<p>In this thesis, we theoretically and experimentally investigate the linear and nonlinear dynamic behavior of a frame structure, which frequently occurs in engineering applications. The structure consists of three continuous steel beams that are connected by two brass hinges. Experimental modal analysis indicates that the obtained natural frequencies are highly sensitive to changes in the oscillation amplitude, even for small motions. Thus, the amplitude range where linear responses can be expected is, in practice, very small. Instead, a strong nonlinear behavior is exhibited by the experimentally obtained backbone curves for small vibrations. Furthermore, the experimentally obtained frequency-response curves exhibit jump phenomena.</p> <p> We investigated experimentally whether the nonlinear dynamic characteristics of the structure are the result of modal interactions, such as internal and combination resonances. We were unable to activate any of these resonances. Next, we investigated whether these characteristics are due to geometric, inertia, material, or damping nonlinearities. The answer is again negative. Finally, we examined the nonideal dynamic characteristics of the hinges. We found that stiffness degradation hysteretic damping in the hinges is the best model that explains the observed nonlinear dynamic behavior. A multilinear stiffness degradation model was used to describe the overall hysteretic load-displacement relation. An approximate analytical approach was used to compute the steady-state response of the structure to a harmonic excitation. A good qualitative agreement between the computations and the experimental results was obtained.</p> / Master of Science

This report is to investigate the use of fracture mechanics parameters (fracture toughness, specific work of fracture) to characterize comminution process. Comminution is a very important industrial process and is extremely low in efficiency. Establishment of a crushing index based on fracture mechanics principles is of great significance for improved machine design and enhanced efficiency. Single particle fracture study has been reviewed because it is considered the most elementary process in and provides the basis for comminution. <p>Rock fragmentation can be best described by fracture mechanics principles and concepts. The most fundamental concept in fracture mechanics is fracture toughness. Extensive review has been done on the fracture toughness application to rock fragmentation problems, and has found it has not been successfully used in comminution process. Further study is necessary to investigate the link between comminution and fracture toughens. Interrelation of fracture. toughness with other rock properties has been studied. Loading rate effects on fracture toughness has also been reviewed. <p>Fracture toughness testing for rock materials has also been studied. The SCB (Semi-Circular Bend specimen) method has been selected for its sound analytical background and ease of operation. A experimental proposal is made based upon the survey results. Single particle fracture is proposed to be conducted on the Allis-Chalmers High Energy Crush Test System, which, compared with other test apparatus, more closely simulates the actual crushers. Detailed procedures on how to use the test system has been given in the report. / Master of Science

<p>A simulation model for traffic loading analysis is needed to aid the designers of landmobile radio communication systems. In the past, our system designers have relied on analytical solutions to perform traffic loading analysis. As our communication system evolved and changed from a voice-only system, to a voice and data system, it became apparent that the assumptions needed for an accurate Erlang C prediction were no longer valid. Thus, the need for a simulation model was realized in order to better predict the radio system's capacity to support a given traffic load.</p> <p> This paper describes the process by which the simulation model was designed, developed, and validated. The simulation modeling system was developed using systems engineering methodologies. This document describes the need for a traffic analysis tool and the development process followed, from conceptualization through test and evaluation. An analysis package is also presented to show the verification and validation of the simulation model. Recommendations and a summary conclude the discussion.</p> / Master of Science

<p>A program for the design of steel frames was developed. The program can be used to design beams and columns in a frame in accordance with the Load and Resistance Factor Design method. The program was coded in C++ using the object oriented programming method. The program runs under the windows graphical operating environment. The Microsoft Visual c++ compiler was used for developing the program. The major classes in the program are joints, members, beams, columns, and loads, and correspond to objects in a real structure. The architecture of the program is based on the relationship between these objects. The accuracy of the program was verified by comparing design results obtained from the program with results from a commercial structural analysis and design program (DAST version 11.0), as wen as with results obtained from hand calculations. It was concluded that the object oriented approach has many advantages that makes it a desirable approach for developing computer applications for structure engineering· for today's graphical windows operating environments / Master of Engineering

see document / This report describes an international effort to investigate the present limitations of some of the commercially available CFD codes and their models. This investigation involves comparing the predictions from these codes with the experimental results of the two selected test cases. The data collection method is briefly described followed by a detailed discussion of the graphical approach used by the group of investigators to compare results. In addition, an attempt to investigate the deviation of the collected results with the experimental data is discussed. / Master of Science

</p> <p>The formation of soot emissions in combustion processes poses environmental and efficiency problems which have long concerned scientists and engineers. A Wolfuard-Parker burner was designed and fabricated, to study soot formation in dual-mode diffusion flames, where the products of a lean premixed flame serve as oxidizer to the eventual diffusion flame, simulating a droplet combustion environment in Diesel engines.</p> <p> Experimental conditions were determined, and the whole burner assembly together . with the laser diagnostic optics were set ready for experiments. An experimental run with a single-mode flame served to confirm the calibration of the optics and demonstrated the flame stability and uniformity. Finally, recommendations for the future work were / Master of Engineering

