Finite Cloud Research Articles

Reanalysis of environmental qualification radiation parameters for Kuosheng nuclear power plant

Abstract Kuosheng BWR-6 plant, owned by Taiwan Power Company, is currently operating at core thermal power of 2 971 MWt. The purpose of this study is to develop a method used to calculate the radiation dose at the reactor auxiliary building and at various rooms accommodating safety-related equipment during the design basis Loss of Coolant Accident (LOCA). The method integrates various aspects, including core inventory calculation using ORIGEN2 code, radioactive material transport and removal calculation using RADTRAD code, activity release calculation based on Technical Specification leakage limit and RADTRAD output, atmospheric dispersion calculation using ARCON96 code, and dose calculation using gamma energy and spectrum based finite cloud model. The assumptions used are based on the Regulatory Guide 1.89 revision 1. The calculation shows that the original Environmental Qualification(EQ) radiation parameters defined in the FASR, for the safety-related electrical and instrumental control equipment in the reactor auxiliary building, can be relaxed significantly and the radiation environment during accident could be reclassified, from “harsh environment” to “mild environment”.

Research on Rock Mass Quality Classification Based on An Improved Rough Set–Cloud Model

Rock mass grading is a basic problem in the construction industry and underground engineering research. Because the index parameters that affect the rock mass quality are ambiguous and random, rock mass quality classification is often uncertain. Based on this issue, this paper selects the rock quality index RQD , rock uniaxial saturated compressive strength Rw , rock mass integrity coefficient Kv , structural surface strength coefficient $K_{f}$ and groundwater seepage quantity $\omega $ as quantitative evaluation indicators to construct an evaluation system. Thirty sets of data collected in China are selected as learning samples. Through the related concepts and finite interval cloud model, the characteristic parameters of the measured data are obtained, and a cloud model is generated with a forward cloud generator to achieve the transformation between qualitative and quantitative concepts. Combined with the basic knowledge of rough set theory, the weight determination problem is transformed into an attribute importance problem. To avoid zero weights in the traditional rough set approach, this paper introduces a calculation method based on the conditional information entropy, and the weight calculation method is modified to obtain the comprehensive weights. According to the principle of the maximum membership degree, the classification of rock mass quality is performed, and the rock mass quality data are determined to have different levels of comprehensive membership. A rock mass quality evaluation method based on the coupled improved rough set–cloud model is established and successfully applied for a rock mass quality evaluation of the 0+000~0+560 test section of the second stage of underground engineering at the Guangdong Pump Storage Power Station. The results show that the model is reliable and practical and provides a new approach for uncertainty analysis and evaluation in rock engineering practice.

Internal and external hazards inside the containment in case of an emergency situation

Abstract The objective of this paper is to estimating radionuclide concentrations in air and radiological dose consequences to indoor workers in a containment of MTR open pool type reactor during emergency situations. A postulated core degradation accident causes fission products to release and the ventilation system will be converted automatically from the normal situation into emergency situation in order to purify the contaminated air by forcing it to pass through a group of filters. The study computes internal and external worker doses from inhalation and submersion in a finite cloud of contaminated air during the emergency mode. A radiological toolbox version 2 was used to evaluate the radiation dose levels inside the containment.

Energy-Efficient Resource Allocation for Mobile-Edge Computation Offloading

Mobile-edge computation offloading (MECO) off-loads intensive mobile computation to clouds located at the edges of cellular networks. Thereby, MECO is envisioned as a promising technique for prolonging the battery lives and enhancing the computation capacities of mobiles. In this paper, we study resource allocation for a multiuser MECO system based on time-division multiple access (TDMA) and orthogonal frequency-division multiple access (OFDMA). First, for the TDMA MECO system with infinite or finite cloud computation capacity, the optimal resource allocation is formulated as a convex optimization problem for minimizing the weighted sum mobile energy consumption under the constraint on computation latency. The optimal policy is proved to have a threshold-based structure with respect to a derived offloading priority function , which yields priorities for users according to their channel gains and local computing energy consumption. As a result, users with priorities above and below a given threshold perform complete and minimum offloading, respectively. Moreover, for the cloud with finite capacity, a sub-optimal resource-allocation algorithm is proposed to reduce the computation complexity for computing the threshold. Next, we consider the OFDMA MECO system, for which the optimal resource allocation is formulated as a mixed-integer problem. To solve this challenging problem and characterize its policy structure, a low-complexity sub-optimal algorithm is proposed by transforming the OFDMA problem to its TDMA counterpart. The corresponding resource allocation is derived by defining an average offloading priority function and shown to have close-to-optimal performance in simulation.

