Tion Method Research Articles

규칙파중 항력을 고려한 TLP의 동적응답해석

AbstractFor predicting the motion and structural responses of tension l eg platforms(TLPs) in regular waves, a numerical scheme is introduced. The numerical approach in this paper is based on a combination of the three dimensional source distribu tion method and the finite element method. The hydrodynamic interactions among TLP members , such as columns and pontoons, are included in the motion and structural response an alysis. The drag forces on the submerged slender members, which are proportional to the sq uare of relative velocity, are newly included in order to estimate the responses of member s with better accuracy. Comparisons with other's results verifies the works in this paper. ※Keywords: TLP(Tension Leg Platform; 인장계류식 해양구조물), Hydrodynamic interaction(유체역학적 상호간섭), Motion response(운동응답), Structural response(구조응답), Drag forces(항력) 1. 서론 최근 심해유전개발의 가속화는 부유식 해양구조물(Offshore floaters)에 대한 관심과 발주증가에 많이 기여하고 있다. 인장계류식 해양구조물(TLP)은 이러한 심해개발을 위한 대표적인 구조물중 하나이고, 실용화를 위한 많은 연구가 진행되어 왔

REVIEW: Slower boat speeds reduce risks to manatees

Collisions with boats account for approximately 25% of all documented manatee Trichechus manatus latirostris deaths in Florida. The state of Florida, as well as the US Fish and Wildlife Service and various local governments, have established boat speed limits in areas fre- quented by manatees as a means of reducing risks. Boat speed limits are believed to reduce risks in 3 primary ways: (1) greater reaction time for the boat operator; (2) greater reaction time for the man- atee; and (3) reduced severity of injuries in the event that a manatee is hit by a boat. We review the current research and other available information that forms the conceptual basis for this risk reduc- tion method and also examine the primary objections that have been raised against requiring slower boat speeds. The available information supports the position that reducing boat speeds in specific areas is an appropriate, reasonable, and defensible management action. Additional research on how manatees detect and respond to boats would be very useful, as would further empirical studies assessing the effectiveness of existing boat speed limits.

A Modified Trefftz Method for Two-Dimensional Laplace Equation Considering the Domain's Characteristic Length

A newly modified Trefftz method is developed to solve the exterior and interior Dirichlet problems for two-dimensional Laplace equation, which takes the characteristic length of problem domain into account. After introducing a circular artificial boundary which is uniquely determined by the physical problem domain, we can derive a Dirichlet to Dirichlet mapping equa- tion, which is an exact boundary condition. By truncating the Fourier series expansion one can match the physical boundary condition as accu- rate as one desired. Then, we use the colloca- tion method and the Galerkin method to derive linear equations system to determine the Fourier coefficients. Here, the factor of characteristic length ensures that the modified Trefftz method is stable. We use a numerical example to ex- plore why the conventional Trefftz method is fail- ure and the modified onestill survives. Numerical examples with smooth boundaries reveal that the present method can offer very accurate numeri- cal results with absoluteerrors about in the orders from 10 −10 to 10 −16 . The new method is pow- erful even for problems with complex boundary shapes, with discontinuous boundary conditions or with corners on boundary. Keyword: Laplace equation, Artificial bound- ary condition, Modified Trefftz method, Char- acteristic length, Collocation method, Galerkin method, DtD mapping

Eficiencia de grupos de pilotes sometidos a carga lateral

This pa per in cludes a bib lio graph i cal re view of the o ret i cal and ex per i men tal be hav ior stud ies of piles sub jected to static lat eral load. The ex per i men tal be hav ior was ob tained from full scale load test and it pro vides a solid ba sis for com par i son with nu mer i cal meth ods of anal y sis, mainly beam on elas tic foun da tion, p-y curves method, and fi nite el e ments with lin ear mod el ing of soil. The com puter re sults were com pared with the ex per i men tal mea sure ments. The p-y curves method pro vides the best re sults, mod el ing ap pro pri ately the dis tri bu tion of lat eral loads and bend ing mo ments of piles in a group. The lin ear fi nite el e ment method mod els par tially the in ter ac tion soil-pile group and gives a rea son able an swer of the group ef fi ciency. The beam on elas tic foun da tion method gives re sults sim i lar to those us i ng the fi nite el e ment method and it im proves when non lin ear be hav ior of soil is con sid ered.