<p>Nitrate is one of the most common groundwater contaminants, with levels commonly exceeding established drinking water limits. In areas of high agricultural or industrial nitrate use, nitrate contaminated groundwater poses a potential health risk. In situ denitrification is the microbially mediated reduction of nitrate to innocuous nitrogen gas compounds and is the principal process for nitrate removal in contaminated aquifers. This process is becoming increasingly recognized for its ability to reduce or eliminate nitrate concentrations in groundwater with minimal site disturbance and cost. Predicting the extent to which denitrification occurs in aquifers as well as the rate, therefore, has become the focus of numerous mathematical models. However, the predictive capabilities of numerical models are constrained because knowledge of the biological processes implicated in denitrification is limited.</p> <p>This report examines the microbial processes involved in <i>in situ</i> denitrification, and then applies this knowledge to assess the capability of a two-dimensional numerical model, NBI02D. NBI02D is a variation of a code, SEAM2D, developed by Widdowson (1988,1992).</p> <p>Model development and model application are presented. The model development overview provides insight to the mathematical methods used to simulate the microbial processes. The model application compares model predictions with data received from a USGS research site on Cape Cod, Massachusetts. Data are derived from a natural gradient experiment in which formate was injected into a carbon-limited aquifer in order to stimulate and accelerate denitrification. NBI02D simulations for the Cape Cod site are developed for model verification and model applicability.</p> / Master of Science

This dissertation presents a new algorithm for optimal power flow in distribution systems. The new algorithm, Discrete Ascent Optimal Programming (DAOP), will converge to the same solution as the Lagrange multiplier approach as demonstrated by example. An intuitive discussion illustrating the path of convergence is presented along with a theorem concerning convergence. Because no partial derivatives, solutions of simultaneous equations, or matrix operations are required, the DAOP algorithm is simple to apply and program. DAOP is especially suited for programming with pointers. Advantages of the new algorithm include its simplicity, ease of incorporating inequality constraints, and the ability to predict the number of steps required to reach a solution. In addition to optimal power flow, the algorithm, heuristic in nature, can be applied to switch placement design, reconfiguration, and economic dispatch. The basic principles of the algorithm have been used to devise a phase balancing routine which has been implemented in the Distribution Engineering Workstation (DEWorkstation) software package sponsored by the Electric Power Research Institute (EPRI). The new algorithm presented in this dissertation works toward a solution by performing a series of calculations within a finite number of steps. At the start of the algorithm, the assumption is made that no power is flowing in the system. Each step adds a discrete unit of load to the system in such a fashion as to minimize loss. As progress toward the solution is made, more and more load is satisfied and the losses in the system continue to increase. The algorithm is terminated when all system load is satisfied. When the algorithm is finished, the sources which should supply each load have been identified along with the amount of power delivered by each source. Discussion will show that the method will converge to a solution that is within the discrete step size of the optimum. The algorithm can be thought of as an ascent method because the cost (losses) continually increases as more and more load is satisfied. Hence, the name Discrete Ascent Optimal Programming (DAOP) has been given to the algorithm. The new algorithm uses the topology of the power system such that the entire system is not considered at each step. Therefore, DAOP is not an exhaustive state enumeration scheme. Only those portions of the system containing loads most closely connected (via least loss paths) to the sources are first considered. As loads become supplied during the course of the solution, other loads are considered and supplied until the system is fully loaded. / Ph. D.

Binary response data is often modeled using the logistic regression model. Experimental design theory for the logistic model appears to be increasingly important as experimentation becomes more complex and expensive. The optimal design work is extremely valuable in areas such as biomedical and environmental applications. Most design research dealing with the logistic model has been concentrated on the one-variable case. Relative little has been done for the two-variable model. The primary goal of this research is to develop and study efficient and practical experimental design procedures for fitting the logistic model with two independent variables. Optimal designs are developed addressing D optimality, Q optimality, and the estimation of interaction between the design variables. The two-variable models with and without interaction usually have to be handled separately. The equivalence theory concerning D optimal designs is studied. The designs are compared using their relative efficiencies in the presence of interaction. Robustness to parameter misspecification is investigated. Bayesian design procedures are explored to provide relatively more robust experimental plans. / Ph. D.

Modern governments often rely on private, nonprofit, and other non-governmental entities for delivery of services. Specifically, state and local governments increasingly contract for social services. This dissertation identifies eight effective practices that successful human service contract managers use in the negotiating and contracting process. It compares practices of successful contract managers with those of less successful contract managers in the Massachusetts' Department of Social Services. Success was based on informed judgment of how managers conducted thE~ contracting process. Another measure was the number of debriefing sessions that did or did not lead to appeals. Interviews were held with managers. Questions were both open-ended and loosely structured. Data from interviews was processed and formatted for use in a computer-assisted analysis program. Interpretation and analysis of the interviews identified eight effective practices that successful managers use in the contracting process. Hence, contemporary government demands that public managers understand and master both technical and relationship aspects of the negotiating and contracting process in order to be successful. Managers emphasize prebid planning activities and multiple needs assessment methods to accurately reflect service needs for the area. They monitor waiting lists and utilization of services regularly to determine who use and need services. Managers rely on a large number of participants to review proposals and they use a standard tool to rate them to insure fairness and competitiveness in the proposal evaluation step. They conduct debriefings as mediation sessions and encourage bidders to become more capable to participate in future bidding. They negotiate rates based on pricing ranges not line-item details, and they assist providers with budget and program support. Also, they rely on experience and technical competence to be successful. within the eight effective practices, managers confirm that contracting is more successful when they have early, ongoing interaction and cooperative working relationships as well as providing competent technical services. Cooperative relationships and interaction especially are important as new and diverse service providers enter the contracting arena. / Ph. D.