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The paper details the method to couple a 1-D hydro-sedimentary model to a 2-D hydro-sedimentary model in order to represent the hydrodynamics and morphological processes during a flood event along a river. Tested on two field cases, the coupled model is stable even in the case of generalized overflow over the riverbanks or of levee breaching. For lateral coupling, the coupled model allows saving computational time compared to a full 2-D model and to provide valuable results concerning the flooding features as well as the evolution of the bed topography. However, despite a similar simplified representation of the sediment features in the 1-D and 2-D models, some discrepancies appear in the case of upstream/downstream coupling along a cross section perpendicular to the flow direction because the assumption of homogeneous velocity and concentration is not valid for estimating sediment transport. Further research is necessary to be able to define a suitable distribution of the sediments on the 1-D side of the boundary between the two models.

In this study reasonable 2D model was established by using FLUENT for start-up of analysis and evaluation of heat transfer flow characteristics in 1/6 scale model of VCS for HTTR. The pressure vessel temperature was set around 200 degrees C, in which the ratio of heat transfer via natural convection has been numerically predicted to be around 20-30% of total heat removal in previous studies. This temperature is useful for the analysis code validation in the prediction of temperature distribution of components such as pressure vessel which is heated up by turbulent flow of natural convection. The numerical results of upper head of pressure vessel by the k-omega-SST intermittency transition model, which can adequately reproduce the separation, re-attachment and transition, reproduced the test results including temperature distribution well in contrast to those by the k-omega model in both cases that helium gas is evacuated or filled in the pressure vessel. It was emerged that any local hot spot did not appear on the top of upper head of pressure vessel where natural convection flow of air is separated in both cases. In addition, the plume of high temperature helium gas generated by the heating of heater was well mixed in the upper head and uniformly heated the inner surface of upper head without generating hot spots.

Recent instances of “excessive disasters,” which can be characterized as unprecedented and catastrophic, cause great damage and loss of life. One such incident is dam failure, which significantly affects downstream regions. Therefore, it is imperative to select flood inundation areas and establish EAP in advance. In addition, to prevent possible damage due to dam failure, flood wave analysis and evacuation map should be based on accurate hydraulic analysis. Accordingly, this study highlights the challenges in existing hydraulic analysis and suggests a method of establishing EAP by applying the 2-D model. Further, it compares the applicability of establishing EAP between 1-D and 2-D models using the Sandae reservoir incident, the actual collapse case. Consequently, it found that compared to the 1-D model, flood inundation analysis using the 2-D model can accurately reflect on topography such as roads and buildings and provide a wide range of information such as flood depth and flood velocity distribution. Thus, this study is expected to recommend an efficient method of selecting flood inundation areas and establishing informative EAP.

We prove that the range of Strichartz estimates on a model 2D convex domain may be further restricted compared to the known counterexamples due to the first author. Our new family of counterexamples is now built on the parametrix construction from our earlier work. Interestingly enough, it is sharp in at least some regions of phase space., 23 pages, 1 figure

Flow behavior was observed in a simplified model cavity of a multiphase High Level Liquid Waste (HLLW) reprocessing glass melter. Electrodes were set to generate Joule-heating flow in the cavity. A chaotic flow occurred because the lower part of the cavity was heated while the top surface of the cavity was cooled. Downflow and upflow occurred alternately in cavities. The shape of the cavity was a sloping bottom cavity, which was similar in shape to the real glass melter. To know the flow behavior in the cavity, 1-D flow behavior and 2-D flow behavior were measured in an experiment and simulated by an original CFD code. In the sloping bottom cavity, chaotic flow occurred in the upper part of the cavity. In the case of the sloping bottom cavity which had the same set of electrodes as the glass melter, the effect of the downflow near the electrodes decreased. The same phenomena could be predicted in the melter. The experimental results were also used to validate the CFD code, which will be helpful for developing a multiphase Joule-heating flow predicting.