Dynamically adapted grids for interacting discontinuous solutions

Further development of the dynamic adaptation method for gas dynamics problems that describe multiple interactions of shock waves, rarefaction waves, and contact discontinuities is consid- ered. Using the Woodward-Colella problem and a nonuniformly accelerating piston as examples, the efficiency of the proposed method is demonstrated for the gas dynamics problems with shock wave and contact discontinuity tracking. The grid points are distributed under the control of the diffusion approx- imation. The choice of the diffusion coefficient for obtaining both quasi-uniform and strongly nonuni- form grids for each subdomain of the solution is validated. The interaction between discontinuities is resolved using the Riemann problem for an arbitrary discontinuity. Application of the dynamic adapta- tion method to the Woodward-Colella problem made it possible to obtain a solution on a grid consisting of 420 cells that is almost identical to the solution obtained using the WENO5m method on a grid con- sisting of 12 800 cells. In the problem for a nonuniformly accelerating piston, a proper choice of the dif- fusion coefficient in the transformation functions makes it possible to generate strongly nonuniform grids, which are used to simulate the interaction of a series of shock waves using shock wave and contact discontinuity tracking. The dynamic adaptation methods (13-21) are less complicated and make it possible to generate grids with a constant (19) or variable (18) number of grid points. In these methods, the control of the distribution of the grid points is achieved by using information about the dynamic behavior of the solution to be found. This makes it possible to concentrate a large number of grid points in the regions where the solution under- goes sharp changes (13). A close relationship between the dynamic behavior of the solution and the location of the grid points requires that the coordinates of the grid points be recalculated at each time layer. This fact places high requirements upon the consistency of the solution dynamics with the grid points motion. For this reason, the algorithms that do not use any fitting parameters have certain advantages (15). These fea- tures are especially pronounced in the generation of adaptive grids for unsteady gas dynamics problems (see (16-22)), which describe rapidly changing processes. The solution of hyperbolic differential equations,

Prediction Method of CME Associated Geomagnetic Disturbances Based on Fuzzy Mathematics

以1997-2003年期间的73个日冕物质抛射(CME)激波扰动事件和模糊数学为基础,提出了一种预报地磁扰动的方法.该方法以CME事件爆发的日面经纬度、相关地磁扰动事件的渡越时间、地磁扰动指数、IPS观测的太阳风速度跃变量为基础,建立了预报CME地磁扰动事件的μθ,μφ,μT,μM,μ△v从属函数,考虑了CME初始速度对激波到达时间的影响.以这5个从属函数为基础并利用模糊数学对1996-2004年期间73个经行星际闪烁(IPS)观测认证的CME激波引起的地磁扰动事件进行了预报实验.实验结果表明,磁扰开始时间预报的相对误差,△Tpre/Tobs≤30%的事件占总事件数的91.78%,而△Tpre/Tobs＞30%的事件占总事件数的12.33%;磁扰幅度(∑Kp)大小的预报,其相对误差△∑Kp/∑Kpobs≤30%的事件占总事件数的60.27%,相对误差≥50%的事件占总事件数的12.33%.这表明该预报方法对空间灾害性事件地磁扰动的定量预报具有很大应用潜力.

Load characteristics of π-bridge electrohydraulic proportional relief valve

A new type electro-hydraulic proportional relief valve with G-πbridge pilot hydraulic resistance network is designed. The principle of the valve operation is analyzed. The construction and parameters of the valve are determined. The steady state equations are written out, which describe the flow pressure performances about the hydraulic resistances and force balance characteristic on the main poppet and pilot poppet. Furthermore, the relational equation of the parameters for the valve with zero override is obtained, which offers the calcula- tion method for the design of the valve. The load characteristic of the valve with different hydraulic resistances is simulated by numerical computation. The new valve is developed and the steady state performance of the valve with different hydraulic resistances is measured. The results of experiment and simula- tion show that load characteristic of the n bridge elec- tro-hydraulic proportional relief valve is much better than tradi- tional proportional relief valve.

