Control Characteristics of Inverter-Fed Induction Motor

Efficient use of an inverter-fed induction motor drive necessitates a knowledge of the characteristics of the induction motor from a " control" point of view. The characteristics of both the voltage -and the current-source inverter-fed induction motor drive are investigated, neglecting the filter time constants in the link and feedback loops. Of particular interest is the role played by the voltage/current and frequency inputs. Their effects on variables that are not often discussed such as torque angle, stator real power, airgap flux- linkages and stator and rotor voltages/currents are studied. A by- product of this aspect of the study leads to the nature of feedback signals and their suitability for control purposes. It is also found that the link filter has little effect on relative suitability of these signals. A study of the current source induction motor drive dynamics for torque angle feedback is included.     

Intentional forgetting as a facilitator for recalling new product attributes.

When market changes alter what product attributes are deemed important, consumers may intentionally try to forget old product information in an attempt to remember new product information. In Experiment 1, the authors demonstrated that intentional forgetting of this nature temporarily inhibits retrieval of old product information and leads to a benefit to memory for new product information. The results show that, after a short delay, benefits continue in the absence of costs, which is supportive of a multiple-process account of intentional forgetting. Experiment 2 extends these effects using an advertising message to stimulate forgetting. Across both experiments, results also show that brand preference is based on learning of new attribute information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Leveraging global resources: a process maturity framework for managing distributed development

The popular and well-tested software process frameworks such as the Software Engineering Institute's Capability Maturity Model and ISO 9001, details key process areas for software development. Focusing more on continuous improvement in code development processes, generic-process frameworks such as the CMM lack key process areas (KPA) that address capabilities for managing distributed software projects, such as establishing mutual knowledge and managing geographically dispersed social networks. We identify 24 new KPAs that address the wide-ranging capabilities needed for managing distributed software development and arrange them in an evolutionary order similar to the CMM framework. The evolutionary or phased approach in improving software management capabilities helps firms systematically assess their situations and plan for improvements. We also report the results of a statistically tested maturity assessment survey and test the overall rigor of our model against industry expert opinion and objective data collected from real-world projects implemented at SAP AG, a leading global-enterprise software firm.     

Metal gate-HfO/sub 2/ MOS structures on GaAs substrate with and without Si interlayer

In this letter, we studied the effects of post-deposition anneal (PDA) time and Si interface control layer (ICL) on the electrical characteristics of the MOS capacitor with high-/spl kappa/ (HfO/sub 2/) material on GaAs. Thin equivalent oxide thickness (EOT<3 nm) with excellent capacitance-voltage (C-V) characteristics has been obtained. The thickness of the Si ICL and PDA time were correlated with C-V characteristics. It was found that high temperature Si ICL deposition and longer PDA time at 600/spl deg/C improved the C-V shape, leakage current, and especially frequency dispersion (<5%).     

Modeling Steel Frame Buildings in Three Dimensions. II: Elastofiber Beam Element and Examples

This is the second of two papers describing a procedure for the three-dimensional nonlinear time-history analysis of steel-framed buildings. An overview of the procedure and the theory for the panel zone element and the plastic hinge beam element are presented in part I. In this paper, the theory for an efficient new element for modeling beams and columns in steel frames called the elastofiber element is presented, along with four illustrative examples. The elastofiber beam element is divided into three segments—two end nonlinear segments and an interior elastic segment. The cross sections of the end segments are subdivided into fibers. Associated with each fiber is a nonlinear hysteretic stress-strain law for axial stress and strain. This accounts for coupling of nonlinear material behavior between bending about the major and minor axes of the cross section and axial deformation. Examples presented include large deflection of an elastic cantilever beam, cyclic loading of a cantilever beam, pushover analysis of a 20-story steel moment-frame building to collapse, and strong ground motion analysis of a two-story unsymmetric steel moment-frame building.     

Thermomechanical Framework for the Constitutive Modeling of Asphalt Concrete

This study is concerned with the constitutive modeling of asphalt concrete. Unlike most constitutive models for asphalt concrete that do not take into account the evolution of the microstructure of the material, this study incorporates the evolution of the microstructure by using a framework that recognizes that a body’s natural configurations can evolve as the microstructure changes. The general framework, on which this study is based, is cast within a full thermomechanical setting. In this paper, we develop models within the context of a mechanical framework that stems from the general framework for models based on the full thermodynamic framework and the resulting equations represent a nonlinear rate type viscoelastic model. The creep and stress relaxation experiments of Monismith and Secor are used for validating the efficacy of the model, and it is found that the predictions of the theory agree very well with the available experimental results. The advantages of using such a framework are many, especially when one wants to model the diverse mechanical and thermodynamic response characteristics of asphalt and asphalt concrete.     