Membrane-based processes have gained a relevant role in many engineering applications. Much effort has been devoted to thoroughly understand the fundamental phenomena behind them. However, membrane deformation has been taken into consideration only recently, although much evidence has shown its impacts in many applications. This work presents a novel 2-D, multi-scale, semi-empirical process model able to predict the behavior and the performance of Electrodialysis (ED) systems in cross-flow configurations in the presence and absence of local membrane deformations. The model exploits the results and the simulation approaches of previous fluid-structure investigations performed by the authors. Low-scale numerical simulations are coupled with a high-scale model to predict the redistribution of channel height, flow rate, friction coefficient and Sherwood number in ED stacks caused by local membrane deformations. Finally, salt and water fluxes, mass balances and electrochemical quantities are computed to assess the performances of cross-flow ED stacks. Different test cases have been simulated for the desalination of seawater by two-stage ED. Interestingly, membrane deformation is found to reduce, albeit slightly, the energy consumption. More pronounced effects are expected if thinner or less stiff membranes are used.

This paper proposes modelling approaches for photovoltaic (PV) modules with a fast and simple numerical method of modelling, the Newton–Raphson method, as the first step. This method has several electric circuit models. We selected and tested the two most convincing models, the 1-D model and the 2-D model, and deduced that the 2-D model faithfully reproduces the curve I(V) of the PV module. This numerical model is used in the calculation of equation parameter extracts from the curve I(V) given in the standard test conditions (STC), but sometimes we don’t have all these parameters. Therefore, to achieve an appropriate characterisation of the behaviour of PV modules, we tested and validated, as a second step, the second method of modelling based on artificial intelligence and specifically artificial neural networks to deduce the I(V)STC curve through the ANN model, and in order to have a complete modelling for electrical PV modules.

This paper aims to develop a robust two-dimensional coupled numerical model based on an unstructured mesh, which can simulate rapidly varying flows over an erodible bed involving wet–dry fronts that is a complex yet practically important problem. Using a modified spatial reconstruction based on the finite volume method, the well-balanced property is preserved, which is important for accurate and efficient simulation of morphological problems. In the present study, the central-upwind scheme is extended to simulation of bed erosion and sediment transport for the first time. It is demonstrated that the proposed scheme shows good accuracy and high efficiency. A modified shallow water system is adopted to improve the model. The shallow water equations, sediment transport equation and bed evolution equation are coupled in the governing system. Multiple test cases are employed to demonstrate the robustness, accuracy, and efficiency of the current model. Furthermore, with a field scale dam-break test case, the efficiency and accuracy of the central-upwind method is verified in comparison with other popular Riemann solvers. The effects of the additional source terms in the adopted modified shallow water equations are also investigated by comparing the numerical results with a laboratory study available in the literature. The proposed scheme can efficiently track wetting and drying interfaces while preserving stability in simulating the bed erosion near the wet-dry fronts. The added terms in shallow water equations can improve the accuracy of the simulation when intense sediment-exchange exists; the central-upwind method adopted in the current study shows great accuracy and efficiency compared with other popular solvers; the developed model is robust, efficient and accurate to deal with various challenging cases.

The friction force observed at macroscale is the result of interactions at various lower length scales that are difficult to model in a combined manner. For this reason, simplified approaches are required, depending on the specific aspect to be investigated. In particular, the dimensionality of the system is often reduced, especially in models designed to provide a qualitative description of frictional properties of elastic materials, e.g. the spring-block model. In this paper, we implement for the first time a two dimensional extension of the spring-block model, applying it to structured surfaces and investigating by means of numerical simulations the frictional behaviour of a surface in the presence of features like cavities, pillars or complex anisotropic structures. We show how friction can be effectively tuned by appropriate design of such surface features., Revised version. Videos related to the paper are attached to the review website

