The electric utility-industrial user partnership in solving powerquality problems

Various views on power quality among industrial end users and utility personnel are summarized. The issues raised include the most salient power quality problems, their causes, and designing the most effective technical and organizational responses to these problems. Recent technological advancement has helped to precipitate power quality problems through the widespread influx of sophisticated electrical equipment that is sensitive to common power quality problems; of particular note here are momentary loss of power and inadvertent noise that infiltrates into sensitive logic circuits. These problems have been exacerbated through the growing use of power electronics equipment which, although beneficial, can generate harmonic distortion and notching of the line voltage. It is pointed out that identifying and technically solving these emerging problems is an engineering challenge that can be met on a case-by-case basis     

Simulation and design of a dual-kanban production system

A procedure to evaluate system design parameters for “pull” production strategies is presented in this paper. The evaluation procedure is based on a cost function which includes the inventory carrying, storage, setup, stockout, and idle costs. A combined SLAM II/FORTRAN simulation model and electronic spreadsheets support the evaluation procedure. A “pull” production strategy using the dual-kanban production control method is modeled. The best design in terms of unit load size/number of kanbans is found to (a) satisfy daily production requirements and (b) minimize the cost function.     

Formant labelling using pole-focused spectra

An algorithm is introduced which labels formants from the peaks of pole-focused spectra. A clustering procedure is first used to produce line segments of possible formants. These can be considered as anchor traces for the later processing. Rule-based labelling is then applied to provide final formant trace estimates. Experimental results show that the proposed algorithm offers improved formant labelling accuracy.     

The nuclear freeze resolution: A question of empowerment.

The American Psychological Association has done little to empower the nuclear freeze resolution (NFR) adopted in 1982. The general debate on the issues of advocacy, competency, and ethics should be suspended so that the issues associated specifically with the NFR can be resolved. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acoustic emission calibration instrumentation

An automatic calibration instrument was developed to improve the calibration accuracy of acoustic emission (AE) instrumentation. The instrument facilitates calibration by automatically displaying the maximum value of the stress used to produce AE calibration pulses and the AE pulse. A repeatable AE signal was generated by breaking a graphite rod on the test assembly. By measuring the breaking load of the rod and the maximum root-mean-square values of the resulting AE signals, a relative calibration of the AE measurement system was achieved. Low-noise amplifiers and filters were developed to improve the sensitivity of AE measurements by more than one order of magnitude over commercially available instruments; thus, the smaller signals obtained in parts testing can be detected     

Extended Thermodynamics Derivation of Energy Dissipation in Unsteady Pipe Flow

Extended irreversible thermodynamics (EIT) provides a framework for deriving extensions to phenomenological equations (e.g., Newton's law of viscosity, Fick's law of mass transport, and Darcy's law for porous media flow) for problems involving high frequencies (i.e., rapid transients). In this paper, a phenomenological equation is derived for energy loss in 1D unsteady pipe flow using an EIT formalism. The resulting wall shear stress is equal to the sum of (1) the steady-state shear stress; (2) a term that is proportional to the local (i.e., temporal) acceleration; and (3) a term that is proportional to the product of the velocity and the convective (i.e., spatial) acceleration. The form of this EIT-based wall shear stress formula shows that EIT provides a physical basis for instantaneous acceleration based unsteady friction formulas. It also illustrates the limitations and underlying assumptions of these models. For example, instantaneous acceleration based unsteady friction formulas are limited to fast transients (i.e., transients in which the water hammer timescale is significantly smaller than the diffusion timescale). A characteristics solution for unsteady pipe flow is proposed in which the phenomenological equation is used to model energy dissipation. Comparison of numerical test results with measured data from upstream and downstream valve closure laboratory experiments shows excellent agreement.     

Analysis of the Stability of I-Walls with Gaps between the I-Wall and the Levee Fill

Following Hurricane Katrina an extensive investigation of the performance of floodwalls in the New Orleans area was undertaken by the U. S. Army Corps of Engineers and others. This investigation included detailed study of failures of cantilevered sheet pile “I-walls” during the hurricane. An important lesson from this investigation was that gaps can form on the canal side of I-walls as the water rises in the canal and causes the I-wall to deflect. Once formed, these gaps filled with water, resulting in significantly higher loads on the walls. Gap formation was a key factor in several I-wall failures, and modeling such gaps correctly is clearly an important aspect of analyzing I-wall stability. This paper describes simple procedures for estimating the depths of gaps behind I-walls, for calculating the loads to which they are subjected, and for including them in stability analyses. The effects of gaps on the stability of the 17th Canal and the London Avenue Canal I-walls are discussed.     

Study of the Free Surface Flow on an Ogee-Crested Fish Bypass

A study of the free surface flow on an ogee-crested fish bypass is presented. The commercial computational fluid dynamics (CFD) code Fluent 6.1 was used to perform the simulations. Structured/unstructured hybrid grids were used to accommodate the complex geometry that included gate slots, flow control gates, and an aeration slot. The volume of fluid (VOF) approach was used to model the water/air interface. The fish bypass exhibits complex free surface features including free nappes and air entrainment from the air slots. Free surface elevations on both sides of the nappe, pressure along the ogee surface, and discharge rating curves were compared against 1:24 experimental data from the laboratory model for different headwater elevations and gate settings. Limited comparison against measured velocities was also performed. Once deemed reliable through validation against experimental data, the computational model was used to analyze the flow field, supplementing the areas of limited experimental data. Though the paper presents the final fish bypass design, CFD was used to guide the design process and provide insight for several variations in the geometry.