COVER: Meet the new Dean

Using data from aerial sensing and the virtual orchard, researchers can estimate the canopy cover of each tree in an orchard.

“If we do this early in the season, we can manage each tree based on its capability and needs.” To do this, the lab uses one of its hallmark innovations— the virtual orchard. Using drone imaging data, the team can create highly-detailed 3D reconstructions of an entire orchard in virtual reality. This allows them to examine data on individual plants in detail and run simulations. In a recent project, the team modeled the mid-season sun position for an almond orchard to model light absorption by each tree’s canopy. This helped the growers predict how much each tree would produce so they could manage each zone of trees differently, as well as optimize pruning to improve the canopy’s ability to absorb sunlight. Recently, the team has worked to expand the virtual orchard’s success by designing a complementary web app. The app lets growers easily view and interact with their simulated orchards and Digital Ag Lab’s data analytics and filter results to look at specific plants to understand the conditions that will make them grow best. SEEING PLANTS IN A NEW LIGHT For many of California’s crops, the best way to collect information is via drone. Drones are versatile because researchers can mount several different devices on them to take high-resolution images and measurements, including thermal, RGB, multispectral and hyperspectral cameras. According to Pourreza, many growers now either own or rent drones and he expects the number to continue rising. “With the availability of drones and the price dropping every day, it’s more accessible to growers and it’s a great tool for monitoring,” he said. One of the most powerful sensing tools the team has is hyperspectral imaging. Hyperspectral imaging covers more than 300 wavelengths of light and captures things that humans can’t

“WITH THE AVAILABILITY see with their eyes. These “hidden” wavelengths contain detailed OF DRONES AND THE PRICE information on each plant, such as how effectively it’s conducting DROPPING EVERY DAY, IT’S photosynthesis or whether it’s sick—one of the leading causes of MORE ACCESSIBLE low yield. TO GROWERS” One of the projects Digital Agriculture Lab Ph.D. candidate Hamid Jafarbiglu has enjoyed the – ALIREZA POURREZA most is identifying walnut trees that are infected with root lesion nematodes (RLN), tiny worms in the soil that attack tree roots. RLN infestation is a common problem in California, and young trees are the most vulnerable. It can leave growers with no other option than to re-plant the entire orchard. However, when infected, the trees give off signals that can be seen through hyperspectral imaging. “If you compare the spectral information from a healthy tree and a tree that is affected by nematodes, you can see that there are very subtle differences and you can use those subtle differences—we call them ‘spectral features’—to separate affected and healthy trees,” said Jafarbiglu. Identifying these spectral features help growers take action COMBATING CLIMATE CHANGE

The Digital Agriculture Lab’s technology is poised to play an important role in combating climate change, where efficiency and sensitivity to the environment are critical. An example comes from the lab’s agricultural mechanization work. Almond growers need to get as large of a pesticide coverage as possible on their plants, but spraying too much means spraying toxic droplets that can pollute the air and drift to nearby schools or residential areas. So, the team designed and built a spray backstop—an orchard sprayer attachment topped with a screen that looks like a large, wide umbrella. The screen is just tall enough to go over the treetops, and it blocks drifting spray droplets before they are released into the air. Pourreza says the growers were thrilled and he sees the potential for the idea to be commercialized. Sensing technology can also be used to accurately measure different crop phenotypes—a plant’s traits like size, shape and color that are influenced by both genetics and the environment. With sensing, researchers can find the best genotype for different environments—such as those that are resistant to droughts or nematodes—and introduce them to the growers. “If we continue growing the plants that we already have, rising temperatures or cold weather in the beginning of the spring might cause us to lose all we have in our orchard,” said Jafarbiglu. “But if we find the most resistant plant with this analysis, we can reach food security.” Optimization is also key to combating climate change. With optimal water and nutrient use on a per-plant basis, growers can save resources and prevent the detrimental effects of over-watering, such as dead soil and contamination of underground water resources. “Because we are dealing with climate change, we need to be prepared to adapt,” said Pourreza. “If we do not have accurate and timely information about agricultural production, we may lose crops due to some unexpected event. Using large-scale monitoring, we can prevent that.” Learn more about the lab.

Photo top: The spray backdrop, developed by the Digital Ag Lab, helps almond growers maximize pesticide coverage on their trees while stopping toxic chemicals from entering the air.