This paper presents two dimensional (2 D) numerical simulations of the shortening of a stiff viscous layer with a pre existing weak zone that is embedded in a weaker viscous matrix. The model bottom remains straight during shortening and represents a detachment surface. Four deformation styles are observed that depend on the ratio of the layer and matrix viscosities µL/µM; the thickness ratio of the bottom matrix and the overlying stiff layer HM/HL; and the power law stress exponent of the matrix nM. The numerical results are used to quantify the conditions for which each deformation style occurs: (1) pure shear dominated deformation occurs for µL/µM50 and HM/HL50 and HM/HL1; and (4) folding and overthrusting occur for a power law viscous matrix and 0.5

An alternative way of induction heating of nonmagnetic cylindrical billets is modeled. The billet rotates in static magnetic field generated by permanent magnets. The mathematical model of the process consisting of two second-order partial differential equations describing the distributions of magnetic and temperature fields is solved numerically in the quasi-coupled formulation. The computations are carried out by a fully adaptive higher order finite-element method that is implemented in own codes Agros2D and library Hermes. The most important results are verified experimentally on a prototype device built in our laboratory.

The 2-D and 3-D numerical model have been developed to predict flow state and outlet velocity distribution by FLUENT based on the high-sludge setting tank in a large scale water treatment plant in Chongqing, and physical model has been built to verify the rationality and accuracy of the models. With the comparison of the two models, the following results can be found: 3-D model is lower in computing efficiency; both of the flow state are in substantial, but the stream lines of 3-D model are more complex; The velocities of 2-D model are slightly higher, both of the velocity distributions and tendency are approximately identical in 5 to 6 meters and 14 to18 meters, but not the same in 6 to 14 meters. 3-D model is more reasonable and accurate compared with 2-D model.

Which the distortion elements appear in the optimization process and the result may be a partial optimum solution are two disadvantages when using the ESO method to optimize 2-D model. In this paper, two algorithms are proposed for solving these disadvantages. One is filtering and deleting algorithm based on the traits of distortion elements. Using this algorithm, only one parameter is needed to control filtering and deleting, and the parameter is determined by the number of elements linked around distortion elements. The other is interval approximation algorithm. Minimum initial rejection ratio RR0min which fulfills removal criterion was ascertained by using this algorithm and it was used as starting value. Thus other initial erasure rate RR0 were obtained by setting a certain increment. Two algorithms mentioned above were implanted into the existing ESO method. Then optimizing respectively with different initial removal rates which were obtained before and the available structures from the results were filtered out in terms of performance parameters. The results of optimization for 2-D structures indicate that the improved ESO method has better suitability and stability than the existing one, and it avoids shortcoming that the results may be a partial optimum solution when using the existing ESO method.

This paper is an attempt to predict the deposition in the Aswan High Dam Reservoir, in Egypt, in order to estimate the effective life span of the reservoir. A two dimensional numerical model (CCHE-2D) was implemented to simulate the sedimentation along a 150 km reach of the reservoir where most of the sediment deposits. During the course of this study, the calibration and validation of the model for flow and sediment deposition were executed during the period 2006–2007. A good agreement, between the observed and modeled results for the whole domain, was obvious. Confident with the obtained results, the model was further tooled to predict the sediment deposition in the reservoir during the period 2009–2014.

The dominant mechanism of enhanced heavy oil recovery by chemical flooding is studied by conducting various chemical slug injections in a two-dimensional physical model. In this study, a total of seven single-chemical-slug tests and another seven two-chemical-slug tests are conducted to test the contribution of alkaline, surfactant, polymer, and their combinations to enhanced heavy oil recovery. The relationship between the tertiary oil recovery and the pressure drop of the seven single-slug floods is analyzed, and it is discovered that the two have a good correlation. Comparison of the tertiary oil recoveries of different chemical slug tests shows that the improved waterflood for the heavy oil used in this study is mainly due to the reduction of water mobility. The results of two-chemical-slug tests show that after regular alkaline/surfactant/polymer flooding, the second polymer slug injection can recover more oil, if a water slug injection is applied between the two chemical slugs.

