Quantum Effects in Three-Dimensional H + D2 Reaction at High Energies

The H + D₂ reactive system was studied in the energy range 0.84 < E_tr < 2.70 eV employing the ordinary Quasi-Classical Trajectory Approach (QCTA), the Classical and the Quantum Reactive Infinite Order Sudden Approximations (CRIOSA and QRIOSA), and the Angle-Oriented Transition State Theory (AOTST). From a detailed analysis of the various integral cross-sections and opacity functions, it was concluded that pronounced quantum effects ( > 10%) are expected in the high-energy region (≤ 2 eV).     

Probabilistic Optimal-Cost Scheduling

During the planning and execution of construction projects, it often becomes necessary to shorten the duration of the project. A widely used technique for reducing the duration of a project is commonly referred to as least-cost scheduling. This procedure is based on deterministically arriving at the shortest project duration for the minimum cost possible. There is, however, one major problem with the typical application of this technique. It does not address the variability inherent in the duration and cost of the project activities. Thus, the resulting compressed schedule value cannot be applied with any stated level of statistical confidence. This paper presents a new procedure that addresses some of the major shortcomings of least-cost scheduling. It does so by accounting for the variability inherent in the duration and cost of the scheduled activities by simultaneously applying range estimating and probabilistic scheduling to the historical data. The resulting data set is then analyzed to provide a compressed schedule duration and cost estimate that have a higher overall confidence of being achieved.     

Activity-Based Costing as a Tool for Process Improvement Evaluations

Many corporate processes common to the design and construction of major engineered projects are composed of individual activities that are variable by nature. Additionally, the process itself may have a high degree of variability, meaning that certain activities may or may not actually be performed in a given pass through the process. We may ascribe to such activities a “probability of occurrence.” True modeling of real world processes will often require that we describe the process as having activities with stochastic durations, each linked together in a precedence logic that itself is variable and subject to uncertainty or chance. If corporate resources, such as labor, material, and equipment, are required to perform the individual activities, then an activity-based costing technique must be developed that can accommodate the inherent variability in a process if actual costs are to be accurately predicted. If process cycle time and process cost per cycle can be accurately predicted for complex, highly variable processes, companies are in a much better position to determine how proposed corporate initiatives for process improvement might actually impact overall process performance. This technique has application across a wide number of disciplines including design, construction, and administrative processes.     

Extreme multielectron ionization of elemental clusters in ultraintense laser fields

In this paper we present computational and theoretical studies of extreme multielectron ionization in Xe_n clusters (n = 55-2171, initial cluster radii R₀ = 8.7-31.0 Å) driven by ultraintense Gaussian infrared laser fields (peak intensity I_M = 10 ¹⁵ -10 ²⁰ W cm⁻², temporal pulse length τ = 10-100 fs, and frequency v = 0.35fs⁻¹). The microscopic approach, which rests on three sequential-parallel processes of inner ionization, nanoplasma formation, and outer ionization, properly describes the high ionization levels (with the formation of {Xe^q+}_n with q = 5-36), the inner/outer cluster ionization mechanisms, and the nanoplasma response. The cluster size and laser intensity dependence of the inner ionization levels are determined by a complex superposition of laser-induced barrier suppression ionization (BSI), with the contributions of the inner field BSI manifesting ignition enhancement and screening retardation effects, together with electron impact ionization. The positively charged nanoplasma produced by inner ionization reveals intensity-dependent spatial inhomogeneity and spatial anisotropy, and can be either persistent (at lower intensities) or transient (at higher intensities). The nanoplasma is depleted by outer ionization that was semiquantitatively described by the cluster barrier suppression electrostatic model, which accounts for the cluster size, laser intensity, and pulse length dependence of the outer ionization yield.     

Genesis of Bimodal Distributions

Conditions for which the density function of a mixture of two normal distributions is bimodal are investigated. For fixed values of the variances σ₁ ² and σ₂ ² of the normal distributions if the difference between the means is sufficiently small, the distribution of the mixture will be unimodal, independent of the proportions p and 1 – p, 0 < p < 1. If the difference exceeds a critical value which depends on σ₁ ² and σ₂ ² the bimodality property then depends on p. Values of p sufficiently close to zero and one always exist for which the distribution is unimodal.     