Photo middle: With the Virtual Orchard, growers can inspect their plants and run experiments in virtual reality. Photo: Digital Ag Lab.

A NEW STUDENT ORGANIZATION AT UC DAVIS is working to give everyone an equal opportunity to gain hands-on experience in an engineering machine shop. The Women Machinists’ Club at UC Davis (WMC) is a place for women and gender minorities to learn technical skills and develop the support network they need to succeed in a traditionally male-dominated shop environment.

This organization is the first of its kind in the UC system and one of only a handful of groups nationwide for women machinists in any capacity. Women and gender minorities make up just four percent of the total workforce in machine shops, which can make the environment even more intimidating for people looking for experience.

“The club creates a safe space where everyone can learn and work with their hands, regardless of gender identity or how much experience they have,” said second-year mechanical and aerospace engineering (MAE) major and WMC historian Ipsita Chauhan.

“You don’t need to have experience; you just need to be open to learning and have a lot of enthusiasm,” said WMC co-founder Kathryn Tarver, a fourth-year biological systems engineering major. “Machining is awesome and I’m motivated to make sure that everyone has the opportunity to see that for themselves.”

BUILDING A COMMUNITY

Tarver, who co-founded the club, had firsthand experience facing the dual challenges of learning to use the equipment in the biological and agricultural engineering (BAE) shop while navigating the experience of being a woman machinist.

She turned to her friend Grace Carley, a fourth-year MAE major and Engineering Student Design Center (ESDC) shop assistant, and Jennifer Mullin, a BAE assistant professor of teaching and “Introduction to Engineering Design” instructor, for support. As the three met for lunch and began discussing their projects and experiences, Tarver and Carley realized the value of having this network of women machinists they could relate to.

“There’s a culture [in machine shops] that isn’t as conducive to women being in STEM as it could be, and people don’t necessarily recognize that,” said Tarver. “It can also be challenging to come into a space where everyone already knows what they’re doing and to not have any frame of reference.”

They enlisted Mullin and their friend, third-year MAE major Ruby Houchens, and recruited more than 50 attendees to their first official meeting in spring 2020. Since then, the club has led a variety of activities, including regular meetings, game nights and workshops on technical skills like using Arduinos, a basic electronics platform used in many engineering applications. The club also helps students sharpen their professional skills, such as building engineering portfolios or describing design projects during job interviews.

The group also has active Instagram and YouTube accounts and its own Slack channel, where members can chat about anything from club events to their experiences in the shop to everyday life. These venues give club members the opportunity to get to know each other better and meet others with similar interests.

“Though I have learned a lot through my classes at UC Davis, I feel like I’ve also learned a lot of valuable things from my fellow students,” said Chauhan. “That’s why I liked the idea of the club to make a community where everyone can learn from each other.”

DEVELOPING HANDS-ON EXPERIENCES

Collaboration is in everything the club does. While Tarver is the co-founder and the officers have distinct roles, they work together to plan events and set the direction of the club.

“There’s such strong leadership and communication skills on that team,” said Mullin. “I think they’ve been so effective because they’re not about just talking, but doing.” Their biggest achievement has been Arduino Acclimate, a month-long design competition hosted in collaboration with the Society of Women Engineers at UC Davis this spring. Mixed teams of college and high school students received free Arduino kits, learned how to use the Arduinos through a series of workshops and designed interactive products to address challenges in the healthcare industry.

The club also worked with BAE lecturer Dan Frank to develop a new hands-on design and manufacturing undergraduate course in the applied biological systems technology machine shop. Frank and Tarver developed it as a computer-aided design (CAD) class with a focus on manufacturing. Each week, it covered a different type of manufacturing—everything from traditional methods like blacksmithing to automated assembly—and inspired students to think about designing products with manufacturing in mind. CHANGING THE CONVERSATION

“A lot of times, we’re taught how to build things, but not about tolerances, or that you can’t have a square pocket on the thing that you’re making,” said Tarver. “It’s these things that are going to get a new engineer’s first design on the job sent back because you cannot actually make it.”

The course was offered again in spring 2021 and Frank plans to work with the University Honors Program this summer to make it a regular offering. The group is poised to build on its success in its first year as students return to campus this fall. WMC members will finally be able to get the hands-on machine shop experience Tarver and Carley envisioned when they first founded the club, and in-person meetings will likely help build a stronger community.

