Efficient Spreadsheet Algorithm for First-Order Reliability Method

A new spreadsheet-cell-object-oriented algorithm for the first-order reliability method is proposed and illustrated for cases with correlated nonnormals and explicit and implicit performance functions. The new approach differs from the writers earlier algorithm by obviating the need for computations of equivalent normal means and equivalent normal standard deviations. It obtains the solution faster and is more efficient, robust, and succinct. Other advantages include ease of initialization prior to constrained optimization, ease of randomization of initial values for checking robustness, and fewer required optimization constraints during spreadsheet-automated search for the design point. Two cases with implicit performance functions, namely an asymmetrically loaded beam on Winkler medium and a strut with complex supports are analyzed using the new approach and discussed. Comparisons are also made between the proposed approach and that based on Rosenblatt transformation.     

Approach for Overcoming Numerical Inaccuracy Caused by Load Discontinuity

It was found that the discontinuity at the end of an impulse will lead to numerical inaccuracy as this discontinuity will result in an extra impulse and thus an extra displacement in the time history analysis. In addition, this extra impulse is proportional to the discontinuity value at the end of the impulse and the size of integration time step. To overcome this difficulty, an effective approach is proposed to reduce the extra impulse and hence the extra displacement. In fact, the novel approach proposed in this paper is to perform a single small time step immediately upon the termination of applied impulse, whereas other time steps can be conducted by using the step size determined from accuracy consideration in period. The feasibility of this approach is analytically explored. Further, analytical results are confirmed by numerical examples. Numerical studies also show that this approach can be applied to other step-by-step integration methods. It seems that to slightly complicate the programming of dynamic analysis codes is the only disadvantage of this approach.     

Computation of Bearing Capacity Factor Nγ?Terzaghi’s Mechanism

A procedure based on K?tter’s equation is developed for the evaluation of bearing capacity factor Nγ with Terzaghi’s mechanism. Application of K?tter’s equation makes the analysis statically determinate, in which the unique failure surface is identified using force equilibrium conditions. The computed Nγ values are found to be higher than Terzaghi’s value in the range 0.25–20%, with a diverging trend for higher values of angle of soil internal friction. A fairly good agreement is observed with other solutions which are based on finite difference coupled with associated flow rule, limit analysis, and limit equilibrium. Finally, the comparison with available experimental results vis-à-vis other solutions shows that, computed Nγ values are capable of making a reasonably good prediction.     

Experimental and computational study of gas–solid fluidized bed hydrodynamics

The hydrodynamics of a two-dimensional gas–solid fluidized bed reactor were studied experimentally and computationally. Computational fluid dynamics (CFD) simulation results from a commercial CFD software package, Fluent, were compared to those obtained by experiments conducted in a fluidized bed containing spherical glass beads of 250– in diameter. A multifluid Eulerian model incorporating the kinetic theory for solid particles was applied in order to simulate the gas–solid flow. Momentum exchange coefficients were calculated using the Syamlal–O’Brien, Gidaspow, and Wen–Yu drag functions. The solid-phase kinetic energy fluctuation was characterized by varying the restitution coefficient values from 0.9 to 0.99. The modeling predictions compared reasonably well with experimental bed expansion ratio measurements and qualitative gas–solid flow patterns. Pressure drops predicted by the simulations were in relatively close agreement with experimental measurements at superficial gas velocities higher than the minimum fluidization velocity, U_mf. Furthermore, the predicted instantaneous and time-average local voidage profiles showed similarities with the experimental results. Further experimental and modeling efforts are required in a comparable time and space resolutions for the validation of CFD models for fluidized bed reactors.     

一种基于序列计算的最近似K对数据搜索方案

多种应用场合需要寻找给定数据库中相似度最大的前k对数据.然而,由于应用领域需要处理的数据规模呈上升趋势,计算这样的最相似k对数据,难度非常大.提出了一种基于序列计算的最相似k对数据搜索方案,首先,将所有数据对分割成多个组,然后,提出了所有数据对分组算法和核心数据对分组算法,通过单独计算每个组中的最近似k对数据,从所有组的最近似k对数据中选择相似度最高的k对数据,进而正确地确定最近似k对数据.最后基于合成数据进行实验,性能评估结果验证了本文算法的有效性和可扩展性.     