Influence of 3D cloud effects on spatial-angular characteristics of the reflected solar radiation field

Spatial-angular characteristics of reflected solar radiation in broken clouds are simulated in the spherical model of the atmosphere using statistical algorithms developed in the Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences. The patterns of formation of radiance fields of scattered radiation, caused by the finite cloud extents, mutual cloud shading, and radiation re-reflection by neighboring cloud elements are considered by the example of individual cloud realizations. It is shown that, for small and moderate cloud fractions, the specific features of the radiance field of reflected solar radiation are mainly determined by cloud localization relative to the viewing direction and direction “toward the Sun”.

A meshless method for unbounded acoustic problems

In this paper an effective meshless method is proposed to solve time-harmonic acoustic problems defined on unbounded domains. To this end, the near field is discretized by a set of nodes and the far field effect is taken into account by considering radiative boundary conditions. The approximation within the near field is performed using a set of local residual-free basis functions defined on a series of finite clouds. For considering the far field effect, a series of infinite clouds are defined on which another set of residual-free bases, satisfying the radiation conditions, are considered for the approximation. Validation of the results is performed through solving some acoustic problems.

Radiation Modeling and Finite Cloud Effects for Atmospheric Dispersion Calculations in Near-field Applications: Modeling of the Full Scale RDD Experiments with Operational Models in Canada, Part II.

Three radiological dispersal devices were detonated in 2012 under controlled conditions at Defence Research and Development Canada's Experimental Proving Grounds in Suffield, Alberta. Each device comprised a 35-GBq source of (140)La. The dataset obtained is used in this study to assess the MLCD, ADDAM, and RIMPUFF atmospheric dispersion models. As a continuation of Lebel et al. (2016), this paper examines different methodologies for making dose estimates with atmospheric dispersion models.

Computing fundamental groups from point clouds

We describe an algorithm for computing a finite, and typically small, presentation of the fundamental group of a finite regular CW-space. The algorithm is based on the construction of a discrete vector field on the $$3$$3-skeleton of the space. A variant yields the homomorphism of fundamental groups induced by a cellular map of spaces. We illustrate how the algorithm can be used to infer information about the fundamental group $$\pi _1(K)$$?1(K) of a metric space $$K$$K using only a finite point cloud $$X$$X sampled from the space. In the special case where $$K$$K is a $$d$$d-dimensional compact manifold $$K\subset \mathbb R^d$$K?Rd, we consider the closure of the complement of $$K$$K in the $$d$$d-sphere $$M_K=\overline{\mathbb S^d\!\setminus \!K}$$MK=Sd\K¯. For a base-point $$x$$x in the boundary $$\partial M_K$$?MK of the manifold $$M_K$$MK one can attempt to determine, from the point cloud $$X$$X, the induced homomorphism of fundamental groups $$\phi :\pi _1(\partial M_K,x)\rightarrow \pi _1(M_K,x)$$?:?1(?MK,x)??1(MK,x) in the category of finitely presented groups. We illustrate a computer implementation for $$K$$K a small closed tubular neighbourhood of a tame knot in $$\mathbb R^3$$R3. In this case the homomorphism $$\phi $$? is known to be a complete ambient isotopy invariant of the knot. We observe that low-index subgroups of finitely presented groups provide useful invariants of $$\phi $$?. In particular, the first integral homology of subgroups $$G < \pi _1(M_K)$$G<?1(MK) of index at most six suffices to distinguish between all prime knots with 11 or fewer crossings (ignoring chirality). We plan to provide formal time estimates for our algorithm and characteristics of a high performance C++ implementation in a subsequent paper. The prototype computer implementation of the present paper has been written in the interpreted gap programming language for computational algebra.

Recrystallization in Finite 3-D Dust Clouds

The recrystallization process of a finite dust cloud is studied experimentally on the kinetic level. The temporal evolution of the coupling parameter allows to reveal that the cluster is molten while laser heated and recrystallizes when heating is switched OFF. The cooling rate can be deduced from the initial stage of recrystallization.