This paper considers the problem of iterative learning control design for linear systems with data quantization, where the system matrices contain uncertain parameters. It is assumed that the control input update signals are quantized before they are transmitted to the iterative learning controller. A logarithmic quantizer is used to decode the signal with a number of quantization levels. Then, a 2-D Roesser model is established to describe the entire dynamics of the ILC system. By using sector bound method, a sufficient asymptotically stability condition for such 2-D system is established and then the ILC design can be given simultaneously. The effectiveness of the proposed method is illustrated by a numerical example.

Formation of the streamer zone of a leader is an outstanding problem in the physics of electric discharges which is relevant to laboratory leaders, as well as to the leaders formed by lightning. Despite substantial progress in the theoretical understanding of this complicated phenomenon, significant puzzles, such as the low propagation velocity of a leader compared to the fast streamers, remain. The objective of this paper is to present 2-D plasma simulations of the formation and propagation of the streamer zone of a leader. In these simulations we will generate a group of streamers that propagate in a discharge gap while interacting with each other. It is shown that interaction between the streamers significantly reduces their propagation velocity. This explains why the leader, which consists of many streamers, is much slower than a single streamer formed in the same discharge gap. It is shown that the mean velocity suppression of the group of streamers is determined by the inter-streamer distance. The critical value of the packing factor of the streamers at which the interactions between them can be neglected, and thus the discussed process can be treated as caused by a single streamer, is obtained.

A theoretical study of a multitubular membrane reactor for the autothermal reforming of methane over a Ni/Al2O3 catalyst is presented. A 2-D model is selected to account for the strong composition and temperature gradients along the axial and radial coordinates. The effect of the degree of reduction of the Ni catalyst on the reforming reaction rates is taken into account in the model. The influence of the main operating conditions on the reactor behavior is studied. The results suggest that the membrane reactor is a promising alternative to carry out ATR of methane at milder conditions than those commonly found in a conventional reactor. The axial distribution of the O2 fed to the reactor is a powerful tool to influence the axial temperature profiles. Nevertheless, a careful design is necessary to avoid risky conditions such as oxygen accumulation in the tubes. Fil: Rodriguez, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Investigaciones en Tecnología Química. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Investigaciones en Tecnología Química; Argentina Fil: Pedernera, Marisa Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina Fil: Borio, Daniel Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina

This research uses a continuum mechanics approach, combined with metallurgical analysis, to understand microscopically the effect of the phases existing within the austenite microstructure. The approach used is a classical continuum mechanics at a microscopic level to understand the stress distribution among the constituents within the austenite grains. Further, by employing simple failure theories, the research predicts the preferential cracking path numerically.

The aim of this paper is to present a fully bounded 2-D model for chaotic attractors or chaotic seas. The relevance of this result is that there are some specific examples of bounded chaotic attractors or chaotic seas. There is no rigorous proof of this property for a general form of mappings.

Crop irrigation with subsurface drip (SDI) is increasing in the semiarid Texas High Plains (THP). Information on drip-tubing positioning, irrigation strategies, and wetted soil area is needed to increase rainwater effectiveness when well capacities are inadequate to meet full irrigation requirements. Time and resources necessary to test SDI strategies for different conditions through field experimentation is too large. However, a mechanistic model such as Hydrus-2D can quantify the effect of different installation geometries and irrigation strategies. Our objective was to experimentally validate the Hydrus-2D in an Amarillo soil in THP so that the model can be used to evaluate different irrigation frequency and timing strategies for SDI cotton. Results showed that Hydrus-2D simulated volumetric soil water content within ±3% of measured values, and simulation bias represented the smaller portion of the simulation error, indicating that the model can be used to evaluate irrigation strategies.

This paper presents a 2-D model to calculate the electric current densities and the biopotential differences generated due to a breast cancerous cell during the hyperpolarization of the G1/synthesis (G1/S) transition. The proposed model is based on semiconductor diffusion-drift analysis, and aims to understand the biophysics associated with growing breast cancerous cells. The effect of the duration of the G1/S transition, and the diffusivity and the mobility of the cancerous cell boundary is investigated. The results show that shorter G1/S transition durations, and higher diffusivity and mobility at the cell boundary provide higher magnitude of the electric signals.

