Improvements to the Copernicus Trajectory Design and Optimization System for Complex Space Trajectories

The purpose of this assessment was to develop updates and new features for the NASA Copernicus Spacecraft Trajectory Design and Optimization analysis tool (version 5.0) for application to NASA programs and projects. These updates will significantly improve the ability to design and optimize complex trajectories over multiple trajectory phases; will allow the use of unique vehicle-specific guidance, control, and trajectory strategies and constraints; and the creation of an almost unlimited number of unique user-defined capabilities. The primary stakeholders for this assessment are the trajectory design and optimization analysts and engineers, and the chief engineers and project managers for existing programs, projects, and/or tasks that involve impulsive, finite burn, and/or continuous thrust trajectories (e.g., Sun, planet, comet, asteroid, halo orbit, Lagrange point, and distant retrograde orbit). The breadth of application spans the preliminary engineering and mission design concepts and optimization, to the development of candidate reference missions and integrated mission design for vehicle system design and operation, to the design and development of flight trajectories and associated propulsive maneuvers for real-time operations

An analytical approach to computing step sizes for finite-difference derivatives

textFinite-difference methods for computing the derivative of a function with respect to an independent variable require knowledge of the perturbation step size for that variable. Although rules of thumb exist for determining the magnitude of the step size, their effectiveness diminishes for complicated functions or when numerically solving difficult optimization problems. This dissertation investigates the problem of determining the step size that minimizes the total error associated with finite-difference derivative approximations. The total error is defined as the sum of errors from numerical sources (roundoff error) and mathematical approximations (truncation error). Several finite-difference approximations are considered, and expressions are derived for the errors associated with each approximation. Analysis of these errors leads to an algorithm that determines the optimal perturbation step size that minimizes the total error. A benefit of this algorithm is that the computed optimal step size, when used with neighboring values of the independent variable, results in approximately the same magnitude of error in the derivative. This allows the same step size to be used for several successive iterations of the independent variable in an optimization loop. A range of independent variable values for which the optimal step size can safely remain constant is also computed. In addition to roundoff and truncation errors within the finite-difference method, numerical errors within the actual function implementation are also considered. It is shown that the optimal step size can be used to compute an upper bound for these condition errors, without any prior knowledge of the function implementation. Knowledge of a function's condition error is of great assistance during the debugging stages of simulation design. Although the fundamental analysis assumes a scalar function of a scalar independent variable, it is later extended to the general case of a vector function of a vector independent variable. Several numerical examples are shown, ranging from simple polynomial and trigonometric functions to complex trajectory optimization problems. In each example, the step size is computed using the algorithm developed herein, a rule-of-thumb method, and an alternative statistical algorithm, and the resulting finite-difference derivatives are compared to the true derivative where available.Aerospace Engineerin

An architecture for incorporating interactive visualizations into scientific simulations

textAs scientific simulations get increasingly complex, so do the requirements of how to deal with the data that is produced. Few scientists and engineers today are satisfied with just looking at streams of numbers; we require graphical visualizations to better understand their meaning. The traditional method of visualization has been to save the simulation's results to a file, then load that file up in another program (eg. Microsoft Excel) for post-processing. Although post-processing data to produce visualizations may be sufficient for some simple simulations, a modern simulation designer usually wants more out of their visualization. Perhaps they want the visualization to be a 3D plot of an interplanetary trajectory, with the ability to zoom, pan, and rotate the scene interactively. Until now, doing so has required the designer to become adept at computer graphics, which is a feat that almost no scientist or engineer has the time to attempt. The research undertaken here introduces an architecture by which a simulation programmer can easily add interactive 3D visualizations to their simulations. This architecture has several benefits over existing visualization packages, the biggest one being that no knowledge of computer graphics is required to use the it in one's own simulations. Another benefit is that the resulting visualization is interactive by default, without any extra programming required on the part of the simulation designer. This thesis begins by introducing the theory behind how scientific simulations want to visualize data. Common aspects of all simulations are identified, and are used to develop a common "visualization language" that can be used by any simulation designer to specify what they want to visualize. The second part of the thesis specifies a particular implementation of this visualization language, called OpenFrames. Open- Frames is a library of functions that can be called from C, C++, or FORTRAN, and automatically implements the visualization specified by the designer.Aerospace Engineerin

Assessment of Dental caries status, Periodontal health and oral hygiene practices among two Populations of Moradabad city, India

Background: Ever since the beginning of the universe mankind had struggled constantly for their livelihood, Moradabad is branded as the “Brass city” of India, which comprises of a large number of populations working in different industries. Objective: To assess and compare the oral health status of workers employed in brass industries with non industrial workers of Moradabad city. Material and Methods: A total of 500 workers from each group aged 30-50 with 5 years working experience were selected through random sampling. Type III examination was performed by recording who oral health assessment form. To compare the proportion chi-square test was used. Mean values were compared using students t-test. SPSS version 15.0 was used for statistical analyses. Results: The prevalence of dental caries as Mean DMFT score was significantly higher in Non Industrial Group i.e. 3.57±2.74 while it was 2.88±2.14 in brass workers. Periodontal diseases were higher among production workers that belong to brass industries. The prevalence of Oral Mucosal Lesions was significantly higher among Production Workers. Bleeding was more pronounced in general population but calculus and pockets were seen more in brass workers. The requirement of prosthetic status was also more prevalent among industry subjects.  Conclusion: The Oral health status of Brass Industry Workers was relatively poor with poor periodontal health when compared to General Population. Further studies of oral occupational disease should be conducted in order to check or confirm previous reports and to discover possible manifestations arising in new industries.DOI: http://dx.doi.org/10.3126/ijosh.v3i2.631

Influence of Sawdust Bio-filler on the Tensile, Flexural, and Impact Properties of Mangifera Indica Leaf Stalk Fibre Reinforced Polyester Composites

The need to have biodegradable composites is aloft in today’s market as they are environment friendly and are also easy to fabricate. In this study, mangifera indica leaf stalk fibres were used as reinforcement along with saw dust as bio-filler material. Unsaturated isophthalic polyester resin was used as the matrix. The fibres were treated with 6 % vol. NaOH and neutralized with 3 % vol. of dilute HCl. Treatment of sawdust fillers was done by using 2% vol. NaOH solution. Hand layup method and compression moulding technique was used to fabricate the composite laminates. Specimens for evaluating the mechanical properties were prepared by using water jet machining. The results indicated an increase in tensile, flexural and impact strength of composites with addition of sawdust upto 3%. Further addition of the bio-filler resulted in decrease of mechanical properties

Influence of Sawdust Bio-filler on the Tensile, Flexural, and Impact Properties of Mangifera Indica Leaf Stalk Fibre Reinforced Polyester Composites

The need to have biodegradable composites is aloft in today’s market as they are environment friendly and are also easy to fabricate. In this study, mangifera indica leaf stalk fibres were used as reinforcement along with saw dust as bio-filler material. Unsaturated isophthalic polyester resin was used as the matrix. The fibres were treated with 6 % vol. NaOH and neutralized with 3 % vol. of dilute HCl. Treatment of sawdust fillers was done by using 2% vol. NaOH solution. Hand layup method and compression moulding technique was used to fabricate the composite laminates. Specimens for evaluating the mechanical properties were prepared by using water jet machining. The results indicated an increase in tensile, flexural and impact strength of composites with addition of sawdust upto 3%. Further addition of the bio-filler resulted in decrease of mechanical properties