Department of Mechanical Engineering

Using 150 interactions between entrepreneurs and potential investors, we study early stage business angel decision making. We show that contrary to the majority of past research that suggests they should, angel investors do not use a fully compensatory decision model wherein they weight and score a large number of attributes. Rather, they use a shortcut decision making heuristic known as elimination-by-aspects to reduce the available investment opportunities to a more manageable size. If an opportunity is diagnosed with a fatal flaw, it is rejected in the first stage of the decision making process, but all opportunities with no fatal flaws do progress beyond that stage.

By analyzing observed interactions between entrepreneurs and business angels on the Canadian reality TV show Dragons’ Den, we find that business angels use a non-compensatory decision-making process when evaluating anticipated risk and return. This is consistent with our hypotheses that business angels use decision heuristics (shortcuts) to conserve cognitive effort when deciding whether or not to invest in business opportunities proposed by entrepreneurs. Our results further our understanding of how and when behavioral decision theory can inform real-life business angel investment decision processes. Additionally, the results offer practical implications for entrepreneurs interested in pitching proposals to business angels.

This article investigates the role of entrepreneurs-in-residence (EIRs) in closing the equity gap born by a lack of venture capital investment in early-stage businesses. We conducted interviews with ten Israeli-based venture capitalists and four EIRs to identify the mechanisms and actions used by EIRs when operating in venture-capital firms, and subsequently in funded ventures, that lead to a greater proportion of funds targeted to seed investments. The findings of our exploratory study suggest that EIRs facilitate investment decisions by acting as catalysts in the development of the relationship between the venture capitalist and the fund-seeking entrepreneur. EIRs can thus prevent some of the problems that preclude venture success through the nurturing of trusted relationships with both fund-seeking entrepreneurs and venture capitalists. Furthermore, ex-ante, during and ex-post investment, through building these trusted relationships, EIRs act as transaction-cost reducers, thus increasing expected return on investments from early-stage ventures. In an attempt to help reduce the equity gap by developing a better understanding of this key phenomenon, these findings provide guidance to rising entrepreneurs as they develop their early-stage businesses, to venture capitalists as they look for investment opportunities, and to governments eager to increase the rate of seed funding.

We investigate how an entrepreneur's behaviors during an initial interaction with a business angel can build, damage, or violate trust, and how the investor's level of trust (prompted by the entrepreneur's behavior) can affect his/her decision to make an investment offer. Our empirical analysis shows that entrepreneurs who receive offers from business angels exhibit a larger number of trust–building behaviors during the initial interaction and a smaller number of unintentional trust–damaging behaviors than those who do not receive an offer, and display few deliberate trust–violating behaviors. We further observe that the investor's deployment of a control mechanism is a prerequisite for receiving an investment offer for all entrepreneurs who damage or violate trust.

Drosophila melanogaster is a widely-studied model organism in developmental biology. Oviposition is an important assay in fly studies which also should be controlled for experiments that study biological pathways through synchronized embryos. It has been used as an assessment tool to investigate biological responses to environmental cues, such as substrate textures, but in relatively uncontrolled manual manners. Microfluidics have recently been introduced to enhance accuracy and control in many Drosophila assays. Here, we have used microtechnology to study oviposition quantitatively in response to accurate and repeatable exposures to various desirable agar surfaces using a polydimethylsiloxane (PDMS)-based through-hole membrane patterning technique.

