Design of Quality Model during Reengineering of Legacy System

The purpose of this paper is design such kind of model that will improve the quality of system during reengineering[1] of legacy system that why this model is known as Quality Model. During reengineering of object oriented system[2,3], the methodology is design in such a way that will create a link/bridge between problem detection and problem correction in the legacy system, as well as simultaneously improvement in object oriented design, that can be used during later reengineering and also reduces the complexity as compared to object oriented design[4,5,6]. The further design of legacy system in such a way to specifying, how branches can be selected, how behavior is preserved and how code transformation applied. Quality of model, depends upon two factor favor and disfavor, attach to each branches, software quality is directly proportional to maintenance cost. Quality model is used for two purpose sketch and blueprint. Sketch is used a thinking tool, which help developer communicates, some aspects of a system and alternative about, what are about to be done. Blueprint intends to be comprehensive and definitive. It is used for guiding the implementation

Methods for sulfate air quality management

Executive Summary Abstract: A study of methods for sulfate air quality control strategy design has been conducted. Analytical tools developed were tested within a case study of the nature and causes of the high sulfate concentrations observed in the Los Angeles area. A principal objective was to investigate the least costly means for sulfate air quality improvement in that locale. A long-run average emissions to air quality model was derived which computes pollutant concentrations from Lagrangian marked particle statistics based on the time sequence of measured wind speed, wind direction, and inversion base motion. Physical assumptions drawn from analysis of existing air quality and meteorological data were used to adapt this model to a specific application -- sulfate air quality prediction in Los Angeles. An energy and sulfur balance on the fate of energy resources containing sulfur was developed to test the consistency of a sulfur oxides emissions inventory for that air basin. Then material balance arguments were used to trace sulfur flows within that regional energy economy through the air quality model which also conserves sulfur mass. Sulfate air quality model predictions were compared to historical observations over the years 1972 through 1974. 'The sulfate air quality impact of individual emission source classes was estimated at a large number of air monitoring sites. A hybrid theoretical-empirical model was constructed which explains the relationship between sulfate air quality and prevailing visibility at Los Angeles. An estimate was made of the visibility improvement which would have accured if Los Angeles sulfate concentrations were reduced by 50 percent on each past day of record. Then two emissions control strategy example calculations were performed to illustrate the means by which the air quality model results could be used to evaluate the cost of attaining such an air quality improvement. Volume 2 Abstract: Particulate sulfate air pollutants contribute to visibility deterioration and are of current public health concern. This study develops the technical understanding needed for sulfate air quality control strategy design. Methods which link sulfate air quality and air quality impacts on visibility to the cost of controlling sulfur oxides air pollutant emissions are presented. These techniques are tested by application to the Los Angeles Basin over the years 1972 through 1974. An air quality simulation model is developed which directly calculates long-term average sulfate concentrations under unsteady meteorological conditions. Pollutant concentrations are estimated from Lagrangian marked-particle statistics based on the time sequence of historical measured wind speed, wind direction and inversion base height motion. First order chemical reactions and ground level pollutant dry deposition are incorporated within a computational scheme which conserves pollutant mass. Techniques are demonstrated for performing both mass balance and energy balance calculations on flows of energy resources containing sulfur throughout the economy of an air quality control region. The energy and sulfur balance approach is used to check the consistency of a spatially and temporally resolved air quality modeling emission inventory for the South Coast Air Basin. Next the air quality model is validated against sulfur oxides emissions and sulfate air quality patterns observed in the Los Angeles Basin over each month of the years 1972 through 1974. A seasonal variation in the rate of SO2 oxidation to form sulfates is inferred. Overall average SO2 oxidation rates of about 6% per hour prevail during late spring, summer and early fall, while mean SO2 oxidation rates of between 0.5% per hour and 3% per hour prevail from October through February of our test years. From the model results, it is concluded that three to five major SOx source classes plus background sulfates must be considered simultaneously at most monitoring sites in order to come close to explaining observed sulfate levels. The implication is that a mixed strategy aimed simultaneously at a number of specified source types will be needed if substantial sulfate air quality improvements are to be achieved within this particular airshed. Techniques are developed for analysis of the long-run impact of pollutant concentrations on visibility. Existing statistical models for light scattering by aerosols which use particle chemical composition as a key to particle size and solubility are modified so that the relative humidity dependence of light-scattering by hygroscopic aerosols could be represented in a more physically realistic manner. Coefficients are fitted to the model based on ten years of air pollution control agency routine air monitoring data taken at downtown Los Angeles. Sulfates are found to be the most effective light scatterers in the Los Angeles atmosphere. It is estimated that the visibility impact of reducing sulfates to a half or to a quarter of their measured historic values on each past day of record would be manifested most clearly in a reduction in the number of days per year of less than three-mile visibility. The number of days of average visibility less than ten miles would be little affected. Two retrospective examples are worked to show how the results of the air quality simulation models may be used to define a variety of sulfate air quality control strategy options. It is suggested that a package of technological emissions control measures and institutional changes (including natural gas price deregulation) may provide greater improvements in both sulfate air quality and visibility at less cost than can be obtained from a purely technological solution to the Los Angeles sulfate problem