功能对研究区进行了刻画;在此基础上,对无防渗方案和拟修4种防渗墙方案的防渗效果进行了模拟预测和对比。结果表明：有坝段防渗对渗漏总量的控制具有十分明显的作用,可以使水库渗漏总量减少约70％;渗漏量及渗透比降基本随防渗长度的增大呈线性趋势减小;南岸东侧防渗1 000 m、西侧防渗1 700 m时,为防渗效果最好的方案。     

A technique to test finite difference schemes to model some geophysical processes in a geological structure

A preliminary problem to solve in the set-up of a mathematical model simulating a geophysical process is the choice of a suitable discrete scheme to approximate the governing differential equations. This paper presents a simple technique to test finite difference schemes used in the modeling of geophysical processes occurring in a geological structure. This technique consists in generating analytical solutions similar to the ones characterizing a geophysical process, given general information on some relevant parameters. Useful information for the choice of the discrete scheme to employ in the mathematical model simulating the original geophysical process can be obtained from the comparison between the analytical solution and the approximated numerical solutions generated by means of different discrete schemes. Two classes of numerical examples approximating the differential equation that governs the steady state earth's heat flow have been treated using three different finite differences schemes. The first class of examples deals with media whose phenomenological parameters vary as continuous space functions; the second class, instead, deals with media whose phenomenological parameters vary as discontinuous space functions. The finite difference schemes that have been utilized are: Centered Finite Difference Scheme (CDS), Arithmetic Mean Scheme (AMS), and Harmonic Mean Scheme (HMS).The numerical simulations showed that: the CDS may yield physically inconsistent solutions if the lattice internodal distance is too large, but in case of phenomenological parameters varying as a continuous function, this pitfall can be avoided increasing the lattice node refinement. In case of phenomenological parameters varying as a discontinuous function, instead, the CDS may yield physically inconsistent solutions for any lattice-node refinement. The HMS produced good results for both classes of examples showing to be a scheme suitable to model situations like these.     

Color display of well logs

Information displayed in image form is conventionally at least two-dimensional. One-dimensional data can also be displayed as imagery by amplitude slicing a function and representing these amplitude slices as grey levels or as intensities of a particular color. An image having length and width can be formed from one-dimensional data by arranging a sequence of such color levels along the length of the image, corresponding to the independent space or time variable, and by extending these color levels arbitrarily along the width of the image. Such an image is of arbitrary width and exhibits changes, or information, only along its length. If three such images are made, one in each of the three primary colors, each image representing a different one-dimensional function over the same range of a common independent space or time variable, standard primary color composition can be used to unite these three images into a single full-color image in either computer graphic or photographic media. When three different well logs from a single borehole are combined in this manner, the resulting full-color image is equivalent to a three-axis cross-plot of the logs involved. Because primary colors appear to the human eye to be orthogonal and miscible, the color image preserves all information present in the three original data sets.Further, because this color representation of data can be arranged conveniently in depth sequence, the color composite image presents both information best visualized in cross-plot presentation (e.g., lithologic clustering and differentiation) and information lacking in cross-plots that is best seen in conventional wiggle-trace displays of well logs (e.g., stratigraphic or depth sequence). Such color presentations of well log data reduce the number of displays competing for an interpreter's attention by uniting three wiggle traces into one display and relieve the burden of mentally combining data from several separate displays. Combined interpretation is particularly essential in well log interpretation where one must analyze individually ambiguous data sets; color log presentation automatically provides combination while leaving interpretation to the scientist. Color log images also present log data to the user in a form that differs from conventional wiggle trace and so appeals to a different and richer set of human perceptions and pattern recognition skills.     

Ontario’s Environmental Farm Plan: Evaluation and research agenda

This paper analyses the operation of the Environmental Farm Plan (EFP) scheme in Ontario, Canada, a voluntary agri-environment scheme established in 1993. Previously unpublished data and interviews with farmers, leaders of farmers’ organisations and government officials are used to detail participation rates, geographical spread and method of operation. Largely developed by farmers’ organisations, the scheme has focused on soil management, water quality and storage/disposal of agricultural wastes. The environmental actions associated with these activities are discussed, revealing both successes and limitations. Distinctions are drawn with agri-environmental schemes in the European Union, and a broader context for the EFP is provided with respect to the proposed post-productivist transition of agri-food systems and the need to examine the way these systems are regulated. A need for further systematic research is proposed, specifically with respect to barriers to participation, the voluntary nature of the scheme, financial incentives and the resultant environmental impacts.