Drosophila melanogaster (fruit fly) is a model organism and its behaviours including oviposition (egg-laying) on agar substrates have been widely used for assessment of a variety of biological processes in flies. Physical and chemical properties of the substrate are the dominant factors affecting Drosophila's oviposition, but they have not been investigated precisely and parametrically with the existing manual approaches. As a result, many behavioral questions about Drosophila oviposition, such as the combined effects of the aforementioned substrate properties (e.g., exposure area, sugar content, and stiffness) on oviposition and viability, and their threshold values, are yet to be answered. In this paper, we have devised a simple, easily implementable, and novel methodology that allows for modification of physical and chemical composition of agar substrates in order to quantitatively study survival and oviposition of adult fruit flies in an accurate and repeatable manner. Agar substrates have been modified by surface patterning using single and hexagonally arrayed through-hole polydimethylsiloxane (PDMS) membranes with various diameters and interspacing, as well as by substrate stiffness and sugar content modification via alteration of chemical components. While pure PDMS substrates showed a significant lethal effect on flies, a 0.5 mm diameter through-hole access to agar was found to abruptly increase the survival of adult flies to more than 93%. Flies avoided ovipositing on pure PDMS and on top of substrates with 0.5 mm diameter agar exposure areas. At a hole diameter of 2 mm (i.e., 0.25% exposure area) or larger, eggs were observed to be laid predominately inside the through-holes and along the edges of the PDMS-agar interface, showing a trending increase in site selection with 4 mm (i.e., 1% exposure area threshold) demonstrating natural oviposition rates similar to pure agar. The surfacemodified agar-PDMS hybrid devices and the threshold values reported for the substrate physical and chemical conditions affecting oviposition are novel; therefore, we advocate their use for future in-depth studies of oviposition behaviour in Drosophila melanogaster with accuracy and repeatability. The technique is also useful for development of novel assays for learning and decision-making studies as well as miniaturized devices for self-assembly of eggs and embryonic developmental investigations.

A droplet which is placed on a surface and is exposed to an airflow, can be shed, if the drag force overcomes the droplet's adhesion force. Presence of other sessile droplets, in proximity, changes the drag force, so the minimum airflow velocity required to shed the droplets (Ucr) can vary. In this thesis, an experimental study on shedding of the multiple sessile droplets was performed on both hydrophilic and hydrophobic surfaces. The effects of the droplets' arrangement type, and the spacing on Ucr were elucidate. For a pair of sessile droplets, a model was proposed to predict the Ucr based on droplets' size, spacing, arrangement, and surface wettability. For three, or four sessile droplets arranged in triangle, square, reversed triangle, and diamond configurations, the effects of the droplets' interaction on variation of the Ucr, was clarified. A critical value for spacing was determined beyond which multiple sessile droplets shed independently.

due to a shearing airflow overcomes the drop adhesion to the surface. Sessile drop shedding is of importance due to its applications in condensation, fuel cells, icing, etc. Majority of the studies so far have considered the shedding of a single sessile droplet; however, in the applications above, multiple sessile droplets appear on a surface. Shedding of sessile drops in different arrangements, i.e. tandem, side by side, triangle, and rectangle have been investigated both experimentally and through VOF simulations. The minimum air velocity (Ucr) at which the drop(s) at the upstream dislodge from the surface was measured. Drops were placed in a wind tunnel with increasing air velocity at a rate of 1m/s2. It has been found that Ucr, deviates from its value for a single drop due to presence of the neighboring drops. The amount of the deviation is closely related to the flow pattern and interaction of drop wakes which are elucidated numerically. The interacting wakes change the drag force on the drops. Generally, the adhesion force is not affected by presence of other drops. As such, when the drops' wakes are interacting strongly, Ucr can increase by 45%.

A review of various factors affecting wetting and spreading has been presented. Various methods for wettability studies and critical issues concerning contact angle measurement are discussed. Reactive wetting has been given a special attention in the paper and recent developments in this area are summarized and discussed. Although advanced understanding of nonreactive wetting is currently available in the literature, complete understanding of reactive wetting is still lacking due to the complexity of the phenomenon. To date, there is no single model that is generally applicable to all reactive wetting systems. Reaction between the liquid drop and substrate can take the form of dissolution, intermetallic formation, or combination of both processes. Factors affecting wettability have been summarized and discussed as well as the major available techniques to investigate wetting behaviour.

A visual study is conducted to determine the effects of operating conditions on the spray cone angle of a two-fluid atomizer. The liquid (water) jets exit from peripheral inclined orifices and are introduced into a high-speed gas (air) stream in the gravitational direction. Using a high-speed imaging system, the spray cone angle is determined for Reynolds numbers ranging from 4×10 4 to 9×10 4 and different Weber numbers up to 140. The droplet sizes (Sauter mean diameter) and their distributions are determined using a Malvern Mastersizer X. The results show that the spray cone angle depends on the operating conditions, especially in lower values of Reynolds and Weber numbers. An empirical correlation is also obtained to predict the spray cone angle in terms of these two parameters.