Radiative transfer in finite volcanic eruption clouds

Radiation transfer through a volcanic aerosol medium has been studied. The radiation transfer properties of the medium as scattering, absorption and extinction coefficients are calculated using the Mie scattering theory. Average coefficients over the size parameter and the radiation wavelength are calculated. The radiation heat fluxes for volcanic eruption ash medium are calculated using the Variational Pomraning–Eddington approximation and compared with those obtained from the Galerkin method. The comparison showed very good agreement.

Correlation buildup during recrystallization in three-dimensional dusty plasma clusters

The recrystallization process of finite three-dimensional dust clouds after laser heating is studied experimentally. The time-dependent Coulomb coupling parameter is presented, showing that the recrystallization starts with an exponential cooling phase where cooling is slower than damping by the neutral gas friction. At later times, the coupling parameter oscillates into equilibrium. It is found that a large fraction of cluster states after recrystallization experiments is in metastable states. The temporal evolution of the correlation buildup shows that correlation occurs on even slower time scale than cooling.

An unconventional adaptation of a classical Gaussian plume dispersion scheme for the fast assessment of external irradiation from a radioactive cloud

This article focuses on derivation of an effective algorithm for the fast estimation of cloudshine doses/dose rates induced by a large mixture of radionuclides discharged into the atmosphere. A certain special modification of the classical Gaussian plume approach is proposed for approximation of the near-field dispersion problem. Specifically, the accidental radioactivity release is subdivided into consecutive one-hour Gaussian segments, each driven by a short-term meteorological forecast for the respective hours. Determination of the physical quantity of photon fluence rate from an ambient cloud irradiation is coupled to a special decomposition of the Gaussian plume shape into the equivalent virtual elliptic disks. It facilitates solution of the formerly used time-consuming 3-D integration and provides advantages with regard to acceleration of the computational process on a local scale. An optimal choice of integration limit is adopted on the basis of the mean free path of γ-photons in the air. An efficient approach is introduced for treatment of a wide range of energetic spectrum of the emitted photons when the usual multi-nuclide approach is replaced by a new multi-group scheme. The algorithm is capable of generating the radiological responses in a large net of spatial nodes. It predetermines the proposed procedure such as a proper tool for online data assimilation analysis in the near-field areas. A specific technique for numerical integration is verified on the basis of comparison with a partial analytical solution. Convergence of the finite cloud approximation to the tabulated semi-infinite cloud values for dose conversion factors was validated.

Homologous gravitational collapse in Lagrangian representation

The classical problem of spherical homologous gravitational collapse with a polytropic equation of state with γ=4/3 is examined in Lagrangian fluid coordinate. The fluid velocity v(t)=dr(t)/dt=ηdy/dt is derived from the evolution function y(t) where η=r(0) is the radial fluid label in Lagrangian formulation. The evolution function y(t), which describes the collapse time history of a finite pressure cloud, is solved which happens to be identical to the well established parametric form of Mestel (Mon. Not. R. Astron. Soc., 6:161–198, 1965) for cold cloud collapse. The spatial structure is described by a nonlinear equation of the density profile function q(z) with z=aη. Due to the nonlinearity, the collapse profile is highly non-uniform in space. For moderate values of q(0), the solutions are homologous. For large q(0), homology is broken leading to the formation of a central core and a central cavity. The stellar envelope bounding the central cavity collapses under the additional external gravity of the central core, generating eventually a sequence of cavity-shell structure in the envelope, until the entire mass of the original cloud is accounted for.

Crystal and fluid modes in three-dimensional finite dust clouds

The spectral properties of three-dimensional dust clusters confined in gaseous discharges are investigated using both a fluid mode description and the normal mode analysis (NMA). The modes are analysed for crystalline clusters as well as for laser-heated fluid-like clusters. It is shown that even for clusters with low particle numbers and under presence of damping fluid modes can be identified. Laser-heating leads to the excitation of several, mainly transverse, modes. The mode frequencies are found to be nearly independent of the coupling parameter and support the predictions of the underlying theory. The NMA and the fluid mode spectra demonstrate that the wakefield attraction is present for the experimentally observed Yukawa balls at low pressure. Both methods complement each other, since NMA is more suitable for crystalline clusters, whereas the fluid modes allow to explore even fluid-like dust clouds.

