Engineering

Comparison of Linear Multi-Step Transesterification and In-Situ Transesterification in Biofuel Production using Chlorella Vulgaris

Ashleigh Branham
Texas A&M University-Kingsville

As carbon dioxide gases continue to rise and concerns about fossil fuel usage increases, there is an increased need for more sustainable and renewable energy sources. Microalgae has gained attention as a potential biofuel because of its high lipid content, rapid growth, and ability to grow in wastewater environments without competing with food crops or land resources. The purpose of this study is to determine if chlorella vulgaris can produce a workable amount of lipids for biodiesel production while comparing two methods for processing microalgae lipids to biodiesel, the traditional linear multi-step transesterification process and in-situ transesterification. This study uses quantitative research methods because numerical data was collected and compared between both methods. C. vulgaris was cultivated under controlled conditions. After cultivation, a portion of the biomass was used for the traditional linear 3 multi-step transesterification method, and the other portion was used for the in-situ transesterification method. Both methods will undergo lipid extraction to isolate the oils required for biodiesel production. The extracted lipid will then be converted into biodiesel through the transesterification process. It is expected that in-situ transesterification will produce biodiesel more efficiently by reducing processing steps, lowering energy consumption, and improving overall cost effectiveness compared to the traditional multi-step method. The practical implications of this study may benefit researchers, environmental scientists, and the renewable energy industry by contributing to improved biodiesel production methods and supporting more sustainable fuel alternatives for future large-scale applications.

Single-Layer Polarization-Independent Guided-Mode Resonance Reflector: Broadband Near-Infrared Reflection (1300–1800 nm) on a Silicon-on-Quartz Platform
 

Typhanne Vieira
The University of Texas at Arlington
 

Broadband optical reflectors are essential components in modern photonic systems, including optical communications, spectroscopy, sensing, laser cavities, and integrated photonic devices. Guided Mode Resonance (GMR) reflectors have emerged as an attractive platform for achieving high optical reflectance through resonant coupling within a single periodically patterned dielectric layer. However, conventional GMR reflectors are inherently polarization-dependent because the resonance behavior differs for transverse electric (TE) and transverse magnetic (TM) polarized light. As a result, broadband polarization-independent operation is generally achieved through increased structural complexity, such as multilayer configurations. To overcome this limitation, this work presents a single-layer, polarization-independent Guided Mode Resonance reflector based on a silicon-on-quartz platform for broadband operation in the near-infrared wavelength range of 1300–1800 nm. 
The proposed structure consists of a subwavelength silicon grating whose geometric parameters are optimized to maximize reflectance for both TE and TM polarizations over the target wavelength range. Rigorous Coupled-Wave Analysis (RCWA) is employed to model the electromagnetic response of the device, while Particle Swarm Optimization (PSO) is used to efficiently explore the design space and determine the optimal grating geometry. The optimized reflector is expected to demonstrate broadband, high-reflectance performance while maintaining a compact single-layer architecture compatible with conventional silicon microfabrication processes. By eliminating the need for additional functional layers, the proposed design offers a simplified solution for broadband, polarization-independent optical reflection. The results highlight the potential of single-layer GMR reflectors for next-generation photonic applications requiring compactness, high efficiency, and robust polarization-independent operation in the near-infrared region.

Tracking Recovery at Home: A Wearable Device for Upper Limb Rehabilitation
 

Terry Nguyen
California State University Sacramento

Monitoring patient progress is essential for evaluating the effectiveness of physical therapy, yet many current assessment methods remain limited in their ability to capture objective data outside of clinical settings. As a result, clinicians often have few reliable ways to assess how patients perform therapy exercises at home, where much of long-term recovery takes place. This work presents a wearable device for individuals with upper limb motor impairments to use during at-home physical therapy. These impairments may result from stroke, surgery, or neurological conditions such as cerebral palsy, which can reduce strength, coordination, and functional arm movement. The proposed wrist-worn system integrates an inertial measurement unit (IMU) and radio frequency identification (RFID) technology to monitor movement and task completion. The IMU captures arm motion and orientation data, while RFID interactions verify completion of predefined therapy tasks through contact with designated exercise targets. Together, these sensors measure useful recovery metrics such as task completion time, repetition count, movement consistency, and relative exercise difficulty. By extending therapy monitoring beyond the clinic, this approach provides clinicians with objective data between appointments and a clearer view of patient progress over time. These insights can support more personalized treatment decisions, allow earlier adjustments to physical therapy plans, reduce the need for frequent in-clinic visits, and lower treatment costs for patients and their families.