Complex dynamics of a chemostat with variable yield and periodically impulsive perturbation on the substrate

tion method, we establish the condition under which the boundary periodic solution is globally asymptotically stable. Moreover, the permanence of the system is discussed in detail. Finally, by means of numerical simulation, we demonstrate that with the increasing of the pulsed substrate in the feed the system exhibits the complex dynamics.

Diseño óptimo evolutivo

This pa per re ports the merg ing of Ge netic Al go rithms (GA) with Fi nite El e ment Anal y sis (FEA) as a tool of op ti mi za tion for de sign of trusses. The de vel op ment of an ex per i men tal CAD tool is re ported Evo lu tion ary Op ti mal De sign (DOPE). This CAD was done us ing DELPHI (Ob ject Pascal) and showed very good re sults in spite of such ba sic con fig u ra tion. The re sults lead us to optimizate within rea son able pro cess ing time, so a fast and ro bust op ti mi za tion method is ob tained. The re search ac tu ally em beds FEA within the GA, and the fit ness func tion is linked to FEA, in stead of the ap proach of pro cess ing with GA’s, con firm ing and re di rect ing with FEA used in other re searches. Three cases of study are re ported for con firm ing the util ity of DOPE ap plied to trusses.

Airborne-pollen map for Olea europaea L. in eastern Andalusia (Spain) using GIS: Estimation models

Estimations based upon geostatistics and mapping have enabled the construction of a spatial model to predict the presence of biological particles in a particular region. This methodological proposal has been tested in a case study, at a regional scale, of airborne Olea pollen, using the data acquired from various sampling stations that are designed for the aerobiological monitoring of pollen levels. These sampling stations have been set up in cities throughout the region of Andalusia (southern Spain) at sites with very different characteristics in terms of biogeography, bioclimate, topography and vegeta- tion. Pollen counts were made daily at all sites during 2003 using a volumetric spore-trap. Data were com- paratively analysed in classical diagrams and by means of spatial-temporal maps. Space-time models were constructed using three coordinates, x, y (the UTM coordinates of each sampling station) and z, (the aerobiological data compiled for a specific per- iod). The aerobiological data were interpolated by applying the traditional geostatistical method of Kriging. The introduction of the variable ''space'' into the model allowed us to predict pollen levels in different areas throughout the region. The interpola- tion method was used to make weekly estimations of Olea pollen values in areas where there was no aerobiological sampling station. In addition, the maps generated present a two-dimensional vision of the study area, showing that bioclimatic diversity of this region promotes a step-wise flowering of Olea.

Land cover change in Ningbo and its surrounding area of Zhejiang Province, 1987∼2000

Ningbo and its surrounding area is the forefront in the rapid economic development in the Yangtse delta, and the main production area for food supplies, cotton, edible oil and hemp; and at the same time, is the main area for wetland protection in Zhejiang Province. Our objectives were to quantify land cover change in Ningbo and its surrounding area from 1987 to 2000 and to analyze the causative factors of the change. Using 30-m resolution Landsat TM/ETM+ data and maximum likelihood classifica- tion method, we classified the study area into six land cover types: forest, agriculture, urban, freshwater, seawater and bottomland. The research results showed that significant changes in land cover occurred in the study area, and that agriculture and urban land cover change dominated most of the land cover change and were main causes for the changes of other types with human activities, such as urbanization, industrialization, etc. being the main factor while it was not very obvious whether climatic conditions have any role in the land cover changes. Agriculture, bottomland and other nature dominated land cover types are undergoing signifi- cant changes due to industrialization and urbanization, which threaten the stabilization of the environment. The study conclusion called for finding reasonable ways to solve the problems between land cover change and land use.

Determination of Autoprotolysis Constants of Water-Organic Solvent Mixtures by Potentiometry

This paper describes a potentiometric titra- tion method for the determination of stoichiometric autoprotolysis constants (pKs) in binary mixtures of water with methanol, ethanol, 1-propanol, 2-propanol, dioxane, and acetonitrile. A combined pH electrode modified by replacing its aqueous KCl solution with 0.01 M NaCl þ 0.09 M NaClO4 saturated with AgCl was used for the first time in aqueous organic solvent mixtures. The potentiometric cell was calibrated be- fore each experiment so that the hydrogen ion con- centration rather than the activity was measured. The calibration constants Eand k were determined by titrating a solution of perchloric acid with sodium hydroxide solution for each medium studied at 25 � C and under nitrogen atmosphere. During each titration the concentration of NaClO4 was maintained at 0.1 M and the pKs values were calculated by using this titra- tion data. It is shown that the combined electrode system could be successfully used to determine auto- protolysis constants in water-organic solvent mixtures. Furthermore, the variation of the pKs values with solvent composition is discussed.