Cone Fields and Topological Sampling in Manifolds with Bounded Curvature

A standard reconstruction problem is how to discover a compact set from a noisy point cloud that approximates it. A finite point cloud is a compact set. This paper proves a reconstruction theorem which gives a sufficient condition, as a bound on the Hausdorff distance between two compact sets, for when certain offsets of these two sets are homotopic in terms of the absence of μ-critical points in an annular region. We reduce the problem of reconstructing a subset from a point cloud to the existence of a deformation retraction from the offset of the subset to the subset itself. The ambient space can be any Riemannian manifold but we focus on ambient manifolds which have nowhere negative curvature (this includes Euclidean space). We get an improvement on previous bounds for the case where the ambient space is Euclidean whenever μ≤0.945 (μź(0,1) by definition). In the process, we prove stability theorems for μ-critical points when the ambient space is a manifold.

Thermal Models for Optical Circuit Simulation Using a Finite Cloud Method and Model Reduction Techniques

This paper presents a procedure for the creation of versatile and powerful thermal compact models of integrated optical devices and demonstrates their use in an optical circuit level simulator. A detailed 3-D model of the device is first built using a meshless finite cloud method, producing a large linear sparse set of equations. This model is then reduced to a compact representation using a Krylov subspace model reduction (MR) technique. Such a reduced model is described by small dense matrices, but can reproduce the original temperature distribution within acceptable error. Three devices are used as demonstration models for the technique: a microdisc laser and two microring-based devices, a modulator, and an optical switch. All three devices are built in a silicon on oxide platform. Using MR the linear systems describing these models are reduced from thousands of unknowns to systems with less than 100 reduced variables. It is then demonstrated how the reduced compact models can be linked together to describe a complete optical system with solution errors of lower than 1%. Finally, it is shown how this reduced thermal model can be utilized in a circuit level opto-electronic circuit simulator and simulations are presented, demonstrating the effectiveness of the reduced models in speeding up simulation times or enabling otherwise intractable problems.

From transport to disorder: Thermodynamic properties of finite dust clouds

The quantities entropy and diffusion are measured for two- and three-dimensional (3D) dust clusters in the fluid state. Entropy and diffusion are predicted to be closely linked via unstable modes. The method of instantaneous normal modes is applied for various laser-heated clusters to determine these unstable modes and the corresponding diffusive properties. The configurational entropy is measured for 2D and 3D clusters from structural rearrangements. The entropy shows a threshold behavior at a critical temperature for the 2D clusters, allowing us to estimate a configurational melting temperature. Further, the entropic disorder increases for larger clusters. Finally, the predicted relation between entropy and unstable modes has been confirmed from our experiments for 2D systems, whereas 3D systems do not show such a clear correlation.

A Meshless Based Solution to Vectorial Mode Fields in Optical Micro-Structured Waveguides Using Leaky Boundary Conditions

Leaky boundary conditions are implemented in a meshless numerical method to solve vectorial mode fields in optical waveguides which allow for the solution of both guided and leaky modes. The modes are found using an approximating solution, the Finite Cloud Method (FCM), to the coupled field equations of the transverse components of the magnetic field. In this paper we extend the method by implementing two absorbing boundary conditions, Transparent Boundary Conditions (TBC) and Perfectly Matched Layers (PML), to solve the leaky modes for several microstructured air hole waveguides. Presented are methods to further refine the boundary conditions and to stabilize the solutions. A comparison between these methods and previously published results show close agreement. Finally, we conclude that the TBC boundary condition is the superior method due to its robustness and lack of fitting parameters.

Negative permeability and negative refraction in composite systems with finite-size inclusions

It is shown that the spatial dispersion in composite systems formed by inclusion of finite size spheres may lead to negative group velocity and, subsequently, to negative refraction. Longitudinal and transverse electromagnetic modes exhibiting negative dispersion are found in the system of finite size charged clouds. It is also shown that similar mechanism due to the electric quadrupole coupling leads to excitation of longitudinal and transverse eigenmodes with negative dispersion in a random set of nonmagnetic metal spheres embedded in a dielectric host. It is shown that the negative refraction related to the spatial dispersion effects may alternatively be viewed as a result of simultaneously negative permittivity and permeability.

Optical mode solving for complex waveguides using a finite cloud method

A meshless method for the solution of full vectorial optical mode fields has been applied to micro-structured optical waveguides. The Finite Cloud Method is used to approximate the solution using a point distribution and material definitions. Presented are two methods of defining material interfaces, one which implements a step index and a second which uses a graded index. Coupled field equations are used to solve for both transverse components of the magnetic field as well as the guided wavelength and effective index of refraction. Comparing results for a ridge waveguide, solid core, micro-structured and air core structures with commercial FEM solvers highlight the methods versatility, accuracy and efficiency.