The club can also begin to focus on its larger mission— changing the culture of machine shops. Having the organization not only raises awareness of the issue, but also creates more opportunities for women and gender minorities to gain hands-on experience in the shop, allowing them to contribute to the conversation about a more inclusive environment.

“This is a really important time for positive change to take place,” said Mullin. “The words haven’t all been written yet. We need to develop an inclusive narrative [for women machinists] and propagate this message at UC Davis through experiences and projects.”

By Rachel Steere

UC DAVIS’ FIFTH ANNUAL GIVE DAY was held this year on April 16-17. Give Day is a 29-hour online fundraising drive that brings the community together to celebrate the Aggie spirit by sharing, following or financially supporting UC Davis programs that have made an impact on the lives of people everywhere. The college, its eight departments and many student clubs have demonstrated tremendous flexibility and resilience in the last couple of years and have gained experience dealing with unforeseen circumstances, solving unique problems, learning innovative technology and connecting in new ways. Donors recognized this, and this past Give Day the College of Engineering broke all of its previous records, raising more than $160,000 from 500 gifts to support clubs, departmental priorities and students facing financial challenges.

Photo courtesy of BMEGG. THE DEPARTMENT OF BIOMEDICAL ENGINEERING is using their Give Day funds for the Biomedical Engineering Graduate Group’s (BMEGG) student retreat. “This is an important opportunity for vertical integration amongst our graduate student classes, said Christal Wintersmith, graduate coordinator and student services advisor for BMEGG. “First- and second-year students will have the opportunity to engage with more senior students over two days of team building activities, research talks and discussions about current issues in academia as they learn the ropes of graduate school.” BMEGG’s mission is to provide the highest standard of student education, research and service in biomedical engineering. They have been educating and mentoring biomedical engineering graduate students for more than 50 years, and their graduates have gone on to be leaders in academia, industry, medicine and many other professional fields.

THE DEPARTMENT OF MATERIALS SCIENCE AND ENGINEERING is using their funds on a number of things, including funding their senior design course, senior awards for graduation and supporting students like Nicole Shuman. Fourth-year materials science and engineering student Nicole Shuman found materials science as a returning college student and is determined to use her knowledge to inspire others through outreach, teaching and mentorship. She was accepted through the UC Davis transfer admission guarantee program and enrolled in fall 2019. Though the transition was difficult, AvenueE and the department supported her at every turn. “I’m so grateful that I picked this major at this college in this department because everyone was so nice and gave me a great experience,” Shuman said. “I want to be the professor that I wish I had when I first attempted college, and I want to be as inspirational and knowledgeable as my materials science professors were so I can help create more leaders.”

Photo courtesy of Nicole Shuman.

THE DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING is using their funds to benefit students through a hardship stipend. Colleen Bronner, an associate professor of teaching and vice-chair of undergraduate studies in the department, has been a big proponent of raising those funds, and getting them to the students who need it most. Michelle Zhang ’22 is one student who benefited. “The Department of Civil and Environmental Engineering has supported many of my peers who faced hardship in the last year with additional aid, including increased research and internship opportunities with faculty, flexible academic accommodations and many resources related to health and well-being. Though we had all been learning remotely, I have never felt a greater sense of belonging and motivation from the department, my professors and my peers,” said Zhang.

Michelle Zhang, Class of ’22. (Karin Higgins/UC Davis)

The Dean’s Executive Committee (DEC), composed of executive-level leaders, venture capitalists and successful entrepreneurs, works closely with staff and faculty to assist the College of Engineering through advocacy, prospective donor identification and cultivation and personal philanthropy. This year, the DEC invited engineering student clubs to submit a one-minute video pitch during their February meeting and they picked three clubs that they wanted to benefit from their Give Day Challenge. Each of those clubs received $10,600, in addition to the funds each club raised on Give Day.

THE SPACE & SATELLITE SYSTEMS CLUB is using their funds to purchase and manufacture all flight unit components and instrumentation for their CubeSat, a class of small research spacecraft. They will also use the funds to perform additional environmental tests needed, such as thermal and vacuum chamber testing, as well as fund their second planned CubeSat mission, REALOP II. “Thank you to all donors, the Dean’s Executive Committee and the College of Engineering for helping us achieve this goal and providing us with this opportunity,” said Christopher Hipolito, co-president of the club.