Effects of Terrain Morphology, Sampling Density, and Interpolation Methods on Grid DEM Accuracy

This paper explores the effects of terrain morphology, sampling density, and interpolation methods for scattered sample data on the accuracy of interpolated heights in grid Digital Elevation Models (DEM). Sampled data were collected with a 2 by 2 meters sampling interval from seven different morphologies, applying digital photogrammetric methods to large scale aerial stereo imagery (1:5000). The experimen- tal design was outlined using a factorial scheme, and an analysis of variance was carried out. This analysis yielded the following main conclusions: DEM accuracy (RMSE) is affected significantly by the variables studied in this paper according to morphologysampling densityinterpola- tion method. Multiquadric Radial Basis Function (RBF) was rated as the best interpolation method, although Multilog RBF performed similarly for most morphologies. The rest of RBF interpolants tested (Natural Cubic Splines, Inverse Multiquadric, and Thin Plate Splines) showed numerical instability working with low smoothing factors. Inverse Distance Weighted interpolant performed worse than RBF Multiquadric or RBF Multilog. In addition, it is found that the relationship between the RMSE and the sampling density N is adjusted to a decreasing potential function that may be expressed as RMSE/Sdz � 0.1906(N/M) � 0.5684 (R 2 � 0.8578), being Sdz the standard deviation of the heights of the M check points used for accuracy estimation, and N the number of sampling points used for creating the DEM. The results obtained in this study allow us to observe the possibility of establishing empirical relationships between the RMSE expected in the interpolation of a Grid DEM and such variables as terrain ruggedness, sampling density, and the interpolation method, among others that could be added. Therefore, it would be possible to establish a priori the optimum grid size required to generate or storage a DEM of a particular accuracy, with the economy in computing time and file size that this would signify for the digital flow of the mapping information.

The synthesis and thermoelectric properties of double-atom-filled BamCenFeCo3Sb12 compounds

The single_phase double_atom_filled p_type BamCenFeCo3Sb12 c ompounds were synthesized using the solid_state reaction method and also the melt reac tion method. Thermoelectric properties of the p_type BamCenFeCo3Sb 12 compound were investigated, and the results indicated that the electri cal conductivity of the p_type BamCenFeCo3 Sb12 is intervenient between the electrical conductivities of single_atom _filled compounds BamFeCo3Sb12 and CenFeCo3Sb12.It d ecreased with increasing Ba and Ce fill ing fraction. With the same filling fraction, the lattice thermal conductivity o f BamCenFeCo3Sb12 is found to be smaller than that of Ba mFeCo3Sb12 and CenFeCo3Sb12.

On the semiclassical approach to cold atomic collisions

We extend the semiclassical description of two-state atomic collisions to low energies for which the impact parameter treatment fails. The problem reduces to solving a system of first-order differential equations with coefficients whose semiclassical asymptotes experience the Stokes phenomenon in the complex coordinate plane. Primitive semiclassical and uniform Airy approximations are discussed. The theory of collisions between two atomic systems goes back to the early days of quantum mechanics (Mott 1931; Teller 1937; Landau & Teller 1936) and the basic 1930s models of state interaction are detailed in the recent review of Nikitin (1999). Typically, the colliding atoms undergo electronic transitions and one needs to solve a number (in the simplest case, two) of coupled radial Schrodinger equations. It has been noted since the early thirties that the relative motion of the heavy nuclei can be described classically (Mott 1931; Rosen & Zener 1932). Semiclassically, Stueckelberg (1932) first suggested the analytical continuation of the JWKB (Jeffreys-Wentzel- Kramers-Brillouin) wave functions into the complex plane of the internuclear sepa- ration and a proper handling of the Stokes phenomenon. His solution of the avoided crossing time-independent problem (Stueckelberg 1932) shows why a description of the interference in terms of adiabatic quasiclassical phases fails if the phase difference accumulated during the adiabatic motion of the two atoms between the centre of the coupling region and the turning points is small. The vexatious problem of the choice of branch cuts and the determination of Stokes constants via the comparison equa- tion method, were largely resolved by Crothers (1971). Equally well, it was shown by Coveney et al . (1985) that the classically forbidden region is less amenable to generalized phase-integral analysis. The classical approximation of the nuclear motion leads to the impact parameter treatment (Gaunt 1927; Landau 1932; Zener 1932). The impact parameter approx- imation (IPA) offers a simple physical picture in which fast electronic transitions occur as the slow nuclei follow a classical trajectory. By its nature, the IPA neglects

