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Master of Science / Department of Industrial & Manufacturing Systems Engineering / Malgorzata J. Rys / The current state of the dental industry shows an increasing number of dentists and dental hygienists who are reducing hours and retiring early due to the injuries sustained while working. These injuries, or cumulative trauma disorders, can be reduced by applying ergonomics in dental tool design. The goal of ergonomics is to reduce current injuries but also prevent future ones. In addition, population demographics have shown an increasing trend in female dentists. With a shift from the male dominated field, design for different anthropometric measurements needs to be investigated. In order to pinpoint sources of pain, a survey was designed and distributed to dentists in Kansas, Missouri, and Texas. Even with a small sample size (n=24), results confirmed past studies in the dental industry of pain originating in the neck, shoulder, lower back, and wrist/hand region. The reasons stemmed from the repetitive motions and forces applied during dental procedures. Responses also found that ergonomic principles need to be applied to the handle and grip portion of dental scaler design. Dental scaling is the procedure to remove deposits on teeth, such as plaque and calculus, most commonly performed by dental hygienists. First, the history of dental tools, angulation, tool weight, and materials currently utilized were researched before looking into specific design factors for modification. Currently, the handle grip area on all dental tools range in size, but a 10 mm grip has been proven to be optimal. The optimal tool weight has yet to be determined as 15 grams is the lowest weight to be tested. Most tools are made of stainless steel and resins, which are not compressible. An experiment was designed to test a new dental scaler (A) made of a titanium rod with added compressibility in the precision grip area. The aim was to help reduce pressure on the fingers and hand muscles and increase comfort during scaling. The experiment utilized a Hu-Friedy sickle scaler (B) and a Practicon Montana Jack scaler (C) as controls to show two design spectrums, weight and material. The subjects (n=23) were taught the basics of scaling and required to scale using a typodont. The change in grip strength (Δ GS), pinch strength (Δ PS), and steadiness of the subjects hand were tested. An absolute and relative rating technique was utilized pinpointing that the new dental scaler was preferred with the eigenvector (A=0.8615, B=0.1279, C=0.0106). Statistical analysis confirmed this tool preference while also finding the interaction of gender and tool and Δ GS Tool A versus Tool B for males to be significant.

Master of Science / Department of Industrial & Manufacturing Systems Engineering / Todd W. Easton / Integer programs (IP) are a commonly researched class of problems used by governments and businesses to improve decision making through optimal resource allocation and scheduling. However, integer programs require an exponential amount of effort to solve and in some instances a feasible solution is unknown even with the most powerful computers. There are several methods commonly used to reduce the solution time for IPs. One such approach is to generate new valid inequalities through lifting. Lifting strengthens a valid inequality by changing the coefficients of the variables in the inequality. Lifting can result in facet defining inequalities, which are the theoretically strongest inequalities. This thesis introduces the Cutting-plane Algorithm in Three Sets (CATS) that can help reduce the solution time of integer programs. CATS uses synchronized simultaneous lifting to generate a new class of previously undiscovered valid inequalities. These inequalities are based upon three sets of indices from a binary knapsack integer program, which is a commonly studied integer program. CATS requires quartic effort times the number of inequalities generated. Some theoretical results describe easily verifiable conditions under which CATS inequalities are facet defining. A small computational study shows CATS obtains about an 8.9% percent runtime improvement over a commercial IP software. CATS preprocessing time is fast and requires an average time of approximately .032 seconds to perform. With the exciting new class of inequalities produced relatively quickly compared to the solution time, CATS is advantageous and should be implemented to reduce solution time of many integer programs.

Master of Science / Department of Industrial & Manufacturing Systems Engineering / Shuting Lei / Polyglycolic acid (PGA) is an important polymer in the field of tissue engineering. It has many favorable properties such as biocompatibility, bioabsorbability, high melting point, low solubility in organic solvents, high tensile strength and is used in a variety of medical related applications. Currently there are various methods such felting, stitching, use of binder/adhesive for joining the non woven meshes of PGA polymer in order to make suitable three dimensional scaffolds. The existing methods for joining the non woven meshes of PGA polymer are usually time consuming and not very flexible. Thus there is a need for a better technique that would overcome the drawbacks of the existing methods. Laser welding offers potential advantages such as high welding rates, easy to automate, improved seam and single sided access such that welds can be performed under various layers of fabric. Therefore, the main objective of this research is to conduct a fundamental study on laser welding of non woven PGA scaffold felts. An experimental setup for spot welding is built that would assist in the formation of tubular structures. A factorial design of experiments is used to study the effects of the operating parameters such as laser power, beam diameter, time duration and pressure on the weld quality. The weld quality is assessed in terms of weld strength and weld diameter. Based on the parametric study, a regression analysis is carried out to form correlations between weld quality and the operating parameters, which could be used to select the optimal operating conditions. The successful welds obtained by the laser welding process have no discoloration and are stronger than the tensile strength of the original non woven sheets of PGA biofelt.