Connectionism,Processing, Memory

computing devices such as Turing machines resolve the dilemma between the necessary finitude of effective procedures and the potential infinity of a function's domain by distinguishing between a finite-state processing part, defined over finitely many representation types, and a memory sufficiently large to contain representation tokens for any of the function's arguments and values. Connectionist networks have been shown to be (at least) Turing-equivalent if provided with infinitely many nodes or infinite-precision activation values and weights. Physical computation, however, is necessarily finite.

The notion of a processing-memory system is introduced to discuss physical computing systems. Constitutive for a processing-memory system is that its causal structure supports the functional distinction between processing part and memory necessary for employing a type-token distinction for representations, which in turn allows for representations to be the objects of computational manipulation. Moreover, the processing part realized by such systems provides a criterion of identity for the function computed as well as helps to define competence and performance of a processing-memory system.

Networks, on the other hand, collapse the functional distinction between processing part and memory. Since preservation of this distinction is necessary for employing a type-token distinction for representation, connectionist information processing does not consist in the computational manipulation of representations. Moreover, since we no longer have a criterion of identity for the function processed other than the behaviour of the network itself, we are left without a competence-performance distinction for connectionist networks,     

Discrimination between accelerated life models via Approximate Bayesian Computation

Accelerated life testing (ALT) is widely used in high-reliability product estimation to get relevant information about an item's performance and its failure mechanisms. To analyse the observed ALT data, reliability practitioners need to select a suitable accelerated life model based on the nature of the stress and the physics involved. A statistical model consists of (i) a lifetime distribution that represents the scatter in product life and (ii) a relationship between life and stress. In practice, several accelerated life models could be used for the same failure mode and the choice of the best model is far from trivial. For this reason, an efficient selection procedure to discriminate between a set of competing accelerated life models is of great importance for practitioners. In this paper, accelerated life model selection is approached by using the Approximate Bayesian Computation (ABC) method and a likelihood-based approach for comparison purposes. To demonstrate the efficiency of the ABC method in calibrating and selecting accelerated life model, an extensive Monte Carlo simulation study is carried out using different distances to measure the discrepancy between the empirical and simulated times of failure data. Then, the ABC algorithm is applied to real accelerated fatigue life data in order to select the most likely model among five plausible models. It has been demonstrated that the ABC method outperforms the likelihood-based approach in terms of reliability predictions mainly at lower percentiles particularly useful in reliability engineering and risk assessment applications. Moreover, it has shown that ABC could mitigate the effects of model misspecification through an appropriate choice of the distance function.     

Fast Isosurface Rendering on a GPU by Cell Rasterization

This paper presents a fast, high‐quality, GPU‐based isosurface rendering pipeline for implicit surfaces defined by a regular volumetric grid. GPUs are designed primarily for use with polygonal primitives, rather than volume primitives, but here we directly treat each volume cell as a single rendering primitive by designing a vertex program and fragment program on a commodity GPU. Compared with previous raycasting methods, ours has a more effective memory footprint (cache locality) and better coherence between multiple parallel SIMD processors. Furthermore, we extend and speed up our approach by introducing a new view‐dependent sorting algorithm to take advantage of the early‐z‐culling feature of the GPU to gain significant performance speed‐up. As another advantage, this sorting algorithm makes multiple transparent isosurfaces rendering available almost for free. Finally, we demonstrate the effectiveness and quality of our techniques in several real‐time rendering scenarios and include analysis and comparisons with previous work.     

Constant round group key agreement protocols: A comparative study

The scope of this paper is to review and evaluate all constant round Group Key Agreement (GKA) protocols proposed so far in the literature. We have gathered all GKA protocols that require 1,2,3,4 and 5 rounds and examined their efficiency. In particular, we calculated each protocol’s computation and communication complexity and using proper assessments we compared their total energy cost. The evaluation of all protocols, interesting on its own, can also serve as a reference point for future works and contribute to the establishment of new, more efficient constant round protocols.     

用ODP视点分析常见网络管理模型

本文运用ODP的分析方法对基于SNMP和CMIP以及分布式的网络管理系统模型进行分析,从信息和计算视点进行对比,找出各自的特点和不足,得出网络管理系统发展的一般趋势以及需要解决的问题,为以后网络管理系统的实施提供参考。