Design of a Thermal Conductivity Measurement Device for Cryogenic Applications; Driving the Danger: Analyzing the Risks and Causes of Oversized Vehicles in the United States

STS Paper In my STS research paper, I investigated how the increasing size of passenger vehicles in the U.S., especially SUVs and pickup trucks, has contributed to a worsening pedestrian safety crisis. My motivation for this topic stems from both my personal interest in the automotive industry and my experience working at the U.S. Department of Transportation, where I saw firsthand how technical data informs policy. I wanted to understand not just the direct impact of vehicle size on crash outcomes, but also what regulatory and societal conditions have allowed these larger, more dangerous vehicles to become so dominant on American roads. Through my research, I found that vehicle size significantly affects pedestrian injury severity. Larger vehicles have taller front ends, which strike higher on the human body, leading to greater risk of chest and head trauma. As these vehicles become heavier and more prevalent, especially in urban and arterial settings, pedestrian fatalities have risen, especially among vulnerable groups like the elderly, children, and low-income populations. I also explored the policy mechanisms that have unintentionally encouraged the shift toward larger vehicles. The CAFE footprint-based fuel economy standards, for example, incentivize manufacturers to produce bigger vehicles, which are allowed to meet lower efficiency targets. Consumers, in turn, often feel pressured to purchase larger cars for perceived safety, creating a self-reinforcing “arms race.” Cultural norms around comfort, utility, and status further solidify the dominance of SUVs and pickups in the market. Ultimately, this paper helped me see how engineering design decisions are deeply shaped by regulatory structures and cultural values. My research reinforces the idea that engineers and policymakers must work together to reframe transportation safety around vulnerable road users, not just drivers. Technical Report For our Mechanical Engineering Design capstone project, we designed a Kelvin Fridge Insert to enable thermal conductivity testing of materials at cryogenic temperatures down to as low as one Kelvin. The equipment will be utilized in an evaporation fridge that is built specifically for use in the UVA Physics Department, and it presented to us challenging problems of thermal insulation, vacuum sealing, and precise temperature measurement. Our design was based on technical research in cryostat and low-temperature materials science. We researched immersion and liquid-flow cryostats and used scholarly sources of information on cryogenic thermal conductivity testing. From this foundation, we iterated through several design ideas, sharpening our concepts using a two-stage screening process with manufacturability, durability, cost, and thermal performance criteria. Our design employs a structural tube of 316 stainless steel, a cryogenic seal using a recyclable indium gasket, and copper and aluminum components in the sample mount for even heat dispersal. Throughout the design process, we applied engineering concepts from heat and mass transfer, mechatronics, materials science, and mechanical systems. We conducted heat flux analysis to select appropriate materials, pressure constraint analysis to ensure vacuum safety, and electrical system design for the 3ω measurement technique. Each subsystem -- structure, vacuum, electronics, and sample mount -- was designed to allow the system to function under extreme temperature gradients without compromising data integrity or accuracy. This project taught us how to fill the theoretical knowledge gap with real engineering practice. We had to balance ideal materials and the real-world constraints of cost, availability, and compatibility against what was already installed within the lab. We learned how to work together through technical problems in various disciplines and maintain continuous communication with our technical advisor as a team.