Modified cubic convolution scaler with minimum loss of information

The authors derive an adaptive version of cubic convolution interpolation for the enlargement or reduction of digital images by arbi- trary scaling factors. The adaptation is performed in each subblock (typi- cally L3L rectangular) of an image. It consists of three phases: two scaling procedures (i.e., forward and backward interpolation) and an op- timization of the interpolation kernel. In the forward interpolation phase, from the sampled data with the original resolution, we generate scaled data with different (higher or lower) resolution. The backward interpola- tion produces new discrete data by applying another interpolation to the scaled one. The phases are based on a cubic convolution interpolation whose kernel is modified to adapt to local properties of the data. During the optimization phase, we modify the parameter values to decrease the disparity between the original data and those resulting from another in- terpolation on the different-resolution output of the forward interpolating phase. The overall process is repeated iteratively. We show experimen- tal results that demonstrate the effectiveness of the proposed interpola- tion method. The algorithm exhibits significant improvement in the mini- mization of information loss when compared with the conventional interpolation algorithms. © 2001 Society of Photo-Optical Instrumentation Engineers.

Dynamics of thraustochytrid protists in the water column of the Arabian Sea

Thraustochytrids, a group of osmoheterotrophic chromistan protists are ubiquitous in the sea. However, little is known of their ecological role, particularly in oceanic waters. To obtain an insight into their dynamics in this realm, we investigated thraustochytrids and bacteria in the water column, up to 2000 m in the central Arabian Sea. Four seasons, namely the end of the southwest sum- mer monsoon (September/October 1993), the summer pre-monsoon (April/May 1994), the end of the northeast winter monsoon (February/March 1995) and the peak period of the southwest monsoon (July/August 1995) were studied. Thraustochytrids were estimated using the acriflavine direct detec- tion method (AfDD) and bacteria by the acridine orange direct counts (AODC). Thraustochytrids were present in substantial numbers throughout the 150 m water column in all the stations investi- gated during the end of the biologically productive summer and winter monsoons (0 to 1313 × 10 3 and 3.7 to 183 × 10 3 cells l -1 water respectively). Their populations in the upper 150 m were positively re- lated to bacteria and particulate organic matter during these 2 periods, the relationship being signifi- cant during the end of the winter monsoon. They were infrequent during the low productive summer pre-monsoon period (present in < 29% of the total 41 samples), a period of high bacterial abundance, as well as in the peak-productive southwest summer monsoon (present in 10 of 19 samples). Vertical distribution was seasonally variable. Thraustochytrids were regularly detected in the Arabian Sea oxygen minimum zone (OMZ) at 200 to 1000 m. Similar to the upper 150 m, thraustochytrids below 200 m were least frequent in the summer pre-monsoon (present in 49% of samples), although high numbers, up to 266 × 10 3 l -1 were found at 1000 m in 1 station. Their numbers in the OMZ ranged from 0 to 38 × 10 3 l -1 during the end of the summer and winter monsoons. Both thraustochytrids and bacteria showed a distinct peak at 250 to 500 m in the OMZ during these 2 seasons. Dense popula- tions of thraustochytrids were detected even at depths up to 2000 m. We hypothesise that seasonal in- creases of thraustochytrid populations are related to particles following phytoplankton degradation at the end of the biologically productive seasons. Our estimates suggest that during the 3 seasons, maximum thraustochytrid C biomass reached values ranging from 36 to 217% of bacterial C biomass in the upper 150 m and 34.5 to 56% of bacterial C biomass between 200 and 2000 m.