Simulations of Extreme Ionization and Electron Dynamics in Ultraintense Laser–Cluster Interactions

We present a molecular dynamics (MD) simulation code for the exploration of extreme multielectron ionization and attosecond–femtosecond electron dynamics in elemental and molecular clusters driven by ultraintense (peak intensity I_M = 10 ¹⁵ –10 ¹⁶ W cm⁻²), ultrafast (temporal pulse widths τ = 10–100 fs), near infrared (photon frequency 0.35 fs⁻¹) laser fields. Validity conditions are presented for the applicability of classical MD simulations to high-energy electron dynamics, which rest on the localization of the wave packet and the distinguishability of identical particles. We also examine the cluster size domain for the applicability of the MD simulation code where the laser intensity is uniform inside the cluster.     

Donald D. Dorfman (1933-2001): Obituary.

Obituary for Donald D. Dorfman (1933-2001). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiple Simulation Analysis for Probabilistic Cost and Schedule Integration

One of the major goals of the construction industry today is the quantification and minimization of the risk associated with construction engineering performance. When specifically considering the planning of construction projects, one way to control risk is through the development of reliable project cost estimates and schedules. Two techniques available for achieving this goal are range estimating and probabilistic scheduling. This paper looks at the integration of these techniques as a means of further controlling the risk inherent in the undertaking of construction projects. Least-squares linear regression is first considered as a means of relating the data obtained from the application of these techniques. However, because of various limitations, the application of linear regression was not considered the most appropriate means of relating the results of range estimating and probabilistic scheduling. Integration of these techniques was, therefore, achieved through the development of a new procedure called the multiple simulation analysis technique. This new procedure combines the results of range estimating and probabilistic scheduling in order to quantify the relationship existing between them. Having the ability to accurately quantify this relationship enables the selection of high percentile level values for the project cost estimate and schedule simultaneously.     

Prediction and control of pillow defect in single point incremental forming using numerical simulations

Pillows formed at the center of sheets in Single point incremental forming (SPIF) are fabrication defects which adversely affect the geometrical accuracy and formability of manufactured parts. This study is focused on using FEA as a tool to predict and control pillowing in SPIF by varying tool size and shape. 3D Finite element analysis (FEA) and experiments are carried out using annealed Aluminum 1050. From FEA, it is found out that the stress/strain state in the immediate vicinity of the forming tool in the transverse direction plays a determinant role on sheet pillowing. Furthermore, pillow height increases as compression in the sheet-plane increases. The nature of in-plane stresses in the transverse direction varies from compressive to tensile as the tool-end geometry is changed from spherical to flat. Additionally, the magnitude of corresponding in-plane stresses decreases as the tool radius increases. According to measurements from the FEA model, flat end tools and large radii both retard pillow formation. However, the influence of changing tool end shape from hemispherical to flat is observed to be more important than the effect of varying tool radius, because the deformation zone remains in tension in the transverse direction while forming with flat end tools. These findings are verified by conducting a set of experiments. A fair agreement between the FEM and empirical results show that FEM can be employed as a tool to predict and control the pillow defect in SPIF.

     

Integrated probabilistic schedules and estimates from project simulated data

Risk management, as it relates to construction, is vital to the successful undertaking and completion of any construction project. One way to manage project risk effectively is to develop more reliable means of accounting for the time and cost variability existing in construction operations. Recent attempts to more reliably quantify the risk inherent in construction projects has focused on range estimating and stochastic scheduling (also referred to as probabilistic estimating and probabilistic scheduling). It is common knowledge in the construction industry that the cost associated with a project is affected greatly by the schedule selected to complete that project. Additionally, the percentile level associated with both of these tools is of significance when they are considered stochastically. This paper looks at the integration of range estimating and probabilistic scheduling, using a new procedure called the empirical cumulative density function technique (ECDF) as a means of further controlling the risk associated with the undertaking of construction projects. In addition to providing a reliable means of relating the results of range estimating and probabilistic scheduling, this technique is graphically based, and has the advantage of not requiring any assumptions regarding the underlying data distributions.