This thesis was submitted to the School of Graduate Studies in partial fulfillment of the requirements for the Degree Master of Applied Science. / <p>Accuracy and surface finishes play an important role in modem industry. However, the deformability of ductile materials induces challenges in achieving high accuracy and surface finish. Undesired projections of material produced during metal cutting, known as burrs, significantly reduces the accuracy of the parts and affect both the assembly process and product quality. Around 30% of total production costs are used for deburring processes. This thesis presents one modem and promising method in reducing burr size through the use of ultrasonic assistance. With ultrasonic assistance, high frequency vibrations are added in the feed direction during cutting. In particular, ultrasonic assisted drilling of 1100-0 aluminum using high speed steel standard twist drills was investigated.</p> <p>Two simulation studies were conducted. Firstly, a finite element model of orthogonal cutting with and without ultrasonic assistance was developed. The results predicted that ultrasonic assistance should produce smaller burrs for the simulated operating conditions. Secondly, a drilling exit burr model was created based on a circular plate deflection model. Unfortunately this simulation failed to predict the experimentally observed burr sizes and thus the model requires further development.</p><p>To provide the ultrasonic vibration a preloaded workpiece holder and a drive circuit were designed and implemented for use with a commercial piezoelectric actuator. This equipment was cost effective (costing about 400 CAN$) and functional.</p><p>The effects of ultrasonic assistance under different vibration and cutting conditions were investigated experimentally. The experimental results demonstrated that, for certain combinations of vibration frequency and amplitude, burr size reduction can be achieved. Under these conditions the ultrasonic impact actions become significant, causing chip segmentation and smaller burrs. The results also show that ultrasonic assisted drilling allows a higher spindle speed and feed to be used without increasing burr size. However, ultrasonic assistance has a negative impact on tool life. Compared with conventional drilling, chipping of the chisel edge and greater wear of the cutting lips was observed after drilling 10 holes. This situation may be improved in the future if drills with suitable coating are used in place of the standard high speed steel drills.</p> / Thesis / Master of Engineering (ME)

<p> The purpose of this research paper is to empirically examine the evolution of the Canadian urban system throughout the past century. This task is completed with the use of the rank-size rule and the parameters that emanate from its logarithmic distribution. This process entails the creation of a historical data set from the inception of the urban areas of each one of the twenty-four CMAs that are used in this study. The collection of the evolving slope and yintercept parameters during the study's fourteen rank-size distribution periods, shows how policy decisions are manifested in the empirical changes of the rank-size rule's slope. Confederation and expansion of the railroad into the prairie frontier are distictly evident in the evolving parameters. It was also found that Canada's geographical distribution of CMAs apparently limits the rank-size rule constant to a value of -1.1 . This distribution is steeper than the optimal market efficiency slope of -1.0 as presented in Zipf's explanation of the forces of attraction and dispersion of economic activity. The statistical results of this paper can be used to· compare different national systems or take a more regional approach in comparing Canadian CMA sub-systems. </p> / Thesis / Bachelor of Arts (BA)

Size premium puzzle, also known as the size effect, is one of the most studied anomalies in asset pricing literature. It refers to the observation that, on average, smaller firms have higher risk-adjusted returns than larger firms over a long period of time. While many studies have debated the existence of the size effect, the question of why it exists has become a subject of heated debate. Thus, this dissertation aims to examine if previously overlooked factors can, at least partially, explain the size effect. Essay 1 examines if merger and acquisition activity can explain a part of the size effect. I find that merger and acquisition activity explain a part of the size effect. The size effect is found to be stronger during merger waves but is not consistent across industries. Further, the size effect tends to be stronger when acquisition activity is concentrated among smaller firms. Essay 2 investigates if expectational errors explain the higher return of small firms. Several empirical studies show that stocks that investors underestimate yield higher returns. However, I do not find support for the underestimation explanation in explaining the higher returns of small firms. Instead, I find that investors are overly optimistic about the growth of small firms. In essay 3, I examine if the size effect can be explained by perceived risk. Using the implied cost of capital (ICC) as a measure of perceived risk, I find that small firms are perceived to be riskier by the market, and the perceived risk explains the size effect.

Thesis advisor: Christopher Kenaley / Bergmann’s rule predicts a change in body size with latitude, with larger members of a taxonomic group occurring further from the equator. This pattern has been described for many groups of organisms; however, no study has assessed this relationship across a substantial number of ray-finned fish species, the largest group of vertebrates. I performed Bayesian phylogenetic modeling using maximum length and latitude data for 3021 species of actinopterygians to assess Bergmann’s rule in the group. The impact of salinity tolerance on the relationship between length and latitude was also considered. Maximum length and salinity tolerance data were obtained from FishBase, and latitude data were obtained from museum records. I found that, overall, Bergmann’s rule holds and is not significantly affected by salinity tolerance except when not considering phylogeny, in which case only marine species show the trend. / Thesis (BA) — Boston College, 2023. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Biology.

The stability and maneuverability of aircraft are some key factors for selecting the locations of wings or canards on the fuselage. Another important variable that is considered in the design of an aircraft is drag force which impacts fuel efficiency. This research investigates how drag force of a surrogate aircraft is affected by the placement of the wing or canard along the fuselage. Unique for this study is the placement of the canard in the fuselage nose region, with the leading edge upstream of the nose, resembling the shape of a hammerhead shark's head. When the leading edge of all considered wing configurations was located 20% or more from the fuselage nose, the platforms produced the least amount of drag force. When the wing was placed in the nose region of the fuselage, the wings with small chords produced less drag when their leading edge was ahead of the nose.

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