Adaptive optical three-dimensional measurement with structured light

The described 3-D measurement system with fringe projec- tion applies the principle of uniform scale representation by the exclusive use of phase measurement values for the coordinates of each point. The test object is successively illuminated with a grating structure from at least three different directions with a telecentric system, where gray code is combined with five 90-deg phase shifts. A CCD camera records the intensity distribution of the fringes that appear as intersection lines on the surface of the object. This provides the linearly independent absolute phase values that are necessary for the calculation of the coordinates. Note that all coordinates (x,y,z) are determined with the same accuracy. To compensate the influence of specular reflections or shadowed areas up to 15 light projection directions can be used. Moreover, the object can be rotated around a second axis, yielding other views of the object. Thus we acquire different patches of the object that are transformed into a global coordinate system without any interactive user help. During this procedure, correlation methods or special points are not necessary. The calibration of the 3-D orientation of the second axis is realized with a special calibration body. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)01701-3) Subject terms: adaptive optical three-dimensional measurement system; struc- tured light; gray code; uniform scale representation; phase measurement; calibra- tion method development.

The nature of heterogeneity in the stomatal behaviour of Phaseolus vulgaris L. primary leaves

The aim of this research was to investigate the nature of heterogeneity in stomatal conductance and, in particular, to determine whether the characteristic `patchy' pattern of water infiltration is reflected in measurements on individual stomata. Silicone rubber replicas were made of primary leaves of glasshousegrown Phaseolus vulgaris L. plants, and the leaves were then infiltrated with water at controlled subatmospheric gas pressures according to their estimated or measured stomatal conductance. Seven leaves examined in detail all showed patchy infiltration, and the mean size of infiltrated areas was negatively correlated with the prevailing stomatal conductance. In four of the leaves, a one millimetre wide transect across the leaf was selected for further detailed study. Measurements of mean peristomatal groove distance (PGD) and stomatal frequency were made along the transect and related to the state of infiltration. Analysis of variance indicated that, in all four cases, variation in PGD among patches was highly significant, but there was no significant difference between patches of different infiltration categories. Thus, local (patch-level) variation in stomatal aperture appeared to bear no relation to the infiltration status of the patches. The dominant source of stomatal variability was between individual pores in the same locality, which accounted for 82% or more of the total variability. Taking into account variation in stomatal frequency, correlations between predicted stomatal conductance and the extent of infiltration were significant in only one out of the seven leaves studied. Possible reasons for these results are discussed. It is suggested that the infiltra tion method misrepresents the underlying state of the stomata as being either open or closed, when there is little evidence for this from measurements of stomatal dimensions. For these unstressed plants under relatively stable conditions, it is concluded that the `unit of variability' in stomatal heterogeneity may rest at the individual pore (`micro') scale, rather than at the areolar patch ('macro') scale, or above.

Matrix-Based Analytical Model of Critical Coupling Length of Titanium In-Diffused Integrated-Optic Directional Coupler on Lithium Niobate Substrate

The critical coupling length Lc is the most important design parameter of an integrated-optic directional coupler, which is the basic building block of a variety of optical integrated circuits. The existing methods of estimating Lc of a Ti in-diffused waveguide directional coupler on LiNbO3 substrate are based on the beam propaga tion method (BPM), which requires huge computing time. A considerably simpler and computationally faster analytical method involving only multiplication of 2 x 2 matrices with no iterations is described in this article. A staircase type step-index profile is generated from the one-dimensional effective index profile in the lateral direction by partitioning the latter into a large number of thin sections of different refractive indices. The overall transfer matrix of the step-index layered structure so obtained may be computed by the progressive multiplication of individual transfer matrices (2 x 2) relating the field components in adjacent layers. Hence the wave amplitude in any layer may be computed as a function of the input wave amplitude for different angles of incidence. This method has been successfully employed to compute the propagation constants for symmetric and asymmetric guided modes in the coupled region of the directional coupler and hence compute the coupling length. The values of Lc computed for a variety of devices agree closely with the published experimental results reported by several research groups. The computer program implementing the model runs reasonably fast in an ordinary PC and is versatile enough to consider arbitrary waveguide dimensions. Ti film thickness, and diffusion parameters for any wavelength of input light and for both transverse electric and transverse magnetic polarizations.