Members of the Space & Satellite Systems Club. (Joshua Moy/UC Davis)

THE CLUB OF FUTURE FEMALE ELECTRICAL ENGINEERS (COFFEE) is using their funds to provide end-ofthe-year scholarships to members in financial need. They also plan to use the money for funding future in-person community building activities and outreach events.

Members of COFFEE. (Joshua Moy/UC Davis)

Members of EWB. (Joshua Moy/UC Davis) ENGINEERS WITHOUT BORDERS (EWB) plans to put their Give Day funds towards their international projects. The Kenya project will be able to fund a remote assessment trip to conduct a hydrogeological and geophysical survey. This will help determine the best location to construct a borehole with a hand pump. The funds will also help cover water quality testing supplies, as well as costs associated with obtaining the necessary environmental permits. The Bolivia project plans to use the funds to support the construction of composting latrines in the Parque Colani community. The Peru program plans on using the funds to conduct a remote monitoring and evaluation trip in the community of La Huaylla and a remote assessment trip in the community of Saparcon Bajo. In the future, they may also use the funds for a remote implementation trip in Saparcon Bajo to build a new spring box.

An artist’s rendering of what an urban air mobility environment might one day look like. Photo: Lillian Gipson/NASA

YOUR FLYING TAXI IS ALMOST HERE UC Davis’ Seongkyu Lee is tackling rotorcraft noise, an important challenge in making flying taxis a reality By Noah Pflueger-Peters

IIn less than a decade, your taxi might come from the sky instead of the street. Once a hallmark of science fiction, flying taxis have become the cutting edge of aerospace engineering thanks to researchers like UC Davis’

Seongkyu Lee, an associate professor of mechanical and aerospace engineering (MAE). Lee’s group is conducting groundbreaking aeroacoustics research to lay the computational groundwork to make air taxis a reality.

The emerging field, known as urban air mobility (UAM), promises to develop electric vertical take-off and landing (eVTOL) vehicles to transport people and goods across short distances. If successful, UAM will create a new method of transportation, alleviate traffic congestion in cities and generate an estimated $1 trillion in the coming decades, according to Morgan Stanley.

“If this is successfully implemented, it is going to change our daily lives, [start] a new golden age in aerospace engineering and completely change the landscape in industry and the job market,” said Lee.

Though the excitement is palpable, one of the biggest obstacles is noise. Anyone who’s been around a helicopter or a drone knows how loud they can be, and air taxis will face that same risk. The goal is to make vehicles blend into existing city noise by being, at most, as loud as cars—about 62 decibels. If the vehicles are too loud, city residents and officials will likely reject them. “Noise is one of the biggest challenges in urban air mobility,” he said. “If the noise is not acceptable, then this business will not be successful.”

Associate professor Seongkyu Lee. (Nikita Mistry/UC Davis) To make viable eVTOL designs, researchers need to accurately predict how loud their aircraft will be. This means accounting for two types of noise—tonal and broadband noise. Tonal noise is the repetitive and intermittent sound rotors make as they spin and interact with the air. Broadband noise is the whooshing sound the aircraft makes as it flies. Both are equally important. Broadband noise is difficult to predict because it’s caused by complex air flow turbulence from rotor blades or wings— which involve difficult fluid physics problems. Lee is among the first to use highly-accurate computational fluid dynamics (CFD) software to unravel the detailed physics of how air flows around of UAM aircraft and creates noise.