Evidence from diverse investigations suggests that arterial growth and remodeling correlates well with changes in mechanical stresses from their homeostatic values. Ultimately, therefore, there is a need for a comprehensive theory that accounts for changes in the 3-D distribution of stress within the arterial wall, including residual stress, and its relation to the mechanisms of mechanotransduction. Here, however, we consider a simpler theory that allows competing hypotheses to be tested easily, that can provide guidance in the development of a 3-D theory, and that may be useful in modeling solid-fluid interactions and interpreting clinical data. Specifically, we present a 2-D constrained mixture model for the adaptation of a cylindrical artery in response to a sustained alteration in flow. Using a rule-of-mixtures model for the stress response and first order kinetics for the production and removal of the three primary load-bearing constituents within the wall, we illustrate capabilities of the model by comparing responses given complete versus negligible turnover of elastin. Findings suggest that biological constraints may result in sub-optimal adaptations, consistent with reported observations. To build upon this finding, however, there is a need for significantly more data to guide the hypothesis testing as well as the formulation of specific constitutive relations within the model.

We derive magnetization vector tomography imaging equations and compare them with the magnetization scalar tomography imaging equation. The derived equations are applicable to 3-D and 2-D magnetization vector inversion problems, vertical component magnetic field data and total intensity of magnetic field data. In the inversion process, an improved Gauss-Sadel iterative method with a weight coefficient determined by magnetic prism's buried depth is introduced. 2-D model forward and inversed studies show that when the model consists of two layers, each has 51 prisms, the inversed vertical and horizontal magnetization components with the zero magnetization initial model are consistent well with the model parameters, except the edge effect near the boundary. When the model consists of five layers, and each has 51 prisms, the inversed vertical and horizontal magnetization components can be obtained with a homogeneous initial magnetization model instead of zero initial magnetization one, and the boundary effect also exists. Up to now, we cannot get much more details of fine magnetization structures from the inversion results. This aim will be reached by further work in the future.

A new method to calculate the inductances of induction machines considering axial nonuniformity is proposed. The proposed method, an extension of the modified winding function approach, allows considering nonuniformity due to skew and static and dynamic air-gap eccentricity. Theoretical fundamentals and experimental results that validate the proposed method are presented.

日本の殆どの山岳地帯においては,多くの集落や構造物が雪崩の被害にさらされている.このような被害を防止するためには煙型雪崩の流動機構の解明が不可欠である.雪崩の流動機構が明らかになれば,それをもとに災害防止地図が作成される.また,雪崩の被害にあわないような構造物を建設することも可能になる.煙型雪崩の流動特性は傾斜面上のサーマルの流動と類似の点が多い.このようなモデルを用い三次元の地形を考慮した新しい流動解析の手法を開発した.モデルの原点は福嶋(1986)の一次元モデルにある.今回の数値モデルでは数値地図を用い,これまでの雪崩の流下速度,最大厚さ,平均濃度,乱れ運動エネルギーに加えて雪崩の走路と流動幅を解析することができる.

Bohai Bay is a large, semi-enclosed shallow water basin located along the western region of the Bohai Sea in the north-eastern part of China. As a result of rapid economic development in the surrounding coastal hinterland, the water quality characteristics within Bohai Bay have been of growing concern in recent years. Details are given herein of an aquatic environmental assessment study undertaken to investigate the hydrodynamic and transport processes within the Bay using an integrated numerical modelling approach and tield measurements. 3-D numerical model was used to simulate the tide flow and 2 D model was deployed with moving boundary to simulate the water quality. In order to improve on the water quality characteristics in the near-shore coastal zone, an ocean disposal plan was also considered, with various scenarios being simulated using the 2-D model. From an analysis of data collected from the held measurements, it was found that both chemical and phytoplankton indicators were important in the as...