Establishing a culture of teaching excellence among faculty with limited prior instructional training raises both practical and philosophical challenges. This paper argues that the departmental unit plays a critical role in setting the conditions necessary for faculty engagement, and that multiple strategies can be coordinated to target change in the teaching norms. The paper introduces the Integrated Course Design and Documentation (ICDD) project at the Department of Mechanical Engineering, York University. The ICDD project demonstrates several of our approaches to effecting change in individual behaviour towards student-centered pedagogy. They include: (1) making the solution easy for the faculty; (2) making the solution a stand-alone resource that the faculty themselves can develop over time; (3) speaking the language of the faculty (relevance, contextualization); and (4) providing the social, organizational, and practical support for faculty to make the transition. Overall, we argue that any effort to create and sustain change must be multi-faceted, and must include: enabling the instructors as the key agents of change; promoting collaboration among faculty; lowering practical barriers to change by developing technical, administrative, and educational resources that are fit to the local context.

—Design education is the backbone of the undergraduate Mechanical Engineering (ME) curriculum at Lassonde School of Engineering (LSE). ME students take project-based design courses every year of their program. Students in the design courses were surveyed and interviewed, in order to examine the key learning outcomes and their development over the undergraduate years. Early-stage coding and analysis on the interview data have resulted in (1) the identification of possible threshold concepts in each year of project-based design learning, (2) the variation and changes in the meaning of design across cohorts, and (3) the three-level factors to design team success. Recommendations are proposed for the instructional training and course structure to enhance their support for design team project experience and outcomes.

– An exploratory study on the students' learning processes in design project settings led to the discovery of important tensions that students experience in their engineering program. Adopting a Critical Discourse Analysis perspective, an we conducted an analysis of dominant images and discourses in engineering student interviews. The results highlighted key conflicting messages about what it means to succeed in engineering education, what engineering means, and who the engineering student is. Certain ideological beliefs posed as serious barriers and threats to mutually respectful and healthy peer relations, resulting work outcomes, and a sense of 'fit' or belonging in engineering. Simultaneously, students demonstrated abilities to critique existing narratives and offer alternative meanings. It is this critical, moral agency of our students that amplifies the call for educational reform towards social justice through, and within, engineering.

Today there is a growing emphasis on responsible engineering design, which commits its practice to sustainable, ethical, equitable outcomes in the broader societal level. For engineers involved in the design, development, and implementation of existing and emerging technologies, such responsibility requires skillfulness on multiple fronts, for example: facilitating the integration of cross-disciplinary expertise and knowledge; translating a detailed problem understanding from its sociocultural settings into technical requirements; and negotiating requirements and priorities with key internal and external stakeholders. In order to understand how design engineers access, acquire, and effectively utilize knowledge outside their technical disciplines, especially pertaining to the human and social contexts of the design problem and designer practice, an online survey and in-depth interviews were conducted with professional engineers. The paper discusses potentially important design engineer capabilities that engineering educators should consider. We welcome discussions and feedback on our ongoing work.

In this paper, the rapid mixing of deionized water and Fe 3 O 4 ferrofluid in a Y-shaped microchannel using a permanent magnet is studied both numerically and experimentally. The microchannel has a rectangular cross section with 500 m in width and 1 mm in depth. The process, assumed to be two-dimensional and steady state, is simulated by COMSOL numerical software. In the numerical simulation, the Maxwell equations are solved to obtain the magnetic potential. Then, the magnetic force can be calculated. Knowing the magnetic force, the momentum and transport-diffusion equations are solved. A setup is designed and fabricated to carry out the experiments. The mixing process is photographed by a CCD camera for 5 min until the mixing process reached a steady state condition. The numerical results are compared with the corresponding measurements to validate the simulations. The effect of different parameters such as magnetic field's strength (1280G, 2000G and 3000G), volume flow rate (30 cc/min, 40 cc/min, and 60 cc/min), and mass fraction of nanoparticles (0.0125, 0.025 and 0.05) is investigated on the mixing efficiency. Applying magnetic field considerably improves the mixing efficiency of the micromixer and reduces the mixing length. Increasing the mass fraction of nanoparticles and magnetic field strength increases the mixing efficiency until the magnetization of the ferrofluid reaches its saturated level. Increasing the fluid flow, however, lowers the mixing efficiency and increases the mixing length.