Since 2019, Lee and his Ph.D. student Sicheng (Kevin) Li have worked through this complexity and developed an efficient, physics-based broadband noise prediction tool called UCD-QuietFly, which has been widely adopted by the eVTOL industry. “Professor Lee’s work is a giant step forward for the semiempirical prediction of rotor broadband noise,” said Ben Goldman, who uses UCD-QuietFly at industry leader Archer Aviation. “With its incorporation in the UCD-QuietFly program, he has created a powerful and accessible tool to aid in the design of the next generation of quiet UAM vehicles.” “Professor Lee and his research group have made important contributions to the modeling of acoustic noise with their UCD-QuietFly software,” said Ben Berry, a lead engineer at the eVTOL company Kitty Hawk. “Reducing noise is critical to public acceptance, and improved prediction capabilities such as UCD-QuietFly will help the industry as a whole make better design choices to achieve this.” “UCD-QuietFly is an especially accurate and practical tool for predicting broadband noise of eVTOLs in conceptual and preliminary design stages,” said Sehwan Park, a lead engineer at Hyundai Motor Company. As part of a new project funded by the U.S. Army under the Vertical Lift Research Center of Excellence (VLRCOE) at Pennsylvania State University, Lee’s group will also develop multi-fidelity models of aerodynamic and aeroacoustic interactions between prop-rotors and wings to inform UAM aircraft development. The goal is to improve the accuracy of medium-fidelity models using tools from the highlydetailed CFD database. Additionally, Lee has been funded by the NASA University Leadership Initiative (ULI) to develop tools for UAM researchers to optimize their designs, given constraints on noise, design and performance. In collaboration with UC San Diego, Lee’s team will develop new acoustic theories and codes that will be implemented in NASA’s multidisciplinary design, analysis and optimization program for simulating aircraft designs. “Our research is not just focused on noise prediction—we also aim to reduce noise and we want to achieve this in the system-level design,” he said.

A detailed CFD model of the flow physics and resulting noise from a UAM quadrotor aircraft, generated with Ph.D. student Zhongqi (Henry) Jia. Graphic courtesy of Seongkyu Lee.

Like any flying vehicle, air taxis will be subject to a regulated flight path—known as an airspace corridor— that’s based on safety, equity and environmental impact. Since air taxis are electric, they pollute mainly through noise. As part of a new project with Caltrans, Lee’s team will collaborate with UC Berkeley to create a “noise map” for a 3D digital UAM airspace corridor simulation software that will help policymakers develop airspace corridor guidelines in California. To do this, they will study how eVTOL noise propagates across the community under different conditions, as aircraft can be much louder when it’s cold, cloudy or windy, and having multiple UAM vehicles flying at once may amplify sound. “The state government will make the final decision about this operation, but we are going to help them make a better decision with this computational tool,” he said. “I’m very excited about this project because it certainly will expand our lab capability to more practical research. This is a first step into this research area, but I think this is the right time.” Lee says UAM is an exciting place to be, especially for students. The MAE department recently created an undergraduate course on drones and quadcopters and a graduate course on rotorcraft—both of which he teaches. The last three NASA university student design competitions, which UC Davis aerospace engineering teams won twice, were also focused on solving a UAM challenge, showing NASA’s interest in the area. Industry demand is also booming. “UAM will open up a new golden age of aerospace engineering,” he said. “This community is growing and students are very excited about the opportunities. I’m glad that students are learning and working on exciting aircraft research at universities and then finding jobs in the same field after graduation. Eventually, they will change the world and make science-fiction dreams come true.”

Lee and Ph.D. student Sicheng (Kevin) Li, who developed UCD-QuietFly together. (Nikita Mistry/UC Davis)

Graphic courtesy of Hyundai Motor Company.

UC DAVIS AEROSPACE ENGINEERING STUDENTS continued their dominance in NASA’s Aeronautics University Design Challenge, with two teams tied for first and another tied for second in the 2020-21 competition. NASA’s annual competition challenges U.S. university students to solve some of the biggest problems facing aerospace engineering today. This year’s competition, titled “Weather-Tolerant Operations for Urban Areas,” challenged students to develop a small rotorcraft vehicle that can operate safely in cities under weather conditions such as high winds, low temperatures and poor visibility during storms, fog and smoke. The winning designs are the culmination of two quarters of work in aerospace engineering students’ senior design course, which has been taught each year by mechanical and aerospace engineering professor Case van Dam. Every year since 2017, UC Davis teams have placed at least third and have finished first or tied for first four times—2021, 2019, 2018 and 2015. Learn more about the competition.

An artist’s conecpt of the Allweather Taxi Pilots Experimental Aircraft, or ATP-XW-Blizzard, one of the winning designs developed by a team of UC Davis aerospace engineering students. (Aristide Fertig/UC Davis)

An artist’s rendering of the Electric Transport 1, designed by UC Davis aerospace engineers to fly in San Francisco under heavy fog. (Grace Carley)