In this paper, the kinematic workspace characteristics of a crab-like legged vehicle are investigated using a 2-D model. The alternative kinematic configurations and their corresponding workspace constraints are discussed, and the vehicle configuration of most interest identified. It is shown that, for constant vehicle body attitude, only two parameters affect the kinematic workspace, foot overlap and thigh length. Analytical methods for calculating the workspace characteristics are presented and, using these methods, the effects of the design geometry on the kinematic workspace are investigated.

An accurate analytical model for the transconductance-to-current ratio (gm/Ids), current–voltage characteristics, and drain conductance is developed for a vertical surrounding-gate (VSG) MOSFET based on the solution of the 2-D Poisson's equation. The dependence of gm/Ids, drain current, and drain conductance on key technological parameters has been analyzed in detail. A design rule to select the device parameters to enhance gm/Ids is proposed. Results show that higher values of gm/Ids can be achieved in VSG MOSFETs as compared to DG MOSFETs. Close agreement with simulated results confirms the validity of the present model. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 415–421, 2001.

We demonstrate how the inclination of descending mantle flow is affected by thepresence of a continent overriding the downwelling zone. The mantle is modelled by a fluidhaving a temperature- and pressure-dependent viscosity which describes a low viscosityasthenosphere and a higher viscosity lower mantle. The fluid occupies a square x:y=10:1 boxheated from below. In the absence of overlying continents thermal convection sets in with colddownwellings being nearly vertical. A continent is placed on the convecting mantle and starts todrift. The continent is assumed to be a thick rigid plate. We consider models of two types. Model1 involves a free-floating continent. The continent is pulled by viscous forces and approaches acold downwelling nearby. Interactions between the convective mantle and the drifting continentlead to an inclined downwelling zone. Model 2 involves a continent moving horizontally with agiven velocity. When the continent approaches a downwelling, it alters the flow and causes thedownwelling to deviate from the vertical. The dip angle of the downflow depends on the velocityof the overriding continent and can take values ranging from 0 to 90 degrees.

A significant mismatch occurs when we predict the gate-induced drain leakage current (GIDL) by using existing one-dimensional (l-D) models. It's found that the gate-induced drain leakage current is attributed to not only the vertical field but also the lateral field near the drain-to-gate overlap region. Therefore, a new quasi-two-dimensional (quasi-2-D) model considering both the lateral and vertical fields for predicting the gate-induced drain leakage current is proposed by using the drain-induced energy-barrier reduction in our model. The calculated results using the developed quasi-2-D model are in good agreement with measured values for a wide range of gate and drain biases. Therefore, the proposed new model can be used to simulate the hot-carrier band-to-band tunneling current for p-channel flash memory device.

A two-dimensional model of radiative, dynamical and photochemical processes in the atmosphere has been developed and used for the simulation of ozone distribution. The results of numerical simulations are compared with LIARS and TOMS measurements. The comparison shows that the overall agreement between simulated and LIARS stratospheric ozone data is within 5–15% for almost all of the stratosphere except for the high latitudes of the winter hemisphere. This kind of disagreement is a common problem for all 2-D models, which cannot resonably reproduce planetary and gravity wave breaking processes over high latitudes. Validation of the simulated total ozone against TOMS data also shows a good overall agreement. The the total ozone difference between the 2-D model results and TOMS measurements is within 5–10% in both Northern and Southern hemispheres during all seasons except 40°S-60°S from June to October. In this region, the difference between simulated and TOMS total ozone is 30%.

Vertical propagation of internal gravity waves (IGWs) generated by tropospheric convection throughout the middle atmosphere under two cases of realistic zonal winds, a summer easterly condition and an additional prescribed back-ground diurnal tidal wind condition are simulated using a non-hydrostatic compressible nonlinear two-dimensional numerical model. Generation of the weak zonal wind layer around the mesopause due to the IGWs breakdown, filtering of the IGWs in the zonal winds, and the interaction between the IGWs and the prescribed diurnal tidal winds are reported.