A genetic algorithm for the design space exploration of datapaths during high-level synthesis

High-level synthesis is comprised of interdependent tasks such as scheduling, allocation, and module selection. For today's very large-scale integration (VLSI) designs, the cost of solving the combined scheduling, allocation, and module selection problem by exhaustive search is prohibitive. However, to meet design objectives, an extensive design space exploration is often critical to obtaining superior designs. We present a framework for efficient design space exploration during high-level synthesis of datapaths for data-dominated applications. The framework uses a genetic algorithm (GA) to concurrently perform scheduling and allocation with the aim of finding schedules and module combinations that lead to superior designs while considering user-specified latency and area constraints. The GA uses a multichromosome representation to encode datapath schedules and module allocations and efficient heuristics to minimize functional and storage area costs, while minimizing circuit latencies. The framework provides the flexibility to perform resource-constrained scheduling, time-constrained scheduling, or a combination of the two, using a simple and fast list-scheduling technique. A graded penalty function is used as an objective function in evaluating the quality of designs to enable the GA to quickly reach areas of the search space where designs meeting user specified criteria are most likely to be found. Since GAs are population-based search heuristics, a unique feature of our framework is its ability to offer a large number of alternative datapath designs, all of which meet design specifications but differ in module, register, and interconnect configurations. Many experiments on well-known benchmarks show the effectiveness of our approach.     

Isolation and characterization of the Saccharomyces cerevisiae DPP1 gene encoding diacylglycerol pyrophosphate phosphatase

Diacylglycerol pyrophosphate (DGPP) is involved in a putative novel lipid signaling pathway. DGPP phosphatase (DGPP phosphohydrolase) is a membrane-associated 34-kDa enzyme from Saccharomyces cerevisiae which catalyzes the dephosphorylation of DGPP to yield phosphatidate (PA) and then catalyzes the dephosphorylation of PA to yield diacylglycerol. Amino acid sequence information derived from DGPP phosphatase was used to identify and isolate the DPP1 (diacylglycerol pyrophosphate phosphatase) gene encoding the enzyme. Multicopy plasmids containing the DPP1 gene directed a 10-fold overexpression of DGPP phosphatase activity in S. cerevisiae. The heterologous expression of the S. cerevisiae DPP1 gene in Sf-9 insect cells resulted in a 500-fold overexpression of DGPP phosphatase activity over that expressed in wild-type S. cerevisiae. DGPP phosphatase possesses a Mg2+-independent PA phosphatase activity, and its expression correlated with the overexpression of DGPP phosphatase activity in S. cerevisiae and in insect cells. DGPP phosphatase was predicted to be an integral membrane protein with six transmembrane-spanning domains. The enzyme contains a novel phosphatase sequence motif found in a superfamily of phosphatases. A dpp1Delta mutant was constructed by deletion of the chromosomal copy of the DPP1 gene. The dpp1Delta mutant was viable and did not exhibit any obvious growth defects. The mutant was devoid of DGPP phosphatase activity and accumulated (4-fold) DGPP. Analysis of the mutant showed that the DPP1 gene was not responsible for all of the Mg2+-independent PA phosphatase activity in S. cerevisiae.     

Active Wegener's granulomatosis is associated with HLA-DR+ CD4+ T cells exhibiting an unbalanced Th1-type T cell cytokine pattern: reversal with IL-10

Wegener's granulomatosis (WG) is a granulomatous vasculitis that affects the upper respiratory tract, lung, and kidney. Since T cells make up a significant proportion of cells infiltrating granulomatous lesions in WG, we investigated the proliferative response and cytokine profile of T cells from these patients. PBMCs were isolated from 12 patients with active WG, 7 patients with inactive disease, and 12 healthy normal donors. PBMCs from clinically active WG patients exhibited increased proliferation following stimulation with either PMA/ionomycin or anti-CD2 and anti-CD28, when compared with normal donors. In addition, these PBMCs exhibited increased secretion of IFN-gamma, but not of IL-4, IL-5, or IL-10. Furthermore, TNF-alpha production from PBMCs and CD4+ T cells isolated from patients with WG was elevated, when compared with healthy donors. In further studies, we investigated the ability of WG patients' monocytes to produce IL-12 and showed that both inactive and active patients produced increased amounts of IL-12. Finally, the in vitro IFN-gamma production by WG PBMC is inhibited in a dose-dependent manner by exogenous IL-10. These data suggest that T cells from WG patients overproduce IFN-gamma and TNF-alpha, probably due to dysregulated IL-12 secretion, and that IL-10 may therefore have therapeutic implications for this disease.