Infrared focal plane arrays (IRFPAs) are rapidly increasing in size. It is shown here that for large FPAs a considerable shift in the operating point occurs, which, if not reduced, introduces unacceptably large nonuniformity in the array response. This shift results because of the variable voltage drop across the HgCdTe active layer, due to its finite distributed resistance. A new analytical two-dimensional (2-D) model to estimate the operating point shift of individual detectors of long wavelength infrared (LWIR) HgCdTe focal plane array (FPA) is presented. Avoiding this operating point shift requires an optimized grid pattern.

Simulations using SAMPEX and HALOE data suggest that NO_y produced by thermospheric processes and by relativistic electron precipitation in the mesosphere and lower thermosphere have been important to stratospheric NO_y and O_3 during the austral spring in 1994. The relative importance of the two NO_y sources is discussed. The results are supported by an analysis of HALOE NO_x and CH_4 data during October 1994 and are in agreement with ATMOS NO_y observations made in November 1994.

The sensitivity behavior of the fixed-bed catalytic reactors is examined using the pseudohomogeneous two-dimensional model with radial dispersion for the first-order irreversible reaction. The sensitivity criteria developed are tested. The relations between self-similarity and thermal runaway are studied. The pseudoadiabatic type of operation is taken into consideration. The boundaries of the sensitivity region in the space Da – Pe are compared with those predicted by the standard one–dimensional model and the criterion of Hagan et all The sensitivity behavior of the system in the space α – Bi is also discussed.

An investigation is made of 3D effects on FEL operation by comparing the 3D simulation code TDA with a 1 1 2 D model. In the latter model, the full spatial dependence of the radiation field is taken into account, whereas the electrons are treated as moving in a 1D, density-averaged ponderomotive potential. Three dimensional effects like a radial beam profile, emittance and betatron oscillations are investigated. For FELIX parameters, the 1 1 2 D model is in good agreement with TDA.

In this paper, a new 1-D/2-D model is proposed for closed-loop thermosyphons with vertical heat transfer sections. This model improves the results of traditional 1-D models for cases where: (i) mixed-convection effects are important in the heated and cooled sections of the loop; and (ii) heat losses (or gains) from the insulated portions of the loop are significant. This is achieved by iteratively coupling local results of 2-D numerical simulations of mixed-convection flows, performed in the heated and cooled sections, and a 1-D analysis. The proposed 1-D/2-D model is validated by comparing its results with those of a complementary experimental study. The results include predictions and measurements of the average velocity in the loop, local wall temperatures in the heated section of the loop, and bulk temperatures of the fluid. The agreement between the model predictions and the experimental results is shown to be very good.

A two dimensional scavenging-circulation model is used to investigate the patterns of sediment 231Pa/230Th generated by the Atlantic Meridional Overturning Circulation (AMOC) and further advance the application of this proxy for ocean paleocirculation studies. The scavenging parameters and the geometry of the overturning circulation cell have been chosen so that the model generates meridional sections of dissolved 230Th and 231Pa consistent with published water column profiles and an additional 12 previously unpublished profiles measured in the North and Equatorial Atlantic. The processes that generate the meridional sections of dissolved and particulate 230Th, dissolved and particulate 231Pa, dissolved and particulate 231Pa/230Th, and sediment 231Pa/230Th are discussed in detail. The results indicate that the relationship between sediment 231Pa/230Th at any given site and the overturning circulation is very complex. They clearly show that constraining past changes in the strength and geometry of the AMOC requires an extensive data set and they suggest strategies to maximize information from a limited number of samples.

An improved ANSYS simulation model for SAW device is discussed. The electric properties of metal fingers which affect the characteristics of a device are simulated. The right and left boundary conditions for the device, which greatly affect the wanted signals, are proposed. To save simulation time, a 2-D model is created, where some mesh skills are applied